United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/540/2-88/002
August 1988
Superfund
Technological
Approaches to the
Cleanup of
Radiologically
Contaminated
Superfund Sites
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EPA/540/2-88/002
August 1988
Technological Approaches to the
Cleanup of Radiologically Contaminated
Superfund Sites
U.S. Environmental Protection Agency
Washington, D.C. 20460
Agency
167Q
Cnicago, 1L 50604
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Notice
This document has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
presentation and publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.
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Abstract
This report identifies technologies that may be useful in removing or stabilizing
radiological contamination at those uncontrolled hazardous waste (Superfund) sites that
contain radionuclides. The radioactive materials at some Superfund sites consist
primarily of waste from radium, uranium, and thorium processing. Twenty existing
Superfund sites are known to contain radionuclides, along with seventy-one sites
managed by the Department of Energy. This report addresses remediation of
contaminated soils; it does not address remediation of contaminated buildings or
ground water. This report is not intended to provide any legal or policy basis for the
selection or use of technology for cleanup of a hazardous waste site.
Sites contaminated with radionuclides pose a unique problem because, unlike organic
wastes, radionuclides cannot be destroyed by physical or chemical means; they can
only decay through their natural process. Thus, alteration or remediation of the
radioactive decay processes, thereby changing the fundamental hazard, is not possible.
Several technologies have potential for eliminating or stabilizing radionuclides at
radiologically contaminated sites. These include both on-site and off-site disposal,
on-site treatment, radon control, chemical extraction, physical separation, and
combined physical separation and chemical extraction technologies. Applicability of
these technologies is controlled by site-specific factors, so their suitability must be
determined on a site-by-site basis.
Issues of significant concern in attempting to apply remedial techniques include
disposal siting, handling of concentrated residuals, public reaction, and cost.
Many of the technologies have not been satisfactorily demonstrated. There is a need
for additional assessment studies. Significant research and development activities,
including bench-scale and pilot-scale studies, would be necessary prior to full-scale
mobilization for site cleanups. These technologies should be evaluated for
implementation as they may have the potential for significantly improving cleanup
efforts.
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Contents
Abstract iii
Figures vii
Tables ix
Acknowledgments x
Executive Summary xi
1. Introduction 1
1.1 Study Purpose and Objectives 1
1.2 Health Concerns 1
1.3 Waste Sources and Contaminated Media 3
1.4 Scope of Report 3
1.5 References 4
2. Disposal 5
2.1 Introduction 5
2.2 On-Site Disposal 5
2.2.1 Capping 5
2.2.2 Vertical Barriers 7
2.3 Off-Site Disposal 8
2.3.1 Land Encapsulation 8
2.3.2 Land Spreading 9
2.3.3 Underground Mine Disposal 10
2.3.4 Ocean Disposal 11
2.4 Typical Costs of Disposal 12
2.5 References 13
3. On-Site Treatment 15
3.1 Introduction 15
3.2 Technologies of Potential Interest 15
3.2.1 Stabilization or Solidification 15
3.2.2 Vitrification 17
3.3 Typical Costs of On-Site Treatment Technologies 18
3.4 References 18
4. Radon Control 19
4.1 Introduction 19
4.2 Methods 19
4.2.1 Radon Control and Reduction in Buildings 19
4.2.2 Electrostatic Precipitators 20
4.2.3 Soil Gas Venting and Areal Control 20
4.3 Typical Costs of Radon Control 24
4.4 References 25
5. Chemical Extraction 27
5.1 Purpose 27
5.2 State of the Art 27
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Contents (continued)
5.3 Technologies of Potential Interest 27
5.3.1 Extraction with Water 28
5.3.2 Extraction with Inorganic Salts 29
5.3.3 Extraction with Mineral Acids 30
5.3.4 Extraction with Complexing Agents 32
5.3.5 Technologies for Separating Radionuclides from Extractant 33
5.4 Typical Costs of Chemical Extraction Technologies 36
5.5 References 37
6. Physical Separation Processes 41
6.1 Purpose 41
6.2 State of the Art 41
6.3 Technologies of Potential Interest 42
6.3.1 Screening 43
6.3.2 Classification 44
6.3.3 Flotation 51
6.3.4 Gravity Separation 53
6.3.5 Support Technologies for Treatment of Liquid Recycle 54
6.4 Typical Costs of Physical Separation Technologies 57
6.5 References 58
7. Combined Physical Separation and Chemical Extraction Processes 61
7.1 Purpose and Mode of Operation ; 61
7.2 State of the Art 61
7.3 Technologies of Potential Interest 61
7.3.1 Soil Washing and Physical Separation 61
7.3.2 Separation and Chemical Extraction 63
7.3.3 Separation, Washing and Extraction 64
7.4 Typical Costs of Separation and Extraction Technologies 65
7.5 References 66
8. General Issues at Radiologically Contaminated Superfund Sites 67
9. Criteria for Further Studies 71
10. Conclusions 73
Appendices
A. Applicable Laws, Regulations, and Guidance 75
Addendum I Combined NRC-EPA Siting Guidelines for Disposal of
Commercial Mixed Low-Level Radioactive and Hazardous Wastes 77
Addendum II Joint NRC-EPA Guidance on a Conceptual Design
Approach for Commercial Mixed Low-Level Radioactive and
Hazardous Waste Disposal Facilities 80
B. Characteristics of Man-Made Radiologically
Contaminated Sites 85
Radiologically Contaminated Superfund Sites 85
Department of Energy Remediation Programs 97
Bibliography 103
Abbreviations and Symbols 112
Conversions 113
Key Chemical Elements 114
Glossary 115
VI
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Figures
Number Page
1 Uranium-238 decay series 2
2 Schematic of a cover profile 6
3 Slurry trench construction operations 7
4 Grout curtain around waste site 7
5 Schematic of a land encapsulation system 9
6 Conceptual view of a mine storage facility 11
7 Subsurface injection machine 16
8 In situ vitrification process 17
9 Tile ventilation where tile drains to sump 21
10 Sub-slab ventilation 22
11 Gas extraction well for landfill gas control 23
12 Schematic diagram of a forced air venting system 24
13 Pilot-scale equipment test for soil decontamination 43
14 Typical separation sizes of the basic screen types 45
15 The basic screen types and their classifications 46
16 Hydrocyclone 51
17 Schematic of a shaking table, showing the distribution of products 53
18 Limits of water content variation 54
19 Conceptual soil decontamination process flow sheet 62
20 Simplified process flow diagram of the EPA soil washer 65
A1 Mixed waste disposal facility 81
A2 Double liner and leachate collection system 81
A3 Cross-sectional view A-A 82
A4 Waste cover system 83
B1 FUSRAP sites as of 1982 98
B2 Locations of UMTRAP sites 100
VII
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Tables
Number Page
A State of the Art of Remediation Technologies x
1 Typical Background Radiation Levels 3
2 State of the Art of Disposal Methods 6
3 Ocean-Disposed Low-Level Radioactive Waste, 1946-1970 12
4 Typical Costs of Various Disposal Methods 13
5 State of the Art of On-Site Treatment Technologies 16
6 Typical Costs of On-Site Treatment Technologies 18
7 State of the Art of Radon Control Technologies 19
8 Representative Exposure to Radon-222 Progeny 20
9 Typical Costs of Various Radon Reduction Techniques in Existing Homes 25
10 State of the Art of Chemical Extraction Technologies 28
11 Physical Separation Technology and Particle Size 42
12 State of the Art of Physical Separation Technologies 43
13 The Major Types of Screens 47
14 Types of Screening Operations and Equipment 48
15 The Major Types of Classifiers 49
16 Typical Costs of Major Physical Separation Equipment 58
17 State of the Art of Combined Physical Separation and
Chemical Extraction Technologies 62
18 Soil Product Plutonium Level from Pilot Plant Operation 62
19 Site and Waste Characteristics that Impact Remediation Technologies 71
B1 Radioactive Waste Superfund Sites 86
IX
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Acknowledgments
This report was prepared under the overall direction and coordination of Paul S.
Shapiro, Program Manager in the Office of Environmental Engineering and Technology
Demonstration (OEETD) of EPA's Office of Research and Development. The
introduction, the appendix on radiologically contaminated sites, and the chapters on
disposal methods and radon control were prepared by Robert Hartley assisted by Adib
Tabri of the OEETD Risk Reduction Engineering Laboratory (RREL) in Cincinnati. The
chapters on chemical extraction, physical separation, and combined physical separation
and chemical extraction processes were prepared by Ramjee Raghavan and Gopal
Gupta of Enviresponse, Inc., who compiled the report as a whole. The chapter on
chemical extraction and physical separation was prepared using information from
"Review of Chemical Extraction and Volume Reduction Methods for Removing
Radionuclides from Contaminated Tailings and Soils for Remedial Action," by William
S. Richardson, Gary B. Snodgrass, and James Neiheisel, Analyses and Support
Division and the Eastern Environmental Radiation Facility, Office of Radiation Programs
(ORP), July 24, 1987. Additional information was provided by William Gunter of ORP.
Frank Freestone and Darlene Williams of the RREL Edison, New Jersey, facility were
Project Officers for Enviresponse. Acknowledgments are also due to the word
processing and editorial staff.
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Executive Summary
Introduction
This document identifies potential technologies that
possibly can be applied in the control and remediation
of radioactive contamination at Superfund sites. This
report provides a discussion of the technologies; it
does not give a detailed critical evaluation of them.
The report does not include in-depth analyses that
would be needed to determine the applicability of any
of these technologies at a particular site.
The report only addresses treatment and disposal of
radiologically contaminated soils, and radon control. It
does not address, for example, remediation of
radiologically contaminated buildings. The report also
does not address treatment of radiologically
contaminated ground water, which is of concern at
some Superfund sites.
The radioactive materials at many Superfund sites are
by-products of uranium, thorium, and radium
processing in the form of tailings, contaminated
buildings and equipment, and stream sediments.
The primary public health threats from the radioactive
materials are through inhalation of radon and radon
progeny, external whole body exposure to gamma
radiation, and ingestion of radionuclides through food
and water. Radon and radon progeny are
continuously produced through the decay and
decomposition of uranium, thorium, and radium.
These hazards will persist throughout the entire
decay time if no remedial action is taken. These
hazards could include the increased risk of cancers in
the exposed whole body and may also increase the
risk of genetic damage that may continue to cause
inheritable defects in future generations.
It should be noted that the radioactive contaminants
are not altered or destroyed by treatment
technologies. The volume of contaminated material
may be reduced, but the concentration of the
contaminants will be much higher in the reduced
volume. Some type of containment and/or burial is
the only ultimate remedy for materials contaminated
at levels above those considered safe for exposure.
Table A on the following page shows the state of the
art of the various disposal, on-site treatment, radon
control, chemical extraction, physical separation, and
combined physical separation and chemical extraction
technologies that are discussed in this report. Since
none of the chemical extraction and physical
separation technologies has been used in a site
remediation situation, their application must be
approached cautiously.
Significant research and development activities would
be necessary prior to full-scale mobilization for site
cleanup. The same holds true for solidification or
stabilization processes. Only excavation and land
encapsulation have been used to remediate
radiologically contaminated sites; ocean disposal has
been used for disposal of low level radioactive
wastes.
Remediation Sites
Twenty sites that contain man-made radioactive
wastes are on or are proposed for inclusion on the
National Priorities List (NPL). These Superfund sites
are described briefly in Appendix B of this document.
(Information provided is accurate as of December
1987.) The sites contain tailings piles and
redistributed tailings, solid waste landfills, hazardous
waste landfills, fabrication plants and laboratories, and
contaminated ground water. Remedial investigation
and feasibility studies (RI/FS) have been completed
on eight sites and are underway on seven sites.
Remediation at none of these sites has been
completed. However, the Department of Energy
(DOE) has completed remedial actions at vicinity
properties associated with DOE NPL sites.
The DOE cleanup projects, which also are described
in Appendix B, mainly stem from DOE's inherited
responsibilities in the area of nuclear materials
production. DOE has four major cleanup projects:
(1) Formerly Utilized Sites Remedial Action
Project (FUSRAP) - 29 sites;
(2) Uranium Mill Tailings Remedial Action Project
(UMTRAP) - 24 sites;
(3) Grand Junction Remedial Action Project
(GJRAP) - 1 site; and
(4) Surplus Facilities Management Program
(SFMP) - 17 sites.
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Table A. State of the Art of Remediation Technologies
Field
Technology
On-site Disposal
Capping
Vertical barriers
Off-site Disposal
Land encapsulation
Land spreading
Underground mine disposal
Ocean disposal
On -site Treatment
Stabilization or solidification
Vitrification
Radon Control
In homes
- ESP
Areal control
Chemical Extraction
With water
With inorganic salts
With mineral acid
With complexing agents
Demonstration
Bench Pilot with
Laboratory Scale Scale Radioactive
Testing Testing Testing Material
X
X
X
X
X
X X
X X
X X
X X
X X
X X
x xxx (from ores)
x xxx (from ores)
Radiologically
Contaminated
Site
Remediation Remarks
x
x
Land spreading of low-level radium sludge
from drinking water is an allowed policy in
Illinois
DOE currently working on mined repository
for radioactive waste
Stringent regulations for radioactive waste
Proposed by DOE for low-level radioactive
waste
Field testing by ORNL
x As a temporary and interim measure
Used in extraction of radium, thorium, and/or
uranium
Used in extraction of uranium
Screening
Classification
Gravity concentration
Flotation
x x (from ores)
x x (from ores)
x x (from ores)
x x (from ores)
Used m extraction of radium, thorium, and/or
uranium
Used in extraction of radium, thorium, and/or
uranium
Used in extraction of radium, thorium, and/or
uranium
Used in extraction of radium, thorium, and/or
uranium
Combined physical separation
and chemical extraction
Soil washing and physical
separation
Separation and chemical
extraction
Separation, washing, and
extraction
Pilot-plant development and testing needed
for radioactive wastes
Various portions of the process have been
developed for extraction of uranium from
ores. Pilot-plant testing and development
needed for radioactive waste
Significant bench-scale and pilot-plant
testing needed for radioactive waste
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Current DOE projects also involve the cleanup of
thousands of vicinity properties, about 4000 in
GJRAP alone. The Grand Junction Remedial Action
Project has excavated and moved contaminated
material to an interim storage site from approximately
700 vicinity sites and is currently evaluating
alternatives for remediation of the interim storage site.
To date, seven sites administrated by DOE under the
FUSRAP project have been remediated. Three of the
FUSRAP sites are also on the NPL. The SFMP
includes over 30 currently active projects. Two of the
SFMP sites are on the NPL.
In addition, DOE's Office of Defense Programs (OOP)
has a program similar to SFMP for its sites. OOP
conducts selected remedial decontamination activities
as required at facilities under their jurisdiction.
In most remedial actions conducted to date, the
radioactively contaminated material has been
excavated and contained in either permanent or
temporary above-ground containment facilities.
These facilities have been designed to include
perimeter air monitoring, surface water runoff
collection and containment features, and ground
water monitoring devices.
All methods used to accomplish remedial action on a
site contaminated with radionuclides will result in
waste materials that require disposal or storage. The
final disposal of these waste materials is the single
largest problem in remedial action.
Some of the Superfund sites contain various types of
hazardous wastes, and the radioactive portion may
pose a relatively minor problem. The presence of
other hazardous materials may complicate
remediation of the radioactive portion of the waste
and vice-versa.
Section 121 of CERCLA mandates that remedies
must be protective, utilize a permanent solution and
alternative treatment technologies or resource
recovery options to the maximum extent practicable,
and be cost effective. In addition, cleanup standards
for remedial actions must meet any applicable or
relevant and appropriate requirements (ARARs).
Standards developed under Section 275 of the
Atomic Energy Act and Section 206 of the Uranium
Mill Tailings Radiation Control Act (UMTRCA) of 1978
may be applicable or relevant and appropriate on a
site-specific basis to the cleanup of radiologically
contaminated Superfund sites. The EPA promulgated
40 CFR 192, Health and Environmental Protection
Standards for Uranium Mill Tailings in January 1983
under authority of these Acts. The pertinent standards
are contained in 40 CFR 192.12, 192.32, and 192.41,
and deal with the acceptable levels of radioactivity in
residual materials and radiation emission levels from
them, and with disposal requirements. The disposal
requirements include a design life of at least 200
years, and preferably 1,000 years where the latter is
reasonably achievable. However, standards are
applicable to uranium mill tailings only. Relevance and
appropriateness must be determined according to
specific site conditions.
Disposal
Disposal can be in one of two categories: on-site
disposal or off-site disposal. Applicability of these
methods to Superfund sites is controlled by site-
specific factors; therefore, their usefulness must be
determined on a site-by-site basis.
On-Site Disposal
Two methods are available for on-site disposal.
These may be applied in situ. They are:
Capping
Vertical barriers
Capping is simply covering the contaminated site with
a thick layer of low-permeability soil. The design
would be chosen to: (1) attenuate the gamma
radiation associated with all the radionuclides present,
(2) protect the ground water and 3) provide
reasonable assurance that release of radon from
residual radioactive material to the atmosphere will
not exceed acceptable limits. Capping has the
advantages of relatively low cost, ease of application,
and having been used for remediating radiologically
contaminated sites.
Capping has certain drawbacks. It does not eliminate
the source of radioactivity; this limits further use of
the site. The cap must be maintained as long as the
contaminant exists at the site. A cap must not be
penetrated for construction or installation of structures
and utility hardware. Therefore, existing structures
must be removed before capping. Also, horizontal
migration of the radionuclides in ground water could
still occur.
Vertical subsurface barriers (barrier walls) could serve
as barriers to horizontal migration of radionuclides,
but perhaps more important, as barriers to the
horizontal movement of ground water that may be
contaminated with radionuclides. Vertical barriers are
relatively simple to install. They perhaps could serve
as the container walls for extraction techniques.
Disadvantages include the difficulty of obtaining truly
low permeability and the possibility of material
incompatibility with waste chemicals. Before
attempting the installation of a barrier wall, detailed
data are required on the physical and chemical
characteristics of the soil.
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Off-Site Disposal
Off-site disposal can be considered for either
temporary storage or permanent disposal. The
purpose would be to limit the exposure of people and
the environment to the radionuclide. This method can
be applied to both untreated materials and materials
that have been modified through a volume reduction
process. The waste materials could be treated before
disposal to reduce their volume or to stabilize them
so that they may be transported more easily. Four
off-site disposal methods are briefly described in this
report:
Land encapsulation
Land spreading
Underground mine disposal
- Ocean disposal
Land encapsulation, either permanent or temporary,
has been the disposal method most used so far for
low-level radioactive waste materials. Land
encapsulation on site can also occur, but this may not
be applicable in all situations. It can be as simple as
excavating the contaminated material and, without
further treatment, hauling it to a secure site designed
for land encapsulation. The containment structure
technology has been used to remediate radiologically
contaminated sites. This technology was originally
developed for the disposal of hazardous wastes.
Joint NRC-EPA Design Guidelines and Combined
NRC-EPA Siting Guidelines for Disposal of
Commercial Mixed Low-Level Radioactive and
Hazardous Waste provide guidance on land
encapsulation siting and design where chemical
contamination is also a problem (see Appendix A).
Selecting a site for a new facility or finding an existing
site that will accept the waste can be very difficult. In
addition, the problems of handling and transporting
the waste must be considered. If the radioactive
portion is first concentrated, as in chemical extraction
and physical separation, additional disposal issues
could result due to higher levels of radioactivity in the
concentrated waste. Advantages of land
encapsulation include the relative maturity of the
technology, the complete removal of the waste from
the affected site, and the relative simplicity of the
prerequisite information needs.
Land spreading is a technology that has been
considered for radiologically contaminated wastes.
This technology involves excavation of the
contaminated material, transporting it to a suitable
site, and spreading it on unused land, assuring that
radioactivity levels approach the natural background
level of these materials when the operation is
completed.
Land spreading might be more appropriate for dry,
granular tailings and soils. It would likely be
inappropriate for materials contaminated with both
radioactive and nonradioactive hazardous wastes.
Another similar method is blending with clean soil
prior to land spreading.
Underground mine disposal could provide secure and
remote containment. Disposal in underground mines,
either new or existing, could be costly. The
radiologically contaminated waste could be excavated
and transported without treatment to the mine site.
Alternatively, it could be pretreated for volume
reduction or solidified to facilitate transport and
placement.
There would be a tradeoff between costs for
treatment or solidification and costs for transportation
and placement. Transportation costs and associated
risks need to be researched further. Movement of
radionuclides into ground water must be considered
and prevented.
Ocean disposal could be an alternative to land-
based disposal options. This alternative should only
be evaluated for low level mill tailing wastes and not
considered for enhanced radioactive materials or
concentrated residuals.
On-Site Treatment
Two methods are available for treating radiologically
contaminated wastes so that the radioactive
contaminants may be immobilized. These are:
Stabilization or solidification
Vitrification
Stabilization or solidification immobilizes radionuclides
(and could reduce radon emanation) by trapping them
in an impervious matrix. The solidification agent—
for example, Portland cement, silica grout, or
chemical grout-can be injected directly into the
waste mass or the waste can be excavated, mixed,
and replaced. It offers the opportunity to leave the
waste materials on site in an immobilized state. It may
be used as additional security for a waste mass that
will be capped. The presence of other hazardous
chemicals could interfere with some solidification
processes. Although the radionuclides are not
removed in this process, their mobility and spread in
the environment are restrained.
Vitrification is another process that can immobilize
radioactive contaminants by trapping them in an
impervious matrix. The in situ process melts the
waste materials between two or more electrodes,
using large amounts of electricity while doing so. The
melted material then cools to a glassy mass in which
the radionuclides are trapped.
Volatilization of waste substances must be contended
with; some of the volatiles may be vaporized
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radionuclides. Excavation and vitrification in a plant
designed for the purpose can be done using an
electric furnace or a rotary kiln, but dealing with the
resulting solids may pose additional problems.
Vitrification is very energy-intensive.
Radon Control Without Source
Remediation
As an interim measure, it may be possible to
remediate on-site properties through radon removal
techniques. In theory, these may include the
following:
Radon reduction in homes
Electrostatic precipitators
Areal soil gas venting and areal removal
Radon and its decay progeny do not pose a
significant health hazard in an open outdoor
environment. However, they can accumulate to
harmful concentrations in confined spaces, such as
residences where there is an underlying radionuclide
source.
Direct radon reduction in homes can be accomplished
in a variety of ways. Techniques include sealing entry
cracks and holes, forced ventilation of soil and
building materials in and adjacent to the foundation,
and passive and forced ventilation of indoor airspace.
The techniques, properly applied, are effective. These
control systems must be maintained as long as the
radionuclide source is present. The particular
techniques to be applied to a specific situation
depend upon the structural characteristics of the
building and the nature of the underlying soil.
Electrostatic precipitators may reduce the number of
the particles in a room including particles to which
radon progeny are attached. The health effects of this
are not known.
Areal soil gas venting may be applicable to reduction
of radon emanation over a waste site. The technology
has been used to remove methane from landfills and
organic vapors from soil. The effectiveness will
depend in part on the soil characteristics. Areal
removal systems would require long-term
maintenance.
Chemical Extraction of Radionuclides
from Contaminated Soil
The objective of this separation technology is to
concentrate the radioactive contaminants by chemical
extraction, with the aim of thereby reducing the
volume of waste for disposal. The chemical extraction
technology ultimately generates two fractions. One
fraction contains the concentrated radioactive
contaminants and may require disposal; the remaining
material is analyzed for residual contamination and
evaluated for replacement at the point of origin or at
suitable alternative sites. The various applicable
chemical extraction techniques include extraction
with:
water
inorganic salts
mineral acids
complexing reagents
Except for the use of inorganic chlorides to remove
radium from liquid effluents at uranium mines, none of
the chemical extraction technologies has been field
demonstrated to remove radionuclides from waste
material at a site. Bench-scale and pilot-scale
testing would be needed to determine whether
chemical extraction can be used for site remediation.
Water can be used to extract a portion of the
radionuclide contaminants. Contaminated soil or
tailings could be mixed with large quantities of water.
The water, with the soluble radionuclide fraction,
could be removed from solids by physical separation.
Since many of the soil-cleaning techniques use
water as part of their process, this method could be
used as pretreatment.
A review of the literature indicates a broad range of
results with the use of salt solutions to remove radium
and thorium from mill tailings and soils. In many
cases the effectiveness of a given salt appears to be
related to several obvious variables, such as the
nature of the tailings (geochemistry, particle size
distribution, and chemical composition); the nature of
the soil; the concentration of the salt solution; pH;
solid-to-liquid ratio; process time; temperature; and
method of extraction.
Mineral acid extraction techniques are being
developed and have been used to extract radium,
thorium, and uranium from mineral ores.
Improvements in these acid extraction processes
have been found to be possible in the laboratory and
at uranium mills. The results show that the acid
extraction processes can remove most of the metals,
both radioactive and nonradioactive, and therefore
may deserve further study for cleanup of
radiologically contaminated sites and tailings.
However, different processes may be needed for
different radionuclides.
Extraction with complexing agents differs from acid
extraction in that complexing agents like EDTA
(ethylenediaminetetraacetic acid) are used instead of
mineral acids. Radium forms stable complexes with
many organic ligands (a molecule that can bind to a
metal ion to form a complex) while thorium is not
likely to be removed by complexation. Laboratory
experiments show that radium forms stable
complexes with EDTA, suggesting the potential for
xv
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extraction in soils and tailings with low concentrations
of thorium.
The above extraction processes produce a pregnant
liquor containing the radionuclides. In treating this
liquor to concentrate and collect the radionuclides for
disposal, the following support techniques are utilized:
precipitation and coprecipitation
solvent extraction
ion exchange
By addition of chemicals, the radionuclides can be
precipitated out from leach liquor. The slurry from the
precipitation tank is dewatered in thickeners; this is
followed by filtration. The filter cake containing the
radionuclide fraction is then ready for disposal.
Precipitation is a difficult, cumbersome operation
requiring complex chemical separation. Close control
of operating conditions is required.
Solvent extraction can be an efficient method for
separating the radionuclides. In solvent extraction, the
dissolved radionuclide fraction is transferred from the
feed solution into the organic solvent phase. The
loaded organic solvent is stripped of the radionuclides
by an aqueous reagent. The barren organic solvent is
recycled back to the extraction step. The radionuclide
is precipitated out from the aqueous liquor. Solvent
extraction offers better selectivity and more versatility
than ion exchange.
Ion exchange involves the exchange of ions between
the solution and a solid resin. Ion exchange does not
extract material from the soil directly. Rather, it
separates the constituents in a solution, such as
might result from chemical extraction. It has been
used extensively in uranium and radium extraction
from ore. There are three types of exchange: fixed
bed, moving bed, and resin-in-pulp. Any of these
are theoretically applicable to radionuclides in liquids
as a technique to complete the chemical extraction
technology.
Because of the need for a combination of extraction
methods to remove uranium, thorium, and radium, the
chemical extraction technologies appear to be quite
expensive and complex.
Physical Separation of Radioactive Soil
Fractions
The radioactive contaminants in soils and tailings in
many cases are associated with the finer fractions.
This is true for uranium mill tailings and radium
processing residue. Thus, size separation may be
used to produce a reduced volume of concentrated
material for disposal, leaving "cleaner" fractions.
These fractions must be disposed as well. Physical
separation may be used with chemical extraction to
produce fractions of smaller volume with even more
concentrated contaminant. The physical separation
technologies may be suitable for removing
radionuclides that originally have been deposited as
solid particulates on the soil.
Four physical separation technologies may be
applicable to the separation of radioactive waste
components of soils and tailings:
Screening - both dry and wet
Classification
Flotation
Gravity Concentration
These processes are already extensively used in the
extraction of uranium from ore. They have not been
used in the field to further extract other radionuclides
from tailings or soils. Pilot plant testing would be
needed to determine the ability of physical separation
technology to clean radiologically contaminated soils.
Screening separates soil (or soil-like material) on the
basis of size. It is normally applied only to particles
greater than 250 microns in size. The process can be
done dry or by washing water through the screen.
Screening is not efficient with damp materials, which
quickly blind the screen.
Screening can be applied to a variety of materials,
and it is relatively simple and inexpensive. It may be
particularly effective as a first operation to remove the
largest particles, followed by other methods.
Screening is a noisy operation, and dry screening
requires dust control. Finer screens clog easily.
Information needs include size distribution and
moisture content of the feed stream, and throughput
required for the equipment.
Classification separates particles according to their
settling rate in a fluid. Several hydraulic, mechanical,
and nonmechanical configurations are available.
Generally, heavier and coarser particles go to the
bottom, and lighter, smaller particles (sometimes
called slimes) are removed from the top.
Theoretically, classifiers could be used to separate
the smaller particle fractions, which may contain
much of the radioactive contamination in waste sites.
Classifiers could be used with chemical extraction in a
volume reduction process. Classification is a relatively
low-cost, reliable operation. Soils high in clay and
sands high in humus, however, are difficult to process
this way. Information required for selecting
classification includes size distribution, specific
gravity, and other physical characteristics of the soil.
Flotation is a liquid-froth separation process often
applied to separate specific minerals (particularly
sulfides) from ores. The process depends more on
physical and chemical attraction phenomena between
the ore and the frothing agents, and on particle size,
XVI
-------
than on material density. If particles can be collected
by the froth, flotation is very effective.
Ordinarily, flotation is applied to fine materials; the
process often is preceded by grinding to reduce
particle size. Process effectiveness has been
demonstrated in extracting radium from uranium mill
tailings (Raicevic, CIM Bulletin, August 1970).
Detailed waste characterization is a prerequisite for
application of the flotation process; mineralogy,
chemistry, specific gravity, and particle size are all
important.
Gravity separation is used in the uranium and radium
ore processing industries. This process takes
advantage of the difference in material densities to
separate the materials into layers of dense and light
minerals. Separation is influenced by particle size,
density, shape, and weight. Shaking (e.g., a shaking
table) and a variety of other motions are employed to
keep the particles apart and in motion; this is an
integral part of the process. Gravity separation can be
used in conjunction with chemical extraction. One
drawback to gravity separation is its generally low
throughput. Information needs are essentially the
same as for flotation.
Additional technologies are required to support
separation methods, including sedimentation and
filtration, both of which are methods used in waste
water treatment. They may be used individually or
together.
Combined Physical Separation and
Chemical Extraction Technologies
The combined physical and chemical separation
techniques that can be applied to decontaminate
radioactive soils are:
Soil washing and physical separation
Separation and chemical extraction
Separation, washing and extraction technique
The soil washing and physical separation process
involves washing the soil with chemical solution,
followed by separation of coarse and fine particles.
The type of solution used for washing will depend on
the contaminant's chemical and physical composition.
In 1972 DOE initiated laboratory-scale studies of soil
cleaning techniques; on the basis of these studies, a
washing and physical separation process was
selected for pilot-plant study of cleaning plutonium-
contaminated soil. The results of that pilot-plant
testing (at Rocky Flats) show this process to have
potential for success.
In pilot-plant test runs, soils contaminated to 45,
284, 7515, 1305, and 675 pCi/g of plutonium were
cleaned to contamination levels of 1, 12, 86, 340, and
89 pCi/g, respectively, using different washing
processes. The coarse particle weight fraction ranged
from 58 percent to 78 percent. Soil washing has been
shown to work in clay soil. This process may not
work for humus soil. The process is simple and
relatively inexpensive and needs no major process
development. It would, however, need further pilot-
plant testing and development work to test its
applicability to contaminated soil.
In combined physical separation and chemical
extraction, the soil is first separated into fine and
coarse particle fractions. The coarse particle fractions
may be washed or extracted. The fine particle
fractions are combined with extracted contaminants
and could be sent to a secure disposal site. The
"clean" coarse fractions are analyzed for residual
contamination and evaluated for placement at the
original site or an alternate site. An advantage of this
process is that soil containing higher levels of
radioactivity could be treated. Also, various sections
of the process have been developed for extracting
uranium, and laboratory work is underway in Canada
for extracting radium from uranium mill tailings. The
main disadvantages of this process are that it is
expensive and has high chemical usage. In addition,
the use of chemicals raises concerns of further
contamination to the environment. The process would
need further development work in order to better
extract radionuclides from soil.
In applying the separation, washing, and extraction
technique, the contaminated soils can conceivably be
washed with a variety of washing fluids, followed by
chemical extraction. The nature of the washing fluids
and chemicals depends on the contaminants and on
the characteristics of the soil. It could be
advantageous to separate the soil into fine and
coarse fractions and use the washing system on the
coarser soil fraction to reduce the throughput and
chemical usage. The treated soil, the finer soil
fractions and the collected contaminants would
require appropriate disposal.
General Issues
Several issues are of significant concern in attempting
to apply remedial technologies at sites contaminated
with radioactive materials. They include:
Final Disposal and Disposal Siting. Publicly
acceptable sites are difficult to find, and there
may be problems in convincing the public that the
"clean" fractions of the treated wastes are truly
acceptable. Some form of disposal may ultimately
be necessary as radioactivity cannot be altered or
destroyed by any treatment technology.
Handling of concentrated residuals. Reduc-
ing the volume of radiologically contaminated
waste will increase the concentration of
XVII
-------
radionuclides and may substantially increase the
safety hazards of the contaminated fractions.
Mixed Wastes. It is important to note that in
some cases there may be two categories of
residual contamination: process wastes and soils
contaminated with isolated radionuclides or
groups of radionuclides. While removal of the
radioactive fractions of soils contaminated with
single radionuclides such as uranium or plutonium
might result in "clean" fractions acceptable for
unrestricted disposal, removal of the radioactivity
from a soil contaminated with process wastes
may not. In this second case, the nonradioactive
fractions of the residues could result in an
unacceptable product. Therefore, before
considering any separation technique, it is
necessary that acceptable limits for both the
radiological contaminants and the non-
radiological contaminants be defined. In some
cases multiple treatments or combined
technologies could be required to achieve
environmental goals.
land. Alternative technologies, which have to be
evaluated and discussed further, may have the
potential for reducing the mobility, toxicity, or volume
of these contaminants. Further studies need to be
completed prior to the implementation of these
alternatives.
Criteria for Further Studies
The utility of any potential treatment process and the
applicability of the overall remedial action depend
heavily on the physical characteristics of the
contaminated media and the surrounding soils. Since
none of the chemical extraction and physical
separation technologies have been used in a site
remediation situation, their application must be
approached cautiously. The same holds true for
solidification or stabilization processes. Only land
encapsulation and ocean disposal have been used.
It is important to study the patterns in waste
characteristics at various sites and develop waste
groups with similar major characteristics. Applicability
studies can identify promising technologies to be
tested for treatment of each waste group. Preliminary
screening of the technologies can be accomplished
based primarily on the waste characteristics.
When one or more remediation concepts are selected
that appear applicable to a site, plans may be made
for treatability studies. Success there could lead to
pilot-scale testing and eventually to full-scale
demonstration of site cleanup. This step-wise
procedure is essential for the development of any
remediation technology, with carefully developed work
plans and quality assurance plans preceding each
step.
Conclusions
The remediation of radioactively contaminated sites
under Superfund, FUSRAP, and UMTRAP has been
hampered by the lack of methods other than
temporary storage or permanent encapsulation on
XVIII
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Chapter 1
Introduction
1.1 Study Purpose and Objectives
The Environmental Protection Agency (EPA) has
identified twenty Superfund sites in the country that
are radiologically contaminated by man-made
sources (see Appendix B). These sites, located
across the United States, vary greatly in size and may
involve radiation exposure to people who reside on
and around them. Radionuclides, unlike other
hazardous wastes, cannot be altered or destroyed to
eliminate their hazard potential.
The principal objective of this document is to identify
the full range of technologies that may be useful in
reducing to acceptable levels the radioactivity at
uncontrolled hazardous waste sites. Many of the
technologies discussed would require significant
research and development activities before they could
be reasonably considered for site cleanup. This report
only addresses treatment and disposal of
radiologically contaminated soils; it does not deal
with, for example, sites whose principal radiological
contamination is in building materials. Radiologically
contaminated ground water is also a concern at some
Superfund sites, but ground water treatment is
beyond the scope of this report.
The document is intended as a first review. This
report provides a discussion of the technologies, but
not a detailed critical evaluation of them. The report
does not include in-depth analyses that would be
needed to determine the applicability of any of these
technologies at a particular site.
In order to better ascertain the applicability of the
technologies, descriptive data have been gathered for
the twenty sites identified on the National Priorities
List (NPL) that are known to contain radioactive waste
materials. These data are presented in Appendix B;
they are accurate as of December 1987.
1.2 Health Concerns
The radioactive materials at Superfund sites consist
primarily of wastes from radium, thorium, and uranium
processing. These wastes contain residual quantities
of these elements and their radioactive decay
products, which have remained as contaminants in
buildings, soil material, and stream channels after
operations at the sites have ceased-or have been
dumped as waste in on-site or off-site disposal
areas. Contaminated soils have sometimes been
utilized as fill material on private and public properties
for various purposes. There are many other
radionuclides that may also be impacted by
technologies in this report.
The radioisotopes of concern belong to the uranium
238 and thorium 232 decay series (see Figure 1).
Hazards to the general population could occur
through several pathways, including:
(1) inhalation of radon decay products,
particularly where radon is concentrated
within building structures;
(2) inhalation of particulates or ingestion of
materials containing radioisotopes of the two
decay series;
(3) ingestion of radionuclides via drinking water
and food; and
(4) external body exposure to gamma radiation.
In the absence of remedial action, these potential
hazards could persist for extremely long periods
(millions of years) because of the long half-lives of
the controlling isotopes.
There are three types of radiation generally believed
to pose health hazards.
One is the alpha radiation (positively charged nuclear
particles) associated with radioactive decay of radon
gas and other radioactive elements, such as radium
and uranium. Although alpha radiation cannot pass
through the outer layers of skin, it can enter the body
through inhalation and ingestion. Inhalation of alpha-
emitting particles is a major health hazard and may
contribute to lung cancer. Ingestion of water, dust,
plants, or animals that contain alpha-emitters may
contribute to cancer in the various parts of the body
where the alpha-emitters lodge.
The second type of radiation that may pose a health
hazard is gamma radiation. Gamma emitters can
contribute to external exposure, since they can
irradiate the human body. Such exposure can
-------
Figure 1. Uranium-238 decay series.
Protactmium-
234
1 2 minutes
beta,
gamma
contribute to cancer in various parts of the body.
Different measures may be required to reduce
exposure to alpha and gamma radiation.
The third type of radiation is beta radiation
(electrons). Energetic beta particles can pass through
skin. The primary hazard from beta radiation,
however, is internal deposition by ingestion or
inhalation. Although decay of radium to radon does
not produce beta radiation, a subsequent portion of
the decay chain produces beta radiation. The beta
radiation is of secondary concern relative to the alpha
and gamma radiation, as the associated risks are
typically much lower.
The principal health concern at sites containing
radioactive wastes has been radon, radon progeny,
and gamma radiation from radionuclide decay. The
primary gamma radiation source at waste sites is
radium in the soil. In addition, radon gas is continually
produced by radioactive decay of radium, as indicated
in Figure 1. Radon and its decay products (radon
-------
"progeny") are alpha emitters that are potentially
injurious if they become lodged in the respiratory
system, and gamma emitters. Radon in the soil can
make its way through cracks and porous building
materials and accumulate in unsafe concentrations
within houses and other buildings and enclosures [1].
Radon has a half-life of 3.8 days; its progeny are
radioactive particles. They can attach themselves to
dust and other particles. If they are inhaled, either
attached or unattached to other particles, they may
deposit in the respiratory system where they emit
alpha particles, which may be damaging to the
tissues. Alpha-emitting particles from decay of radon
and progeny are considered to be a cause of lung
cancer [2].
Residences and other buildings have been built on
and around some waste disposal sites contaminated
with radioactive materials. The radiation hazard
derives from elevated indoor concentrations of radon
gas and elevated outdoor and indoor gamma radiation
levels that approach and sometimes exceed the
radiological standards for the general public. It is
important to note that there are average background
radiation levels associated with these materials.
Typical levels are shown in Table 1; they may not be
the same as the average level in any particular
location.
Sites that contain radioactive waste materials may
also contain other types of hazardous waste. Some of
the Superfund sites, for example, contain various
types of hazardous wastes, and the radioactive
portion may pose a relatively minor threat by
comparison. The presence of other hazardous
materials may complicate dealing with the radioactive
portion of the waste and vice-versa. EPA is
developing special regulatory approaches to these
"mixed wastes."
1.3 Waste Sources and Contaminated
Media
Radioactive wastes at uncontrolled sites have come
from a variety of sources. Perhaps the most common,
at least at Superfund sites, has been the residual
material derived from ore processing to obtain
radioactive elements. Examples are wastes from the
beneficiation of uranium-, radium-, and thorium-
bearing ores and from the process use of these
elements. A common use for radium has been
luminous watch dials; thorium has been used for
mantles for gas lanterns.
It appears that most of the contaminated wastes are
in tailings, a soil-like matrix. The radium and thorium
wastes exist in relatively small quantities at most sites
in comparison to uranium mining and mill tailings and
the wastes from nuclear fuel processing and handling.
Table 1. Typical Background Radiation Levels*
Component Typical Background
Gamma radiation
Ra-226 or Ra-228 in soil
Uranium in soil
Th-232 in soil
Ra-226 in water with Ra-228
U-238 in water
Radon in air (outdoor)
Radon in air (indoor)
8-13nR/h
~ 1 pCi/g
~1 pCi/g
~1 pCi/g
~1 pCi/l
~1 pCi/l
0.2 pCi/l
~1 pCi/l
These may not be the same as the average level in any particular
location.
Fuel processing, handling, and use may result in
relatively highly contaminated containers, equipment,
and even spent fuel residuals. Nuclear fuel wastes
are generally maintained in containers at the use site
(e.g., nuclear power and generating plants) until their
final disposition. Superfund sites for the most part do
not appear to contain these types of materials.
1.4 Scope of Report
Chapters 2 through 7 describe the range of
technologies for the removal of radioactive materials
from contaminated soil. These sections deal,
respectively, with disposal of contaminated materials,
on-site treatment, radon control chemical extraction,
physical separation, and process combinations to
remove contaminants from soil. The descriptions are
the result of literature surveys and discussions with
experts who have dealt with similar problems. It
should be noted that the radioactive contaminants are
not altered or destroyed by treatment technologies.
The volume of contaminated material may be reduced
by treatment, but the concentration of the
contaminants will be much higher in the reduced
volume. Some type of containment and/or burial is
the only ultimate remedy for materials contaminated
at levels above those considered safe for unrestricted
release.
Chapter 8 briefly points out some of the issues that
may inhibit or otherwise affect the remediation of sites
containing radioactive waste. The issues include, for
example, siting for final disposal, public reaction, and
costs.
Chapter 9 looks at potential experimental work
(bench-scale studies, for example) to test the
applicability of the alternative remediation
technologies.
Chapter 10 presents the conclusions of this report.
Appendix A briefly presents some of the
laws,regulations, and guidance that are part of the
framework within which technologies may be selected
for remediation of Superfund sites. This report does
-------
not attempt nor is it intended to provide a complete or
detailed analysis of how various laws, regulations, and
guidance apply in general or at a specific Superfund
site, nor is it intended to set or interpret policy for the
selection or use of technologies to clean up any
Superfund or other hazardous waste site.
Existing Superfund sites known to contain radioactive
materials are briefly characterized in Appendix B.
Descriptive data include: the location, size and
volume of the site; the character of the matrix
materials; proximity to population centers; the degree
of contamination; and the status of survey and
cleanup activities. Data also have been gathered on
sites being managed and remediated by the
Department of Energy (DOE) [3]. This information is
also presented in Appendix B.
Descriptive data on Superfund sites where
radioactivity is a concern were obtained from the EPA
Office of Solid Waste and Emergency Response and
from each of the pertinent EPA Regional Offices,
Information on DOE sites was obtained from literature
provided by the Oak Ridge National Laboratory
(ORNL) and the EPA Research Library in Cincinnati,
from DOE personnel, and from the staff of EPA's
Office of Radiation Programs.
Site-specific information is not complete at this time.
For example, only limited information has been found
on the soil or matrix characteristics at some of the
Superfund sites. Detailed information on the physical,
chemical, and radiological characteristics is absolutely
necessary before attempting to apply any of the
alternative technologies.
1.5 References
1. Nero, A. V. Airborne Radionuclides and Radiation
in Buildings: A review. LBL-12948. Lawrence
Berkeley Laboratory, University of California.
1981.
2. U.S. Environmental Protection Agency. Radon
Reduction Techniques for Detached Houses:
Technical Guidance (Second Edition). EPA-
625/5-87-019 Office of Research and
Development, Washington D.C. 1987.
3. U.S. Department of Energy. Office of Remedial
Action and Waste Technology Program Summary,
DOE/NE-0075, November 1986.
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Chapter 2
Disposal
2.1 Introduction
This chapter discusses remediation methods that
show potential for use in the final disposal of radio-
active waste materials. Final disposal is generally
regarded as some sort of containment that separates
the materials from any further contact with the public
and the environment. The radioactive waste materials
may be in the form of tailings or tailings mixed with
soil.
If some of the technologies described in this report
are applied prior to containment, the contaminated
waste volume may be reduced with a concomitant
increase in the concentration of the radioactive
material. Additionally, the larger fractions of the
treated soil may be suitable for replacement at the
point of origin without any long-term management, if
the treatment technology succeeds in reducing the
residual radiation to an acceptable level. No matter
what technologies are applied, there will always be
some portion of the material that will require long-
term disposal.
On the other hand, the radioactive waste materials
may not be in a form amenable to volume
reduction-e.g., contaminated equipment; these also
must be permanently contained if they cannot be
cleaned.
Disposal can be in one of two categories: on-site
disposal and off-site disposal. The state of the art of
on-site and off-site disposal methods is shown in
Table 2. Applicability of these methods to Superfund
sites is controlled by site-specific factors; therefore,
their usefulness must be determined on a site-by-
site basis. At present, capping and land encapsulation
are the only two methods used for radiologically
contaminated site remediation.
2.2 On-Site Disposal
It may be possible to deal with radioactive waste
materials, particularly if they are in a soil matrix, by
methods that do not remove either the soil or the
radionuclides from the site. Methods include: capping
and vertical barriers.
2.2.7 Capping
2.2.1.1 Description and Development Status
This concept involves covering the contaminated site
with a barrier sufficiently thick and impermeable to
minimize the diffusion of radon gas. Barrier materials
can be either natural low-permeability soils (e.g.,
clay) or synthetic membrane liners, or both. Both
types of materials are generally available. A barrier
might consist of several feet of compacted clay,
depending upon radiation levels, and extending a few
feet beyond the perimeter of the contaminated area.
Cap design and construction should consider the
need to: 1) confine radon until it has essentially
decayed to its progeny (for normal soils, the depth of
cover required is about 150 cm for Rn-222 and 5
cm for Rn-220); 2) attenuate the gamma radiation
associated with all the radionuclides present (for
normal soils, the depth of cover required for gamma
radiation shielding is on the order of 60 cm); 3)
provide long-term minimization of water infiltration
into the contaminated material; 4) function with
minimum maintenance; 5) promote drainage and
minimize erosion; and 6) have a permeability less
than or equal to the permeability of any bottom liner
system present or the natural subsoils.
Radon is continually produced from the radium
source, but the radon itself decays in a few days. A
schematic diagram of one potential cap design is
shown in Figure 2 [1]. A number of DOE facilities
have been constructed using the criteria contained
therein. The technology of caps is well developed,
and several good references are available [2-7].
However horizontal migration of radium or other
radionuclides in ground water could still occur.
2.2.1.2 Potential Applicable Situations
Capping a waste mass in situ is applicable over a
large, discrete, contaminated area or as a continuous
cover over several smaller areas that are close
together. Since there is a greater likelihood of
penetration through the cover if structures are built
upon it, capping is best used when no structures are
planned for the site. All reasonable steps should be
-------
Table 2. State of the Art of Disposal Methods
Laboratory
Method Testing
Bench
Scale
Testing
Pilot
Plant
Testing
Field
Demonstration
with
Radioactive
Material
Radiologically
Contaminated
Site
Remediation
Remarks
On-site Disposal
Capping
Vertical barriers
Off-site Disposal
Land encapsulation
Land spreading
Underground mine disposal
Ocean disposal
Land spreading of radium sludge from
drinking water is an allowed policy in Illinois
DOE currently working on mined repository
for radioactive waste
Stringent regulations for radioactive waste
taken to prevent or prohibit construction of buildings
on capped wastes as long as possible.
2.2.1.3 Advantages and Disadvantages
Advantages - The advantages of capping are ease
of application, the fact that it is a well-known
technology, and its high reliability when maintained
properly. Another advantage of in situ capping is its
relatively low cost. Covers that are effective Rn-222
barriers may be effective gamma radiation shields.
The soil characteristics are not as critical as they may
be for stabilization or other treatment technologies.
Disadvantages - Capping the radon-emitting site
does nothing to eliminate the source of radioactivity
from the area of concern. It simply impedes release
by shielding and trapping. Thus, the cap must remain
Figure 2. Schematic of a cover profile. (Reprinted from [1].)
Swale
• Select 3 ;
i Soil £ c
Cover
3'-0" Thick
Rip-Rap
T-6" Thick
Encapsulated Radioactively
Contaminated Material
Original —/
Ground
Surface
Select Soil
1'-0" Thick
Rip-Rap
5 /- 1'-6" Thick
i
n
— Rip-Rap
2'-6" Thick
-------
intact, without penetrations, indefinitely. Tree roots,
excavations for various purposes, such as utilities
repair, and unwitting excavations or penetrations
(e.g., post holes) could result in significant leaks.
Building construction, as indicated above, is a clear
threat to a cap. In addition migration of uranium and
radium in the ground water could still occur.
2.2.1.4 Information Needs
As noted above, capping probably can be applied
without the detailed site materials characterization
necessary for most other types of remediation.
However, it must be determined whether other
hazardous materials are present; remediation
requirements for nonradioactive hazardous materials
may take precedence.
2.2.2 Vertical Barriers
2.2.2.1 Description and Development Status
Vertical barrier walls may be installed around the
contaminated zone to help confine the material and
any contaminated ground water that might otherwise
flow from the site. The barrier walls, which might be
in the form of slurry walls or grout curtains [8,9],
would have to reach down to an impermeable natural
horizontal barrier, such as a clay zone, in order to be
effective in impeding ground-water flow. A barrier
wall in combination with a surface cap could produce
an essentially complete containment structure
surrounding the waste mass.
Slurry walls are constructed by excavating a trench
under a slurry. The slurry could be bentonite and
water or it could be Portland cement, bentonite and
water. In cases where strength is required of a
vertical barrier, diaphragm walls are constructed with
pre-cast or cast-in-place concrete panels [9].
An illustration of the slurry wall construction process
is shown in Figure 3.
Grout curtains [9] are constructed by pressure-
injecting grout directly into the soil at closely spaced
intervals around the waste site (Figure 4).
The spacing is selected so that each "pillar" of grout
intersects the next, thus forming a continuous wall or
curtain. Various kinds of grout can be used, such as
Portland cement, alkali silicate grouts, and organic
polymers.
2.2.2.2 Potential Applicable Situations
Vertical barriers could be considered for use to
prevent or delay escape of liquids and perhaps gases
(if installed in combination with a cap), until a more
Figure 3. Slurry trench construction operations. (Reprinted
from [9].)
Figure 4. Grout curtain around waste site. (Reprinted from
[9].)
Semicircular
Grout Curtain
Secondary
Grout Tubes
Primary
Grout Tubes
desirable permanent remediation technology is
adopted.
Barrier walls could be considered only for large
discrete masses of waste materials or around several
smaller masses close together. Barrier walls are not
totally impermeable to water.
2.2.2.3 Advantages and Disadvantages
Advantages - Vertical barriers in soil and soil-like
materials are relatively simple to install. They may
save the expense of excavating and removing the
contaminated material. In addition, they might serve
as a vessel within which an in situ treatment process,
such as contaminant extraction, could be carried out.
Disadvantages - It is difficult to obtain truly low
permeabilities in grout curtains constructed in
-------
unconsolidated materials [6]. Neither slurry wall nor
grout curtain does anything, in itself, to eliminate the
problem of radioactivity or any other contaminant.
Each simply improves the confinement of the
contaminants to the site.
Another potential disadvantage is the possible
deterioration of the barrier walls resulting from the
chemicals contained in the waste, particularly organic
chemicals. A vertical barrier would not stop vertical
contamination to ground water below.
As with caps, barrier walls do not eliminate the
radioactive contents of the enclosed waste. They can
only inhibit the spread of the contaminants. They do
not inhibit the release of radon as a cap would.
2.2.2.4 Information Needs
The successful installation of a vertical barrier wall by
the slurry wall or grout curtain technique requires
detailed prior knowledge of the soil's physical and
chemical characteristics [9]. As a minimum, the
characterization of any liquid contaminants is
required. Many common chemical (particularly
organic) contaminants at uncontrolled waste sites can
destroy certain grout materials or prevent them from
setting.
2.3 Off-Site Disposal
Off-site disposal, as the term is used here, means
controlled disposal at a site that is engineered or
chosen for the purpose because of certain
characteristics. Hydrogeological conditions at the site
is one of the factors that must be considered in
selecting off-site land disposal sites. Disposal may
be very near the contaminated site or it may be very
remote. The choice may depend upon site availability,
security, public acceptance, cost, safety, and other
factors. Off-site disposal is considered here to be a
final stage of remediation, whether it is applied to
untreated waste or to the extracted, encapsulated, or
solidified wastes. Land encapsulation, land spreading,
underground mine disposal, and ocean disposal are
the off-site disposal methods reviewed in this
chapter.
In the case of radioactive waste it is not clear that
disposal with treatment will be superior to disposal
without treatment. The off-site disposal technologies
are discussed here without attempting to judge their
relative acceptability. Given the length of time that the
radioactive waste will be a hazard, the design must
include greater attention to degradational
characteristics of construction materials than has
been normally considered for hazardous waste
disposal sites.
2.3.7 Land Encapsulation
2.3.1.1 Description and Development Status
Land encapsulation is a proven, well-demonstrated
technology. EPA has produced many publications
dealing with the technology of hazardous waste land
encapsulation (all of the Technical Resource
Document series) [10]. Figure 5 is a cross-section
of a conceptual design of a land encapsulation
structure [1,11]. Nuclear Regulatory Commission
(NRC) and EPA have jointly developed guidance on
land encapsulation siting and design for commercial
mixed low-level radioactive and hazardous waste
disposal facilities [6,7] (see Appendix A, Addenda).
Land encapsulation is a technology that is likely to be
considered at some stage in every site remediation
case, especially with radioactive wastes, because the
radioactivity cannot be altered or destroyed.
Alternative technologies may be applied to the waste,
as described later, to reduce its volume, but the
concentrated contaminants must still be contained.
DOE has used land encapsulation or some variant of
it at the FUSRAP sites that have been remediated
(see Appendix B).
Land encapsulation can occur on site, but this may
not be an option in all situations. If a radioactive
material processing plant is the source of the waste
and is near the contaminated area, the plant site
could be a prime possibility for the land encapsulation
location.
Alternatively, a remote site dedicated by a state or
other government entity to radioactive waste
containment, possibly could receive waste from any
number of sources within the state. The control
inefficiencies associated with operating diverse sites
over long periods could thus be minimized.
A variation of the in-state concept might be the
placement of the radioactive waste in the base of a
new municipal solid waste landfill. The landfill would
require a low-permeability liner. The solid waste atop
the radioactive waste would delay the emission of
radon until it had decayed and would absorb gamma
radiation. Since the eventual land encapsulation cover
would not be breached, at least for many years, the
radioactivity would not be of significant concern.
There is potential for problems if landfill leachates
were to mobilize the radionuclides buried below the
garbage. Another possible problem with this concept
is methane generation in the municipal waste. If the
methane should escape, radon might escape with it.
There are three existing NRC-licensed (by states)
commercial low-level radioactive waste sites, at
Hanford, WA; Beatty, NV; and Barnwell, SO. The
Barnwell site cannot accept radium waste. Although
probably capable of safely containing the waste from
-------
Figure 5. Schematic of a land encapsulation system. (Reprinted from [1].)
— Cover
3'-0" Thick
Swale
Rip-Rap
2'-6" Thick
r
Select Soil
1'-0" Thick
- - Encapsulated Radioactively'
rnntammated Material
Rip-Rap
5 /—1'-6" Thick
Liner
2'-0" Thick
Capillary
Break
1'-0" Thick
-- Original Ground
Surface
Select
Fill
Material
Filter Bed --jrT
0'-9" Thick K—V1 1
'S—Rip-Rap
^ 1'-6" Thick
vri
\'» Detention
':" Basin
Superfund sites, the other two may be reluctant to
accept the wastes for many reasons, not the least of
which is the scarcity of containment space. States in
which these facilities are found are beginning to
refuse wastes from outside their state or outside their
compact states, and are permitted to do so under
LLRWPA. Disposal at such remote out-of-state
sites may well be the most difficult, and the most
expensive, of the land encapsulation options [1].
2.3.1.2 Potential Applicable Situations
Land encapsulation may be appropriate for wastes
that have not been treated, as well as for
radionuclides extracted from a soil or other type of
matrix. In fact, it may be the most appropriate final
disposal method in most situations. To date, DOE has
been utilizing either temporary storage or permanent
encapsulation as the most viable remedial
alternatives.
2.3.1.3 Advantages and Disadvantages
Advantages - Land encapsulation is a proven,
workable technology for the disposal of low-level
radioactive wastes. It can be a viable solution at a
reasonable cost. The radionuclides would be removed
from the site and would not be a significant problem
at that site.
Disadvantages - Finding an appropriate site for
construction of a land encapsulation may be difficult
due to the current public aversion to this technology.
Finding an existing secure site outside the
containment property that will accept radioactive
wastes may also be difficult. Outside the
contaminated property the wastes will require
transportation and handling. Transportation of large
volumes of radioactive materials also carries certain
costs and risks. There will be considerations of safety
and permitting in any case, but if the radionuclides
have been concentrated by extraction and separation
processes, these problems may become more
difficult. Longevity is a consideration in the design of
the disposal site. An appropriate site will have to be
found for the radionuclide concentrated fraction of the
material. In any case, the disposal site issue will have
to be faced at some future date.
2.3.1.4 Information Needs
Relative to other technologies, minimal information
about the site soil characteristics is required prior to
land encapsulation. The levels of radioactivity and
quantities of nonradioactive hazardous materials are
certainly important, but soil grain size and other
physical characteristics do not have a significant
impact on applicability of encapsulation. Other
characteristics of the potential disposal site, however,
must be fully analyzed.
2.3.2 Land Spreading
2.3.2.1 Description and Development Status
A disposal option not often considered for radioactive
waste is spreading on land [12]. This could be an
option for untreated soil with low radioactivity levels.
The material could be transported to an appropriately
selected and sufficiently large expanse of remote
-------
open land and spread to a degree that the soil
radioactivity level approaches the natural background
radiation level of these materials. The material can
also be blended with clean fill for dilution and then
spread over the land or disposed under road beds.
This technology has not been demonstrated for
radioactive waste. Land spreading of radium sludge
from drinking water treatment systems has been an
allowed policy in Illinois since 1984.
2.3.2.2 Potential Applicable Situations
Land spreading appears to be more appropriate for
dry, granular, soil-like materials or tailings that are
not mixed with other contaminants.
2.3.2.3 Advantages and Disadvantages
Advantages - The technology appears simple and
relatively inexpensive; it could result in a permanent
remedy for the contaminated sites involved.
Disadvantages - Selecting a site to receive the
materials would likely be a politically and socially
sensitive issue. The types of materials that could be
accepted would probably fall within a very narrow
range of physical and chemical characteristics. The
technology has not been demonstrated. Convincing
the public of its safety would be very difficult. A
potential problem may be emitting respirable particles
into the air. Land spreading could contribute to a
non-point source pollution problem generated by
native soil.
2.3.2.4 Information Needs
Because this technology is an untried concept,
information needs have not been worked out.
However, there seems to be no doubt that detailed
physical and chemical characteristics of the waste
matrix would need to be gathered. Site selection
criteria would have to be developed for the receiving
site.
2.3.3 Underground Mine Disposal
2.3.3.1 Description and Development Status
Abandoned mines could provide sites for the
permanent disposal of radiologically contaminated
wastes. A conceptual layout of a mine disposal facility
is shown in Figure 6. This is one way to plan for
distance between the radioactively contaminated
material and the human population, although ground
water could provide a route for the contaminated
material to reach the population. Some research has
been done on the possibility of using mines for the
disposal of hazardous waste [12-14] and, more
specifically, for dioxin-contammated wastes in
Missouri [15]. In the latter case, abandoned mines in
that state were examined. The results were
encouraging from a technical standpoint, but the
concept has never been implemented in the United
States.
The DOE is currently working on a mine repository for
radioactive waste called the Waste Isolation Pilot
Project (WIPP) in New Mexico. While this repository
is designed for higher activity materials than most of
the Superfund material, the concept might be
applicable, particularly in light of the possibility of
volume reduction. Mine containment of hazardous
waste in Europe has been successful [16].
Multipurpose use of a mine for hazardous waste and
for low-level radioactive waste might be considered
and would likely reduce the per-unit costs of waste
disposal.
Underground mine disposal would not be appropriate
for radiologically contaminated bulk liquids or
noncontamenzed waste.
For mine disposal, as for any off-site disposal,
excavation of the contaminated materials would be
necessary, and they would have to be transported to
an appropriate site.
Any of the waste volume reduction and solidification
or vitrification techniques described in this document
might be used prior to mine disposal. Solidification or
vitrification of the material, whether or not the volume
has been reduced, could provide even more security
for final containment in the mine.
The principal drawback to the mine disposal option
may be cost. The use of an existing abandoned mine
might overcome that obstacle. With appropriate site
selection, there are few, if any, technical disad-
vantages to this option.
2.3.3.2 Potential Applicable Situations
Mine disposal might be considered for use for a
variety of radionuclide and matrix types. As noted
above, it could be used to dispose of wastes with or
without prior treatment, although volume reduction
and/or solidification or vitrification might facilitate the
process. Wastes that have been concentrated by
extraction or separation techniques may be
particularly appropriate for mine disposal, since they
are likely to be more radioactive, requiring disposal
that is more remote and more secure.
2.3.3.3 Advantages and Disadvantages
Advantages - Mine disposal, if done properly,
should provide a very secure and remote containment
of radioactive wastes. This technology has been used
successfully in Europe for hazardous waste.
Disadvantages - The mine disposal of hazardous
radioactive waste may be among the more costly
10
-------
Figure 6. Conceptual view of a mine storage facility. (Reprinted from [1 3].)
Maintenance
Shops
Reprocessing
Plant
Administrative
Offices
Security
Office
Hazardous Waste
Storage Cells
Area Shown
disposal alternatives, particularly if a mine must be
excavated for only that purpose. Wastes must be
excavated and transported with the associated permit
and safety concerns. The use of an abandoned mine
would involve the cost of reconstruction and may
pose safety hazards. Also, the ground water must be
protected.
2.3.3.4 Information Needs
As with most technologies, the waste being dealt with
must be carefully characterized. The mine site must
also be carefully described and judgments made as to
feasibility or applicability on the basis of the
information gathered. For example, the hydrogeology
must be known in detail, so that any ground water
contamination may be prevented.
2.3.4 Ocean Disposal
2.3.4.1 Description and Development Status
The concept of ocean disposal of low-level
radioactive wastes is not new. As shown in Table 3, a
sizable amount of these wastes was disposed at sea
between 1946 and 1970 [17].
The radioactive wastes that have been disposed at
sea were usually in concrete-filled drums or
containers. Three sites were used in the Atlantic
Ocean. One was 12-15 miles from the coast in 300
feet of water near Massachusetts Bay. The other two
were in water deeper than 6,000 feet, one 150 miles
off Sandy Hook, NJ, and the other 105 miles off Cape
Henry, VA.
Two sites were used in the Pacific about 48 miles
west of San Francisco [17].
2.3.4.2 Potential Applicable Situations
Ocean disposal could be considered for tailings and
other radiologically contaminated soils that are free of
other hazardous wastes. This alternative should not
be considered for enhanced radioactive materials or
concentrated residuals. Stabilization techniques could
be applied to the waste before emplacement to
provide for more security against leaks. For those
materials contaminated with hazardous chemicals, the
potential danger to marine biota must be evaluated.
2.3.4.3 Advantages and Disadvantages
Advantages - Ocean disposal offers the opportunity
for extreme isolation of low-level radioactive waste.
Disadvantages - Transportation of the contaminated
materials will involve transfer between land and sea. If
11
-------
Table 3. Ocean-Disposed Low-Level Radioactive
Waste, 1946-1970
Year
1946-1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
Number of
Containers
76,201
4,067
6,120
129
114
24
43
12
0
26
3
Estimated activity at time of
disposal (in curies)
93,600
275
478
9
20
5
105
62
0
26
3
Totals 86,758 94,673
the radioactive contaminants should be released, the
potential for dispersal and dilution is immense.
2.3.4.4 Information Needs
Detailed characterization of the matrix, including other
hazardous materials, would be required before ocean
disposal could be considered. If solidification or
vitrification, as used in past disposal of radioactive
materials, were first applied to the waste, the
chemical compatibility of the solidification agents and
the waste would need to be determined. However,
solidification or vitrification is not required; alt that is
needed is an assurance that the material will reach
the bottom and will not stay suspended in the water.
2.4 Typical Costs of Disposal Methods
The cost of the application of any of the disposal
methods described in this chapter will depend upon
many factors, including waste and site characteristics.
Thus the costs cannot be estimated reliably for any
method and for any site at this stage, because most
of the prerequisite information is not available. It also
must be cautioned that many, if not most, of the
controlling factors will be site-specific. The cost for a
method at one site may be vastly different than for
the same method applied at another site, especially
when transportation costs are involved. Costs for
off-site disposal would include transportation as well
as disposal costs, and all but in situ options must take
into account excavation costs for the contaminated
materials. Those disposal methods requiring waste
treatment will involve treatment costs as well.
Despite the limitations and cautions, some typical
costs of disposal methods are presented in Table 4.
These costs are not intended to be applicable to any
particular site. Costs of returning "clean" treated
material to a site are not included.
12
-------
Table 4. Typical Costs of Various Disposal Methods*
These costs are presented to give some typical costs under the referenced conditions. They are not
intended to be applicable to any particular site. Costs of returning "clean" treated material to a site
are not included.
Remediation Method
Capping with claya
Vertical barrier slurry
wallb
Grout curtain0
Costing Units
cu m
sq m
cu m
Materials &
Installation"
$13-200
$33-377
$208-403
First Year
O&M"
$0.44
Comments
Area units for
vertical face
Cost for grouted
soil volume
Excavation and secure cu m
land encapsulation01
Land spreading
New underground cu m
mine6
$276-895
$.045
No data found
$399-942 $2.50-18.00
Existing underground
mine6
Ocean disposal*
cu m
cu m
$185-523
$332-401
$2.50-18.00 -
* Costs are mid 1980s. Costs are from different sources and may be derived from different
assumptions and therefore may not be directly comparable.
a Low cost includes cost of capping only [11]. The material consists of radiation residues from
uranium processing and contaminated soil. The high cost includes cost of excavation,
transportation, and legal assistance. Cost for site acquisition is not included. The material consists
of contaminated soils.
b Low costs are for soft soil with 9m depth of excavation, and the high costs are for hard soil with
37m depth of excavation [3,9], These costs are for hazardous waste. Specific soil conditions have
not been identified.
c Low costs are for Portland cement grout and high costs are for 40% sodium silicate grout in rocky
soil [9]. These costs are for hazardous waste; the specific soil conditions have not been identified.
d Low cost includes cost of excavation and transportation, but does not include cost for disposal site
acquisition [1]. Transportation costs are from Montclair/West Orange and Glen Ridge to a land
encapsulation cell in Glen Ridge. High cost includes cost of transportation and excavation, etc., but
does not include cost of disposal site acquisition. Transportation cost is from Niagara Falls, NY to
Hanford, WA [11],
6 Costs are for storage of nonradioactive hazardous waste. Specific conditions could not be identified
[15].
' Low cost includes cost of excavation and transportation to ocean dump site off New Jersey/New
York shore [11]. High cost includes cost of excavation and transportation to an undetermined
ocean dump site [1]. Material is radiologically contaminated soil.
2.5 References
1. Camp, Dresser & McKee et al. Draft Final
Feasibility Study for the Montclair/West Orange
and Glen Ridge, New Jersey Radium Sites,
Volume 1. USEPA Contract 68-01-6939, 1985.
2. Lutton, R. J. Design. Construction, and
Maintenance of Cover Systems for Hazardous
Waste: An Engineering Guidance Document
EPA-600/2-87-039 Hazardous Waste Engin-
eering Research Laboratory, Cincinnati, OH,
1987.
3. McAneny, C. C., P. G. Tucker, J. M. Morgan, C.
R. Lee, M. F. Kelley, and R. C. Horz. Covers for
Uncontrolled Hazardous Waste Sites. EPA-
540/2-85-002, Office of Emergency and
Remedial Response, Washington, DC, 1985.
4. Lutton, R. J., G. L. Regan, and L. W. Jones.
Design and Construction of Covers for Solid
Waste Landfills. EPA-600/2-79-165, Municipal
Environmental Research Laboratory, Cincinnati,
OH, 1979.
5. Lutton, R. J. Evaluating Cover Systems for Solid
and Hazardous Waste. SW-867, USEPA,
Municipal Environmental Research Laboratory,
Cincinnati, OH, 1980.
6. Combined NRC-EPA Siting Guidelines for
Disposal of Commercial Mixed Low-Level
Radioactive and Hazardous Wastes, 1987.
13
-------
7. Joint NRC-EPA Guidance on a Conceptual
Design Approach for Commercial Mixed Low-
Level Radioactive and Hazardous Waste Disposal
Facilities, 1987.
8. U.S. Environmental Protection Agency. Slurry
Trench Construction for Pollution Migration
Control. EPA 540/2-84-001, Municipal
Environmental Research Laboratory, Cincinnati,
OH, 1984.
9. U.S. Environmental Protection Agency. Handbook
- Remedial Action at Waste Disposal Sites
(Revised). EPA-625/6-85/006, Hazardous
Waste Engineering Research Laboratory,
Cincinnati, OH, 1985.
10. U.S. Environmental Protection Agency. Technical
Resource Documents on Hazardous Waste Land
Disposal. SW860 and SW870 Series. Office of
Solid Waste, Washington, DC, 1979-1987.
11. U.S. Department of Energy. Long Term
Management of the Existing Radioactive Wastes
and Residues at the Niagara Falls Storage Site,
DOE/EIS-0109D, Washington, DC, 1984.
12. Gilbert, T. L., J. M. Peterson, R. W. Vocke, and
J. K. Alexander. Alternatives for Management of
Wastes Generated by the Formerly Utilized Sites
Remedial Action Program. ANL/EIS-20, Argonne
National Laboratory, Argonne, IL, 1983.
13. Stone, R. B., P. L. Aamodt, M. R. Engler, and P.
Madden. Evaluation of Hazardous Wastes
Emplacement in Mined Openings. EPA-600/2-
75-040. Municipal Environmental Research
Laboratory, Cincinnati, OH, 1975.
14. Stone, R. B., K. A. Covell, T. R. Moran, L. W.
Weyand, and C. U. Sparkman. Using Mined
Space for Long-Term Retention of
Nonradioactive Hazardous Waste. EPA-600/2-
85-021, Hazardous Waste Engineering
Research Laboratory, Cincinnati, OH, 1985.
15. Esposito, M. P., W. E. Thompson, and J. S.
Greber. Using Mined Space for Long-Term
Placement of Dioxin-Contammated Soils. EPA
Contract 68-02-3693, 1985.
16. Jacoby, C. H. Inspection Visit of the Hazardous
Waste Storage at Herfa-Neurode, Germany, of
Kali & Salz. Prepared for EPA under Bechtel
Subcontract. 1977.
17. Council on Environmental Quality. Ocean
Dumping - A National Policy. A Report to the
President. U.S. Government Printing Office, 1970.
14
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Chapters
On-Site Treatment
3.1 Introduction
This chapter discusses on-site treatment tech-
nologies that may immobilize radioactive
contaminants. These technologies include:
stabilization or solidification
vitrification
These technologies do not reduce the amount of the
contaminated material. However, they immobilize the
contamination in the waste material and limit the
spread of radioactive material.
Each of these is discussed below. The state of the art
of these on-site treatment technologies is shown in
Table 5.
3.2 Technologies of Potential Interest
3.2.1 Stabilization or Solidification
3.2.1.1 Description and Development Status
Solidification is a process that produces a monolithic
block of waste with high structural integrity. The
contaminants do not interact chemically with the
solidification agents but are mechanically bonded. A
stabilization process usually involves addition of
reagents, which limit the solubility or mobility of the
waste constituents. Solidification and stabilization
techniques are often used together [1].
The intent of solidification and/or stabilization of the
contaminated soil materials would be to limit the
spread of radioactive material via leaching, etc., and
to trap and contain radon within the densified soil
mass. While the contaminants would not be removed
and would remain active, the mobility of the
contaminants would be eliminated or reduced.
Waste materials at Superfund sites could be solidified
in two ways. One is to inject the solidifying agent into
the materials in place. The other is to dig up the
materials and machine-mix them with the solidifying
agent. The solidified materials from the latter process
could then be re-deposited on or off site in
engineered containment systems [1,2].
In in situ solidification utilizing grout injection
technology, grout would be injected directly into the
soil containing the radioactive source materials
(Figure 7). This technique has been proposed by
DOE for by-product radioactive wastes [3]. If
successful, the materials would be solidified and
radon would be contained long enough to decay to its
daughters. The solidified material also might reduce
mobility of radioactive and nonradioactive
constituents; if not, the material would require
isolation. The solidification technique thus might be
better suited to materials that are already buried
and/or capped.
In situ grouting for stabilization purposes requires
extensive and detailed characterization of the waste
matrix before the process is undertaken [Oak Ridge
National laboratories, staff, personal communications,
May 19, 1987]. Chemical grouts are better suited to
fine-grained soil with small pores, while cement
grouts are best for coarse-grained materials. Greater
effectiveness might be achieved if both techniques
are used together: cement grouting first, followed by
chemical grouting. Lime and fly ash have been
injected together to stabilize abandoned solid waste
sites [4].
The second way to solidify the waste materials is to
excavate and mix the waste with solidifying agents in
either a continuous or batch process [4]. Portland
cement, pozzolanic fly ash, or any of a number of
chemical fixation agents can be used in the process.
Bitumen (asphalt), because of its excellent binding
and sealing properties, and its weatherabihty, can be
an effective solidifying agent.
Excavation and mixing would be followed either by
placing the solidified soil in containers or by burial on
the site. The use of containers provides greater
assurance against release of radioactive materials and
allows for flexible storage, either on- or off-site.
On-site burial with or without containers would
require a soil cover of sufficient thickness to absorb
the gamma radiation.
15
-------
Table 5. State of the Art of On-Site Treatment Technologies
Field
Demonstration Pathologically
Bench Pilot with Contaminated
Laboratory Scale Plant Radioactive Site
Technology Testing Testing Testing Material Remediation
Remarks
Stabilization or solidification
Vitrification
Proposed by DOE for low-level radioactive
waste
Field testing by ORNL
Figure 7. Subsurface injection machine. (Reprinted from
[3].)
3.2.1.2 Potential Applicable Situations
Solidification could be considered for use in a variety
of situations. It offers the opportunity of leaving the
waste materials on-site in a relatively immobilized
state. It could be applied to materials with a range of
physical characteristics, and is particularly applicable
to highly porous and permeable matrices.
Solidification may be useful where increased material
strength is desired, such as in a matrix of municipal
solid waste.
For residential sites, the in situ method may not be
suitable, since maintenance of utilities would be
difficult. Also, it probably is insufficient to reduce
gamma radiation exposure substantially.
The injection solidification technique is best suited to
materials that are already buried and/or capped and
may provide more security against the escape of
radioactive material entering the environment.
3.2.1.3 Advantages and Disadvantages
Advantages - Solidification may be able to reduce the
release of radon and associated radioactivity to
acceptable levels at the waste site without removal of
materials for off-site containment.
Solidification may also facilitate transportation and
off-site disposal of radioactive contaminants with the
use of containers, especially where volume reduction
or extraction techniques have been applied
previously.
Disadvantages - While solidification may work
initially, its long-term effectiveness is not known.
Working against the in situ solidification technique
may be the location and configuration of the
contaminated masses. If they are thin, discontinuous,
and at or near the surface, injection grouting would
obviously face significant difficulties. In situ
solidification would be impractical for residential
areas. In situ solidification, as with other disposal
technologies, may trap the radioactivity, but does not
eliminate it. If other types of hazardous waste are
included in the waste, they may interfere with the
solidification process. Organic chemicals could be
particularly troublesome and could eliminate
solidification processes from further consideration.
Excavation coupled with solidification may be more
costly than excavating and land encapsulation.
3.2.1.4
Information Needs
Before a decision can be made concerning the
usefulness of the process for the site being
considered, detailed information on the matrix (e.g.,
16
-------
soil) and associated waste characteristics must be
known.
3.2.2 Vitrification
3.2.2.1 Description and Development Status
Vitrification is a process in which the contaminated
material is heated to its melting temperature, then is
allowed to cool and solidify to a glassy mass. In the
sintering process the contaminated material is heated
to produce a coherent mass without melting. The
process may be applied in situ or it may be applied to
material excavated and transported to a fixed process
site.
The in situ vitrification process has been
experimentally applied to soils by Battelle Pacific
Northwest Laboratories [5] with the intent of
potentially applying it to radioactive waste sites and/or
Superfund hazardous waste sites. The concept is
depicted in Figure 8. Presumably, the radionuclides
would be trapped, and some radiation would be
attenuated by the resulting material.
Figure 8. In situ vitrification process. (Reprinted from [5].)
U Off Gas Hood
I
Vitrification is a high energy consuming process. In
the in situ vitrification process, electricity is applied to
electrodes placed in the ground over the waste mass.
The ground and waste mass heat and melt, and the
melting zone grows downward. A hood to catch
gases is placed over the zone, and the gases are
treated or removed to prevent air pollution.
In the full-scale concept, electrode spacing would be
3.5 to 5 m, and the power required would be 3750
kW, for an expected vitrified mass of 400 to 800 tons
[5].
An in situ pilot-scale experiment was completed in
the summer of 1987 at ORNL on natural soil spiked
with cesium and strontium to simulate the radioactive
contaminants. Results of this experiment are under
evaluation. In July 1987 an in situ vitrification process
was field demonstrated on a transuranic waste site at
Hanford, Washington. The results of this field
demonstration are being evaluated [Battelle
Northwest Laboratories, Personal Communication,
February 1988; and ORNL, Personal Communication,
May 17, 1987].
The vitrification also could be performed on
excavated materials on site or off site in an electric
furnace or in a rotary kiln [6]. In the first, the
materials would be melted and poured into molds. In
the second, the contaminated materials are sintered
in a rotary kiln. While sintering may not necessarily
produce a solid monolithic mass, it may reduce
availability of the radioactive constituent for leaching
and therefore may be appropriate for containing the
radioactivity.
The products in either case are likely to require an
engineered final disposal method.
3.2.2.2 Potential Applicable Situations
The in situ vitrification process has been developed
specifically for application to low-level radioactive
waste sites, particularly to be used by DOE in its
remediation programs. In situ vitrification works on a
variety of materials to a limited extent.
The effectiveness of the process is very different for
different radionuclides and different chemicals. The
volatility and mobility of the element or compound are
important factors in the applicability of the method.
3.2.2.3 Advantages and Disadvantages
Advantages - In in situ vitrification the materials do
not require excavation; the process could be applied
to materials with minimal prior preparation. The
radioactive material is trapped in the vitrified mass,
and releases to the environment are reduced.
Electric furnace vitrification on excavated material
would produce a glassy mass, which can be poured
into molds of some convenient size. The glassy
blocks might supplant waste containers or
solidification blocks. Such treatment might be a
preprocessing step to mine or ocean disposal. The
rotary kiln is significantly more energy-efficient than
the electric furnace.
Disadvantages - Many substances would probably
volatilize in the process, requiring gas collection and
treatment devices. Radon trapped in the material
matrix could be released during the process, and
radium may volatilize. The use of the process in
residential areas may pose difficulties, including
problems in future underground utility repair work.
Even if this were to be successful, the vitrified
material will remain radioactive. Additional shielding
may be required for protection from gamma radiation.
The vitrified material, if near the surface, may still
require removal from residential areas.
17
-------
Fixed plant vitrification on or off site would require
excavation and transport of the waste materials to the
vitrification site. This would add to the cost. The
rotary kiln may not be suitable for radioactive wastes,
as it does not produce a secure, solid, monolithic
mass.
3.2.2.4 Information Needs
Detailed waste characterization will likely not be
required to make the process work. However, the
characteristics of the materials, including the matrix
and the contaminants, need to be known in some
detail in order to determine the volatilization
characteristics, so that control of off-gases may be
planned correctly.
3.3 Typical Costs of On-Site Treatment
Technologies
The cost of the application of any of the treatment
technologies described in this section will depend on
many factors, including waste and site characteristics.
Thus, the costs cannot be estimated reliably for any
technology and for any site at this stage, because
most of the prerequisite information is not available. It
also must be cautioned that many, if not most, of the
controlling factors will be site-specific.
Despite the limitations and cautions, some typical
costs for treatment technologies that immobilize the
radioactive contaminants are presented in Table
6.These costs are not intended to be applicable to
any particular site.
3.4 References
1. U.S. Environmental Protection Agency. Handbook
- Remedial Action at Waste Disposal Sites
(Revised). EPA-625/6-85-006, Hazardous
Waste Engineering Research Laboratory,
Cincinnati, OH, 1985.
2. U.S. Environmental Protection Agency. Handbook
- Remedial Action at Waste Disposal Sites. EPA
625/6-82-006, 1982.
3. Tamura, T., and W.J. Boegly, Jr. In Situ Grouting
of Uranium Mill Tailings Piles: An Assessment.
ORNL/TM-8539, Oak Ridge National
Laboratory, Oak Ridge, TN, 1983.
4. Blacklock, J. R., and P. J. Wright. Stabilization of
Landfills, Railroad Beds and Earth Embankment
by Pressure Injection of Lime/Fly Ash Slurry.
Proceedings - Ash Tech 84, Second Inter-
national Conference on Ash Technology and
Marketing, London, England, 1984.
5. Fitzpatrick, V. F., J. L. Buelt, K. H. Oma, and C.
L. Timmerman. In Situ Vitrification - A Potential
Remedial Action Technique for Hazardous
Wastes. Proceedings of the Fifth National
Conference on Management of Uncontrolled
Hazardous Waste Sites, Washington, DC, 1984.
6. Camp, Dresser & McKee et al. Draft Final
Feasibility Study for the Montclair/West Orange
and Glen Ridge, New Jersey Radium Sites,
Volume 1. USEPA Contract 68-01-6939, 1985.
7. U.S. Department of Energy. Long Term
Management of the Existing Radioactive Wastes
and Residues at the Niagara Falls Storage Site,
DOE/EIS-0109D, Washington, DC, 1984.
Table 6. Typical Costs of On-Site Treatment Technologies*
These costs are presented to give some costs under the referenced
conditions. They are not intended to be applicable to any particular
site. Costs of returning "clean" treated material to a site are not
included. Costs are mid 1980s.
Treatment
Technologies
Stabilization/
solidification
(chemical fixation)3
In situ vitrification b
On-site
vitrification c
Costing Units
ton
cu m
-
Materials &
Installation*
S 33 - 248
$161 - 224
$400 - 600
* Costs are from different sources and may be derived from different
assumptions and therefore may not be directly comparable.
a Costs provided are for hazardous waste [1]. Specific soil conditions
could not be determined. Low costs are for in situ mixing; high costs
are for in-drum mixing. The solidification agent is silicate and
cement. The cost includes labor, equipment and material.
b These are typical estimated costs for hazardous waste [1]. Soil
moisture and electricity cost can increase the cost. Specific soil
conditions have not been identified..
c Cost includes excavation and on-site vitrification, but does not
include cost for disposal of slag [7]. The material is radioactive
residue from uranium ore processing. Cost increases with increasing
moisture and electricity cost.
18
-------
Chapter 4
Radon Control
4.1 Introduction
Although the main intent of this report is to
summarize technologies that might be used to
remove, contain, or immobilize the radioactive source
materials in Superfund sites, where radioactivity has
resulted from material processing or waste disposal
operations, there may be sites where it is more
desirable or logical not to disturb these materials, at
least for an interim period.
Control processes using ventilation are already used
to some extent to lower the radon concentration in
residences contaminated with naturally occurring
radon. Radon control from soil can be approached in
three ways: (1) radon reduction in homes through soil
gas ventilation; (2) electrostatic precipitator control;
and (3) areal ventilation from the soil above the
contaminated source mass. Each of these is
discussed below. Table 7 shows the state of the art
of radon control technologies.
4.2 Methods
4.2.7 Radon Control and Reduction in
Buildings
4.2.1.1 Description and Development Status
Radon may accumulate to unacceptable
concentrations indoors. EPA has provided guidance
that recommends action at levels above 0.02 WL (4
pCi/l) to reduce annual average exposure to below
those levels. Note in Table 8 that the average indoor
concentration is estimated to be 0.005 WL. Although
exposures between 0.005 and 0.02 WL do present
Table 7. State of the Art of Radon Control Technologies
some risk of lung cancer, reductions of these levels
may be difficult and sometimes impossible.
EPA has developed and implemented a program to
evaluate various methods to reduce radon
concentrations in residences [1]. The program is
aimed at developing cost-effective technologies for
reducing radon from naturally occurring sources in
existing and new homes of all structural types. The
first demonstration projects are underway in homes
located in Pennsylvania, New York, New Jersey,
Maryland, Tennessee, Alabama, and Ohio.
Radon reduction in homes is simple in concept. The
EPA program recognizes three basic methods:
(1) diversion of soil gas flow away from the
house;
(2) barriers to prevent entry to the house; and
(3) reduction of concentration once it has entered
the house.
The techniques that may be used to implement these
methods are described in reference 2. The
techniques include sealing entry cracks in
foundations, forced ventilation of soil in and adjacent
to the foundation, and natural and forced ventilation of
the airspace inside the house. Examples of the
techniques that may be used are depicted in Figures
9 and 10. However, each house must be addressed
individually.
A variety of soil parameters influence radon
movement, including thickness, densities, specific
gravities, permeabilities, porosities, and moisture
Technology Laboratory Testing
Bench Scale
Testing
Pilot Plant
Testing
Field Demonstration
with Radioactive
Material
Radiologicaliy
Contaminated Site
Remediation
Remarks
Radon Control
in homes
ESP control
areal control
Requires
maintenance
Requires
maintenance
Requires
maintenance
19
-------
Table 8. Representative Exposure to Radon-222 Progeny
Location Average WL* Average pCi/r
Outdoors
Indoors
0.001
0.005
0.2
1.0
" WL = Working Level = a measure of exposure rate to radon
progeny. Under equilibrium conditions of radon and its
progeny, 1 WL equals the activity of 100 pCi/l of air. At
the equilibrium (50%) generally considered representative
of most indoor environments, 1 WL equals 200 pCi/l [2].
content. These parameters in turn affect the diffusion
and emanation coefficients of radon [3].
4.2.1.2 Potential Applicable Situations
Site-specific house remediation techniques for radon
levels are currently being demonstrated. The
techniques apply to radon emanating from the
underlying soil, whether the source is natural or a
man-made waste mass. Radon control from
buildings may be a viable interim technique while
considering and implementing source removal
alternatives.
4.2.1.3 Advantages and Disadvantages
Advantages - Radon reduction techniques for existing
homes can be simple, effective, and relatively
inexpensive. They may be temporary alternatives
while awaiting removal of the source radionuchdes, if
this is being considered. However, in many instances,
the solutions can be relatively difficult and expensive
when the problem is not completely understood.
Costs can run into thousands of dollars for a house if
90 + percent reductions are needed, especially for
large highly-finished houses with poor sub-slab
permeability.
Disadvantages - Radon reduction techniques do not
affect the source of the radon, and therefore radon
production at current rates can be expected to
continue indefinitely. Thus, the reduction system must
be maintained for as long as the building is occupied
or the source is present. Radon removal systems do
not address gamma radiation problems, potential
ingestion pathways, or the potential for unearthing
existing contaminated material.
4.2.1.4 Information Needs
Information needs include the levels of radon
concentration inside the structure, an inventory of all
the avenues of radon entry, the characteristics of the
soil underlying the building, and the structural
characteristics of the building.
4.2.2 Electrostatic Precipitators (ESPs)
4.2.2.1 Description and Development Status
Electrostatic precipitators (ESPs) are a form of indoor
air cleaner. ESPs work on the principle that when
particles suspended in air enter an electrostatic field
they become charged and migrate under the action of
the field to the positive electrode, where they are
collected. The collected material is removed by
rapping the collecting surface to slough off the
particles. An ESP would be installed in a room or area
so as to maximize the air contact. The ESP may
reduce the number of particles (e.g. dust and smoke)
to which radon progeny may be attached, resulting in
a reduction of radon progeny in the air. The health
effects of using ESPs in reducing radon progeny are
not known.
4.2.2.2 Potential Applicable Situations
ESPs have been used to reduce the radon progeny
levels in a store built with contaminated adobe bricks
[4]. The technique could be applied for buildings
where the source of contamination is building
materials or the underlying soil.
4.2.2.3 Advantages and Disadvantages
Advantages - ESPs are easy to install in rooms or
enclosed areas.
Disadvantages - ESPs do not affect the source of
the radon. The reduction system must be maintained
for as long as the building is occupied or the source
is present. The ESPs do not reduce gamma radiation.
The health effects of using ESPs are not known.
4.2.2.4 Information Needs
Information needs include the level of radon and
radon progeny concentrations inside the room or
area; the structural characteristics of the building; and
air flow, volume, and pattern.
4.2.3 Soil Gas Venting and Areal Control
4.2.3.1 Description and Development Status
The term "soil gas venting," as used in this section,
refers to techniques that may be applied across the
entire area of gas production. For example, the gas
extraction that is now relatively common in and
around municipal solid waste landfills fits in this
category.
Soil gas venting has been used to remove methane
from municipal waste landfills and to remove organic
vapors from underground leaks of organic
compounds. Both active systems, where a fan or
pump is used to induce gas flow, and passive
20
-------
Figure 9. Tile ventilation where tile drains to sump. (Reprinted from [2].
Exhaust
Outside
fan
(option)
Close major
openings m walls
Optional
piping
configuration
Iv^OT^v*1,
' 'tf\S?'^:L'-::' '
Aggregate
To exhaust fan
mounted in attic
or on roof
Notes:
1. Closure of major
slab openings is
important
2 Closure of major
wall openings might
also be important
• Suction
pipe
- Bracket
(option)
Sealant.
&y*5S&3E4S
**•*4>••*<-•.. o*V . LV
•• •••»•• .,«'<*. r&'
.A*. J^^.-xrl^
• Existing dram tile
circling the house
Drain pipe
(to discharge)
Masonry bolts
Sealant
;•,.*&<.• M.
•J.a.'*•?'» W
21
-------
Figure 10. Sub-slab ventilation. (Reprinted from [2].)
Exhaust (preferably
released above
eaves)
Outside
fan
(option)
Optional
piping
configuration
To exhaust fan
mounted in attic
or on roof
Close major mortar
cracks and holes in
wall2
Connection to other
suction points
Notes
1 Closure of major slab
openings (e g , major settling
cracks, utility penetrations,
gaps at the wall/floor joint)
is important
2 Closure of major wall
openings might also be
important
House air through unclosed
settling cracks, cold joints,
utility openings
Open hole
(as large as
reasonably
practical)
22
-------
systems, which rely on the natural flow, have been
used to vent soil gases. These types of systems
might be applied to vent radon from soils where radon
diffusion and migration occur.
In landfill soil gas venting, a narrow perforated pipe is
installed in the center of the extraction well and
backfilled with coarse rock. The upper part of the well
is sealed around the pipe with impervious material to
prevent air from being pulled into the well, as shown
in Figure 11. The perforated pipe is connected to a
header system and fan to extract the gas. Gas
withdrawal rates vary widely from site to site
depending on the rate of methane and carbon dioxide
generation and the landfill's porosity [5].
Figure 11. Gas extraction well for landfill gas control.
(Reprinted from [4.)
Gas Flare
Exhaust Blower
Impervious Backfill
Perforated Pipe
Gas Flow
Gas Flow
Permeable Material
Based on the same general principle, Terra Vac has
successfully removed volatile organics from the soil at
several sites in the United States. Terra Vac utilizes a
vacuum pump to apply vacuum to the soil through
wells, causing an in situ air stripping of volatile
organic compounds. The extracted gases are
discharged to the atmosphere through an activated
carbon bed which adsorbs most volatile organics [6].
If used for radon removal, direct venting to the
atmosphere may be appropriate. In some cases, the
highly concentrated radon in the vented gas may be
of such quantity that it cannot be released to the air
immediately. In this case, the gas can be passed
through a packed bed of activated carbon. Since soil
gas tends to be saturated with moisture (1 - 2% by
volume) the retention capacity of the carbon is
somewhat reduced. At 20°C, activated carbon can
adsorb 5000 to 9000 cc of radon-bearing air per
gram of carbon depending on the type of carbon,
temperature, and flow rates [7]. However, over years
this could cause the carbon to become a low-level
radioactive waste.
Active soil gas venting has also been applied to
remove organic vapors from soil. In this remedial
technology, soil gas is drawn from a well or set of
wells constructed near one edge of the contaminated
zone. To better induce the flow of vapor and to dilute
the vapors, another well or set of wells is constructed
on the opposite edge of the zone. By drawing air from
one set of wells, a flow gradient is established across
the contaminated zone, and vapors are drawn off [8].
Another type of active gas ventilation system, which
relies upon pumping air into the soil at one location
and pumping gases out at another location, may be
more effective than other methods [9]. Figure 12 is a
schematic diagram of this system.
Passive soil vent systems are relatively simple and
inexpensive to construct and operate. However, they
may be less effective than active systems in
removing soil gas since much less gas flow occurs.
The passive flow would be caused by barometric
pressure changes and diurnal temperature changes
that affect soil gas movement.
The effectiveness of any soil radon removal system is
likely to be very site-specific, depending largely on
the porosity of the soil, soil moisture content, the
distribution of radium in the soil, and the
chemical/physical matrix containing the radium. For
example, if the radium were contained in a tightly
compacted and/or wet matrix, the radon would not
diffuse readily and probably would remain trapped
until it decayed to its progeny. It should be noted that
radon should not be removed from soil gas unless it
is a proven source of indoor radon for an on-site or
a nearby occupied structure. Radon in subsurface
soil, unlike methane, presents no fire or explosion
potential.
Even though soil gas venting is a popular
methodology for dealing with volatile organic
chemicals (VOC) in the soil and/or ground water, it
has some large potential problems in radioactive
applications. This method has been shown to be in
violation of some State radiation emission standards,
and charcoal beds may collect more than exempt
quantities of radon decay products, making them
hcensable or registerable under State radiation
statutes. Moreover, when these charcoal beds are
incinerated to remove the VOC, they may impact
Department of Transportation (DOT) regulations for
radioactive materials (transport to out-of-state
incinerator) and may impact a second state's
radionuclide emission standards (at the incinerator).
4.2.3.2 Potential Applicable Situations
Radon gas venting from a radioactive waste site
could be applied where the materials are highly
porous (high permeability) and the radon could move
freely to the extraction point. Sweden has used soil
23
-------
Figure 12. Schematic diagram of a forced air venting system. (Reprinted from [9], Courtesy of American Petroleum Institute).
o
CN
o
CO
o
JZ
Q.
0)
Q
Air Inlet
Well
Velocity
Pressure Head
Sample
Port
2" PVC
Pipe
Vapor
Recovery. f
Ground Surface Well /I J-
Velocity
Port
Stand Pipe
2" ID
Magnehehc Differential
Pressure Gauge
Static
Pressure ^Vacuum
Head V Gau9e PVC Pipe
^"Schedule 40
Vacuum Pump
r=? _fCZI*r
r\rrr
Standard Reducer
Pitot
Vacuum Pump
Temporary
-. Electrical Power
I 220V, 3 Phase
Flow
Control
Valve
Water Recirculation
Line to Vacuum
Solenoid Pump Suction
Valve
2" Schedule 40 PVC
Well Screen
Perforation
£1 from 14'to 20'
4" Bore
Hole
gas venting for radon removal in small areas for
venting naturally occurring radon.
4.2.3.3 Advantages and Disadvantages
Advantages - Radon venting might supplant other
remediation techniques. The entire operation could
take place on the site without disturbing surrounding
properties. It may be relatively low m cost.
Disadvantages - The radionuclide source material
would remain in place. As long as it does, the radon
removal system would have to operate, since radon
would be produced indefinitely. The system would
require a long-term maintenance program.
The soil, if it is not totally uniform and highly porous,
would probably not be vented uniformly. Also,
absence of sufficient data on this approach makes it
somewhat unpredictable. This method does not
address gamma radiation. Adsorbing radon onto
carbon in large quantities may be unworkable. Areas
with a high water table may generate large quantities
of radioactively contaminated ground water, which
must be treated and/or disposed.
4.2.3.4 Information Needs
The waste site would require detailed physical
characterization in order to determine if the areal
venting concept is practical and feasible.
4.3 Typical Costs of Radon Controls
Rough estimates of costs are provided in "Radon
Reduction Techniques for Detached Houses -
Technical Guidance" [2] for various radon reduction
techniques for residences. The cost estimates are
based upon the experience of EPA and a number of
investigators. A summary of these rough estimates is
included in Table 9.
Typical capital costs for soil gas venting systems
range from $10 - $12 per cu m for shallow VOC
deposits (at less than 20 feet) [10]. The cost includes
site preparation, drilling, piping, blowers, electricals,
decontamination and demobilization. The typical
operating cost for a soil gas venting system is $12 -
$14/cu m/yr. The operating cost includes cost of
electricity, carbon, water, and labor.
24
-------
Table 9. Typical Costs of Various Radon Reduction Techniques in Existing Homes [2]
Reduction Technique Operating
Natural ventilation
Forced ventilation
Forced ventilation with heat
recovery
Avoidance of appliance
depressunzation
Sump ventilation
Sealing entry routes
Drain tile ventilation
Active wall ventilation
Sub-slab ventilation
Installation Cost ($)
0
50-1000
800-2500
100-300 (install ducts)
800-2500
(contractor-mstallated)
300
(home owner-installed)
300-500*
700-1500 (contractor)
300 (home owner)
1500-250
900-2500
Annual Cost ($)
1.1 to 3 x normal heating cost
1 1 to 3 x normal heating cost
+ $275/yr for electricity
1.1 to 2.0 x normal heating
cost + $30/yr for electricity
small
$130/yr
low
$130/yr$
$230-460/yr$
$130/yr$
* For average sealing. A comprehensive sealing job would run much higher.
4.4 References
1. U.S. Environmental Protection Agency. Report to
Congress on Radon Mitigation Demonstration
Programs under Section 118(k) of the Superfund
Amendments and Reauthorization Act of 1986,
1987.
2. U.S. Environmental Protection Agency. Radon
Reduction Techniques for Detached Houses -
Technical Guidance. Second Edition EPA-
625/5-87-019. Office of Research and
Development, Washington, DC, 1987.
3. Nuclear Regulatory Commission. Calculation of
Radon Flux Attenuation by Earthen Uranium Mill
Tailings Covers. (Draft) 1987.
4. Nichols, F. D., J. M. Brink, and P. C. Nyberg.
Cleanup of Radiation Mill Tailings from Properties
in Monticello, Utah. Presented at the Hazardous
Materials Control Research Institute Superfund
Conference, November 1984.
5. Shafer, R. A., A. Renta-Babb, J. T. Bandy, E. D.
Smith, and P. Malone. Landfill Gas Control at
Military Installations. Technical Report N-173,
U.S. Army Corps of Engineers, Construction
Engineering Research Laboratory, 1984.
6. Malot, J.J., and P.R. Wood. Low-Cost, Site-
Specific Total Approach to Decontamination.
Presented at the Environmental and Public Health
Effects of Soils Contaminated with Petroleum
Products Conference. University of
Massachussetts, Amherst, 1985.
7. A. D. Little, Inc. Advanced Techniques for Radon
Gas Removal. Bureau of Mines Publication PB-
243898. 1975.
8. Benneds M. B. Vacuum VOCs from Soil. Pollution
Engineering, 1987.
9. Crow, W. L., E. P. Anderson, and E. Minugh.
Subsurface Venting of Hydrocarbon Vapors from
An Underground Aquifer. API Publication 4410,
pp. 3-10, Washington DC, 1984.
10. Roy F. Weston, Inc. Task II, In Situ Air Stripping
of Soils Pilot Study. U.S Army Toxic and
Hazardous Materials Agency, Final Report,
October 1985.
25
-------
-------
Chapter 5
Chemical Extraction
5.1 Purpose
There are several separation techniques that have the
potential to clean radiologically contaminated soils and
tailings. The objective of these technologies would be
to concentrate the radioactive contaminants, thereby
reducing the volume of soil for disposal. Chemical
extraction is one type of separation technology, which
uses chemicals to extract the radionuclides from soils
and tailings. Other separation technologies that might
be used to clean soils and tailings are discussed in
Chapters 6 and 7 of this report.
The chemical extraction technology generates several
soil fractions. One or more fractions contain the
concentrated radioactive contaminants; the other
"cleaner" soil fractions may contain unextractable
traces of radioactive contaminants.
The concentrated radionuclide-contammated soil
fractions would require off-site disposal. The intent
could be to return the "cleaner" soil fractions, which
would be a major portion of the soil by volume, to the
point of origin (the original excavation). Standards for
returning the cleaner soil fractions to the point of
origin do not currently exist.
It should be emphasized that none of the chemical
extraction techniques have been demonstrated at full
scale to remove radionuclides from waste masses.
Many of these techniques are used in ore
beneficiation processes to remove a single
constituent. The waste soils often contain radium,
thorium and uranium, which must all be removed. The
real practicability of these techniques to remove
radionuclides in a field application remains to be
demonstrated. The various potential chemical
extraction techniques are discussed in this section.
5.2 State of the Art
Concern about environmental and health problems
related to uranium mill tailings has resulted in an
extensive study of methods for extracting
radionuclides from soils and uranium mill tailings.
These studies were initiated in order to examine the
migration characteristics of radium in contaminated
soils and uranium mill tailings, and to examine
chemical extraction as a potential method for tailings
remediation [1-4].
References at the end of this section contain reviews
of those techniques with the potential for cleaning
radiologically contaminated soils and mill tailings.
These include extraction with:
water
inorganic salts
mineral acids
complexing reagents
There are notable differences in the extractabihty
rates of these methods. These extractabihty
differentials are caused by the types of soils, ores,
and tailings studied as well as varying conditions
within and between the methods. There also have
been occasional inconsistencies in results obtained
under similar experimental conditions. In spite of
these differences and inconsistencies, significant
trends in each method are evident and are reported
here.
Though the chemical extraction technologies have
been extensively used in extraction of uranium from
mineral ores, their use in cleaning contaminated soils
and tailings to acceptable limits has been limited to
laboratory and pilot plant testing. Table 10 shows the
state of the art of the chemical extraction tech-
nologies. The applicability of these technologies
would be controlled by site-specific factors, and their
capability must be determined on a site by site basis.
Research and development activities would be
necessary prior to full scale mobilization of these
technologies for site cleanup.
5.3 Technologies of Potential Interest
This section discusses the four chemical extraction
techniques listed previously. These technologies
produce an extractant containing a radionuclide,
which must be treated to concentrate and collect it for
disposal. This section also discusses the following
chemical methods for separation and collection of
extracted radionuclides from the extractant:
Precipitation and coprecipitation
27
-------
Solvent extraction
Ion exchange
Membrane filtration, which is a physical method used
to separate and collect the radionuclide from the
extractant, is briefly discussed in Chapter 6 of this
report.
5.3.1 Extraction of Radionuclides from Soil or
Tailings with Water
5.3.1.1 Description and Development Status
This process would use water to extract the
radionuclide contaminants. Contaminated soil or
tailings would be mixed with large quantities of water.
The water, with the soluble radionuclide, could be
separated from solids by a combination of physical
separation methods described in Chapter 6.
The radionuclide would then be extracted from the
liquid by coprecipitation, solvent extraction, or by ion
exchange (discussed later in this chapter).
Water solubility studies have been performed
primarily to examine the teachability of radionuclides
from soils and mill tailings [5-9]. Extraction of
uranium from water is also being studied [10-13],
even for uranium concentration less than 3 ppb.
The water solubility of radium salts varies. Chloride,
bromide, nitrate, and hydroxide are water soluble,
while fluoride, carbonate, phosphate, biphosphate,
and oxalate are only slightly soluble.
The sulfate is essentially insoluble in water and dilute
acids but is soluble in concentrated sulfunc acid
(H2S04). Radium sulfate is the least water soluble of
the alkaline earth sulfates and probably the least
water soluble radium compound known. Barium
sulfate is only slightly more soluble than radium
sulfate. The water soluble salts of thorium include
nitrate, sulfate, chloride, and perchlorate. Most
prominent of the insoluble thorium salts are
hydroxide, oxide, fluoride, oxalate, phosphate,
peroxide, and hydride. Uranium salts that are soluble
in water include bromide, chloride, carbide, sulfate,
Table 10. State of the Art of Chemical Extraction Technologies
and hexafluoride. The key insoluble uranium salts are
oxide, tetrafluoride, and tribromide.
The extraction of radium from soil is dependent on
the liquid to solid ratio and optimum time for leaching.
Reference materials in this area [5-7] indicate that a
15-minute leaching time removes the optimum
amount of radium; the incremental amount extracted
declines after that time to almost no extraction after 2
hours.
Generally, the extraction of radium with deionized
water removes less than 10 percent of the cation
from the samples studied. As little as 0.1 percent [8]
has been extracted, but as much as 40 percent has
been removed [6] under exceptionally high liquid to
solid ratios (10,000:1). In one study [9] water
removed 75 percent of the RaSC>4 from very fine (-
150 mesh) slime solids. The removal of thorium with
water was reported to be 3 percent in a study of
uranium mill tailings (4.5 percent radium and 22
percent uranium were removed), but the water was
probably acidic as a result of H2SO4 in the mill pond
from the uranium leaching process [12]. Soil samples
from the sites of former radium extraction companies
in Denver, Colorado and East Orange, New Jersey
that were extracted with water released only 0.1 to
2.3 percent of the radium present and less than 1.5
percent uranium [8].
A detailed investigation of corresponding experiments
carried out in Japan, West Germany, and the U.S.
has led to the development of specific plant concepts
for extracting uranium from sea water [10,11,13].
The typical cost of extracting uranium from sea water
is around $300/lb. However, enormous cost
differentials, ranging from $11 to $1,400/lb, have
been reported [13].
5.3.1.2 Potential Applicable Situations
This method of extraction has not been demonstrated
in the field for cleaning soil or mill tailings. Laboratory
testing is needed to identify an applicable situation.
Since many of the soil cleaning techniques use water
as part of their process, this method can be used as
Chemical
-
-
_
With
With
With
Technology
Extraction
water
inorganic salts
mineral acid
Laboratory
Testing
X
X
X
Bench
Scale
Testing
X
X
X
Pilot
Plant
Testing
X
Field
Demonstration
with
Radioactive
Material
X
Radiologically
Contaminated
Site
Remediation Remarks
Used in extraction of radium, thorium and
With complexing agents
uranium from ores
Used in extraction of uranium from ores
28
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pretreatment. Presence of sulfate in the soil will
decrease the amount of radium that can be extracted.
5.3.1.3 Advantages and Disadvantages
Advantages - The main advantages of using water
are that it is very inexpensive, completely nontoxic,
uses ambient temperatures, and utilizes simple
extraction vessels. The technique can be used to
dissolve some radionuclide salts. It can be used as a
pretreatment technique to reduce interference at
subsequent extractions.
Disadvantages - This method requires a large
quantity of water. The process is relatively ineffective
for removing radioactivity from soils; less than 10%
removal for radium and virtually none for thorium has
been demonstrated.
5.3.1.4 Information Needs
Extraction with water requires the following
information:
Physical, chemical, and mineralogical
characteristics of the soil.
Radionuclide concentration for each particle
size fraction.
Amount of water available.
Water analysis for total suspended solids, pH,
hardness, background radiation, etc.
5.3.2 Extract/on of Radionuclide from Soil and
Tailing with Inorganic Salts
5.3.2.1 Description and Development Status
Radionuclide contaminants can be extracted by
thoroughly mixing soil and mill tailings in a solution
containing inorganic salt. The slurry is filtered,
separating the extractant from the solid. The
radionuclide contaminant is separated from the
extractant by ion exchange, coprecipitation, or
membrane filtration [4]. No field demonstration of soil
cleaning using this process has yet been attempted;
all the research work so far consists of laboratory
experiments.
A review of the literature indicates a broad range of
results with the use of salt solutions to remove radium
and thorium from mill tailings and soils. In many
cases the effectiveness of a given salt appears to be
related to several obvious variables, such as the
nature of the tailings or soil (geochemistry,
radionuclide concentration, method of extraction,
particle size distribution, and chemical composition),
the concentration of the salt solution, temperature,
pH, solid to liquid ratio, time, and temperature [3-
7,9,12,14-16].
An increasing ratio of salt solution to solid, as with
water, plays a positive role in the effectiveness of the
salt solution in removing radionuclides from ore
tailings and soils [3,5,9]. Multistage extraction
increases the effectiveness of the radium extraction
essentially by increasing the ratio of solution to solid
[4,5,15]. One study [12] reported as little as 0.4
percent of radium removed from radium mill tailings
with 0.1 M sodium chloride (NaCI). On the other
hand, another study [4] reported 94 percent removal
with a 3 M NaCI solution at room temperature in a
three-stage process using 20 liters of solution per
kilogram of tailings, and 90 percent with 1 M NaCI. In
another study 50 percent of the radium was removed
in a single-stage extraction with a 3 M NaCI solution
[5]. Using 3 M potassium chloride (KCI), 91 percent
of the radium-226 was removed in a two-stage
leaching process at room temperature [16].
The extraction of thorium by salt solutions has
received less attention than the extraction of radium.
One study [12] reported that, while 13 percent of the
radium was removed from uranium mill tailings with a
0.1 M NaCI solution, only 0.02 percent of the thorium
was removed. In another experiment, no thorium was
removed by a 3 M NaCI solution, while 62 percent of
the radium was extracted. However, a study of
various inorganic phosphates [17] indicates that 60-
80 percent of both radium and thorium can be
removed by sodium hexametaphosphate ((NaPOaJe)
from a fine particle fraction (-200 mesh) of uranium
tailings that were produced by leaching with H2SO4.
The study also indicated that salt interferes with the
removal of uranium during the H2S04 extraction
process. Other phosphate salts (orthophosphate,
pyrophosphate, tnpolyphosphate) were not effective in
extracting thorium from the tailings.
The ability of the salt to extract radium or thorium is
primarily reflected in the solubility of the compound or
complex that it forms with radium and thorium. The
presence of sulfate in soil greatly affects the ability of
the inorganic salts to extract radium, since the radium
sulfate that is formed is the least soluble radium
compound encountered in mill tailings. Hydroxide is
the analagous anion in thorium chemistry since
thorium hydroxide is the least soluble thorium
compound encountered. It is reported in one study of
uranium mill tailings [3] that the radium-leaching
power of several anions decreases as follows: Cr >
NO3- > HCO3- > HO4- > PO4-3. It was also
found that washing to remove soluble sulfates before
radium leaching helps dissolve the radium.
The effectiveness of aluminum salts in dissolving
radium and thorium is minimal, probably as a result of
the hydrolysis of the cation, producing a gelatinous
precipitate that retains radium by adsorption. This is
particularly important since many soils and tailings
contain aluminum and similar cations. The barium
cation also was found to be less effective than
sodium in solubilizmg radium, supporting the
hypothesis that an insoluble barium radium sulfate
29
-------
(Ba(Ra)SO4) salt is a major form of radium in most
mill tailings. [5]
The barium cation would be expected to be effective
in releasing radium bound by adsorption on particles
containing metal hydroxides, silicas, and clays but
ineffective in solubilizing the Ba(Ra)SC>4.
The effectiveness of cations of various salts in
releasing radium decreases in the following order [3]:
Cs+> Ca + 2> Mn + 2> NH4+ > K+ > Na+ > Li + .
5.3.2.2 Potential Applicable Situations
Inorganic salt extraction has not undergone field
demonstration for cleaning radiologically contaminated
sites. Laboratory or pilot plant testing will be needed
to identify applicable situations. The presence of
sulfates in the soil will greatly affect radium removal,
as sulfates will form radium sulfate, the least soluble
radium compound. The presence of hydroxide in soils
and tailing will similarly affect thorium removal. The
use of salts interferes with the removal of uranium by
sulfunc acid. This process should not be used as
pretreatment to an acid extraction process.
5.3.2.3 Advantages and Disadvantages
Advantages - A high percentage of radium and
thorium may be removed. Processes may operate at
ambient temperatures. Most salts are relatively
innocuous. Simple extraction vessels are required.
Recycling of salts may be possible.
Disadvantages - Large amounts of salts may be
required with large solution-to-solid ratios. Some
salts, such as chloride, may be environmentally
undesirable.
5.3.2.4 Information Needs
For extraction by salt solution, the following
information is required.
Physical, chemical, and mmeralogical
characteristics of the soil.
Amount of water available.
Water analysis for total suspended solids, pH,
hardness.
Background radiation, etc.
5.3.3 Extraction of Radionuclide from Soil and
Tailings with Mineral Acids
5.3.3.1 Description and Development Status
Historically, radium has been extracted from carnotite
ores with mineral acids - H2S04, hydrochloric acid
(HCI), or nitric acid (HNOa) [18,19]. Under favorable
conditions, up to 97 percent of the radium was
removed. Thorium ores are extracted industrially with
(among other reagents) fuming H2SO4 or HNO3 [20].
Uranium is also extracted from mineral ores by acid
leaching [21].
Sulfuric acid, rather than hydrochloric or nitric acid, is
commonly utilized for leaching in uranium extraction
due to its less corrosive nature and lower costs.
In all these processes the ores are ground to 28
mesh and mixed with water to form a slurry. The
slurry is pumped into a leach circuit, maintaining a
pulp consistency of 50 percent solids. The solids are
separated from the leach liquid by physical methods.
The radionuclides are removed from the leach
solution by ion exchange, solvent extraction, or
precipitation [21].
It appears from a survey of recent reports on the
extraction of radium and thorium that these metals
are readily extracted by several mineral acids from
soils and soil components [3,5,7,22], ores, and ore
tailings [8,9,14,15,23-28]. Although fuming H2S04 is
used in industrial processes for the removal of
thorium from ores as soluble thorium sulfate
Th(SC>4)2) [20], one would not expect the acid to be
useful for the extraction of radium, considering the
insolubility of radium sulfate (RaS04). However,
RaSO4 is somewhat soluble in concentrated H2S04
[29], and several studies have indicated that the hot
acid will remove between 70-80 percent of the
radium and 80-90 percent of the thorium from
uranium mill tailings [24,28]. A recent study [25]
demonstrated that between 14-40 percent radium
can be removed from uranium ores by dilute H2S04
in a countercurrent process at 72°C, in the presence
of oxidizing agents; approximately 86 percent of the
thorium was removed.
Nitric acid has proved to be very efficient in the
extraction of radium and thorium [9,26,30]. Generally,
the best results with ores and ore tailings have been
achieved with approximately 3 M HNOs solution at
temperatures between 70° and 80 °C for about 5
hours in two- or three-stage processes with
hquid-to-solid ratios of 2:1 to 4:1. For example, 97
percent radium and 99 percent thorium were removed
from uranium ore or ore tailings (H2SO4 or carbonate
leached) with 3 M HNOa at 70°C in a two-stage
process, with a reaction time of 5 hours [26]. Over 99
percent of the uranium was also removed from the
ores. The resulting Ra-226 level was as low as 17
pCi/g, and the thorium level was 7 pCi/g [26]; the
tailings before nitric acid extraction contained 716
pCi/g Ra-226 and 88 pCi/g Th-230, respectively.
Similar results were achieved using HNO3 with ores,
slimes, solids, and sand tailings [9], with 89 percent
removal of radium in a one-stage process with 6
percent solid loading. A six-stage, batch
crosscurrent process [31] removed 98 percent of the
radium from ores and tailings with a final Ra-226
30
-------
level of 10 pCi/g. Remarkably similar results have
been obtained with HCI solutions [9,8,23,25]. Like
HNOa extractions, the best results occur with 1.5 to 3
M HCI at about 70°- 85°C with multiple extractions.
Ninety-three percent of radium (< 28 pCi/g) and 86
percent of thorium removal was achieved in a four-
stage, countercurrent process in the presence of
other oxidants [25].
More than 95 percent of the radium was removed
with 3 M HCI at 85°C in one hour with a liquid-solid
ratio of 4:1 [9] and 92 percent radium-226 was
removed with 1.5 M HCI at 60°C in a three-stage
leaching process with a 4:1 solid to liquid ratio [23].
Depending on the size of the soil particles and the
nature of the soil, 27% to 100% of Ra-226
extraction has been demonstrated in the laboratory
from soil contaminated with radium mill tailings using
0.1 M HCI.
Combining dilute acids with inorganic salts has
produced leaching solutions that achieve results
similar to those of the more-concentrated acid
solutions [9,14,15,27]. Mixed NaCI and HCI solutions
were used to extract radium from mill tailings [9,14].
In a three-stage process (30 minute stage) 94
percent of radium was removed with 0.3 M NaCI in
0.1 M HCI at 25°C [14]. Calcium chloride (CaC^) in
HCI has produced very good results even at room
temperature. Removal of 96 percent of the uranium,
97 percent of the radium, and 75 percent of the
thorium with 0.045 M CaCl2 in 0.125 M HCI at room
temperature in a two-stage leaching process has
been reported [27]. A 91 percent removal of Ra-226
and 79 percent removal of Th-230 were obtained
from tailings with 1 M CaCl2 in 0.1 M HCI at 21 °C
and a 2:1 liquid-to-solid ratio with 30 minutes
contact time.
An acidic environment would be expected to have a
positive influence on the release of cations such as
radium and thorium from soils and tailings that have
the potential to bind metal ions. This is especially
important in determining the extracting power of
various acid solutions on ores and tailings, since most
of these materials contain soil particles with a large
amount of amorphous silica (up to 90 percent) and
hydrated metal oxides such as aluminum and iron
oxides.
Adsorption on surfaces of amorphous silica or
hydrated metal oxides is strongly affected by the
acidity of the environment [2,3]. The surface charge
of silica is positive at pH < 1, is zero between pH 1
and 3, and becomes progressively more negative
above pH 3 [2].
Hydrated metal oxides that have aged will not readily
dissolve in acid solutions, but an increase in acid
concentration will diminish the number of oxide sites
available for binding [3], thus enhancing the
dissolution of radium and thorium. Natural organic
acids, such as humic and fulvic acids found in soils,
tend to decrease their binding capacity thus
increasing the dissolution of radium and thorium.
Increased concentrations of HNOa and HCI also will
promote the dissolution of Ba(Ra)S04. With
increased concentration, the salt dissolves in water
with the formation of barium hydroxide (Ba(OH)2), a
slightly soluble base, and the more soluble radium
hydroxide (Ra(OH)2), which are converted by the
acids to more soluble salts, barium chloride (BaCl2)
or barium nitrate (Ba(N03)2) and radium chloride
(RaCl2) or radium nitrate (Ra(N03)2) [25].
5.3.3.2 Potential Applicable Situations
Mineral acid extraction techniques are being
developed and have been used to extract radium,
thorium, and uranium from mineral ores. Improvement
to these acid extraction processes has been
demonstrated in the laboratory. These demonstrations
show that the acid extraction processes can remove
most of the metals, both radioactive and
nonradioactive, and therefore may be applicable for
cleaning radiologically contaminated sites.
5.3.3.3 Advantages and Disadvantages
Advantages - An advantage of extraction with acids is
that a high percentage of radium and thorium removal
is possible. Uranium and other metals would also be
removed. These processes require relatively small
liquid-to-solid ratios compared to extraction with
water or inorganic salts, thus requiring less pumping
power and smaller holding and reaction vessels.
Costs can be reduced if the acids are recycled.
Disadvantages - The main disadvantage of this
process would likely be the increased operating and
capital costs due to expensive reagents, higher
operating temperatures, and the stainless steel
reaction vessels and pipes needed because of the
corrosiveness of acid. A multistage process is
needed, which adds to the costs. A major
disadvantage of these techniques is that the anions,
such as N03~ or CI", are environmentally
undesirable. The resulting chemically leached material
may create a waste stream that is more harmful than
the original tailing mixture.
5.3.3.4 Information Needs
The analyses and requirements listed below are
required in implementing treatment procedures.
Physical, chemical, and mineralogical
characteristics of the soil.
Radionuclide concentration in each particle
size fraction.
Amount of water available.
31
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5.3.4
Water analysis for total suspended solids, pH,
hardness, background radiation, etc.
Extraction of Radionuclides from Soil
and Tailings with Completing Agents
5.3.4.1 Description and Development Status
This process differs from acid extraction in that
complexing agents like EDTA (ethylenediamine-
tetraacetic acid) are used instead of mineral acids.
Radium forms stable complexes with many organic
ligands (a molecule or anion that can bind to a metal
ion to form a complex). For that reason, several
complexing agents have been investigated as
potential candidates for extraction of radium from
uranium mill tailings [3,9,31-34] and, in one case,
from soils [35]. Thorium is not likely to be removed
by complexation.
Several successful radium extraction tests with
complexing agents have been reported. Up to 92
percent (to 40 pCi/g) of radium content was removed
from mill tailings using 0.15 M Na4 EDTA at 60°C, pH
10, and a liquid-to-sohd ratio of about 7/1 in a
three-stage process [23]. After collecting the Ra as
Ba(Ra)S04, the EDTA was recovered for reuse by
lowering the pH. Another study [33] removed 80-85
percent of the Ra with a 0.04 M EDTA solution at pH
10, 23°C, and a liquid-to-solid ratio of 2:1. A pre-
wash with water (25 l:kg) removed calcium sulfate
(CaS04), which tends to interfere with the extraction.
Using 6.65% sodium diethylenetnammepentaacetic
acid complex (Na$ DTPA), another study [34]
reported removing up to 85 percent of the radium.
The crosscurrent or countercurrent process used m
this study obtained maximum yields after 2 hours at
20°-25°C with a liquid-to-sohd ratio of about 9:1.
A recent study [32] described a reducing-
complexing treatment for the leaching of radium from
uranium mill tailings. A reducing agent, sodium
hydrosulfite (N32S204), is added in order to reduce
Fe + 3 and similar cations. Using 0.04 M Na2 EDTA,
0.04 M N32S204 and 1 M KCI (to mask the
adsorption sites on silica) for 1 hour at pH 10 with a
hquid-to-solid ratio of 10:1, 87 percent of the
radium was removed, leaving 44 pCi/g in the residue.
Adopting a procedure of keeping the hquid-to-solid
ratio initially high and slowly adding the tailings to the
leach solution had a major effect on radium
extraction, reducing the residue from 44 to 31 pCi/g
radium. A comparison with several other complexing
agents using 0.1 M solutions of the agents under the
same conditions was made: Citrate removed 67
percent to 120 pCi/g, and nitnlotriacetic acid (NTA)
removed 85 percent to 48 pCi/g. Note that these
solutions are 2.5 times more concentrated than the
Na2 EDTA solution (0.04 M). This study also reported
the recovery of 92 percent of the Na2 EDTA by
bringing the leach solution to pH 1.8.
Most of the studies of radium extraction with
complexing agents have been with EDTA. Radium
extraction during leaching is improved by keeping the
radium concentration low in the solution, particularly
in order to shift the equilibrium representing the
dissolution of Ba(Ra)SO4 [3].
One would expect thorium extraction to be assisted
by complexing with EDTA or another suitable
complexing agent. Leaching of radium with EDTA is
generally performed at pH 8 and 10. Unfortunately,
above pH 3 thorium forms a very insoluble hydroxide
whose formation competes with the formation of the
thorium EDTA complex. Thus, at a pH where the
formation of an EDTA complex with thorium would be
favored, the thorium cation is not available for
complexation.
Other cations found in soils and tailings, such as
Fe"1"3 and Ti + 4, behave in a similar fashion and
compete with Ra + 2 dissolution by forming insoluble
hydroxides that adsorb the cation. Studies [3] have
determined that the result of these competing
equilibria will prevent the dissolution of radium with
EDTA. But with the appropriate reducing agent,
Fe + 3, Ti + 4, and similar cations will be reduced to
lower oxidation states that tend to form more soluble
hydroxides.
The radium EDTA complex formation will then
compete favorably with hydroxide formation, causing
the hydroxides to be solubilized, releasing radium
adsorbed on these materials [2,3]. Thorium cations
are not reduced to lower oxidation states,
subsequently forming more soluble hydroxides.
Therefore, radium extraction would be assisted by
prior extraction of thorium.
5.3.4.2 Potential Applicable Situations
This method of extraction has not been field
demonstrated for radiologically contaminated soils and
tailings. Laboratory experiments show that radium
forms stable complexes with EDTA, suggesting its
potential for application in cleaning radium from soils
and tailings with low concentrations of thorium. Soils
and tailings with high concentrations of thorium may
require prior extraction of thorium before using this
technique to extract radium.
5.3.4.3 Advantages and Disadvantages
Advantages - One of the mam advantages of
extraction of radionuclides with a complexing agent
would be the expected high percentage of radium
removal. Low reagent concentrations are required,
and the reagent can be recycled, thus reducing
operating costs. The process works at ambient
32
-------
temperatures, and many of the reagents are
innocuous. Therefore, expensive materials such as
stainless steel for vessels and piping would not be
needed.
Disadvantages - Complexing reagents are very
expensive. This process would not remove thorium,
therefore, other processes might be required to
remove thorium prior to the removal of radium by
complexing agents. A multiple-stage process is
probably required, adding to the capital and operating
cost.
5.3.4.4 Information Needs
The following information is required prior to
extraction with complexing agents.
Physical, chemical, and mineralogical
characteristics of the soil.
Radionuclide concentration in each particle
size fraction.
Amount of water available.
Water analysis for total suspended solids, pH,
hardness, total dissolved solids, background
radiation, etc.
5.3.5 Technologies for Separating
Radionuclides from Extractant
The previous section discussed the leaching and
extraction technologies that produce a pregnant liquor
containing the radionuclides.
Radium and thorium extracted from soils and mill
tailings will be in solution with many other molecular
and ionic compounds. Some of the ions may be
simple, while others will be complex, depending upon
the nature of the sample to be extracted and the
leaching solution(s). Other molecular substances and
material will probably be present as colloids. Still
other fractions will be in suspension and will separate
upon settling or filtering.
The support technologies utilized in treating the
extractant to remove the radionuclides for disposal
are:
precipitation and coprecipitation
solvent extraction
ion exchange
membrane filtration
The first three technologies are chemical methods
and are discussed in this chapter. The last,
membrane filtration, is a physical separation method
and is discussed in Chapter 6.
5.3.5.1 Description and Development Status
Precipitation and Coprecipitation - By addition of
chemicals the radionuclides can be precipitated.
Several stages of precipitation at controlled pH are
used. The pH is readjusted in the precipitation tank
near the end of the circuit. The slurry from the
precipitation tank is dewatered in thickeners and
followed by filtration (see Chapter 6 for description of
dewatering technologies). The filter cake, containing
the concentrated radionuclide, is then ready for
disposal. Precipitation, however, produces products
with impurities. This may not be a problem on
cleaning soils and tailings. However, in extraction of
uranium from ore, solvent extraction or ion exchange
is used before precipitation to obtain a purer product.
Radium forms a very insoluble salt with sulfunc acid.
Sulfunc acid is commonly used to form a precipitate
of RaSC>4, but sodium sulfate (Na2SC>4) is also used
[29]. Thorium may be precipitated as a highly
insoluble, gelatinous hydroxide with alkali or
ammonium hydroxide [1]. Thorium is also precipitated
by sodium oxalate/oxalic acid solutions at a pH of 1.2
from acid solutions [36]. The concentration of radium
and thorium cations in the extractant from soil and
mill tailings may be low enough that a direct
precipitation process would not be appropriate to the
collection of these radionuclides. Radium and thorium
may be coprecipitated by the addition of a simple
precipitating agent such as H2S04.
Small quantities of radium cations can be
coprecipitated from solution with many different
carrier compounds [29,37].
The use of the classical radium carrier, BaS04, to
precipitate radium from leach solutions has been
reported by several investigators [4,23,31,32,38,39].
A review [36] of other natural organic carriers (such
as tannin and gelatin) reported that these carriers
removed 90 to 100 percent of the radium in
coprecipitation processes. In a study [4] it was found
that BaS04 is slightly soluble in a HNOa 'each
solution (0.07 g/l in 3 M HMOs); however, 95 to 100
percent of radium may be coprecipitated from nitric
acid leach solutions using very dilute (<10 mM)
BaCl2 solutions in the presence of sulfate ions [4,31].
The use of a silica-bed filter to remove Ba(Ra)SO4
has also been suggested for the removal of radium
from uranium mill tailings [32].
Thorium coprecipitates with a wide variety of insoluble
hydroxides such as iron, zirconium, and lanthanum as
well as zirconium iodate or phosphate from acid
solutions [20]. Calcium fluoride and calcium oxalate
are also used as coprecipitants [38]. One study [40]
reported that 60 to 100 percent of the thorium
coprecipitates with BaS04 solution; lower
concentrations of thorium (<0.09 mM) removed the
largest amount of the cation. Another study [39] used
33
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an oxalate to remove thorium from a 3.6 M HNC>3
leach solution. The oxalate is very insoluble in HNOa;
no radium was carried by the coprecipitate. Using 20
percent NaOH, more than 96 percent of the thorium
was coprecipitated in the presence of Fe at a pH of
4.2 as ferric hydroxide (Fe(OH)3) [38].
Uranium is precipitated from solution by addition of
sodium hydroxide, gaseous ammonia, hydrogen
peroxide, or magnesia. Precipitation using sodium
hydroxide, sulfunc acid, and gaseous ammonia
produces purer uranium with little sodium.
For a plant processing 10,000 tons of uranium ore per
month, the typical capital and operating cost of
precipitation circuits are estimated to be 8750,000
and $0.50 per ton of ore processed, respectively.
[41,42,47]. These costs are in 1985 dollars. These
costs are for uranium ore processing and are not
intended to be applicable to any particular site.
Solvent Extraction - Solvent extraction is an efficient
method for separating uranium on a commercial scale
[42]. There are no commercial solvent extraction
processes to extract radium or thorium. The solvent
extraction, as applied to uranium extraction plants,
consists of a two-step process. In the first step,
termed "extraction," the dissolved uranium is
transferred from the feed solution (or aqueous phase)
into the organic or solvent phase. The second step,
called "stripping," recovers the purified and
concentrated uranium product into a second aqueous
phase after which the barren organic is recycled back
to the extraction step. The aqueous and organic
solutions flow continuously and countercurrently to
each other through the required number of contacting
stages in the extraction and stripping portions of the
circuit. The uranium is recovered from the second
aqueous solution by precipitation.
The extraction of metal from the aqueous solution and
its eventual transfer to another aqueous solution (the
strip liquid) involves the use of various reagents
(extractants, diluents, and modifiers) and requires a
suitable vessel to bring about intimate contacts
between the different liquids. The extractants are the
reagents in the solvent that extract the metal ions.
Extractants that are used in recovery of uranium from
acid leach solutions are alkylphosphoric acid, amines,
tri-n-butyl phosphate (TBP) and trioctyl phosphine
oxide (TOPO).
The diluents comprise the bulk of solvent and are
inert ingredients whose principal function is to act as
carrier for the relatively small amount of extractant.
Kerosene is the most commonly used diluent,
although other organics such as fuel oil, toluene, and
paraffins are also used. The most commonly used
modifiers for increasing the solubility of the extracted
species are long chain alcohols such as isodecanol
[41,42].
Radium compounds have very low solubilities in
organic solvents [43]. In most extraction procedures
for separating radium from other elements, those
other elements are usually extracted into the organic
phase [29]. For example, the use of 2-thenoyl-
trifluoroacetone (TTA) or tnbutylphosphate (TBP) has
been successful in the separation of radium from
other elements. However, a mixture of TTA and TBP
in carbon tetrachlonde (CCU) has been used to
extract radium for quantitative analysis [29]. Radium
tetraphenylborate has been removed by nitrobenzene
from an alkaline solution, and solutions of 8-
hydroquinoiine (HOQ) and some of its derivatives will
also remove radium from an alkaline solution
[43,44,45]. This extraction characteristic may be
significant in the separation of radium from thorium in
leach solutions. There is no reported use of these
solvent systems for the removal of radium from soils,
ores, or mill tailings.
Organic solvents are used extensively for the
extraction of thorium from ore and mill tailings leach
solutions [31,36,38,39] and for the extraction of the
cations in analytical procedures [20,43,29]. Generally,
these procedures take advantage of the solubility of
inorganic complexes such as thorium chlorides,
thorium nitrates, or thorium sulfates in organic
solvents. Thorium sulfates are formed during leaching
of the ore with H2S04 and thorium nitrates, and
thorium chlorides are produced by the HN03 or HCI
dissolution, respectively, of precipitated thorium
hydroxide. The most common organic solvent used in
these extractions is TBP. For example, a 30 percent
TBP in kerosene was used in the extraction of
thorium from the H2S04 [38] liquor. In another study
[39] 30 percent TBP in normal-hexane was used.
Still another study [31] used 30 percent TBP in
normal- dodecane for HNO3 solutions of thorium
from leach solutions. A review of the extraction of
thorium [36] listed over two dozen organic solvent
systems involving TBP, other organophosphates, and
various amines, which are applied to remove thorium
and actinides from leaching acids such as H2SO4,
HCI, and HBr.
Primary amines and straight-chain secondary
amines have also been used to extract thorium in the
processes for the recovery of uranium and thorium
from ores. After the extraction of uranium with
triisooctylamine, thorium is removed with 5 percent
sec-dodecyl or 5 percent di(tridecyl)amine in
kerosene.
For processing of uranium ore at a rate of 10,000
tons of ore per month, the typical capital and
operating costs for a solvent extraction circuit were
estimated as one million dollars and $1.00/ton of ore
processed, respectively [42,47]. These costs are in
34
-------
1985 dollars. These costs are based on uranium ore
processing and are not intended to be applicable to
any particular site.
Ion Exchange - Leaching used in extraction of
uranium and other minerals is a nonselective process
resulting in the dissolution of elements in addition to
the desired constituents. Ion exchange is one process
used for concentrating the desired constituents from
the leached solutions. The resin ion exchange
technique involves the interchange of ions between
the aqueous solution and a solid resin. This provides
for a highly selective and quantitative method for
recovery of uranium and radium. The process of
removing dissolved ions from solution by an ion
exchange resin is usually termed adsorption in the
uranium industry [4,21,42,46,47].
There are several resins available for extraction of
both radium and uranium. For uranium extraction by
ion exchangers, strong and intermediate base anionic
resins are loaded from either sulfuric acid or a
carbonate leach feed solution. The loaded resin is
stripped with a chloride, nitrate, bicarbonate, or an
ammonium sulfate-sulfuric acid solution to remove
the captured uranium. These resins are semirigid gels
prepared as spherical beads. Radium can be
extracted by using synthetic zeolites.
The total amount of uranium that may be adsorbed is
a function of the quantity of anionic complex in
solution. Two to five pounds of UaOs can be captured
for each cubic foot of resin. Higher capacity is not
possible because of competition for ion sites in the
resin by other anions present.
The other anions present in the acid solution that
compete with uranium for resin sites include HSO4",
S04~2, and various impurities that dissolve along with
the uranium during leaching. The extent to which one
of these anions adsorbs on the resin is influenced by
its concentration in solution relative to other ions, pH,
and by the relative affinity of the resin for the anion.
Removal of the uranium from the saturated resin is
termed elution. It is customary to refer to the eluting
solution as the eluant and to the final effluent as the
eluate. Chloride elution is best accomplished in acid
circuits with concentrations of from 0.5 to 1.5 M CI".
Nitrate elution can also be used at a 1 M NOa"
content.
The ion exchange process is, in most plants, a
semicontinuous series of operations integrating the
adsorption and elution steps with various stages of
washing, resin regeneration, etc.
There are three types of ion exchange systems: fixed
bed, moving bed, and resin-in-pulp.
For a fixed bed ion exchange system, cylindrical
pressure vessels with dished ends are usually
constructed of steel and lined with rubber for
corrosion resistance. The resin bed rests upon a bed
of crushed and sized rock, which is in turn supported
either by a flat rubber-covered steel false bottom or
the dished bottom of the column.
For a moving bed ion exchange system, the resin is
transferred to separate columns for adsorption,
backwashing, and elution. This procedure has been
performed in six Canadian plants, one U.S.
processing plant, and two U.S. mine water recovery
plants. The major plant installations utilize ten
columns per set, with two groups of three on
adsorption, one group of three on elution, and one
special column for transfer and backwashing. This
arrangement eliminates the danger of mixing leached
solution and eluate solution due to improper
operation.
The moving bed processing cycle does not vary
significantly from that in the fixed bed plants, except
that either two or three columns are continuously on
adsorption without interruption, and elution is
conducted with three columns in series.
For a basket resin-in-pulp ion exchange system,
the resin is contained in cube-shaped baskets
formed of stainless steel and covered with either
stainless steel or plastic screen cloth.
The baskets are moved up and down at a rate of
between six and twelve strokes per minute in
rectangular shaped tanks containing flowing slurry or
eluting solution. The basket movement consolidates
the resin bed during an up stroke, thereby squeezing
out residual solution, and expands the bed for free
solution access during the down stroke. From six to
eight stages are employed in adsorption and from
seven to fourteen in elution, with more stages
required when sulfuric acid is used for elution.
Some of the new developments in ion exchange
equipment are:
Porter and Stanton contactor. Resin passes
downward and solution flows upward.
Higgins contactor. A single column divided
into two sections by rotating valves.
Jigged bed ion exchange. Uses jigged action
in the resin to cause more dense uranium
loaded resin. Department of Defense is
investigating the use of the equipment to
clean a missile site in New Jersey.
Winchester Fixed Bed. Pulp flow is introduced
through an oscillating distributor.
35
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Bureau of Mines ion exchange. Divides the
adsorption column into compartments
separated by orifice plates.
Based on an ion exchange system with a capacity of
200 tons per day, the typical capital cost estimates
range between $300,000 and $1,000,000. The
operating cost estimates for that tonnage capacity
range between $1 and $3 per ton of soil processed.
[42,47] These costs are for processing of uranium
ore and are not applicable to any particular site.
5.3.5.2 Potential Applicable Situations
Precipitation and Coprecipitation - Precipitation and
coprecipitation have been used in some extraction
schemes to separate uranium from the leach liquor.
All currently operated uranium extraction plants, with
the exception of a few using a carbonate leaching
circuit, employ precipitation to recover the uranium
from the solvent extraction stripping liquor or from the
ion exchange eluate. Precipitation could be used
directly to extract the radionuclide from the water and
inorganic salt extraction pregnant liquor.
Solvent Extraction - Solvent extraction is the
preferred technology for extracting uranium from acid
leach liquor circuits. However, it has not proved
feasible to apply solvent extraction to carbonate leach
liquors or to slurries containing appreciable amounts
of solids [42].
Ion Exchange - The use of ion exchange has been
documented in a number of applications. These
include:
Decontamination of uranium mill processing
water and water pumped from the mine. Ion
exchange also has been used to remove
radium from uranium mill tailings [47].
The Mining Science Laboratory in Canada
has demonstrated ion exchange extraction as
a means of cleaning the leach liquor from
tailings for uranium, thorium, and radium [48].
Extraction of uranium in several plants in the
U. S. [42].
An alkaline leaching process in which ion
exchange is used to extract the impurities and
produce a high grade liquor for precipitation
and recovery of uranium [21].
5.3.5.3 Advantages and Disadvantages
Advantages - Precipitation and coprecipitation are
used extensively in uranium recovery operations.
They can be operated in both batch and continuous
operation mode, and involve low capital cost.
Since solvent extraction technology involves only
liquid-liquid contacts, it is readily adaptable to other
systems and can be performed as a continuous
operation. Solvent extraction is also readily adaptable
to efficient and economical automatic continuous
operation. Other advantages of solvent extraction are
better selectivity and greater versatility than ion
exchange.
Ion exchange is an excellent and economic method
for removing very fine radioactive contaminants from
liquids. In the absence of ion exchange equipment,
more expensive ultrafiltration or solvent extraction
techniques are used. Ion exchange is less sensitive to
the volume or grade of liquor than the solvent
extraction techniques. Ion exchange has been
extensively used in cleaning radioactive contaminants
from nuclear power plant water streams, providing a
valuable database for the development of ion
exchange equipment to clean contaminated soils.
Disadvantages - Precipitation and coprecipitation
involve a difficult, cumbersome, and costly operation
requiring complex chemical separation. Close control
of operating conditions is required. The pH must be
monitored and controlled to have better product
recovery. The precipitation procedure is not adaptable
to automatic control, and most plants currently
operate on manual.
The mam disadvantage of solvent extraction is that
the feed solution must be essentially free of solids. It
has not proved economically feasible to apply solvent
extraction to carbonate leach liquors. Emulsion
formation in solvent circuits causes trouble. The small
loss of solvent to tailings is not only costly, but may
be a source of stream pollution. Solvent reagents are
also very costly. The solvent extraction process is
more sensitive to the volume and grade of liquor than
the ion exchange process. Molybdenum is strongly
extracted by amines and builds up in the amine,
acting as poison.
In using ion exchange, impurities in the liquor can
overload the ion exchange resins. Trace metals such
as molybdenum, vanadium, radium, and sulfate in the
leached liquor can poison the resin, reducing its life.
5.3.5.4 Information Needs
The analyses listed below must be considered in
preparing to implement precipitation, solvent
extraction, and ion exchange procedures.
Chemical composition and trace ion analysis
of the leach liquor.
Solid content and pH of the liquor.
Trace element content
5.4 Typical Costs of Chemical Extraction
Technologies
It is estimated that the typical cost for chemical
extraction would range from $50-150 per ton of soil,
36
-------
assuming that the waste is in a form suitable for the
use of these technologies. Transportation and
disposal costs for the concentrated and "clean"
fractions are not included in the above figure.
Because of lack of process data, the costs of some
of the chemical extraction technologies are based on
profitable ore processing techniques and not on the
costs of removing enough radioactivity from the
contaminated material to render it "clean." As such,
these costs could be much higher. Since more
detailed process information is lacking, these figures
represent an educated guess. These costs are not
intended to be applicable to any particular site.
5.5 References
1. Landa, E. R. Isolation of Uranium Mill Tailings and
Their Component Radionuclides from the
Biosphere - Some Earth Science Perspectives.
Circular 814, U.S. Geological Survey, Arlington,
Virginia, 1980.
2. Shoesmith, D. W. The Behavior of Radium in Soil
and in Uranium Mill Tailings. AECL-7818,
Whiteshell Nuclear Research Establishment,
Pinawa, Canada, 1984.
3. Nirdosh, I., S. V. Muthuswami, and M. H. I. Baird.
Radium in Uranium Mill Tailings - Some
Observations on Retention and Removal.
Hydrometallurgy, 12:151-176, 1984.
4. Ryan, R. K., and D. M. Levins. Extraction of
Radium from Uranium Tailings. CIM Bulletin,
October, 1980, pp. 126-133.
5. Levins, D. M., R. K. Ryan, and Strong. Leaching
of Radium from Uranium Tailings, OECD Nuclear
Agency Publication. In: Proceeding of the
OECD/NEA Seminar on Management,
Stabilization and Environmental Impact of
Uranium Mill Tailings, pp. 271-286, Albuquerque,
New Mexico, 1978. OECD, Paris, France, 1978.
6. Shearer, S. D., Jr., and G. F. Lee. Leachability of
Ra-226 from Uranium Mill Solids and River
Sediments. Health Physics, 10:217-227, 1964.
7. Havlik B., J. Grafova, and B. Nycova. Radium-
226 Liberation from Uranium Ore Processing Mill
Waste Solids and Uranium Rocks into Surface
Streams. Health Physics, 14:417-422, 1968.
8. Landa, E. R. Geochemical and Radiological
Characterization of Soils from Former Radium
Processing Sites. Health Physics, 46:385-394,
1984.
9. Seeley, F. G. Problems in the Separation of
Radium from Uranium Ore Tailings.
Hydrometallurgy, 2:249-263, 1977.
10. Best, F. R., and M. J. Driscoll (Eds.),
Proceedings of a Topical Meeting. Energy Lab.
Rep. MIT-EL80-031, 1980.
11. Kanno, M. Energy Developments in Japan, Vol. 3.
Rumford Publishing Company Inc., 1980. pp
67-89
12. Landa, E. R. Leaching of Radionuclides from
Uranium Ore and Mill Tailings. Uranium, 1:53-
64, 1982.
13. Organization for Economic Cooperation and
Development (OECD). Uranium Extraction
Technology - Current Practice and New
Development in Use Processing. OECD, Paris
1983.
14. Torma, A. E. A New Approach to Uranium Mill
Tailings Management. NMERDI 2-69-1308,
New Mexico Energy Research and Development
Institute, Santa Fe, New Mexico, 1983.
15. Torma, A. E., N. R. Pendleton, and W. M.
Fleming. Sodium Carbonate - Bicarbonate
Leaching of a New Mexico Uranium Ore and
Removal of Long Half-Life Radionuclides from
the Leach Residue. Uranium, 2:17-36, 1985.
16. Torma, A. E. Extraction of Radionuclides from
Low-Grade Ores and Mill Tailings. EMD 2-68-
3620, New Mexico Energy Research and
Development Institute, Santa Fe, New Mexico,
1981.
17. Hawley, J. E. Use of Phosphate Compounds to
Extract Thonum-230 and Radium-226 from
Uranium Ore and Tailings. NSF/RA-800528,
Hazen Research Corp., Golden, Colorado, 1980.
18. d'Aguiar, H. D. Radium Production in America I.
Chemical and Metallurgical Engineering, 25:825-
828, 1921.
19. Landa. E. R. A Historical Review of the Radium-
Extraction Industry in the United States (1906-
1926) - Its Processes and Waste Products. In:
Proceedings of the Fourth Symposium on
Uranium Mill Tailings Management. Fort Collins,
Colorado, 1981. pp. 3-32.
20. Albert, R. E. Thorium: Its Industrial Hygiene
Aspects. Academic Press, New York, 1966.
37
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21. Clark, D. A. State of the Art: Uranium Mining,
Milling and Refining Industry. USEPA/600/2-74-
038, 1974.
22. Nathwani, J. S., and C. R. Phillips. Rates of
Leaching of Radium from Contaminated Soils: An
Experimental Investigation of Radium Bearing
Soils from Port Hope, Ontario. Water, Air, and
Soil Pollution, 9:453-465, 1978.
23. Borrowman, S. R., and P. T. Brooks. Radium
Removal from Uranium Ores and Mill Tailings.
RI-8099, U.S. Bureau of Mines, Salt Lake City
Research Center, Salt Lake City, Utah, 1975.
24. Dreesen, D. R., M. E. Bunker, E. J. Cokal, M. M.
Denton, J. W. Starner, E. F. Thode, L. E.
Wangen and J. M. Williams. Research on the
Characterization and Conditioning of Uranium Mill
Tailings 1. Characterization and Leaching
Behavior of Uranium Mill Tailings. LA-9660-
UMT, Vol. 1, DOE/DMT-0263, Los Alamos
National Laboratory, Los Alamos, New Mexico,
1983.
25. Hague, K. E., and J. J. Laliberte. Batch and
Counter-Current Acid Leaching of Uranium Ore.
Hydrometallurgy, 17:229-238, 1987.
26. Ryon, A. D., F. J. Hurst, and F. G. Seeley. Nitric
Acid Leaching of Radium and Other Significant
Radionuclides from Uranium Ores and Tailings.
ORNL/TM-5944, Oak Ridge National Laboratory,
Oak Ridge, Tennessee, 1977.
27. Torma, A. E., and S. Y. Yen. Uranium Ore
Leaching with Brine Solutions Containing
Hydrochloric Acids. Erzletall, 37:548-554, 1984.
28. Williams, J. M., E. J. Cokal, and D. R. Dressen.
Removal of Radioactivity and Mineral Values from
Uranium Mill Tailings. In: Proceedings of the
Fourth Symposium on Uranium Mill Tailings
Management, Fort Collins, Colorado, 1981. pp.
81-95.
29. Vdovenko, V. M., and Dubasov, Yu. V. Analytical
Chemistry of Radium, Analytical Chemistry of the
Elements. D. Malament, ed. John Wiley and Sons
(Halstead Press), New York, 1975.
30. Seeley, F. G. Removal of Radium and Other
Radionuclides from Vitro Tailings. Memo to A.D.
Ryon, Oak Ridge National Laboratories, Oak
Ridge, Tennessee, 1976.
31. Scheitlin, F. M., and W.D. Bond. Removal of
Hazardous Radionuclides from Uranium Ore
and/or Mill Tailings: Progress Report for the
Period October 1, 1978, to September 30, 1979.
ORNL/TM-7065, Oak Ridge National Laboratory,
Oak Ridge, Tennessee, 1980.
32. Nirdosh, I., S. V. Muthuswami, M.H.I. Baird, C.R.
Johnson, and W. Trembley. The Reducing-
Compiex Treatment for the Leaching of Radium
from Uranium Mill Tailings. Hydrometallurgy,
15:77-92, 1985.
33. Nixon, A., D. Keller, K. Fritze, A. Didruczny, and
A. Corsmi. Radium Removal from Elliot Lake
Uranium-Mill Solids by EDTA Leaching.
Hydrometallurgy, 10:173-186, 1983.
34. Yagnik, S. K., M.H.I.Baird, and S. Banerjee. An
Investigation of Radium Extraction from Uranium
Mill Tailings. Hydrometallurgy, 7:61-75, 1981.
35. Taskayev, A. I., V. Ya. Ovchenkov, R.M.
Altkaskhm, and I. I. Shuktomova. Effect of pH and
Liquid Phase Cation Composition on the
Extraction of 226Ra from Soils. Pochvovedeniye,
12:46-50, 1976.
36. Phillips, C. R., and Y. C. Poon. Status and Future
Possibilities for the Recovery of Uranium,
Thorium, and Rare Earths From Canadian Ores,
with Emphasis on the Problem of Radium Part I:
Ores, Special Problem, and Leachings. Minerals
Science Engineering, 12:53-72, 1980.
37. Sedlet, J. Radon and Radium, pp. 219-316. In:
Treatise on Analytical Chemistry, Vol. 4. I. M.
Kolthoff, and P. J. Elvmg, eds. John Wiley and
Sons (Interscience Publishers), New York, 1966.
38. Kluge, E., K. H. Lieser, I. Loc, and S. Quandt.
Separation of 230Th (Ionium) from Uranium Ores
in Sulfuric Acid and in Nitric Acid. Radiochemica
Acta, 24:21-26, 1977.
39. Ryon, A. D., W. D. Bond, F. J. Hurst, F. M.
Scheitlin, and F.G. Seeley. Investigation of Nitric
Acid for Removal of Noxious Radionuclides from
Uranium Ore or Mill Tailings. In: Proceedings of
Two OECD/NEA Workshops on Uranium Mill
Management, OECD Nuclear Agency Publication,
OECD, Pans, France, 1982. pp 139-147.
40. Ambe, S. and K. H. Liefer, Coprecipitation of
Thorium with Barium Sulfate, Radiochemica Acta,
25:93-98, 1978.
41. Buskin, A.R. The Chemistry of Hydrometallurgical
Processes. Span Limited, London, 1966.
38
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42. Merritt, R. C. Extraction Metallurgy of Uranium,
Colorado School of Mines Research Institute,
1971.
43. Kirby, H. W., and M. L. Salutsky. The
Radiochemistry of Radium, NAS-NS-3057,
National Technical Information Service,
Springfield, Virginia, 1964.
44. Sebesta, F., J. John, and V. Jirasek. Extraction of
Radium and Barium Phosphomolybdates into
Nitrobenzene in the Presence of Poly-
ethyleneglycol. Radiochem, Radioanal, Letters,
30:357-364.
45. Sebesta F., E. Bilkova, and J. Sedlacek.
Extraction of Radium and Barium into
Nitrobenzene in the Presence of Polyhedral
Borate Anions. Radiochem, Radioanal, Letters,
40:135-144, 1979.
46. Raicevic, D. Decontamination of Elliot Lake
Uranium Tailing. CIM Bulletin, 1970.
47. Logsdail, D.H. Solvent Extraction and Ion
Exchange in the Nuclear Fuel Cycle. John Wiley
& Sons, New York, 1985.
48. Rulkens, W.H., and J.W. Assmk, et. al.
Development of an Installation for On-Site
Treatment of Soil Contaminated with Organic
Bromine Compounds. Conference on
Management of Uncontrolled Hazardous Waste
Sites, Washington, DC, 1982.
39
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Chapters
Physical Separation Processes
6.1 Purpose
Radioactive contaminants in soils and in uranium mill
tailings may be associated with fine soil particles [1-
3]. Separation of the fine soil particles should
concentrate the radioactive contaminants in fine soil
fractions, and thus reduce the volume of soil for
disposal, permitting more manageable soil disposal.
The physical separation techniques that can be
utilized to separate out or concentrate radioactive
contaminants within soils are discussed in this
chapter. These separation techniques are also utilized
in the pre- or post-treatment phases of chemical
extraction treatment schemes. Physical separation
techniques are mechanical methods for separating
mixtures of solids to obtain a concentrated form of
the desired constituents. Chemical agents are added
in some cases to enhance the separation process.
Methods for separation by mechanical rather than by
chemical means are usually low in cost and trouble-
free. There are a variety of physical separation
techniques, each with a particle size range; they are
shown in Table 11 along with the physical attributes
that govern the separation processes [4-6]. In any
given process a combination of these physical
separation techniques is employed to achieve the
required concentration of the desired constituents.
6.2 State of the Art
Most of the radium in uranium mill tailings occurs in
very fine particles, or slimes. Borrowman and Brooks
used physical separation techniques to separate
tailings into sand (coarse particle) and slime [1]
Physical separation of the tailings, which contained
radium levels of 500 and 450 pOg, resulted in
coarse particle fractions with 50 and 140 pCi g
radium, respectively.
Garnett et al. scrubbed plutonium-contaminated soil
with wash solution and then used physical separation
techniques to separate the clean sand [2]. Results
from a few of the tests showed that coarse particle
fractions of the soil can be cleaned to contamination
levels of <1, 12, and 86 pCi/g for soils contaminated
with 45, 284, and 7515 pCi/g of plutomum,
respectively.
Treatment of Elliot Lake uranium mill tailings in
Canada showed that much of the radium, thorium,
and uranium can be removed using physical
separation techniques [3]. The laboratory test at
CANMET and bench-scale testing at the Denison
Mill employing physical separation techniques
reduced the radium contamination levels in tailings
from 290 and 266 pCi/g to 57 and 45 pCi/g,
respectively.
Based on a literature review, the following physical
separation technologies show potential for cleaning
soils contaminated with radioactivity:
screening, both dry and wet
classification
flotation
gravity concentration
Sedimentation and filtration supplement these
techniques.
All the above physical separation processes are used
extensively in uranium extraction. Screening, gravity
concentration, and flotation comprise part of the
physical separation methods used in preparing the
uranium ore for extraction. The prepared ore is then
normally acid-leached, and the particles are
separated using classification and ion exchange.
References 7-10 discuss the physical separation
techniques used in many uranium processing
operations. Shown in Figure 13 is a process used to
clean plutonium-contaminated soil using physical
separation techniques. In this process a variety of
technologies, including screening, classification,
sedimentation, and filtration are employed to separate
the soil into different size fractions and to separate
out the water. Other processes used to decon-
taminate soil probably would include some
combination of these.
The state of the art physical separation technologies
are shown in Table 12. As can be seen from this
table, although these technologies have been field
demonstrated for radioactive material extraction from
ores, they have not been used in remediating any
radiologically contaminated sites. Pilot plant testing
41
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Table 11. Physical Separation Technology and Particle Size
Physical Attributes
Microfiltration
MBI^^H
Ultrafiltration
[Screen Staining
Cyclones/Cones/Drums
Slime Tables
I
Liquid Cyclones
J I
Sedimentation
n
Centnfugation
Size
and
Density
Ultracentnfugation
Mag Separation
Pry
Magnetic
Permeability
Magnetic Separation—Dry
Electrostatic
Separation
Electrical
Conductivity
Surface
Activity
Foam & Bubble Fractionation
Membrane Technology
Angstroms
Microns
Millimeters
10
10"
Ionic Range
102
TO'2
10"5
103
10"
10"
10"
1
10"
10s
10
10"
106
102
10"
107
103
1
108
10"
10
109
105
1005
Macromolecular _^
Range
Micron
Particle
Range
Fine
Particle
Range
Coarse Particle Range
would be needed to determine their capability for
radiologically contaminated site cleanup.
Selection of the physical separation technology for
soil cleaning is dependent on the properties of the
contaminated soil and concentration of radionuchdes
in each particle size fraction.
There are several other separation techniques used in
the mining industry, which will be described briefly but
not in detail because of their limited applicability for
removing radioactive contaminants from soils and
tailings. These techniques include:
heavy media separation
magnetic separation
electrostatic separation
Heavy media separation techniques use heavy liquids
of suitable density to separate light and heavy
particles [6,11,12]. Heavy media separation is
possible if the contaminant is in loosely aggregated
coarse particles. If the contaminant is finely
disseminated throughout the soil, then this technique
will not work. Also, the heavy liquids used give off
toxic fumes.
Magnetic separation [6,11-13] and electrostatic
separation [6,11,12,14] exploit the difference in
magnetic and conductive properties between the
radioactive contaminants and the soil to effect the
separation. As with heavy media separation, if the
contaminant is finely disseminated throughout the
soil, these separation techniques are not likely to
work.
6.3 Technologies of Potential Interest
This chapter discusses the physical separation
technologies mentioned above. With the exception of
42
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Figure 13. Pilot
Soil Feed
'(lot-scale equipment test for soil decontamination. (Reprinted from [2].)
Clean Soil (+5 mesh)
Contaminated j
>| Scrubber
Qn»l PooH ' *
Makeup
Clean Soil (+35 mesh)
Underflow
Hydrocyclone y Clanfuge
NaOH & Water
i
Ultrafiltration
Overflow
4-
i
j Overflow
v
!
Reject I
Stream i
i
To Waste
Treatment
I I
Backwash
Stream Contaminated
| Soil
Ship for
Disposal
dry screening, all technologies — screening,
classification, flotation, and gravity concentration--
use substantial quantities of water as part of the
process. The final concentrate must be separated
from the water before disposal. The separated water
is normally purified and recycled, thereby reducing
the water usage. The solid/liquid separation
techniques, sedimentation and filtration, are also
discussed in this chapter.
In general, one has to be concerned with dust control
for dry physical separation processes and the
treatability of liquid wastes which are generated in wet
physical separation processes. These are important
issues that need to be addressed carefully before
technology selection.
6.3.7 Screening
6.3.1.1 Description and Development Status
Screening is the mechanical separation of particles
on the basis of size. Such separations are achieved
using a uniformly perforated surface. Particles larger
than the screen openings are retained on the surface,
while smaller particles pass through. Material retained
on the surface is the oversize or plus (+) material;
that passing through is the undersize or minus (-)
material; and material passing one surface but
retained on a subsequent surface is intermediate
material. Perfect separation is seldom achieved.
There are always some undersize particles left in the
oversize fraction. Nevertheless, an almost complete
separation can be achieved with the use of a slow
feed and a consequently long screening period [6-
8,11,15-17].
Table 12. State of the Art of Physical Separation Technologies
Field
Demonstration Radiologically
Bench Pilot with Contaminated
Laboratory Scale Plant Radioactive Site
Technology Testing Testing Testing Material Remediation
Remarks
Physical
Separation
- Screening
- Classifica-
tion
- Gravity
concentra-
tion
x x Used
x x Used
x x Used
in
in
in
extraction
extraction
extraction
of
of
of
radium,
radium,
radium,
thorium,
thorium,
thorium,
and
and
and
uranium from
uranium from
uranium from
ores
ores
ores
- Flotation
Used in extraction of radium, thorium, and uranium from ores
43
-------
Screening is normally limited to materials larger than
250 microns, with finer sizing obtained by
classification. In addition to size, there are many
factors affecting the passage of the particle through
the screen, including screening efficiency, particle
shape, angle of approach, and particle orientation to
the screen. The closer to the perpendicular the angle
of approach, the higher the chance of passage.
Taggart gives some probabilities of passage related to
the particle size [8].
The amount of moisture in the feed also affects
screening efficiency, as does the presence of clays
and other sticky materials. Damp feeds screen very
poorly as they tend to agglomerate and blind (plug)
the screen apertures. Screening must always be
performed on either dry or wet material, but never on
damp material. For best screening efficiency, wet
screening is always superior: Finer sizes can be
processed, adhering fines are washed off by large
particles, and the screen is cleaned by the flow of
pulp. There is no dust problem. There is. however,
the increased cost of dewatering and drying, and for
this reason dry screening is preferred.
Particle size separation achievable by the basic
screen types is illustrated in Figure 14. A common
problem with screens is the blinding of the screen
apertures with particles that are just slightly oversize.
The problem increases as aperture size decreases,
and it can result in a significant reduction in capacity.
Blinding can often be minimized by correct screen
motion or by a suitable surface material.
Problems caused by small amounts of moisture can
be alleviated by using electrically heated screen
cloths. Although this increases the capital cost of the
screen, operating costs may decrease because of
longer surface life. Another approach is to use a gas
flame underneath and parallel to the screen surface.
With screens having apertures between 0.5 and 5.0
mm, ball decks are sometimes employed for cases of
severe blinding.
Screening equipment can be classified as either
stationary or dynamic. Figure 15 shows the various
screen types, and Table 13 describes them.
6.3.1.2 Potential Applicable Situations
Table 14 describes the typical situations in which the
basic screen types are used. Grizzly screens are
normally used for separating large pieces like stones.
The size of particles screened on grizzly screens can
range from 20 mm to 300 mm. In most applications a
grizzly is used to separate large particles, followed by
other screens for finer separation. Sieve bends can
be used for separation as low as 50 microns, since
these devices give sharper separation than can be
achieved by wet classifiers.
6.3.1.3 Advantages and Disadvantages
Advantages and disadvantages of the various screen
types are included in Table 14.
Advantages - Screens are an inexpensive method for
separating coarse and fine particles.
Disadvantages - Screens are subject to plugging,
thus decreasing their efficiency. Fine screens are
very fragile and clog easily with retained particles.
High throughput reduces particle dwell time on the
screen and generally produces a thick bed of
materials through which fines must travel to reach the
screen surface. This results in decreased efficiency.
Screens are noisy, and dry screening requires dust
control. To control dust emissions, dust covers are
used. Most manufacturers can supply fully enclosed
screening, which can be connected to a dust
extraction system.
6.3.1.4 Information Needs
The information listed below must be gathered and
considered in selection of the screens and
implementation of a screening process.
Particle size distribution of the feed.
Radionuclide distribution with particle size.
Moisture content.
Mineralogical composition.
Dust control requirement.
Throughput required.
6.3.2 Classification
6.3.2.1 Description and Development Status
Classification is the separation of particles according
to their settling rate in a fluid. Water is the fluid most
commonly used in mineral processing
[2,3,6,8,10,11,13,14,17-19].
Classifiers typically produce two streams-one
containing the faster settling particles called sands
(underflow or oversize) and another containing slow-
settling particles called slimes or overflow.
Classifier types fall into three basic categories: (1)
nonmechanical, (2) mechanical, and (3) hydraulic.
Functionally, mechanical and nonmechanical
classifiers are similar and differ only in the means of
sand removal. In hydraulic types the character of
separation is different because of the hindered
settling induced by the hydraulic water.
Table 15 illustrates different classifier configurations.
Mechanical classifiers are designated by M-S,
nonmechanical classifiers by N-S, and hydraulic
classifiers by M-F or N-F. All hydraulic classifiers
are of the fluidized-bed type; some of them use
44
-------
Figure 14. Typical separation sizes of the basic screen types. (Reprinted from [6]. Copyright © 1982. Reprinted by permission
of John Wiley & Sons, Inc.)
• Static
Sieve Bends
Grizzly
Inclined
(Mech Vibration)
Inclined & Horizontal
(Mechanical Vibration)
High Speed Inclined
.;.;.;.;.;.;.;.;.;.;.;.;.;.;.;.;.;.! ( El 6Ct rOfTia QnBt 1C Vlbr
Grizzly
(Mech )
Rod Deck
Probability
Rod Grizzly
"'"'"'"'"'"'"'"'"''
: Flat ::::::::::::::::::::
Rotary Sifters
Shaking
E: Revolving'''||:i|||^^i:;ffl Centrifugal
Trommel
10 Aim
100 /jm
1 mm
Aperture Size
1 0 mm
100 mm
mechanical means to remove sand. These are
identified as M-F in Table 13. The table lists ranges
of suitable operating conditions for each classifier.
Hydraulic Classifier - With the hydraulic classifier,
water or air is introduced so that its direction of flow
opposes that of the settling particles. The simplest
form of a hydraulic separator is the settling-cone.
Solid/liquid flows into the settling-cone like a fluid
being poured into a funnel. The heavy, solid-laden
flow exits the bottom, and the liquid flows radially over
the lip of the cone.
The more complex hydraulic classifiers are the Jet
Sizer by Dorr-Oliver and the SuperSorter by Deister
Concentrator Co. These multicompartment,
multiproduct classifiers operate on the basis of
hindered settling. Each compartment is served with
low-pressure hydraulic water. The amount of
hydraulic water is controlled so that in each
succeeding compartment the coarsest particles are
maintained in hmdered-settlmg condition, and the
finer fractions pass along.
D-O Siphon Sizer is a single-compartment type
built by Dorr-Oliver. Sands are discharged by
siphons extending to the bottom of the hmdered-
settlmg zone. A hydrostatically actuated valve controls
the siphon flow. Discharge for an intermediate fraction
from the upper column can be obtained by additional
siphons. Hydraulic water consumption is considerably
lower than required for multicompartment sizers.
Mechanical Classifiers - In mechanical classifiers, the
slow-settling particles are carried away in a liquid
overflow, and the particles with a higher settling
velocity are deposited on the bottom of the equipment
and dragged upwards against the flow of liquid by
some mechanical means. The size and quality of
separation depends on feed rate, speed of removal,
degree of agitation, and height of the overflow weir.
Mechanical classifiers are widely used in closed-
circuit grinding operations and in the classification of
products from ore-washing plants. Various
mechanical classifiers are described below.
The rake classifier utilizes rakes which dip into the
settled material and move it up the incline for a short
distance. The rakes are then withdrawn and returned
45
-------
Figure 15.
The basic screen types and their classifications. (Reprinted from [6]. Copyright © 1982. Reprinted by permission
of John Wiley & Sons, Inc.)
Screens
, I .
Dynamic
Fixed (Static)
Revolving
Oscillating
Conveying Grizzly Sieve Bend Probability
J
Relative [ *+.
Particle/Screen i \_J
Motion Revolving
r
Rotary
i
1
Reciprocating
__„ J
i ^
j Motion of [ C *D
Surface v- -
L
Flat
r
i
Sifters Shaking
1
Gyratory
J J
i Motion in Plane of Screen
J
t
Casting
Vibrating
i
Horizontal
1
Re
Gri;
Flow
1 Rotation
j
Motion in Plane
0
Along and
II
.zly
1
Inclined
I
1
Counterflow
Rotation
o
Perpendicular to
1
Traveling
Belt
1
Probability
Electric
Vibration
1 j
Screen i
to the starting point, where the cycle is repeated; the
settled material is thus slowly moved up the incline to
the discharge.
Spiral classifiers use a continuously revolving spiral to
move the sands up the slope. They can be operated
at steeper slopes than the rake classifier, which
results in drier product. Also, there is less agitation in
the pool, which is important in separations of very fine
material.
A sedimenting centrifuge consists of a bowl into
which a suspension is fed and rotated at high speed.
The liquid is removed through a skimming tube or
over a weir while the solids that remain in the bowl
are removed either intermittently or continuously.
Centrifugal sedimentation is based on a density
difference between solids and liquids; the particles
are subjected to centrifugal forces which make them
move radially through the liquid either outwards or
inwards, depending on whether they are heavier or
lighter than the liquid.
There are a variety of bowl designs and discharge
mechanisms available for industrial centrifuges.
Drag classifiers are single endless belt or chain
suspensions with cross flights running in an inclined
trough. They have long been used for draining and
classifying. They may be any of a variety of shapes
and sizes.
The countercurrent classifier is an inclined, slowly
rotating cylindrical drum; continuous spiral flights
attached to the interior of the drum form helical
troughs. The direction of rotation is such that material
in the troughs moves toward the higher end. Wash
water introduced at the upper end drains from the
lifting flights above the normal water level and
progresses countercurrent to the material toward the
overflow.
The countercurrent classifier is normally used for
sand-slime separations, washing, and for closed
construction restricting escape of heat and chemical
fumes.
The air classifier, similar to the hydrocyclone (to be
discussed in the next chapter on nonmechamcal
classifiers) uses air to produce coarse and fine
fractions. The air classifier is used where solids must
be kept dry, for example, in cement grinding.
Nonmechamcal Classifiers - Nonmechamcal
classifiers rely on gravitational or centrifugal force to
separate the coarse particles. The hydrocyclone,
settling cone, and elutnator are three types that are
commonly used.
A hydrocyclone is a widely used, small, inexpensive
device that gives relatively efficient separation of fine
particles in dilute suspension. The hydrocyclone is a
continuous-operating classifying device, which
utilizes centrifugal force to accelerate the settling rate
of particles. It is one of the most important devices
used in the minerals industry; there are over 50
hydrocyclone manufacturers in the world.
46
-------
Table 13.The Major Types of Screens. (Reprinted from [6]. Copyright • 1982. Reprinted by permission of John Wiley & Sons,
Inc.)
>
TIONA
RIZZLY
£
ROLL
GRIZZLY
SIEVE BENDS
tsi
z
cc
u
VI
o
z
>
o
>
cc
VJ
z
IBRATING SCRE
rj w
ZH
FTERS
«
>
X
r-
O
CC
!££££.«•. C,aSS,,ca,,ons
C 1
Heavy duty
surface of
fixed bars
Probability
Surface of
rotating rolls
Slurry feed. Straight or
fixed bar curved surface
surface
Trommel
Screen surface Centrifugal
rotating around
cylinder axis
Probability
Inclined
(Subclassified
by vibrator
mechanisms)
High speed
motion,
designed
primarily to Horizontal
lift particles
off surface
Probability
Slow linear
essentially in
Reciprocating
Circular motion
applied to Gyrating
screen surface
Gyrating
Description
Heavy bars running in
flow direction, sloped to
allow gravity transport
length to minimise
blinding
Bars divergent in
vertical plane
Essentially a stationary
screen surface but non
uniform shape of rolls
conveys material
Stationary parallel bars
at right angles to slurry
flow Surface may be
straight (with steep
incline) or curved to
300°
Slightly inclined
cylindrical screen May
have concentric surfaces
Vertically mounted
cylindrical screen
centrifuges particles
through screen
Particles drop through
surface formed by bars
radiating out like spokes
on a wheel
Inclined rectanqular
screening surface which
allows material to flow
with aid of vibrations
Horizontal rectangular
Linear vibration must
have horizontal component
to convey material along
screen
Series of relatively
small inclined screen
statistics rather than
Usually slightly inclined
apertures
Rectangular screen
surface with slight (^5°)
incline
Circular screen surface
Circular screen surface
Speed
Motlon Amplitude
Stationary surface
(Vibrating grizzlies also
available bar vibrating
Stationary
Below critical speed 1 5 20
(c f ball mill) r p m
Operates above critical
speed Also has vertical 60 80
action of 800 1000 r p m
cycles mm
Radiating bars rotate
about vertical axis
Speed of rotation
determines cut size
Mechanical vibrations
give circular motion at 6QO OOQ
center elsewhere it r m
depends on vibrator r p m
Electro .
» K . Low
magnetic vibrators may s~yz>
give linear vibration
at center
Linear motion, with 600 3000
provide lift, and
horizontal component for Low
conveying ' 25 mm
Linear motion, 30 800
to remain in contact 25-1000
with screen surface mm
Circular motion is
applied at feed end and
produces reciprocating
motion at discharge end
500 600
Circular motion over ' p m
most of the screen
surface Low
Screen moves with
circular motion but
also has oscillating
vertical component
Applications
Scalping before crushers
Coarse separations before
crushing Primarily a
conveyor
Separations in range
2 mm to 45 Mm or those
too coarse for
hydrocyclone, or where
density effects make
classifier unsuitable
Dewatermg
Wet or dry separations
60 to 10 mm if dry
smaller if wet
Wet or dry separations
1 2 mm to 400 Lim
Dewatermg
Developed for separating
coal "^6 mm
Wide applications,
generally down to 200 >jm
in mineral industry but
down to 38 jm m
chemical industry using
the high speeds
Similar to inclined
screens
screens
Down to 1 2 mm for coal
down to 250 Mm
Generally used for finer
separations (12 mm to
45 Mm, wet or dry) m
non-metallurgical
Advantages and
Disadvantages
Simple, robust
Probability form blinding
resistant
Conveying action allows
near horizontal operation
in low head room
situations
Relatively high
efficiency and capacity
Sharpness of cut less
than true screen
Separation slightly
affected by mineral
density Excessive
dewatenng can be a
problem
Simple, useful for
scrubbing or rough size
separations High wear
low surface utilisation
High wear
Relatively high capacity
with fine separations
Cut size easily changed
and controlled by varying
speed
Relatively high
efficiency and capacity
but capacity generally
inadequate below
200 urn
Similar to other
vibrating screens but
can also be used where
head room is restricted
Generally superior to
conventional vibrating
screen High capacity
space, low noise, low
at low loading
Low headroom and power
requirements May be
used for conveying and
maintenance cost, low
capacity
Suitable for finer
separations, but with
low capacity
47
-------
Table 14.Types of Screening Operations and Equipment. (Reprinted from [6J. Copyright » 1982. Reprinted by permission of
John Wiley & Sons, Inc.)
Operation and Description
Type of Screen
Scalping: Strictly, the removal of a small amount of oversize from a
feed that is predominately fines Typically the removal of oversize
from a feed with, approximately, a maximum of 5% oversize, and a
minimum of 50% halfsize.
Coarse, grizzly.
Intermediate and fine: same as used for separations
Separation, Coarse Making a size separation at 4 75 mm and
larger
Separation. Intermediate: Making a size separation smaller than
4 75 mm and larger than 425 micron
Separation. Fine Making a size separation smaller than 425 micron.
Vibrating screens, horizontal or inclined.
Vibrating screens, high-speed, sifter, and centrifugal screens Static
sieves
High-Speed, sifter, and centrifugal screens. Static sieves
Dewatering Removal of free water from a solids-water mixture.
Generally limited to 4 75 mm and larger.
Horizontal vibrating, inclined (about 10°), and centrifugal screens
Static sieves.
Trash Removal. Removal of extraneous matter from a processed
material Essentially a form of scalping operation Screen type will
depend on size range of processed material
Vibrating screens; horizontal or inclined. Sifter and centrifugal
screens. Static sieves.
Other Applications: Desliming, conveying, media recovery,
concentration
Vibrating screens, horizontal or inclined. Oscillating and centrifugal
screens. Static sieves.
A typical hydrocyclone (Figure 16) consists of a
conical vessel open at its apex, where underflow
discharge occurs, joined to a cylindrical section,
which has a tangential feed inlet. The top of the
cylindrical section is closed, with a plate through
which passes an axially mounted overflow pipe. The
pipe is extended into the body of the cyclone by a
short, removable section known as the vortex finder,
which prevents feed from flowing directly into the
overflow.
Because of a tangential inlet, the slurry entering the
cone rotates at high velocity, causing heavier
particles to move to the wall of the cyclone and
discharge through the apex opening. The smaller or
lighter particles move toward the vortex in the center,
discharging through the overflow.
The settling cone is the simplest form of classifier.
There are many different designs of cone. The
machine essentially consists of a suspended circular
tank, the base of which is in the shape of a truncated
cone closed by a valve. Feed is introduced at the top.
The sand settles in the cone, while the water and
slimes overflow into a circular peripheral launder. As
the sand accumulates in the cone, the weight of the
whole machine increases. This opens the discharge
valve. When the sand is discharged, the machine
lightens, automatically closing the valve.
Elutnation is a process of sizing particles by means
of an upward current of fluid, usually water or air. The
process is the reverse of gravity sedimentation.
Those particles having a terminal velocity less than
that of the velocity of the fluid will overflow, while
those particles having a terminal velocity greater than
the fluid velocity will sink to the underflow.
6.3.2.2 Potential Applicable Situations
Classifiers can be considered for use in soil-washing
schemes. A typical equipment arrangement is shown
in block diagram form in Figure 13. In this figure a
number of classifiers are used.
The front end uses a scrubber, which is a drum
washer. A spiral classifier could also be used for this
purpose. A hydrocyclone is used at an intermediate
location in the scheme to separate the coarser
fraction from the finer fraction. A centrifuge is used to
remove the fines from the finer fraction. Each device
is used to handle a particular size fraction in the
process.
Other classifiers discussed in this subchapter can
also be used; the application is determined by soil
size fraction and solid concentration.
6.3.2.3 Advantages and Disadvantages
Advantages - The principal advantages of these
classifiers are their high continuous processing
capability and their extensive industrial processing
track record. The mining industry relies on them as
prime movers in ore refining and processing. Low
cost per quantity of material being processed and
equipment reliability are the major reasons for
selecting the equipment.
Disadvantages - A drawback to classification is that
soil with a lot of clay and sandy soil with humus
materials are very difficult to process. In general,
sandy soils low in clay and humus constituents with a
high specific gravity are successfully processed with
the classifiers.
48
-------
Table 15.The Major Types of Classifiers. (Reprinted from [6]. Copyright o. Reprinted by permission of John Wiley & Sons, Inc.)
CLASSIFIER iType")
Sloping Tank Classifier (M-S)
(spiral rake, drag)
\jjH^^
Log Washer IW S)
°'~' * ' — -iiV*\—
'"V***^0*
Bowl Classifier (M S)
Hydraulic Bowl Classifier |M F!
Q- f> ^^^
U<>(,sggi^^^D'*
"W 1^^
Cylindrical Tank Classifier (M SI
2r 'ff
^*^%*y£#^
Hydrsuhc Cylmdncaf Tank (M Fl
Class.fier
2: 'ff,
Cone Class.fier IN SI
0- r.l
-i\ r i /i
Hydraulic Cone Classifier IM F)
n I
u) II IT
Vil/
DESCRIPTION
Classification occurs near
deep end of sloping,
elongated pool Spiral
rake or drag
pool
classtfiet with paddles
Extension of sloping tank
classifiers with settling
occuring in large Circular
pool which has rotating
mechanism to scrape sands
inwards (outwards in Bowl
Oesiltor] to discharge rake
or spiral
Class.fier Vibrating
plate replaces rotating
Hydraulic water passes
plate and fluidises sands
Effectively an overloaded
thickener Rotating rake
underflow
Hydraulic form of over
loaded thickener Siphon
Sizer IN F) uses siphon to
(otatmq take
Similar to cylindrical tank
classifier except tank is
conical to eliminate need
for rake
Open cylindrical upper
section with conical lower
section containing slowly
rotating mechanism
SIZE (ml LIMITING C(:cn VOL % SOLIDS CMITARIL ITV
W.dth SIZE J™ Feed POWER S ,TND
Diameter [Max Feed 7* .'^ Overflow (kW) APPLICATIONS
Max Length Sue) lt/hr! Sands APPLICATIONS
Used for closed circuit grinding,
0 3 to 7 0 - w washing and dewatermg, deslimirtg,
mm j. No1 cntlcal particularly where clean dry sands
2 4 to b t in are imP°rtant (Drag classifier
(spiral) *° M *° z lo *u '°_ sands not so clean) In closed
(25 mm) 45 to 65 C'rCUIt 9rmdl°9 dischar9«
give enough lift to eliminate pump
0 8 to 2 6
.-.,;,.. removing trash clay from sand
0 6 to 1 1 to to A|SQ jo fMemove 0|, break down
450 60 agglomerates
4 6 to 11 (100 mm)
Not critical Q°^ Used for closed circuit grinding
0 5 to 6 0 150 Mm (particularly regrind circuits)
to 5 0 4 to 8 , 5 where clean sands are necessary
1 2 to 1 5 45 um to R h Larger pool allows finer
225 50 to 60 7, jr separations Bowl Desiltor has
12 (12 mm) (15 to 25 in u D larger pools (and capacities)
Bowl Desiltor) ^o Relatively expensive
Vlb Gives verv clean sands and has
1 2 to 3 7 1 mm Not critical relatively low hydraulic water
to 5 g requirements (0 5 t t sand) One
225 R^k® classifiers available for closed
'° Relatively expensive
Simple but gives relatively
1 50 ^m Not cnt.cal ^efficient separation Used for
to 5 u /b primary dewatermg where the
3 to 45 45i,m to 0 4 to 8 to separations involve large feed
625 1 1 volumes and sand drainage is not
(6 mm) 15 to 25 critical
14 mm Not cmical Two product device giving very
to 1 075 clean sands Requires relatively
1 0 to 40 45 ,;m to 0 4 to 1 5 to little hydraulic, water (2 ft sands)
(25 mml 20 to 35 closed circuit grinding
600 -m Not critical lo^lly^^ndTimplfcTycan0 ^ ^^
06,037 45°., ,o 5,030 None C'ra,'-' utV foI'dTsl.ng
3B,o60 ru-X™^*"'"^0'""
400 ^m Net critical
to 10 3 Used primarily m closed circuit
0 G to 1 6 1 0O^m to 2 to 1 5 to grinding to reclassify
(6 mm} 30 to 50
49
-------
Table 15.(Continued)
SIZE (ml LIMITING
CLASSIFIER (Type*} DESCRIPTION Dimeter (Max^eed
Max Length Size)
Hydrocyclone (N S)
0 "ill (Pumped) pressure feed - 300 um
"1H] generates centrifugal to
\ / action to give high 0 01 to 1 2 5 um
\ / discharge - (1 400 ^m to
\ / 45 Mm]
V*
Air Separator
^
Solid Bowl Centnfu
^5^
i ~
*o»
Scrubber
°t...I
r^w-
(N S)
^ Similar shape to hydro
^•fe- —in^^e »"»" 32£
/ / within classifier M
ev,
ge (M S)
settling forces Slurry £ m
Xl1"^ centrifuged against 0 3 to 1 4 1 Mm
(P=^ — it rotating bowl and removed
/V fl bV slower rotating helical 1 g (6 mm)
" ^ "M 1 screw conveyor within bowl
•Q-
M SI
L/ Essentially a rotating drum
J 3 to 10 (150 mml
— tr
Counter Current Classifier (M-FI ^ ^m bi^ ^ ^^
another on spiral -
o^A
Elutnator
Pocket Classifier
;:crTT=
Wv
i ; i
S Sedimentation c
— , |"i water added to flow 0 5 to 3 3 2 mm
^ 1 L-_ essentially horizontally m (spiral type) to
\ P which are conveyed and 1 2
T>
IN Fl
u-» Basically a tube with
G_ hydraulic water ted near ^ 4 mm
bottom to produce hindered
Column may be filled with ,-, c
J network to eyen out flow ~ <7 S mm)
Q*
IN Fl
aw^~~~~~ c= A series of classification n R t K n 5 a
1 « P / pockets with decreasing 0 5 to 6 0 2 4 mm
1 1 guantit.es of hydraulic . , „„
?\/\/ HW range of product sizes ,2 (10 mml
1 i
assifier
ssifier
FEED V°L °teSedL'°S POWER SUITASILITV
(t/hr6) °Sand°sW '^ APPLICATIONS
4 to 35 Small cheap device widely used
to Ann for closed circuit grinding Gives
20 2 to 15 JSim* relatively efficient separations
m'/m,n ores sure of fine Parlicles in dllule
30 to 50 head suspensions
Used where solids must be kept dry,
to 4 such as cement grinding Air
2100 to classifiers may be integrated into
500 grinding mill structure
10 0 4 to 20 to capacity for a given floor space
, 110 used for finer separations
m 'mm 5 to 50
Similar applications to log
1 washer but lighter action
.. ° to Tumbling (85% critical speed;
Not critical
3 02 Very clean sands product, but
to 2 to 1 5 to relatively low capacity for a
600 19 given size
50 to 65
15 to 35 Simple and relatively efficient
4 075 separation Normally a two product
to 0 4 to 5 for device but may be operated in
120 valves series to give a range of size
20 to 35 fractions
15 to 35 Efficient separations but requires
4 3 t hydraulic water/t sand Used
to 0 4 to 5 to produce exceptionally clean
120 sands fract.oned into narrow size
20 to 35 ranges
50
-------
Figure 16.
Hydrocyclone. (Reprinted from [6]. Copyright £
1985. Reprinted by permission of Pergamon
Press, Ltd.)
Overflow
Vortex Finder
Feed
Entrance
Apex Valve
Underflow
Discharge
6.3.2.4 Information Needs
The characterization listed below must be considered
in selecting a classifier type and implementing a
classification process.
Particle size distribution of the feed.
Radionuchde distribution with particle size.
Specific gravity and chemical analysis of the
soil.
Mineralogical composition.
Characteristics of the soil
sand, humus, clay, or silt.
Composition of the organics in each soil
fraction.
Moisture content.
- pH.
6.3.3 Flotation
6.3.3.1 Description and Development Status
Froth flotation is used extensively in mineral
processing to concentrate constituents such as
uranium from ores. Great strides have been made
both in the chemical aspects of flotation and in
equipment development. Today flotation is used for
almost all sulfide materials and is widely used for
nonsulfide metallic minerals, industrial minerals, and
coal. Flotation is the most economical method for
separating particles in the size range of 0.1-0.01
mm.
Metallic ores are normally ground finer than 48 to 65
mesh for treatment in froth flotation, whereas coal
and certain nonmetallic ores are generally treated by
grinding to finer than the 10 to 28 mesh range. As a
rule, coarser feed cannot be suitably mixed and
suspended by a flotation machine. Fineness of grind
is determined by the particle size at which the desired
minerals are liberated from gangue (waste) particles.
In flotation machines, the ore is suspended in water
by means of mechanical or air agitation at a pulp
density generally from 15 to 35 percent solids. The
surfaces of suspended particles are treated with
chemicals called promoters or collectors which render
those particles air-avid and water-repellent.
Through the use of modifying agents, undesired
minerals are depressed or rendered non-floatable.
With vigorous agitation and aeration in the presence
of a frother-a chemical added to create bubbles-a
layer of froth or foam forms at the top of the flotation
machine. The air-avid minerals become attached to
air bubbles and rise to the surface where they collect
m the froth and are skimmed off [2,3,6,10,
11,13,14,17,20,21].
Flotation of sulfide compounds is well established.
Sulfides are separated using alkyl xanthates or
dithiophosphates. Oxide mineral forms can be floated
from acid or basic solutions.
The pH level is established for each mineral oxide
type. Oxides are separated with surfactants. Silicates
and aluminosilicates accept ionic surfactants in the
same way as oxides. Salt-type minerals respond to
anionic surfactants.
Promoters or collectors are added with the ore to
enhance flotation of the particles. The collector also
serves as a water-repellent, which reduces the
moisture content of the froth. Typical collectors for
flotation of metallic sulfides and native metals are
alkyl xanthates and dithiophosphates. These ionized
collectors are adsorbed on a sulfide mineral surface,
with bonding through the sulfur atoms.
In flotation, collectors of fluorspar, phosphate rock,
iron ore, and other nonmetallics are likely to be crude
or refined fatty acids and their soaps, petroleum
sulfonates, and sulfonated fatty acids. Cationic
collectors such as fatty amines and amine salts are
widely used for flotation of quartz, potash, and silicate
minerals.
51
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Commonly used frothers are pine oil, cresylic acid,
polypropylene glycol ether, and 5- to 8-carbon
aliphatic alcohols such as methylisobutylcarbinol and
methyl amyl alcohol. Quantities of frothers required
are usually 0.01 to 0.2 Ib/ton.
Depressants assist in selectivity (sharpness of
separation) or to stop unwanted minerals from
floating. A typical depressant is sodium or calcium
cyanide to depress pyrite (FeS2).
Alkalinity regulators such as lime, caustic soda, soda
ash, and sulfuric acid are used to control or adjust
pH, a very critical factor in many flotation separations.
The choice of reagent is based on past experience
and trial and error, guided by a sketchy knowledge of
surface chemistry. Over the past 40 years a good
deal of research has gone into this problem, but a
great deal more is needed.
Limited information is available in the literature on
flotation cells. Some fundamental research into the
physics of particle capture by bubbles is being
pursued in several Eastern European countries,
presumably in the conviction that a better
understanding of flotation kinetics will lead to practical
improvements in this technique [12].
Mechanical flotation devices are the most commonly
used. Often one type of machine will be used for
roughing and another for cleaning. These machines
provide mechanical agitation and aeration by means
of a rotating impeller on an upright shaft.
In addition, some cells utilize air from a blower to
help aerate the pulp. In recent years, there have been
dramatic increases in the size of individual flotation
cells.
In a cell-type mechanical flotation machine, froth
product discharge is obtained by overflow with or
without the use of mechanical paddles.
In pneumatic flotation machines of both cell and tank
types, mixing of air and pulp occurs in injection
nozzles. In the flotation column, countercurrent flow is
established in the lower section of the column.
Although extensively tested, pneumatic flotation
columns are not common in industry.
Dissolved-air flotation involves the dissolution of air
(or other gas) into the liquid while under pressure,
followed by precipitation. Electroflotation is another
method to create ultrafine gas bubbles, but this
technique uses electrolysis.
6.3.3.2 Potential Applicable Situations
Flotation cells can be considered for use in mill
tailings to reduce the level of radioactivity. The
Palabora Mining Company in South Africa treats
complex ore using flotation and physical separation
techniques to recover copper, magnetite, uranium,
and zirconium [22].
Canadians have used flotation cells to extract radium
from uranium mill tailings [3] and uranium from Elliot
Lake ore [8]. Research conducted at the U.S. Bureau
of Mines shows that 95% of uranium can be
extracted from sandstone ores containing 0.25%
uranium oxide by means of flotation [8].
Of all the ores treated by flotation in the U.S., 66%
were sulfides, 7% metal oxides and carbonates, 24%
nonmetallic minerals, and 3% coal [11]. Although
increasingly used for nonmetallic and oxidized
minerals, flotation is primarily used to extract sulfides
of copper, lead, and zinc from complex ore deposits.
6.3.3.3 Advantages and Disadvantages
Advantages - If the particle fraction containing the
contaminants can be collected by the froth, then
flotation is a very effective tool. High separation rates
for fine particles can be achieved.
Disadvantages - If no suitable additive (promoter or
collector) can be found, then flotation will not be
effective. New additives may have to be developed to
permit successful flotation separation for radiologically
contaminated materials.
Flotation is a complex process, depending for
effective separation on particle size, rate of feed,
control of chemical additives, and handling of the
refined product. The process is also expensive.
Flotation uses small, compact equipment of lower
capital cost but with higher operating costs than for
gravity separation equipment.
6.3.3.4 Information Needs
The characteristics listed below must be considered
in preparing to implement a flotation procedure.
Particle size and shape distribution of the
feed.
Radionuclide distribution with particle size
Characteristics of the soil - clay, humus,
sand, or silt.
Specific gravity and chemical analysis of the
soil.
Mineralogical analysis.
Concentration ratio of solids to liquid forming
the suspension.
The nature of pretreatment.
52
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6.3.4 Gravity Separation
6.3.4.1 Description and Development Status
Gravity methods of separation are used to treat a
great variety of materials. With the advent of the
froth-flotation process, which allows the selective
treatment of low-grade complex ores, use of gravity
separation declined. However, in recent years, many
companies have been using gravity separation
methods due to increasing costs of flotation reagents,
the relative simplicity of gravity processes, and the
fact that they produce comparatively little
environmental pollution. One of the world's largest
uranium processing plants, Palabora Mining Company
in South Africa, recovers both uranium and
baddeleyite using gravity separation techniques [22].
Modern gravity techniques have proved to be efficient
for the concentration of minerals having particle sizes
in the 50-100 micron range [6,8-12,14,17].
Gravity separation techniques exploit differences in
material densities to bring about separation.
Therefore, separation is influenced by particle size,
density, shape, and weight.
All gravity separation devices keep particles slightly
apart so that they are able to move relative to each
other and thus separate into layers of dense and light
minerals. Gravity separators or concentrators are
classified by the means used to achieve this
interparticle spacing. The type represented by jigs
applies an essentially vertical oscillating motion to the
solids-fluid stream. The shaking concentrators or
shaking tables form the second group. These apply a
horizontal shaking motion to the solids-fluid stream
by vibrating the surface. Included in this type are the
shaking table, the Bartles-Mozley concentrator, and
the traditional miner's pan. Gravity flow concentrators
such as sluices and troughs form the third type, in
which interparticle space is maintained by the slurry
flowing down an inclined surface. Jigs and gravity
flow concentrators, which are mainly used in coal,
beach sand, and iron ore processing, will not be
discussed here. However, shaking concentrators
(called tables) used in soil decontamination processes
[23] will be addressed in this chapter.
The shaking table is the most versatile of all gravity
devices that in one pass can produce a high-grade
concentrate over a wide range of particle sizes. The
shaking table is a relatively old device that has slowly
evolved. Generally, shaking tables treat materials finer
than jigs are able to handle, but this is achieved at
the expense of capacity; single deck tables have
relatively low capacity for their cost and space
requirements.
Shaking tables are very versatile units, and are used
for a wide range of functions: from roughing to
cleaning; from the treatment of sands to slimes; from
the separation of two heavy minerals to coal
preparation.
A typical table is illustrated in Figure 17. Feed enters
through a distribution box along part of the upper
edge. The wash water and shaking action spread the
feed out over the table. Product discharge occurs
along the opposite edge and the end. The essentially
rectangular table has an adjustable slope of about
0°-6° from the feed edge down to the discharge
edge. The surface is a suitably smooth material (e.g.
rubber or fiberglass) and has an arrangement of
riffles, which decrease in height along their length
toward the discharge end. Different duties may
require a different deck size or riffle pattern, and a
range of decks are offered by most manufacturers.
Figure 17. Schematic of a shaking table, showing the
distribution of products. (Reprinted from [6].
Copyright © 1982. Reprinted by permission of
John Wiley & Sons, Inc.)
Slurry
FeecL
High Density^
Mineral
Asymmetric
Head
Motion
o
Low Density Mineral
Middlings
Modifications on the basic shaking table design
include the Bartles-Mozley separator, the Holman
slime table, and the Bartles crossbelt concentrator.
6.3.4.2 Potential Applicable Situations
In the soil decontamination processes installed at
Heijmans Milieutechniek and HWZ Bodemsanenng,
both in Holland, tables are used in separating fine
particles from extracting agents [23]. Concentration
by gravity method is limited to those soils in which
the contaminants are relatively coarse and capable of
resisting breakage and sliming or are associated with
other minerals that may themselves be separated by
gravity differential. The concentrate thus obtained can
be processed further by extraction. COG Mineral
Corporation Mill in Utah uses a gravity separator as
part of the uranium extraction process [14].
53
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6.3.4.3 Advantages and Disadvantages
Advantages - Gravity separation is highly efficient
and is a proven process for a wide range of
applications. It gives a high-grade concentrate over
a wide range of particle sizes and functions well with
most soil types.
Disadvantages - A drawback is its low handling
capacity: high throughput requires multiple decks.
Gravity separation requires clean water, so that if
water is recycled care must be taken to ensure there
is no slime buildup.
6.3.4.4 Information Needs
The prerequisite information listed below must be
considered in preparing to implement gravity
separation procedures.
Throughputs.
Feed preparation (natural, sized, classified
hydraulically, etc.).
Feed density.
Characteristics of the soil-sand, clay, humus,
or silt.
Particle size and shape distribution of the
feed.
Specific gravity and chemical analysis of the
soil.
6.3.5 Support Technologies for Treatment of
Liquid Recycle
Most mineral-separation processes require
substantial quantities of water; the final concentrate
has to be separated from a pulp in which the
water/solids ratio may be high. Partial dewatering is
performed at various stages in the treatment, so as to
prepare the feed for subsequent processes. The
separated water is purified and normally recycled.
Dewatering is basically a solid-liquid separation
technique and can broadly be classified into two
types:
sedimentation
filtration
Dewatering is normally needed in any chemical and/or
physical separation process and is a combination of
several methods. The bulk of the water is first
removed by sedimentation, which produces a
thickened pulp with 55-60% solid loading. Filtration
increases the solid loading to 80-90%.
With the exception of dry screening, the various
technologies require the feed to be in the form of a
pulp. Each of these technologies tolerate certain
ranges in the water content beyond which they do not
work efficiently. Figure 18 shows the limits of variation
of the water content in feed pulp that can be tolerated
by screening, gravity concentration, classification,
sedimentation (thickening), and filtration.
Also shown in Figure 18 are limits of water content for
other mineral processing operations, such as
Figure 18. Limits of water content variation. (Reprinted
from [6]. Copyright © 1982. Reprinted by
permission of John Wiley & Sons, Inc.)
I
Mining
Coarse Storage
Crushing
Screening
• Fine Storage
Grinding |
Slurry Transportation
Classification
Concentration
0 10 20 30 40 50 60 70 80 90 100
Water, Volume %
crushing, grinding, storage, drying, and slurry
transportation. Even though these operations may not
apply to a radioactive soil cleaning process, they are
shown for clarity.
6.3.5.1 Description and Development Status
Sedimentation Technologies - Sedimentation
technology can be classified into gravity
sedimentation and centrifugal sedimentation
[6,8,10,11,13,17,18,24].
Gravity sedimentation is the removal of suspended
solid particles from a liquid by settling.
Rapid settling of solid particles in a liquid produces a
clarified liquid, which can be decanted. A thickened
slurry, which may require further dewatering by
filtration remains. Very fine particles, of only a few
microns diameter, settle extremely slowly by gravity
alone.
Coagulants and flocculants are added, producing
relatively large lumps, called floes, which settle out
more rapidly. There are several equipment designs
available for sedimentation. These are:
Deep cone thickeners
Tank thickener
High capacity thickeners
Lamella thickeners
The most common type of sedimentation unit is the
cylindrical continuous tank thickener with mechanical
sludge-raking arms. Feed enters the thickener
through a central feed well, and clarified liquor
overflows around the periphery. Thickened sludge
(the sludge blanket) collects in the conical base and
54
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is raked by the slowly revolving mechanism to a
central discharge point. One of the main
disadvantages of these thickeners is the large floor
area required.
With introduction of flocculant, the settling rates of
suspension could be increased tenfold or more. High
capacity thickeners take advantage of this by
providing mechanical mixing of flocculant and slurry,
and staged additions of flocculant. The high capacity
thickeners are more expensive to operate but provide
better performance and use less space.
The lamella thickener uses a nest of inclined plates,
thus providing a large effective settling area in a
compact space. Flocculants are added to aid the
settling.
Deep cone thickeners are over 4-meter conical
containers equipped with stirrers and overflow and
underflow arrangement. High flocculant dosages are
used to obtain high solid concentrations.
Selective flocculation is an important technique that
uses a high-molecular-weight polymer, which
selectively adsorbs only one of the constituents of a
mixture. Selective flocculation is followed by removal
of the floes of one component. Selective flocculation
has been applied to the treatment of clays, iron,
phosphate, and potash ores.
Centrifugal sedimentation is appropriate for slurries
with very fine particles, since gravity sedimentation
may be very slow. Due to high centrifugal forces,
separation of particles occurs quickly with high
throughputs. The two types of centrifugal
sedimentation designs are hydrocyclone and solid
bowl centrifuges. Hydrocyclones are described in the
chapter on classifiers.
The solid bowl centrifuge is a cylinder into which
slurry is fed and rotated at high speed. The
centrifugal action forces the heavier particles to the
wall of the cylinder, while the liquid forms an inner
layer and is removed. The solids are removed
continuously or intermittently. There are several bowl
designs available.
Newly developed centrifuges can separate particles
as fine as 0.5 micron. Centrifuges have been
engineered that integrate flocculations to ease solid
removal. The newer centrifuges have abrasive-
resistant coatings, require less power to operate, and
are quieter than older versions.
Filtration - Filtration normally follows the thickening
operation [6-8,10, 11,13,14,17-19,24] The filtration
process can be classified into three types:
Deep bed filtration
Screening
Cake filtration
Deep bed filtration uses a deep bed of granular
media, usually sand, as a filter. Mainly used in water
and wastewater treatment plants, it is inexpensive but
cannot remove fine particles.
Screens are also used as dewatering media; they are
described in the previous chapter.
Cake filtration is the most widely used dewatering
technique in mineral processing. Cake filtration is the
removal of solid particles from a fluid by means of a
porous medium that retains the solids while allowing
the fluid to pass. The porous medium used in
industrial filtration is a relatively coarse material;
therefore, clear filtrate is not obtained until the initial
layers of cake have formed. Factors affecting the
cake filtration operation are: the filtering surface,
viscosity of the filtrate, resistance of the filter cake
and filter media, and operating pressure or vacuum
required to overcome the resistance.
Flocculants are sometimes added to aid filtration and
prevent fine particles or slimes from blinding the filter
media.
Cake filtration can be operated in two basic modes:
constant pressure or constant rate. Constant pressure
filtration maintains a constant pressure, but flow rates
fall off as solid cake is formed and resistance
increases. Most of the continuous filters operate on
this principle, using vacuum to provide the pressure
difference. Constant rate filtration requires gradually
increasing pressure as the cake builds up and
increases the resistance to flow.
Cake filtration systems utilize either pressure filters or
vacuum filters. Pressure filters are normally operated
in batch processing mode and vacuum filters
generally in continuous mode.
Pressure filters are widely used in the chemical
industries. The driving force for filtration is the fluid
pressure generated by pumping. Since the filters
work mainly in batch processing mode and are
therefore labor intensive, they have seldom been
used in mineral processing. New concepts such as
continuous filter press are not really continuous
operation systems but go through a series of
automated cycles.
Another new development is the belt filter press
(Manor tower press). Developed in Europe, it is a
continuous pressure filter used in treatment of paper
mill sludge, coal, and flocculated clay slurries [18].
All vacuum filtration techniques use a porous filter
medium to support the filter deposits, beneath which
pressure is reduced by connection to a vacuum
system. The vacuum filtration can be operated in
55
-------
batch or continuous mode. Batch vacuum filters are
rarely used in commercial operation.
The most widely used continuous vacuum filters in
mineral processing are drums, discs, and horizontal
filters. Although different in design, all continuous
vacuum filtration equipment is characterized by a
filtration surface that moves by mechanical or
pneumatic means from a point of slurry deposition
under vacuum to a point of filter cake removal.
A typical drum filter essentially consists of a
horizontal cylindrical drum that rotates while partially
immersed in an open tank, into which slurry is fed
and maintained in suspension by agitators. The drum
shelf itself is covered with a drainage grid and a filter
medium. Vacuum is applied from the interior of the
drum. As the drum revolves, the cake is raised above
the liquid level, and wash water, if required, is
sprayed on the surface.
Various methods are used for discharging the solids
from the drum. The most common form is the use of
a reversed blast of air and a scraper to remove the
cake. Another form is the belt discharge, in which the
filter medium leaves the drum and passes over
external rollers before returning to the drum.
Disc filters operate in a similar fashion and consist of
a number of discs partly immersed in a slurry and
mounted along a hollow shaft, through which vacuum
is applied. The disc is ribbed and supports the filter
media.
The horizontal continuous vacuum filters are
characterized by a horizontal filtering surface in the
form of a belt, table, or series of pans in a circular or
linear arrangement. Horizontal belt filters have been
rapidly accepted in the uranium mining industries,
because of their ability to filter heavy dense solids.
One new development in filtration is filter cake
pressing, in which a squeezing action is applied to a
previously formed filter cake to compress the cake
and remove further moisture. Steam-assisted
vacuum filtration is another new technique to reduce
cake moisture [13].
Electrofiltration is a new technique used for
separation of ultra fine particles (up to 10 microns).
Here the slurry is placed in a direct current electric
field; the negatively charged particles migrate toward
the anode, forming a cake which is further dewatered
by electroosmosis. In the cathode, the slurry is
filtered through a filter cloth by vacuum filtration.
Membrane separation is a new technology that uses a
semipermeable membrane to separate a solid/liquid
system into its components. Physical, chemical, and
electrical means can be applied to enhance the
operation. Membrane separation is expensive and so
is not used in the mining industry. This technique is
usually used to separate very fine particles (0.1-
0.001 micron) from liquid. A manganese-
impregnated acrylic fiber filter has been used to
remove radium from a 3 M NaCI extractant solution
and shows significant promise [20]. A review [25] of
various membranes for uranium extraction concluded
that there is a particularly promising membrane
process called selective membrane mineral extraction
(SMME). The SMME system has been shown to
remove 98 percent of radium from water containing
1,500 pCi/l of the radionuclide. The membrane
techniques can be used with chemical extraction
technology to extract the radionuclide from the
extractant.
6.3.5.2 Potential Applicable Situations
The selection of the particular technique depends on
the throughput required, the particle size, and the
density of the materials. Cylindrical tanks are normally
used as thickeners but, because of the large area
required and the low efficiency of tanks, centrifuges
or high capacity thickeners are appropriate where
there is a space limitation and high throughputs are
required.
Pressure filters used in the chemical processing
industry are rarely used in mining, as batch
operations are expensive; however, pressure filters
can remove fine particles.
Disc filters, and to a large extent drum filters, are the
mainstay for most dewatering systems because of
their ability to remove fine particles. Centrifugal
filtration or electrofiltration may be used to remove
very fine particles.
6.3.5.3 Advantages and Disadvantages [24]
Advantages - Gravity sedimentation is economical; it
carries low maintenance and operating costs. The
technique has a good long track record and is the
simplest of the sedimentation methods.
Centrifuge sedimentation offers high efficiency, high
throughput, and effective separation of fine particles.
One of the main advantages of the drum filters is the
wide range of design (method of discharge, cloth
design, etc.) and operating variation (drum speed,
vacuum operation, submergence cycle, etc.) that
permits treatment of a wide range of particles of
diverse nature. Drum filter operations are clean,
continuous, and automatic with minimal operating
labor. Drum filters are also low in maintenance cost.
Drum filters provide for effective washing of filter cloth
and can also handle very thin filter cakes, resulting in
increased filtration and draining rates with drier
products.
56
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One of the main advantages of disc filters is that they
can handle large volumes of relatively free-filtering
solids (typically 40-200 mesh range). It is possible to
handle different slurries on one unit simultaneously by
partitioning the filter tank and using one or separate
automatic valves. The disc filter equipment provides
for large filter areas on minimum floor space.
Another advantage of disc filters is the rapid medium
replacement made possible by virtue of their design.
in addition, the capital cost of disc filters per unit area
is generally less than for drum filters.
The main advantage of horizontal filters is that large
tonnage per unit area can be processed with rapid
dewatering . Cakes ranging in thickness from 10 mm
to 200 mm can be formed and washed. Horizontal
filtering provides excellent washing with sharp wash
liquid and filtrate separation. In this respect it is better
than the drum filter. Horizontal filter equipment is very
flexible in operation. Since in horizontal filtration the
settling of solid assists the filtration, horizontal filters
are ideal to handle quick settling slurries.
Disadvantages - Gravity separation is ineffective for
fine particles. It involves a long settling time and
requires a large floor area, especially when tank
thicknesses are involved. It chemicals are used,
operating costs will increase.
Disadvantages of centrifuge sedimentation include
high capital cost, with a high maintenance cost that is
higher than other sedimentation procedures.
Equipment is noisy, and is subject to abrasive wear.
Another disadvantage of centrifuge sedimentation is
its high power requirements.
The mam disadvantage of the drum filters is the high
capital cost. Also, certain types of feed cannot be
handled by drum filters, such as quick settling
slurries. Use of blow-back air and a scraper knife to
discharge the filter cake may produce wetter cakes
and greater filter medium wear.
One of the main disadvantages of disc filters is that
they are inflexible in operation. A good washing of the
vertical cake surface is difficult, and because of
limited cake drying time, wetter cakes are formed.
Some designs result in excessive filtrate blow back,
causing the cakes to be moist. Also, the discharge of
thin cakes is difficult. The disc filter equipment has no
means of separating different filtrates if the unit is
used to filter more than one slurry simultaneously.
The rate of medium wear will be high if scraper
discharge is used.
The mam disadvantage of horizontal filters is the
heavy wear and tear of the flexible drainage belts,
which results in loss of vacuum and poor drainage.
The horizontal filter requires a large floor area. In the
case of belt filters, only 45% of the belt area is
effective. Horizontal filters are more expensive than
drum filters, but this disadvantage is offset by the
higher capacity per unit area, since horizontal filters
can handle thicker cakes at higher speeds.
6.3.5.4 Information Needs
The prerequisite information listed below must be
considered in implementing treatment procedures.
Particle size and shape distribution of the
feed.
Radionuclide distribution with particle size.
Specific gravity and chemical analysis of the
soil.
Characteristics of the soil - sand, humus,
clay, or silt.
Mineralogical analysis.
The concentration ratio of solids to liquid
forming the suspension.
The nature of pretreatment.
6.4 Typical Costs of Physical Separation
Technologies
The cost of the application of any of the physical
separation technologies described in this section will
depend upon several factors. Thus the costs cannot
be reliably estimated for any technology and for any
site at this stage, because most of the required
prerequisite information is not available.
Among the cautions must also be included the fact
that many, if not most, of the controlling factors will
be site-specific. The cost for a technology at one
site may be vastly different than for the same
technology applied at another site.
Despite the limitations and cautions, some typical
cost information is provided in Table 16 for the
technologies described in this chapter. The costs
shown do not include cost of transportation and
disposal of concentrated fractions. The cost of
returning "clean" treated material to a site is not
included.
The purpose, capacity, equipment and operating
costs in 1987 dollars, and factors affecting both cost
and capacity are presented for the major types of
physical separation equipment.
57
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Table 16. Typical Costs of Major Physical Separation Equipment
These costs obtained from vendors are presented to give some typical costs. They are not intended to be applicable to any particular site. Cost
of returning "clean" treated material to a site is not included.
Equipment
Soil Prep. Package
(grizzly crusher,
screen, feeder)
Screw Classifier
Hydrocyclone
Corrugated Plant
Interceptor
Clanfier
Drum Filter
Centrifuge
Flash Dryer
Flotation Unit
Purpose
To prepare soil for
leaching
Preliminary separation of
coarse and fines
Intermediate Classification
of sand and silt
Gravity separation of siit
and fines
Gravity separation of fines
Removal of all suspended
solids
Removal of unfilterable
solids
To dry settled or filtered
solids
For the selective
separation of fines
Capacity
50 - 600 TPH
10 - 950 TPH
50 - 500 GPM
60 - 1000
GPM
60-6000 GPM
0.5 - 90 TPH
10 -600 GPM
700 - 36K
# water/hr
30 - 1000
GPM
Equipment
Cost in
1987 $
500K-
2500K
9K - 167K
1K-5K
4K - 74K
40K - 520K
50 - 400K
60K - 850K
200K -
1800K
25K - 160K
4 -
3 -
1 -
Gal
2 -
6-
80
77 •
Gal
120
15
Gal
Operating
Cost in
1987 $
1/Ton
1ATon
0.30/1000
1/1000 Gal
1/1 000 Gas
• 2/Ton
• 7/1000
- 21/1000*
•3/1000
Factors Affecting Cost and Capacity
Soil type, site conditions, truck access,
dust control
Soil type, availability of water radioactive
shielding, corrosive resistance
Corrosion and abrasion resistance
Corrosion resistance, radioactive
shielding, degree of separation
Same as above
Corrosion resistance, radioactive
shielding, shelter
Corrosion resistance, radioactive
shielding, shelter
Corrosion resistance, radioactive
shielding, multilevel construction,
emissions control
Corrosion resistance, radioactive
shielding
6.5 References
1. Borrowman, S.R., and P.S. Brooks. Radium
Removal from Uranium Ores and Mill Tailings.
U.S. Bureau of Mines Report 8099, 1975.
2. Garnett, John, et al. Initial Testing of Pilot Plant
Scale Equipment for Soil Decontamination. U.S.
Dept. of Energy, RFP 3022, 1980.
3. Raicevic, D. Decontamination of Elliot Lake
Uranium Tailing. CIM Bulletin, 1970.
4. G. Weismantle. Liquid Solids Separation and
Filtration - Current Development. Chemical
Engineering, Feb. 6, 1984.
5. Roberts, E. J., and P. Stavenger, et. al.
Solid/Solid Separation. Chemical Engineering
Desk Book Issue, February 15, 1971.
6. Kelly, E.G., and D.J. Spottiswood. Introduction to
Mineral Processing. John Wiley, New York, 1982.
7. Galkin, N.P. The Technology of the Treatment of
Uranium Concentrates. Pergamon Press, New
York, 1963.
8. Organization for Economic Cooperation and
Development. "Uranium Extraction Technology."
OECD, Paris 1983.
9. Clark, Don A. State of the Art: Uranium Mining,
Milling, and Refining Industry. EPA-660-2-
74-038 USEPA, Corvallis, Oregon, 1974.
10. Merritt, R.C. The Extractive Metallurgy of
Uranium. Colorado School of Mines Research
Institute, 1971.
11. Wills, B.A. Mineral Processing Technology.
Pergamon Press, New York, 1985.
12. O'Burt, Richard. Gravity Concentration
Technology. Elsevier, New York, 1984.
13. Wills, B.A., and R.W. Barley. Mineral Processing
at a Cross Road - Problem and Prospects.
Martinus Nijhoff Publishers, Boston, 1986.
14. Mular, A.L., and R.B. Bhappu. Mineral Processing
Plant Designs. American Institute of Mining,
Metallurgical and Petroleum Engineers, Inc., New
York, 1980.
15. Mathews, Chris W. Screening. Chemical
Engineering Desk Book Issue, February 15, 1971.
16. Institute of Mechanical Engineers. Screening and
Grading of Bulk Materials. Mechanical
Engineering Publications Ltd., London, 1975.
58
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17. Perry, R., and C.H. Chilton. Chemical Engineer's
Handbook. McGraw Hill, New York, 1973.
18. Svarovsky, L. Advances in Liquid-Solid
Separation. Chemical Engineering, July 1979.
19. Poole, J.B., and D. Doyle. Solid-Liquid
Separation. Chemical Publishing Co., New York,
1968.
20. Ryan, R.K., and D.M. Levins. Extraction of
Radium from Uranium Tailings. CIM Bulletin,
October 1980.
21. Ives, Kenneth J. The Scientific Basis of Flotation.
Martinus Nijhoff Publishers, Boston, 1984.
22. Burt, R.O. Gravity Concentration Technology.
Elsevier, New York, 1984.
23. Assink, S.W. Extraction Method for Soil
Decontamination: A General Survey and Review
of Operational Treatment Installation. In:
Proceeding of 1984 International TNO Conference
on Contaminated Soil. Martinus Nijhoff Publishers,
Boston, 1985.
24. Svarovsky, L. Solid-Liquid Separation.
Butterworths, Boston, 1977.
25. Kosarek, L. J. Uranium Extraction and In Situ Site
Restoration via Membrane Technology. 1979
Mining Yearbook. 1979.
59
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Chapter 7
Combined Physical Separation and Chemical Extraction Processes
7.1 Purpose and Mode of Operation
Employing physical separation techniques, it may be
possible to decontaminate soil to low radiation levels
by separating the highly contaminated particles on the
basis of particle sizes. While the coarse soil particle
fractions might still contain radiation above acceptable
levels, removal of radioactive contaminants from them
might allow return of the soil to the place of origin or
placement in a nonhazardous waste landfill. While
applying further physical separation techniques would
not lower the radiation levels, chemical separation
technologies applied to the separated coarse particles
might bring the treated soil radiation to acceptable
levels. This chapter discusses the various combined
physical and chemical separation techniques that
might be applied to decontaminate radioactive soils.
7.2 State of the Art
Three physical and chemical separation techniques
will be discussed:
soil washing and physical separation
separation and chemical extraction
separation, washing and extraction
Soil washing and physical separation has been used
in two pilot plant tests to decontaminate plutonium
contaminated soil [1] and to extract radium from
uranium mill tailings [2].
Separation and chemical extraction have been used
extensively in the mining industry, in particular for
extracting uranium. Palabora Mines in South Africa
uses gravity separation techniques followed by
chemical extraction to separate uranium from complex
copper ores [3-6].
Separation, washing and extraction have been used
to decontaminate soils [7-10].
Table 17 shows the state of the art of the combined
physical separation and chemical extraction
technologies. All these technologies are in the pilot
plant testing stage, and none have been field
demonstrated with radioactive material. Major pilot
plant testing and development work are needed prior
to application of these technologies to radiologically
contaminated site remediation.
7.3 Technologies of Potential Interest
7.3.7 Soil Washing and Physical Separation
7.3.1.1 Description and Development Status
This process involves washing the soil with chemical
solution, followed by separation of coarse and fine
particles [1]. The type of solution used for washing
will depend on the contaminant's chemical and
physical composition.
The process water, which may lead to radioactive
buildup in process streams, is treated-preferably
by ion exchange-end the resulting decontaminated
water is recycled.
In 1972 the Department of Energy initiated
laboratory-scale studies of techniques for
decontaminating soils [1]. Experiments were
conducted to evaluate a variety of chemical and
physical separation techniques. The techniques
included chemical oxidation, calcination, flotation,
desliming, heavy media separation, magnetic
separation, wet and dry screening, and washing.
Based on laboratory-scale studies, the washing and
physical separation process was selected for pilot
plant investigation. The pilot-plant process flow
sheet is shown in Figure 19.
In the pilot-plant testing at Rocky Flats, the
plutonium-contammated soil was washed in a
rotating drum washer using a pH 11 NaOH solution
as a washing agent. A trommel screen was used to
separate the coarse particles ( + 5 mesh), and a
vibrating screen was used for further particle
separation ( + 35 mesh). This was followed by use of
a hydrocyclone and classification to separate +10
micron particles. Centrifugation and ultrafiltration were
employed to separate the fine contaminants. The
water was sent back for recycle without any
purification.
The results of the pilot-plant testing show this
process could have potential for success, but
61
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Table 17. State of the Art of Combined Physical Separation and Chemical Extraction Technologies
Technology
Bench Pilot
Laboratory Scale Plant
Testing Testing Testing
Field
Demonstration Radiologically
with Contaminated
Radioactive Site
Material Remediation
Remarks
Combined Physical
separation and chemical
extraction
Soil washing and
physical separation
Separation and
chemical extraction
Separation, washing
and extraction
Pilot plant development and testing needed for
radioactive materials
Various portions of the process have been
developed for extraction of uranium from ores.
Pilot plant testing and development needed for
radioactive materials
Significant bench scale and pilot plant testing
needed for radioactive material
additional pilot development work is needed before
scale-up to production level. In pilot-plant test runs,
soils contaminated to 45, 284, 7515, 1305, and 675
pCi/g were cleaned to contamination levels of 1, 12,
86, 340, and 89 pCi/g respectively, using different
processes (Table 18). The coarse particle fraction
ranged from 58% to 87%. The results of pilot-plant
testing showed the fine soil particle fraction containing
the concentrated contaminants to have much higher
levels of radiation than the feed, ranging from 1440
pCi/g to 90,000 pCi/g. Feed rates ranged from 45
kg/hr to 120 kg/hr.
Recommendations based on the pilot-plant testing
were that applying multistage washing and rinsing
instead of single stage would be beneficial.
Hydrocyclones and filtration techniques were
recommended for removal of fine particles.
Centrifuging of flocculated solution was not
recommended, as the centrifuge action tends to
break the floes.
The Canadians used the froth flotation technique to
separate radium from uranium mine tailings [2].
Results of their laboratory testing and bench-scale
Table 18. Soil Product Plutonium Level from Pilot Plant
Operational
Runa
1
2
3
4
5
Feed
(pCi/g)
45
284
7515
1305
675
Product
Coarse
Fraction
( + 35 Mesh)
0.5
12
86
340C
89
Weight
Fraction
%
__b
58
78
87
58
Fine
Fraction
(-35 Mesh)
1440
1485
90,000
10,800
5.850
Weight
Fraction
%
42
22
13
42
3 Each run represents a different process.
b Not available.
c Attributed to inadequate washing and scrubbing
testing at CANMET show that radium in uranium mill
tailings can be reduced from 290-230 pCi/g to 50-
60 pCi/g by flotation.
However, in the pilot-plant testing at Dennison Mill
using the same process, the decontaminated tailings
showed radium levels of 123-151 pCi/g. This was
Figure 19. Conceptual soil decontamination process flow sheet (Reprinted from [2].)
Recycle Water
—>| Physical
Separation
)! Water Recycle ]
Contaminated '
Soil
Return to <- _.
Landfill
Ship for
Disposal
62
-------
attributed to recycling the water. Whereas both the
laboratory and bench-scale testing used fresh city
water with no radium in it, the pilot-plant test water
contained relatively high amounts of dissolved radium,
ranging between 586 and 1179 pCi/g.
7.3.1.2 Potential Applicable Situations
The soil washing and physical separation process can
be considered for use in situations where radioactive
contaminants are closely associated with fine soil
particles. Better success can be obtained with sandy
soils; humus soils will be difficult to clean.
7.3.1.3 Advantages and Disadvantages
Advantages - The process is simple and relatively
inexpensive and should require no major process
development. It has achieved some degree of
separation with clay soil in pilot-plant testing [1].
Disadvantages - The main disadvantage is that this
process may not work for humus soil. Also, pilot-
plant development and testing are needed. The
process may work only for low level radiologically
contaminated soils; this is yet to be determined by
pilot-plant testing. The recycled water must be
stripped of radioactive contaminants or the process
will become inefficient.
7.3.1.4 Information Needs
The information listed below must be collected and
considered before implementing soil scrubbing and
physical separation procedures.
Nature of the soil: sandy, clay, humus.
Nature of the particle: size, shape, specific
gravity, mineralogical and chemical properties,
etc.
Radionuclide distribution with particle size.
Nature of the contaminant-chemical and
physical properties.
7.3.2 Separation and Chemical Extraction
7.3.2.1 Description and Development Status
The soil would first be separated to fine and coarse
particle fractions. The coarse particle fraction would
be acid leached, the radioactive contaminants
stripped by solvent extraction and separated by
precipitation and/or ion exchange. The extractant
would be cleaned and recycled. The fine particle
fraction would be combined with extracted
contaminants and sent to a secure disposal site. The
clean coarse fraction would require appropriate
disposal.
Processes using solvent extraction, ion exchange,
and acid leaching, etc., have been used in extraction
of uranium from ores and radium from uranium mill
tailings [6,11-13]. In mining, since the objective is to
extract maximum quantities of the desired
constituents (uranium and radium) from the ores and
tailings, the leaching is applied to the feed as a
whole, without separating into fine and coarse
fractions. Although the process can be applied to the
unseparated soil, this may not bring contaminant
concentrations to the acceptable levels. Since the
weight fraction of the coarse soil particle portion
ranges from 60-80% [1], and since its contaminant
radiation levels will be lower to start with, cleaning the
coarse fraction could possibly clean a large
percentage of the soil to acceptable standards.
There are several variations on the above process.
Two-stage acid leaching instead of solvent
extraction is one variation [14]. Another is to use ion
exchange instead of solvent extraction, a technique
used in several uranium extraction processes [6]. A
third variation is to use a solvent to extract uranium
and a salt solution to extract radium from acid leach
residues [12].
The Canadians [14] have used leaching solution to
extract thorium, radium, and uranium from uranium
ore. Two-stage hydrochloric acid leaching was
employed, which resulted in mill tailings with radium
levels of 15 to 20 pCi/g.
In Europe, several solvent extraction techniques have
been used to clean soil contaminated with cyanides,
heavy metals, and organics [7]. In these processes, it
is the fine fraction that receives the benefit of soil
cleaning methods, since the contaminants are mainly
associated with the fine particles. The estimated
typical cost to clean soil in Europe is around $100/ton
[7]. This is exclusive of excavation and transportation
costs, overheads, profits, and cost for safety
measures [10].
Details of different chemical extraction techniques are
discussed in Chapter 5 of this report. Physical
separation techniques that can be used are discussed
in Chapter 6.
7.3.2.2 Potential Applicable Situations
Separation and chemical extraction can be
considered for use in sandy, clay, and humus soils.
This type of process has been used, with limited
success, to extract radium from uranium mill tailings
in pilot plant testing. A large concentration of sulfide
in the soil will have a marked effect on the radium
extraction [12].
7.3.2.3 Advantages and Disadvantages
Advantages - An advantage of this process over
other methods discussed in this chapter is that soils
containing higher levels of radioactivity can be
63
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treated. Also, various facets of the process have been
developed for extracting uranium, and laboratory work
is underway in Canada for extracting radium from
uranium mill tailings. However, the development of
various facets of a process does not mean the entire
process will work.
Disadvantages - The main disadvantages of this
process are that it is expensive and has high
chemical usage. The chemical required will depend
on the soil analysis. A problem may arise with high
sulfur content in the soil interfering with radium
extraction. Also, the process needs major
development work prior to application in extracting
radium from soil. In addition, the use of chemicals
raises concerns of plant safety and environmental
pollution. This approach may not be successful in
extracting radium, thorium, and uranium in a single
process.
7.3.2.4 Information Needs
The information listed below must be considered in
implementing treatment procedures.
Nature of the soil: sandy, clay, humus, silt.
Physical and chemical properties of the soil.
Nature of the particle: size, shape, specific
gravity, mineralogical properties.
Radionuclide distribution with particle size.
Nature of the contaminant: chemical,
physical, and mineralogical properties.
Concentration ratio of solid to liquid forming
the slurry.
The nature of pretreatment.
7.3.3 Separation, Washing and Extraction
7.3.3.1 Description and Development Status
Following separation, contaminated soils conceivably
can be scrubbed with a variety of washing fluids,
followed by chemical extraction. The nature of the
washing fluids and chemicals would depend on the
contaminants and the characteristics of the soil. It is
most effective to separate the soil into fine and
coarse fractions and use the scrubbing system on the
coarser soil fraction to reduce the throughput and
chemical usage. The treated coarse soil might then
be returned to the site. The finer soil fractions and
contaminants could be sent to disposal. Depending
on the soil grain size distribution, reduction in disposal
volume of 60-80% may be possible.
The agents that can be applied to soil washing are:
Surfactants that improve the solubility of the
contaminants and the tendency for fine
particles to separate from larger ones.
Chelating additives used to chemically react
with metals.
Acid or alkaline solutions to mobilize and/or to
improve solubility of the contaminant.
Washing solutions are basic aqueous solutions
(caustic, lime, slaked lime, or industrial alkali-based
washing compounds); acidic aqueous solutions
(sulfuric, hydrochloric, nitric, citrus, phosphoric, or
carbonic acids); or solutions with surfactant or
chelating agents. Hydrogen peroxide, sodium
hypochlorite, and other oxidizing agents may also be
used. A strong basic surfactant solution could be
used for organic extraction, and strong acidic or
chelating agent solutions can be used for metal
extraction. Strong base or acid might be used in
cases of high contaminant concentration, where the
cost of chemicals is affordable and the wastewater
can be treated for safe disposal. Surfactant and
chelating agent soil cleaning are being developed to
reduce chemical and equipment costs, make the soil
reusable, and simplify wastewater treatment. The
surfactant and chelating solutions have a moderate
(almost neutral) pH, making equipment operation
safer.
The EPA Soil Washing System, developed by the
EPA Risk Reduction Engineering Laboratory at
Edison, NJ, uses a scrubber extraction process to
clean soil. Pilot studies were performed to select the
equipment for the EPA soil washer. Three unit
operations were developed and proved by testing:
• Water Knife Concept - A thin, flat, high-speed
water jet breaks up clumps of soil and scrub
contaminants from larger soil particles like stone
and gravel. Testing showed that this concept is
very effective.
• Rotary Drum Screener - A rotary drum was
employed as a pretreatment to mix the soil with
the extractant and separate the soil into two
particle size categories ( + 2mm and -2mm).
• Extraction and Separation Concept - A four-
stage counterflow extraction train was designed
and built to treat the -2mm soil fraction
separated by the drum screener. Each stage
consists of a tank, stirrer, hydrocyclone, and
circulating pump. The pump moves the soil from
one stage to the adjacent stage. The
hydrocyclone discharges the soil slurry in the next
stage and returns the extractant. The extractant
flows by gravity as a tank overflows in a stream
from one tank to another, counter to the direction
of the soil. Fresh extractant is added to the fourth
stage, and spent extractant is removed from the
first stage.
A mobile soil washing pilot-plant was built using the
above features [15]. The pilot-plant scheme (Figure
20) was designed for water extraction of a broad
64
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Figure 20. Simplified process flow diagram of the EPA soil washer. (Reprinted from [15).
Contaminated
Soil
^
Soil/Size
] Classification
1 System
Oversize
Materials/
Debris
Air cleaner j
'T-
i
j Countercurren
! >| Chemical
! | Extractor
"
Spent j
t 1 Pressure Filter Reclaimed
1 I Drying Bed Soils
-•
Recycled
| Solvent 1
Squeezate/
Runoff etc
Waste
Sludge
range of hazardous materials from spill-
contaminated soils.
The system can (1) treat excavated contaminated
soils, (2) return the treated soil to the site, (3)
separate the extracted hazardous materials from the
washing fluid for further processing and/or disposal,
and (4) decontaminate process fluids before
recirculation or final disposal. The washing fluid
(water) may contain additives, such as acids, alkalies,
detergents, and selected organics solvents to
enhance soil decontamination. The nominal
processing rate will be 3.2 cu m (4 cu yd) of
contaminated soil per hour when the soil particles are
primarily less than -2mm in size and up to 14.4 cu
m (18 cu yd) per hour for soil of larger average
particle size.
7.3.3.2 Potential Applicable Situations
The concept can be considered for use with granular
soil. Clay and humus soil may be difficult to clean
using countercurrent extraction. Pilot-plant testing is
needed to determine the effectiveness of the process.
The EPA Mobile Soil Washer was used to remove
nonradioactive contaminants from soil. With
equipment modifications and additions and significant
bench-scale and pilot-plant testing, the unit can be
considered for use to clean radiologically
contaminated soils.
7.3.3.3 Advantages and Disadvantages
Advantages - It is possible that soils can be cleaned
to acceptable limits. The same countercurrent
decantation technology has been used in uranium
extraction. However, pilot plant testing is needed to
determine the effectiveness of this process.
Disadvantages - The Soil Washing System needs
further development to determine washing fluids that
are effective in removing radioactive contaminants
from soils.
The most suitable type of washing fluid must be
determined using a bench-scale test for each soil. A
process to clean the contaminated washing fluid for
recycle must be established through pilot-plant
testing. The process may not work for clay or humus
soils. Significant bench-scale and pilot-plant testing
is needed.
7.3.3.4 Information Needs
The soil and contaminant characteristics listed below
must be considered in implementing treatment
procedures.
Nature of the soil: sandy, clay, humus.
Nature of the particle: size, shape, specific
gravity, mineralogical and chemical properties,
etc.
Radionuclide distribution with particle size.
Nature of the contaminant: chemical and
physical properties.
7.4 Typical Costs of Separation and
Extraction Technologies
It must be noted that most of the cost controlling
factors for cleaning soil using the separation and
extraction technology will be site specific. In addition,
the combined technology has not been demonstrated
to clean radiologically contaminated sites. Since the
65
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detailed process information is lacking, the cost for
this technology cannot be reliably estimated.
However, the estimated typical cost for cleaning
nonradioactive contaminated solid using separation
and extraction technology ranges from $45 -
$100/ton (1985 $) [7], exclusive of excavation,
transportation, and disposal costs for all fractions.
These costs are not intended to be applicable to any
particular site. Costs of returning "clean" treated
material to a site are not included.
7.5 References
1. Garnett, John, et al. Initial Testing of Pilot Plant
Scale Equipment for Soil Decontamination, US
Dept. of Energy, RFP 3022, 1980.
2. Raicevic, D. Decontamination of Elliot Lake
Uranium Tailing. CIM Bulletin, August 1970.
3. Wills, B.A. Mineral Processing Technology.
Pergamon Press, New York, 1985.
4. Wills, B.A., and R.W. Barley. Mineral Processing
at a Cross Road - Problem and Prospects.
Martinus Nijhoff Publishers, Boston, 1986.
5. Merritt, R.C. The Extractive Metallurgy of
Uranium. Colorado School of Mines Research
Institute, 1971.
6. Clark, Don A. State of the Art: Uranium Mining,
Milling, and Refining Industry. EPA-660-2-
74-038 USEPA, Corvalhs, Oregon, 1974.
7. Assink, S.W. Extraction Method for Soil
Decontamination: A General Survey and Review
of Operational Treatment Installation. In:
Proceeding of 1984 International TNO Conference
on Contaminated Soil. Martinus Nijhoff Publishers,
Boston, 1985.
8. Schulz, Robert, and Joseph Milanowski. Mobile
System for Extracting Spilled Hazardous Materials
from Excavated Soils. In: Hazardous Materials
Spill Conference, Milwaukee, Wisconsin, 1982.
9. Rulkens, W.H., and J.W. Assink, et. al. Extraction
as a Method for Cleaning Contaminated Soil:
Possibilities, Problems and Research. In:
Conference on Management of Uncontrolled
Hazardous Waste Sites, Washington, DC, 1984.
10. Rulkens, W. H., and J. W. Assink, et. al.
Development of an Installation for On-Site
Treatment of Soil Contaminated with Organic
Bromine Compounds. In: Conference on
Management of Uncontrolled Hazardous Waste
Sites, Washington DC, 1982,
11. Logsdail, D.H. Solvent Extraction and Ion
Exchange in the Nuclear Fuel Cycle. John Wiley
& Sons, New York, 1985.
12. Ryan, R.K., and D.M. Levins. Extraction of
Radium from Uranium Tailings. CIM Bulletin,
October 1980.
13. Ives, Kenneth J. The Scientific Basis of Flotation.
Martinus Nijhoff Publishers, Boston, 1984.
14. Perry, R., and C. H. Chilton. Chemical Engineer's
Handbook. McGraw Hill, New York, 1973.
15. Traver, R. D., In-Situ Flushing and Soil Washing
Technologies for Superfund Site.
RCRA/Superfund Engineering, Technology
Transfer Symposium, 1986.
66
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Chapter 8
General Issues at Radiologically Contaminated Superfund Sites
8.1 Introduction
This chapter discusses some of the issues likely to
be associated with remediating Superfund sites that
contain radioactive materials. The discussion is not,
by any means, comprehensive. These issues include:
disposal siting;
handling of concentrated residuals;
site information needs;
mixed wastes;
public reaction and acceptance; and
costs.
8.2 Disposal Siting
Every site remediation involving radioactive materials
must include a final, environmentally safe disposal
site for the radioactive materials. The total activity of
the radionuclides will not be lessened by any
remediation process, although the matrix in which
they are included may be reduced in volume by some
of the technologies discussed.
Site selection for disposing of radioactive materials is
already a sensitive issue. As noted in the discussion
of land encapsulation in Chapter 2, states are
beginning to restrict the use of land within their
borders for the disposal of commercial low-level
waste from other states.
Any disposal site for radioactive waste must be
selected or constructed such that it contains the
radionuclides as long as their concentrations are
unacceptable for release to the environment.
There are several guidance documents available from
EPA that provide information that should be
considered in selecting the location of a disposal site
[1-4].
8.3 Handling of Concentrated Residuals
Chemical extraction and physical separation
techniques applied to soil to remove radionuclides are
intended to clean the soil and reduce the volume of
contaminated materials. If that is done, there will be
fractions in which the radionuclides will be much
more concentrated--!.e., the radioactivity per unit
volume will be much higher. Handling and disposal of
the concentrated materials will require precautions
appropriate to the activity level. DOT and NRC
regulations for containment and storage of radioactive
materials provide guidance for this situation.
Final disposal may be even more difficult after volume
reduction than it would be if the material were to be
excavated, transported, and disposed of without
treatment for volume reduction. In addition the
"clean" fractions may contain traces of toxic
chemicals used in the treatment process, along with
some traces of the radioactive contaminants.
Therefore, these fractions also may require
environmentally safe disposal.
Any attempt to put "cleaner" soil off site is likely to
meet with the same resistance as locating a disposal
site for all the material in the first place. The goal
would be to have a portion clean enough to be
replaced at the site.
8.4 Site Information Needs
For many sites, available information is limited
regarding the detailed physical, chemical, and
mineralogical characteristics of the matrix materials
associated with the radioactive contaminants. In some
cases, even the nature of the radionuclides present
does not appear to be known with certainty. More
detailed information is essential if use of chemical
extraction and/or physical separation techniques is
considered.
8.5 Mixed Wastes
Sites that contain radioactive waste materials may
also contain other types of hazardous waste. Some of
the Superfund sites contain various types of
hazardous wastes and the radioactive portion may
pose a relatively minor threat by comparison. The
presence of other hazardous materials may
complicate dealing with the radioactive portion of the
waste and vice-versa. This is an issue that is likely
to arise at many Superfund sites and would impact
the possible utility of some of the remediation
technologies. The disposition of waste containing both
67
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radiological and chemical constituents ("mixed
wastes") poses unique problems that will have to be
addressed early in the technology screening process.
8.6 Public Reaction and Acceptance
Public concerns with respect to Superfund sites may
be magnified where radioactive wastes exist.
Concerns can be expected regarding the
contaminated site, moving the material (if necessary),
any processing or treatment location, and final
containment.
8.7 Costs
All methods with the exception of in situ techniques
will involve excavation costs for the materials.
Application of some of the technologies may result in
a reduced volume of radiologically contaminated
materials to be sent to a secure disposal suitable for
such materials. The cost of such disposal would
include transportation and land encapsulation. The
"cleaner" fractions remaining after a treatment
process is completed must be analyzed for residual
contamination and evaluated for replacement at the
point of origin or at a suitable alternative site. There is
a cost associated with this placement.
Costs associated with a treatment technology can be
divided into development and implementation costs.
Development costs include several stages of
laboratory tests, studies and process designs leading
to pilot-scale testing, and final design. Additional
development costs involve fabrication, shakedown,
and final testing of a full-scale system under
controlled and field conditions. These costs could
range from under $1 million for a small system
applicable to one specific type of problem to many
millions for a larger system with numerous
subsystems, and applicable to numerous types of
problems.
Implementation costs when a treatment option is
chosen for a given site include mobilization and
demobilization, and operating costs. The mobilization
costs include all costs associated with performing
site-specific laboratory and/or pilot-scale testing;
selecting an operating site; preparing any permit
application materials or other administrative
documentation necessary for operations; interface
with local, state, and federal officials for such permits;
transportation, setup, and shakedown of the treatment
system on the site (including any site modifications
such as installation of water supply wells, power, road
access, operating areas, buildings, and other such
logistical site features); performing site-specific
testing to determine if the full-scale system performs
according to the laboratory and pilot-scale
predictions; and any other pre-operating types of
costs. Mobilization costs may range from a few tens
of thousands of dollars for a simple, small site to
multiple millions at a site with a large, complex
installation where complicated permitting issues have
been involved.
After operations are complete, demobilization costs
incurred include those associated with
decontamination of the entire system and surrounding
operating site, disassembly and transport of the
system, final determination and documentation that
the treatment site has met the ARARs and has been
brought to a state protective of human health and the
environment, preparation of operations documenta-
tion, and any other site-specific costs associated
with the post-operation period. These costs can
range from a few tens of thousands of dollars to a
million dollars or more, depending upon the
complexity of the installation and the degree of
contamination.
Operating costs include all those labor and material
costs needed to operate the treatment system at the
site, sometimes on a 24 hour-per-day basis; to
provide for site security and personnel safety; to
maintain record-keeping including permit-related or
mandatory administrative documentation for all site
actions; and to maintain the system in good operating
order. The costs per ton or per cubic yard must
include all applicable operating costs. These
operating costs per cubic yard are dependent upon
the capacity of the treatment system and the
percentage of the time that the system is operating as
opposed to being in a maintenance mode.
Operating costs depend largely upon the cost of labor
at the site. Special protective clothing and special
handling of the contaminated materials (particularly
the concentrated materials) could raise labor costs
well above those that might be expected for a
comparable crew size working at a nonradioactive
Superfund site. Some costs may be reduced due to
efficiencies in personnel monitoring and
decontamination of workers and equipment compared
to some of the lengthy procedures required for
hazardous chemicals, since radiation is relatively easy
to measure, especially compared to many chemicals.
Overall, the operating cost, if it is assumed to be
similar to on-site incineration operations would
probably range from several hundred dollars per cubic
yard for a large, high-capacity system with a high
percentage of operating time, to several thousand
dollars per cubic yard for smaller capacity systems
having numerous maintenance problems and a large
crew.
The costs must include disposal costs for
concentrated material and will be highly dependent on
how far treatment must be taken to allow unrestricted
disposal of the "cleaner" portion.
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The costs of treatment for individual sites and groups
of similar sites can be examined in further detail to
determine the likely costs of such treatment and how
those costs compare with the costs of transportation
off site and land encapsulation.
8.8 References
1. U.S. Environmental Protection Agency. Combined
NRC-EPA Siting Guidelines for Disposal of
Commercial Mixed Low-Level Radioactive and
Hazardous Waste, OSW-USEPA. March 13,
1987.
2. U.S. Environmental Protection Agency. Criteria for
Location Acceptability and Existing Applicable
Regulations - Phase I - Permit Writers' Guidance
Manual for Hazardous Waste Land Storage and
Disposal Facilities, USEPA. OSW-Fmal Draft,
February 1985.
3. U.S. Environmental Protection Agency. Criteria for
Identifying Areas of Vulnerable Hydrogeology
under RCRA - Statutory Interpretive Guidance -
Guidance Manual for Hazardous Waste Land
Treatment, Storage, and Disposal Facilities,
OSW-USEPA, Interim Final, July 1986.
4. U. S. Environmental Protection Agency.
Standards for Cleanup of Land and Buildings
Contaminated with Residual Radioactive Materials
from Inactive Uranium Processing Sites. 40 CFR
192.12, 48 FR 602. January 5, 1983.
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Chapter 9
Criteria for Further Studies
9.1 Introduction
Any choice of remediation technologies for radioactive
wastes at Superfund sites would have to be site-
specific. Since none of the chemical extraction and
physical separation technologies has been used in a
site remediation situation, their application must be
approached cautiously. The same holds true for
solidification or stabilization processes. Essentially,
only land encapsulation has been used to remediate
similar sites; ocean disposal has been used for low
level radioactive wastes [1-3].
9.2 Alternative Assessment Studies
A complete site characterization would include
mineral analysis, particle size distribution, radionuclide
contaminant distribution on various size fractions, soil
texture and permeability, moisture content, etc. A list
of some important site and waste characteristics that
may affect the applicability and effectiveness of
various technologies is presented in Table 19 [4].
Since further developments and studies on alternative
technologies for each Superfund site may be very
expensive, it is important to study the patterns in
waste characteristics at various sites and develop
waste groups with similar major characteristics.
Alternative assessment studies can be used to help
select the alternative technologies to treat each waste
group. Thus, a preliminary screening of technologies
can be accomplished based primarily on the waste
characteristics.
Based on these alternative assessment studies, one
or more technologies, individually or in combination,
can be selected for further investigation.
Physical separation and combined physical separation
and chemical extraction techniques will not apply if
radionuclides are uniformly distributed through all the
soil size fractions. This, however, is unlikely. The
highest concentration of radioactive materials appears
to be contained in very fine particles [5,6].
Chemical extraction technologies may be applicable
to tailings and contaminated soils but may not be
applicable to building debris and contaminated
Table 19. Site and Waste Characteristics that Impact
Remediation Technologies
Site Characteristics
Site Volume
Site Area
Site Configuration
Disposal Methods
Climate
- Precipitation
- Temperature
- Evaporation
Soil Texture and Permeability
Soil Moisture
Slope
Drainage
Vegetation
Wasfe Characteristics
Quantity
Chemical Composition
Mineral Composition
Acute Toxicity
Persistence
Biodegradability
Total Radioactivity
Radioisotopes and Concentration
Ignitability
Reactivity/Corrosiveness
Treatability
Thermal Properties
Depth of Bedrock
Depth to Aquicludes
Degree of Contamination
Cleanup Requirements
Direction and Rate of Ground-
water Flow
Receptors
Drinking Water Wells
Surface Waters
Ecological Areas
Existing Land Use
Depths of Ground Water
or Plume
Infectiousness
Solubility
Volatility
Density
Partition Coefficient
Safe Levels in the Environment
Compatibility with Other
Chemicals
Particle Size Distribution
Radioactivity Distribution with
Particle Size
Source. [4]
equipment. Chemical extraction techniques may not
clean soil and tailings that contain a large quantity of
refractory minerals [7-9].
Discussed in this chapter are the various studies
needed to evaluate the technologies for their
applicability to site remediation.
9.3 Treatability Studies
When one or more remediation concepts are selected
that appear applicable, plans may be made for
bench-scale laboratory studies. Success there could
lead to pilot-scale testing and eventually to full-
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scale demonstration of site cleanup. This step-wise
procedure can permit stopping or redirecting
development of a remediation technology that
appears unfruitful. Carefully developed work plans
and quality assurance plans must precede each step.
More detailed information about the selected
technologies would be developed at the bench-scale
stage. Examples of bench-scale studies required
include:
For solidification or stabilization-selection and
performance evaluation of solidifying agents
compatible with the chemical composition of
the specific waste group.
For flotation-development of surfactants that
enhance the removal of the contaminant in
specific mineral form while suppressing the
other minerals in the specific waste group.
For chemical extraction with inorganic salts -
identification of specific inorganic salts and
determination of relevant process parameters
to effectively extract the radionuchde
contaminant from the specific waste group.
Based on the information developed in these studies,
detailed remediation processes can be selected that
may involve multiple technologies. Selection of any
process must include consideration of whether
appropriate disposal methods are available for both
the concentrated fractions and the "clean" fractions.
Preliminary cost information relative to each of these
processes would be developed along with
performance expectations. The criteria used to
evaluate these processes so that some processes
could be selected for further development could
include:
Amount of expected waste volume reduction;
Radioactivity of the expected "clean"
fractions;
Applicability to other waste groups;
Technological uncertainty;
Potential risks to remediation personnel;
Potential to construct mobile or transportable
units;
Generation of any toxic by-products or
effluents;
Potential to coremediate other hazardous
chemicals in the specific waste group;
Total cost of remediation; and
Disposal site availability.
9.4 Pilot-Plant Studies
After all the criteria listed above are weighed
appropriately, it is expected that no more than one or
two processes may qualify for pilot-scale testing for
a specific waste group.
The pilot testing would be used to develop better
information on the performance of the process,
assessment of technical problems, and costs. Testing
must be carried out over a significant duration to
obtain reliable data.
For field demonstration and full-scale site
remediation, the criteria applied earlier could be used
to select a remediation process.
9.5 References
1. U.S. Environmental Protection Agency. Technical
Resource Documents on Hazardous Waste Land
Disposal. SW860 and SW870 Series. Office of
Solid Waste, Washington DC. 1979-1987.
2. U.S. Environmental Protection Agency. Minimum
Technology Guidance on Double Liner Systems.
Draft. Office of Solid Waste. May 1985.
3. Council on Environmental Quality. Ocean
Dumping - A National Policy. A Report to the
President. U.S. Government Printing Office. 1970.
4. U.S. Environmental Protection Agency. Guidance
on the Preparation of Feasibility Studies.
Municipal Environmental Research Laboratory,
Cincinnati Ohio Office of Emergency and
Remedial Response, Washington, D.C. 1983.
5. Olsson, R.K. Geological Analysis of and Source
of the Radium Contamination at the Montclair,
West Orange, and Glen Ridge Radium
Contaminated Sites. Department of Geological
Sciences, Rutgers University, New Brunswick,
New Jersey, 1986.
6. Borrowman, S.R., and P.T. Brooks. Radium
Removal from Uranium Ores and Mill Tailings.
U.S. Bureau of Mines Report 8099, 1975.
7. Ryan, R.K., and D.M. Levins. Extraction of
Radium from Uranium Tailings. CIM Bulletin,
October, 1980, pp. 126-133.
8. Yagnik, S.K., M.H.I. Hurst, and S. Seely. An
Investigation of Radium Extraction from Uranium
Mill Tailings. Hydrometallurgy, 7:61-75, 1981.
9. Ryon, A.D., F.J. Hurst, and F.G. Seely. Nitric
Acid Leaching of Radium and Other Significant
Radionuclides from Uranium Ores and Tailings.
ORNL/TM-5944, Oak Ridge National
Laboratories, Oak Ridge, Tennessee, 1977.
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Chapter 10
Conclusions
This report provides a technical review of the
technologies that may be useful in removing
radionuclides from radiologically contaminated
Superfund sites. As a result of this review, the
following conclusions have emerged:
10.1 Technological Approaches
Alteration or remediation of the radioactive
decay process, thus changing the
fundamental hazard, is not possible.
Remediation, to date, has only involved
removing contaminated material and
containing it in above-ground land
encapsulation, drums, or temporary storage
sites. This approach has substantial technical
backup.
Alternative treatment technologies that may
warrant further study include solidification,
vitrification, chemical extraction, physical
separation, and combinations of physical
separation and chemical extraction. Even if
these treatment technologies were effective,
some form of final disposal would always be
needed.
Various remediation technologies may have
potential to reduce the volume of the
contaminated waste with an associated
increase in concentration of the radioactive
material.
Remediation technologies generally result in
the disturbance of contaminated material. The
additional risk to human health and the
environment must be weighed against leaving
the contaminated materials on-site in a
contained state, if that is an option.
Physical separation and/or chemical extraction
technologies can potentially concentrate the
contamination, thereby reducing the volume
and weight of the waste material for final
disposal.
Remediation may include soil ventilation and
shielding around homes to protect people
from radon and gamma radiation exposure.
Ocean disposal could potentially be a
technically viable method.
10.2 Disposal
All nonresidual waste must be disposed at a
final site that is designed to meet security and
longevity criteria appropriate for the
concentration of radioactivity that is present.
Capping could be a more suitable method
than areal removal of radon for controlling
radon emissions from large sources.
10.3 On-Site Treatment
Solidification and vitrification technologies do
not reduce the amount of the contaminated
material. However, they may immobilize the
contamination in the waste material thereby
increasing the effectiveness and safety of the
conventional remediation (e.g., land
encapsulation). Solidification may actually
increase the volume by the addition of the
solidifying materials.
10.4 Chemical Extraction Technology
Several chemical extraction technologies
have been studied in the laboratory by
various investigators. These include the use
of salt solutions, mineral acids, and various
complexing agents to extract the radioactive
contaminants from the soil. Several of these
experiments had relatively high extraction
efficiencies. For example, up to 97 percent
radium and 99 percent thorium were removed
using nitric acid and up to 92 percent of
radium was removed from uranium mill
tailings using EDTA.
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Chemical extraction technologies potentially
applicable for treating radioactive wastes at
Superfund sites are being researched and
investigated. Significant development work at
bench and pilot scale would be required
before these technologies could be utilized at
full scale.
10.5 Physical Separation and Reduction
Physical separation technologies can only be
useful for those waste materials in which the
radioactive contamination resides in a certain
particle size fraction. This information about
the waste materials at the 20 Superfund sites
is not presently available in sufficient detail.
Extensive soil characterization is required at
these Superfund sites to better establish the
applicability of the physical separation
technologies.
The physical separation technologies are at a
mature stage of development. A significant
selection and variety of hardware are
available in the uranium mining industry. If
detailed soil characteristics at the
radiologically contaminated Superfund sites
are developed, it could be possible to design
specific systems for further bench-scale and
pilot-scale testing and evaluation.
10.6 Combined Physical Separation and
Chemical Extraction
At a specific site, using a combination of
physical separation and chemical extraction
technologies is likely to be more effective
than using either type of technology
separately.
10.7 General Issues
It is important to note that in some cases
there may be two categories of residual
contamination: process wastes and soils
contaminated with isolated radionuclides or
groups of radionuclides. While removal of the
radioactive fractions of soils contaminated
only with single radionuclides such as
uranium or plutonium might result in "clean"
fractions acceptable for unrestricted disposal,
removal of the radioactivity from a soil also
contaminated with process wastes may not.
In the second case the nonradioactive
fractions of the residues could result in an
unacceptable product. Therefore, before
considering any separation technique, it is
necessary that acceptable limits for both the
radiological contaminants and the non-
radiological contaminants be defined. In some
cases, multiple treatments or combined
technologies could be required to achieve
environmental goals.
Every site remediation involving radioactive
materials must involve a final, environmentally
safe disposal site for the radioactive
materials.
Even if it proves feasible at a particular site to
lower the concentration of radionuclides in the
soil by physical separation and/or chemical
extraction to some acceptable level, the
"clean" fractions are likely to contain traces
of radionuclides. Therefore, adequate
attention must be given to whether the
"clean" fractions may be returned to the
original site or an unrestricted location or
must be sent to a disposal site.
When developing technologies for cleanup at
a site, it is essential that a step-wise
procedure be used. This should begin with
assessment studies and bench-scale
testing, followed by pilot-scale testing. Only
if these are successful should full-scale
demonstrations be attempted. Carefully
developed work plans and quality assurance
plans should precede each step.
10.8 Site Characteristics
Twenty Superfund sites have radiologically
contaminated soil spread over 9500 acres. Of
these sites, five are DOE sites (3 FUSRAP
and 2 SFMP). [Data presented here are
accurate as of December 1987.]
Any choice of remediation technologies for
radioactive waste at Superfund sites would
have to be site specific. Extensive site soil
characterization studies, such as complete
mineral analysis, particle size distribution,
radionuclide-contaminated distribution, soil
texture, and permeability, would be required
prior to development and application of most
of the technologies, land encapsulation being
an exception.
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Appendix A
Applicable Laws, Regulations, and Guidance
This appendix briefly presents some of the laws,
regulations, and guidance that are part of the
framework within which technologies may be selected
for remediation of Superfund sites. This report does
not attempt nor is it intended to provide a complete or
detailed analysis of how various laws, regulations, and
guidance apply in general or at a specific Superfund
site, nor is it intended to set or interpret policy for the
selection or use of technologies to clean up any
Superfund or other hazardous waste site.
Superfund sites are remediated under the provisions
of the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980 (CERCLA) as
amended by the Superfund Amendments and
Reauthonzation Act of 1986 (SARA). Several sections
of CERCLA and SARA are pertinent to the intent of
this document.
EPA undertakes remedial investigation and feasibility
studies (RI/FS) at National Priorities List (NPL) sites
where there is a release of a hazardous substance or
pollutant or contaminant, or threat of release, to
identify those releases and their nature, along with
planning and investigations necessary to direct
response actions. Radiologically contaminated sites
have qualified for the NPL.
Section 311 of CERCLA, commonly referred to as the
Superfund Innovative Technology Evaluation (SITE)
program, provides for demonstrations of alternative
technologies in the cleanup of sites on the NPL.
Radiologically contaminated sites and treatment
technologies, such as those described in this
document, may qualify for demonstration under this
program. The SITE program generally requires that a
technology developer bear the cost of demonstrating
his technology, while EPA bears the cost of its
evaluation. Proof of concept laboratory results must
be supplied by the technology developer before EPA
can consider funding a demonstration under this
program.
SARA Section 1l8(m) (not an amendment to
CERCLA) states that it is the sense of Congress that
fully demonstrated remediation methods, such as
off-site transport and disposal, are not necessarily
required at sites on the NPL because of the presence
of radon. This section states that innovative or
alternative methods that protect human health in a
more cost effective manner may be used.
SARA Section 121 (Cleanup Standards) states a
strong statutory preference for remedies that are
highly reliable and provide long-term protection. In
addition to the requirement for remedies to be both
protective of human health and the environment and
cost-effective, additional remedy selection
considerations in 121 (b) include:
• A preference for remedial actions that employ
treatment that permanently and significantly
reduces the volume, toxicity, or mobility of
hazardous substances, pollutants, and
contaminants as its principal element.
• Offsite transport and disposal without treatment is
the least favored alternative where practicable
treatment technologies are available.
• The need to assess the use of permanent
solutions and alternative treatment technologies
or resource recovery technologies and use them
to the maximum extent practicable.
Section 121(d)(2)(A) of SARA incorporates into law
the CERCLA Compliance Policy, which specifies that
Superfund remedial actions meet any Federal
Standard requirements, criteria, or limitations that are
legally applicable or relevant and appropriate
requirements (ARARs) under any Federal or state
environmental law.
CERCLA Section 104(a)(3) limits Federal response
authority for releases of naturally occurring
substances in locations where they are naturally
found. However, this section does not apply for many
of the radiologically contaminated Superfund sites.
The Low-Level Radioactive Waste Policy
Amendments Act of 1985 (LLRWPAA) requires states
and compacts to develop siting plans for low-level
radioactive waste (LLW) disposal facilities by January
1, 1988. These disposal facilities may receive
commercial mixed low-level radioactive and
hazardous waste (Mixed LLW), which is regulated by
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the U.S. Nuclear Regulatory Commission (NRC)
under the Atomic Energy Act (AEA) as amended, and
by the EPA under the Resource Conservation and
Recovery Act of 1976 (RCRA), as amended. NRC
has promulgated LLW regulations and EPA has
issued guidance that pertains to the siting
requirements for disposal facilities for Mixed LLW.
Section 5(e)(1)(B) of the LLRWPAA requires states
and compacts to develop siting plans for LLW
disposal facilities by January 1, 1988. In addition to
other information, these siting plans must identify, to
the extent practicable, the process for (1) screening
for broad siting areas, (2) identifying and evaluating
specific candidate sites, and (3) characterizing the
preferred site(s). It is anticipated that this process will
be based primarily on the site suitability requirements
that apply to LLW disposal. If facilities also receive
Mixed LLW, their siting requirements will reflect
additional requirements that apply to disposal of
hazardous waste as defined by RCRA.
Combined NRC-EPA Siting Guidelines for Disposal
of Commercial Mixed Low-Level Radioactive and
Hazardous Waste (see Addendum) provide guidance
to facilitate development of siting plans for disposal
facilities that may receive Mixed LLW.
Joint NRC-EPA Guidance as a Conceptual Design
Approach for Commercial Mixed Low-Level
Radioactive and Hazardous Waste Disposal Facilities
(see Addendum) presents a conceptual design
approach that meets the regulatory requirements of
both agencies for the safe disposal of Mixed LLW.
Other designs, or variations on the proposed design
concept, may also be acceptable under the
requirements of both agencies and will be reviewed
on a case-by-case basis as received.
Standards developed under Section 275 of the
Atomic Energy Act and Section 206 of the Uranium
Mill Tailings Radiation Control Act of 1978 may be
applicable or relevant and appropriate on a site
specific basis to the cleanup of radiologically
contaminated Superfund sites. In January 1983, the
EPA promulgated 40 CFR 192, Health and
Environmental Protection Standards for Uranium and
Thorium Mill Tailings under authority of these Acts.
The pertinent standards are contained in 40 CFR
192.12, 192.32, and 192.41, and deal with the
acceptable levels of radioactivity in residual materials
and radiation emission levels from them, and with
disposal requirements. The disposal requirements
include a design life of at least 200 years and
preferably 1,000 years where reasonably achievable.
The Department of Energy (Office of Nuclear Energy)
operates four remedial action projects for
radiologically contaminated sites that parallel EPA's
Superfund program. Remedial actions have been
completed or are in advanced stages at some of
these sites. These DOE projects are as follows:
1. Formerly Utilized Sites Remedial Action Project
(FUSRAP) under authority of the Department of
Energy Organization Act of 1977.
2. The Uranium Mill Tailings Remedial Action Project
(UMTRAP) under authority of Public Law 95-
604, the Uranium Mill Tailings Control Act of
1978.
3. The Grand Junction Remedial Action Project
(GJRAP) under Public Law 92-314 (1972)
amended by Public Law 95-236 (1978).
4. The Surplus Facilities Management Program
(SFMP) under authority of the Department of
Energy Organization Act of 1977.
These projects are described in Appendix B.
In addition, DOE's Office of Defense Waste and
Transportation Management (DWTM) is responsible
for safely managing defense waste as generated,
transporting it, and storing it, and is also responsible
for developing and implementing the technology
needed for long-term management and eventual
disposal of the waste.
One of the options for radioactive waste disposal is
ocean disposal. Ocean disposal is controlled by
regulations under the Marine Protection, Research,
and Sanctuaries Act of 1972, as amended. The
regulations are contained in 40 CFR Parts 220
through 229 and are currently being revised. Perhaps
the most pertinent are found in 40 CFR 227, Criteria
for the Evaluation of Permit Applications for Ocean
Dumping of Materials. A unique provision of the Act is
that a permit may not be issued by EPA for ocean
disposal of radioactive materials without the approval
of both Houses of Congress. The Act prohibits ocean
disposal of high level wastes; only low level wastes
are eligible to be considered for a permit.
Although this document has been specifically directed
at the remediation of Superfund sites, it may have
applicability to permitted sites that require corrective
actions under RCRA as amended by the Hazardous
and Solid Waste Amendments of 1984 (HSWA). A
RCRA site can be placed on the CERCLA NPL if the
operator is bankrupt, unwilling to carry out corrective
action, or has lost his authorization to operate (see
Preamble to 40 CFR Part 300, June 10, 1986).
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Addendum 1 - Combined NRC-EPA
Siting Guidelines for Disposal of
Commercial Mixed Low-Level
Radioactive and Hazardous Wastes
Introduction
The Low-Level Radioactive Waste Policy
Amendments Act of 1985 (LLRWPAA) requires states
and compacts to develop siting plans for low-level
radioactive waste (LLW) disposal facilities by January
1, 1988. These disposal facilities may receive
commercial mixed low-level radioactive and
hazardous waste (Mixed LLW), which is regulated by
the U. S. Nuclear Regulatory Commission (NRC) the
Atomic Energy Act (AEA), as amended, and by the U.
S. Environmental Protection Agency (EPA) under the
Resource Conservation and Recovery Act (RCRA),
as amended. Mixed LLW is defined as waste that
satisfies the definition of LLW in the LLRWPAA and
contains hazardous waste that either is listed in
Subpart D of 40 CFR Part 261 or causes the LLW to
exhibit any of the hazardous waste characteristics
identified in Subpart C of 40 CFR Part 261. To assist
in applying that definition, NRC and EPA recently
developed joint guidance entitled "Guidance on the
Definition and Identification of Commercial Mixed
Low-Level Radioactive and Hazardous Waste and
Answers to Anticipated Questions" (Jan. 8, 1987).
NRC has promulgated LLW regulations and EPA has
promulgated hazardous waste regulations that pertain
to the siting requirements for disposal facilities for
Mixed LLW. Because of uncertainty about the precise
content of EPA's future location standards, states and
compacts may have questions regarding the site
selection process. This document provides combined
NRC-EPA siting guidelines, to be used before EPA's
new location standards are promulgated, to facilitate
development of siting plans for disposal facilities that
may receive Mixed LLW.
Section 5(e)(1)(B) of the LLRWPAA requires states
and compacts to develop siting plans for LLW
disposal facilities by January 1, 1988. In addition to
other information, these siting plans must identify, to
the extent practicable the process for (1) screening
for broad siting areas, (2) identifying and evaluating
specific candidate sites, and (3) characterizing the
preferred site(s). It is anticipated that this process will
be based primarily on the site suitability requirements
that apply to LLW disposal. If facilities also receive
Mixed LLW, their siting requirements will reflect
additional requirements that apply to disposal of
hazardous waste as defined by RCRA.
In 1982, NRC promulgated regulations which contain
minirnum site suitability requirements for LLW land
disposal facilities in 10 CFR 61.50. EPA has also
promulgated minimum location standards for
hazardous waste treatment, storage and disposal
facilities in 40 CFR 264.18. Considerations affecting
siting are also found in 40 CFR 270.3, 270.14(b) and
(c). Although both NRC and EPA have incorporated
siting requirements in existing regulations for LLW
and hazardous waste disposal, respectively, the 1984
Hazardous and Solid Waste Amendments (HSWA) to
RCRA require EPA to publish guidance identifying
areas of vulnerable hydrogeology. In July 1986, EPA
published this guidance in "Criteria for Identifying
Areas of Vulnerable Hydrogeology under the
Resource Conservation and Recovery Act -
Statutory Interpretative Guidance, July 1986, Interim
Final (PB-86-224953)." The 1984 HSWA also
requires (in Section 3004(o)(7)) that EPA specify
criteria for the acceptable location of new and existing
hazardous waste treatment, storage, and disposal
facilities. EPA anticipates proposing these location
standards in September 1987 and promulgating them
in final form by September 1988.
EPA's scheduled date for promulgating its final
location standards is nine months after the LLRWPAA
January 1, 1988, milestone for non-sited states and
compacts to develop siting plans. Therefore, states
and compacts may require some assistance in their
efforts to develop siting plans for LLW disposal
facilities that may receive Mixed LLW. The two
agencies are issuing these combined guidelines to
promote the development of siting plans by states
and compacts. Both NRC and EPA consider that the
absence of EPA's final comprehensive location
standards for hazardous waste disposal facilities is an
adequate basis for states and compacts to delay
development of siting plans for LLW disposal.
States and compacts should proceed at this time to
develop siting plans in accordance with the existing
NRC and EPA requirements. The following combined
NRC-EPA guidelines are provided for use by the
states and compacts, and are based on existing NRC
regulations in 10 CFR Part 61 and EPA regulations in
4 CFR Parts 264 and 270. As EPA continues its
development of location standards, both agencies will
strive to keep states and compacts informed about
the status of the developing siting requirements.
Combined NRC-EPA Siting Guidelines
Site suitability requirements for land disposal of LLW
are provided in 10 CRF Section 61.50. These
requirements constitute minimum technical require-
ments for geologic, hydrologic, and demographic
characteristics of LLW disposal sites. Several of
these requirements identify favorable site
characteristic for near-surface disposal facilities for
LLW. The majority of the site suitability requirements,
however, identify potentially adverse site
characteristics that must not be present at LLW
disposal sites. The site suitability requirements in 10
CFR Part 61 are intended to function collectively with
the requirements for facility design and operation, site
77
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closure, waste classification and segregation, waste
form and packaging, and institutional controls to
assure isolation of LLW for the duration of the
radiological hazard. The NRC Technical Position
entitled "Site Suitability, Selection, and
Characterization" (NUREG-0902) provides detailed
guidance on implementing the site suitability
requirements in 10 CFR Part 61.
EPA has also promulgated certain minimum location
standards for hazardous waste treatment, storage,
and disposal facilities. These standards are provided
in 40 CFR Section 264.18. As previously noted, the
hazardous waste regulations also include other
location considerations as well as applicable
provisions of other Federal statutes. For example,
Subpart F of 40 CFR Part 264 requires establishment
of ground-water monitoring programs capable of
detecting contamination from land disposal units.
While not a siting criterion per se this requirement
can preclude siting in locations that cannot be
adequately monitored or characterized. A further
description of location-related standards and
applicable provisions of other Federal statutes can be
found in the "Permit Writers" Guidance Manual for
Hazardous Waste Land Storage and Disposal
Facilities: Phase I Criteria for Location Acceptability
and Existing Applicable Regulations" (Final Draft -
February 1985). This guidance manual describes five
criteria for determining location acceptability; ability to
characterize, exclusion of high hazard and unstable
terrain, ability to monitor, exclusion of protected lands,
and identification of areas of vulnerable hydrogeology.
The first four of these criteria have a basis in the
regulations and are fully described in the manual. The
fifth criterion, vulnerable hydrogeology, is defined in
the RCRA interpretive guidance manual mentioned
above (Criteria for Identifying Areas of Vulnerable
Hydrogeology under the Resource Conservation and
Recovery Act-Statutory Interpretive Guidance, July
1986, Interim Final (PB-86-224953)).
However, since HSWA also added other requirements
in addition to location standards to prevent or mitigate
ground-water contamination, EPA recognizes that
vulnerable hydrogeology must be considered in
conjunction with design and operating practices.
Vulnerability should not be the sole determining fact
in RCRA siting decisions. Rather, this criterion
provides a trigger for more detailed evaluation of sites
that are identified as having potentially vulnerable
hydrogeology. The extent of necessary site review
and evaluation is related directly to the extent to
which a location "fails" or "passes" the vulnerability
criterion. Sites that are determined to be extremely
vulnerable will require much closer examination than
sites that are deemed non-vulnerable. The results of
this more detailed review may then provide a basis
for eventual permit conditions or modifications in
design or operating practices.
By combining the above technical requirements,
standards, and guidance of both agencies, NRC and
EPA have formulated the eleven guidelines listed
below. The use of terms in the guidelines is
consistent with their regulatory definition in 10 CFR
Part 61 and 40 CFR Parts 260 and 264. The
combined set of location guidelines is intended by the
agencies to apply only as guidance to states and
compacts developing siting plans for LLW disposal
facilities that may receive Mixed LLW. These
combined guidelines are not intended to displace
existing standards and guidance. In addition, the
independent guidance of both agencies should be
considered in any application of the combined siting
guidelines.
The combined siting guidelines for a commercial
Mixed LLW disposal facility are as follows:
I. Primary emphasis in disposal site suitability should
be given to isolation of wastes and to disposal site
features that ensure that the long-term performance
objectives of 10 CFR Part 61, Subpart C are met.
2. The disposal site shall be capable of being
characterized, modeled, analyzed, and monitored. At
a minimum, site characterization must be able to (a)
delineate ground-water flow paths, (b) estimate
ground-water flow velocities, and (c) determine
geotechnical properties sufficiently to support facility
design. At a minimum for site ground-water
monitoring disposal site operators must be able to (a)
assess the rate and direction of ground-water flow in
the uppermost aquifer, (b) determine background
ground-water quality, and (c) promptly detect
ground-water contamination.
3. The disposal site must be generally well-drained
(with respect to surface water) and free of areas of
flooding or frequent ponding.
4. The disposal site shall not be in the 100-year
floodplam.
5. The site must be located so that upstream
drainage areas are minimized to decrease the amount
of runoff that could erode or inundate waste disposal
units.
6. Disposal sites may not be located on lands
specified in 10 CFR Section 61.50(a)(5), including
wetlands (Clean Water Act) and coastal high hazard
areas (Coastal Zone Management Act). Location of
facilities on the following lands must be consistent
with requirements of applicable Federal statutes:
archeological and historic places (National Historic
Places Act); endangered or threatened habrnU
(Endangered Species Act); national parks,
monuments, and scenic rivers (Wild and Scer,,c
Rivers Act); wilderness areas (Wilderness Protection
78
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Act); and wildlife refuges (National Wildlife Refuge
System Administration Act).
7. The disposal site should provide a stable
foundation for engineered containment structures.
8. Disposal sites must not be located in areas where:
(a) tectonic processes such as faulting, folding,
seismic activity, or vulcanism may occur with such
frequency and extent to affect significantly the ability
of the disposal facility to satisfy the performance
objectives specified in Subpart C of 10 CFR Part 61,
or may preclude defensible modeling and prediction
of long-term impacts; in particular, sites must be
located more than 200 feet from a fault that has been
active during the Holocene Epoch;
(b) surface geologic processes such as mass
wasting, erosion, slumping, landsliding, or weathering
occur with such frequency and extent to affect
significantly the ability of the disposal facility to meet
the performance objectives in Subpart C of 10 CFR
Part 61, or may preclude defensible modeling and
prediction of long-term impacts;
(c) natural resources exist that, if exploited, would
result in failure to meet the performance objectives in
Subpart C of 10 CFR Part 61;
(d) projected population growth and future
developments within the region or state where the
facility is to be located are likely to affect the ability of
the disposal facility to meet the performance
objectives in Subpart C of 10 CFR Part 61; and
(e) nearby facilities or activities could adversely
impact the disposal facility's ability to satisfy the
performance objectives in Subpart C of 10 CFR Part
61 or could significantly mask an environmental
monitoring program.
9. The hydrogeologic unit beneath the site shall not
discharge ground water to the land surface within the
disposal site boundaries.
10. The water table must be sufficiently below the
disposal facility to prevent ground-water intrusion
into the waste, with the exception outlined under 10
CFR Section 61.50(a)(7).
11. In general, areas with highly vulnerable
hydrogeology deserve special attention in the siting
process. Hydrogeology is considered vulnerable when
ground-water travel time along any 100-foot flow
path from the edge of the engineered containment
structure is less than approximately 100 years
(Criteria for Identifying Areas of Vulnerable
Hydrogeology Under RCRA-Statutory Interpretive
Guidance, July 1986, Interim Final (PB-86-
224953)). Disposal sites located in areas of
vulnerable hydrogeology may require extensive, site-
specific investigations which could lead to and
provide bases for restrictions or modifications to
design or operating practices. However, a finding that
a site is located in an area of vulnerable hydrogeology
alone, based on the EPA criteria, is not considered
sufficient to prohibit siting under RCRA.
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Addendum II - Joint NRC-EPA
Guidance on a Conceptual Design
Approach for Commercial Mixed Low-
Level Radioactive and Hazardous Waste
Disposal Facilities
Introduction
The Low-Level Radioactive Waste Policy
Amendments Act of 1985 (LLRWPAA) requires that
the three operating low-level radioactive waste
(LLW) disposal facilities remain available through
1992. By that time, all states and compact regions
are required to assume complete responsibility for
LLW disposal. Both existing and new disposal
facilities may receive commercial mixed low-level
radioactive and hazardous waste (Mixed LLW), which
is regulated by the U.S. Nuclear Regulatory
Commission (NRC) under the Atomic Energy Act
(AEA), and by the U.S. Environmental Protection
Agency (EPA) under the Resource Conservation and
Recovery Act (RCRA). Mixed LLW is defined as
waste that satisfies the definition of LLW in the
LLRWPAA and contains hazardous waste that either
(1) is listed as a hazardous waste in Subpart D of 40
CFR Part 261 or (2) causes the LLW to exhibit any of
the hazardous waste characteristics identified in
Subpart C of 40 CFR Part 261. To assist in applying
this definition, NRC and EPA issued joint guidance
entitled "Guidance on the Definition and Identification
of Commercial Mixed Low-Level Radioactive Waste
and Answers to Anticipated Questions" on January 8,
1987.
This jointly developed NRC-EPA guidance document
presents a conceptual design approach that meets
the regulatory requirements of both agencies for the
safe disposal of Mixed LLW. Other designs, or
variation of the proposed design concept may also be
acceptable under the requirements of both agencies
and will be reviewed on a case-by-case basis as
received.
EPA regulations in 40 CFR Part 264, Standards for
Owners and Operators of Hazardous Waste
Treatment, Storage, and Disposal Facilities, identify
the design and operating requirements for owners
and operators that dispose of hazardous waste in
landfills [264.300 to 264.317]. These regulations
involve requirements for the installation of two or
more liners and a leachate collection and removal
system (LCRS) above and between the liners to
promote human health and the environment.
Exceptions to the double liner and leachate collection
system requirements are allowed, if alternative design
and operating practices, together with location
characteristics, are demonstrated to EPA Regional
Administrator to be equally effective in preventing the
migration of any hazardous constituent into the
ground water or surface water.
NRC regulations in 10 CFR Part 61, Licensing
Requirements for Land Disposal Radioactive Waste,
indicate that long-term stability of the waste and the
disposal site require minimization of access of water
to the waste [61.7(b)(2)] and that the disposal site
must be designed to minimize, to the extent
practicable, the contact of water with waste during
storage, the contact of standing water with waste
during disposal, and the contact of percolating
standing water with wastes after disposal
[61.51(a)(6)j. The primary objective of the above
NRC regulations is to preclude the possibility of the
development of a "bath-tub" effect in which the
waste could become immersed in liquid (e.g., from
infiltration of surface water runoff) within a disposal
unit below grade with a low-permeability bottom
surface.
The guidance on a conceptual design approach that
is offered in the subsequent paragraphs is intended to
present basic design concepts that are acceptable in
addressing the regulations of both the NRC and EPA
with respect to requirements for liners, leachate
collection systems and efforts to minimize the contact
of liquid with the waste. It should be recognized that
the guidance is being provided at the conceptual level
and that the design and details that are
complementary to specific site conditions need to be
engineered by potential waste facility owners and
operators. The application of the guidance in this
document will not affect the requirements for
licensees of waste disposal facilities to comply with all
applicable NRC and EPA regulations.
Conceptual Design
Sketches and a brief discussion of the design
considerations for an above grade disposal unit are
provided. This design concept has been developed
primarily to demonstrate the integration of EPA's
regulatory requirements for two or more liners and a
leachate collection system above and between liners
and the regulations of the NRC that require the
contact of water with the waste be minimized. In
addition, the design concept fulfills the need under
both agencies' regulations to assure long-term
stability and minimize active maintenance after site
closure.
In this approach, the Mixed LLW would be placed
above the original ground surface in a tumulus that
would be blended into the disposal site topography.
Schematic details of some of the principal design
features of an above grade Mixed LLW disposal unit
are provided in the sketches accompanying this
guidance document. Figure A1 depicts the three
dimensional overall view of a concept Mixed LLW
disposal unit; Figure A2 provides details of the
perimeter berm, liners, and leachate collection
system; Figure A3 presents a cross-sectional view
80
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of the covered portion of the disposal unit; and Figure
A4 describes the final cover system.
In the overall view of the Mixed LLW disposal facility,
the double liners leachate collection and removal
system are installed before the emplacement of the
Mixed LLW; and the cover system is added at
closure. The leak detection tank and leachate
collection tank are encircled by a berm that controls
surface water runoff from precipitation that would fall
directly on the waste facility site. The drainage pipes
in the upper primary collection system would collect
any leachate that could possibly develop above the
top flexible membrane liner and below the emplaced
waste. Any leachate collected would drain through
pipes to the primary leachate collection tank where
Figure A1. Mixed waste disposal facility.
Final Cover
Double Liner & Leachate
Collection & Removal System
Leachate (LCRS)
Collection Pipes
Leachate Collection Manifold
Leachate Collection Tank
Leak Detection Tank
Figure A 2. Double liner and leachate collection system.
Separation to Assure
Leachate Flow into LCRS
Solidified Waste
Bottom of Waste .7
Primary LCRS
Top Liner (Flexible Membrane Lmer-FML)
Perimeter Berm for
Leachate Runoff Control
- Leachate Detection, Collection
and Removal System
Bottom Liner (Composite-
FML & Compacted Clay*
j/-o- o'.: •
-------
the leachate would be tested and treated, if required.
Any leachate collected by the lower leachate
collection and removal system would dram to the leak
detection tank. The development of significant
amounts of leachate from the solidified waste after
closure is not anticipated. This is because the closure
requirements provide that the cover must be
designed and constructed 1) to provide long-term
minimization of water infiltration into the closed
disposal facility, 2) to function with minimum
maintenance, 3) to promote drainage and minimize
erosion, and 4) to have a permeability less than or
equal to the permeability of any bottom liner system.
It is anticipated that the area shown on Figure A3
between the slope of the final cover and the run-on
control berm, where the tanks are located, would be
regraded and the tanks removed at the end of the
post-closure care period (normally 30 years) when
leachate development and collection is no longer a
problem.
Figure A2 provides the general details required by
EPA regulations for the double liner and leachate
collection and removal system. The perimeter berm
for leachate runoff control would assure that all
leachate is collected below the waste and safely
contained and transported through the drainage layers
and pipes to the tanks located outside the final cover
slope. NRC's regulation requiring minimizing contact
of the waste with water are fulfilled by requiring the
waste to be placed above the level of the highest
water table fluctuation and above the drainage layers
where ieachate would collect. The bottom elevation of
the solidified Mixed LLW would be required in all
Figure A3. Cross-sectional view A-A
(vertical scale exaggerated).
instances to be at elevations above the top of the
perimeter berm.
In Figures A3 and A4, the design concepts for the
final cover over the solidified waste zone and the
perimeter berm are presented. The actual zone for
placement of solidified Mixed LLW may consist of
different options, depending on the licensee's
selection. Options that would be acceptable include
use of stable high integrity waste containers (HICs)
that have the spaces between containers filled with a
cohesionless, low compressible fill material or
placement of the waste in an engineered structure,
such as a reinforced concrete vault. A cover system
over the waste that would be acceptable to the EPA
and NRC is shown in Figure A4. The cover system
would consist of (1) an outer rock or vegetative layer
to minimize erosion and provide for long-term
stability, (2) a filter and drainage layer that transmits
infiltrating water off of the underlying low permeability
layers, (3) an impervious flexible membrane liner
overlying a compacted low permeability clay layer,
and (4) a filter and drainage layer beneath the
compacted clay layer. If the solidified waste zone
does not consist of an engineered vault structure with
a top roof, an additional compacted clay layer should
be placed immediately above the emplaced waste to
direct any water infiltration away from the waste zone.
Mixed LLW that contains Class C waste as
designated by NRC's regulations would need to
provide sufficient thickness of cover materials or an
engineered intruder barrier to ensure the required
protection against inadvertent intrusion.
Area Regraded Following
Post-Closure Care Period
Final Cover
(See Fig A4)
& Leachate Collection System
rm
— Perimeter
Berm for
Leachate
Run-off
Control
Leak Detection Tank
(To EPA Standards)
Unsaturated Soil
Run-on
Control Berm
JL
Ground water
82
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Figure A4. Waste cover system
(vertical scale exaggerated).
FML
Slope Designed for
Long-term Stability
Filter & Drainage
Layer
Rock or Vegetative Cover
Pipes Cutoff at Slope Following
Post-Closure Care Period
Backfill -
Compacted Clay —
Filter & Drainage
Layer
Double Liner & Leachate
Collection System
Perimeter Berm for
Leachate Control
Surface Drainage Channel
Primary LCRS Collection Pipe —,
Leachate Detection Pipe —\ \
Separation to Assure
Leachate Flow into LCRS
Variations on the above described design approach
may include placement of the Mixed LLW in an
engineered reinforced concrete vault, a steel fiber
polymer-impregnated concrete vault, or double-
lined high integrity containers that are hermetically
sealed. If proposed by license applicants, these
variations would be reviewed by both the EPA and
NRC on a case-by-case basis to evaluate their
acceptability and conformance with established
federal regulations.
For questions related to NRC regulations and design
requirements, contact:
Dr. Sher Bahadur, Project Manager
Division of Low-Level Waste Management and
Decommissioning
Mail Stop 623-SS
U.S. Nuclear Regulatory Commission
Washington, DC 20555
Facility specific questions, permitting requirements,
variances and other related concerns should be
addressed to either the EPA regional office or state
agency authorized to administer the mixed waste
program as appropriate. For general questions related
to EPA regulations and design requirements, contact:
Mr. Kenneth Skahn, Senior Engineer
Waste Management Division
Mail Stop WH-565E
U.S. Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
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Appendix B
Characteristics of Man-Made Radiologically Contaminated Sites
Introduction
The type of remediation that may be reasonably
applied to sites contaminated with radioactive wastes
depends to a great extent upon the physical,
chemical, and mmeralogical characteristics of the
matrix (e.g., soil) material. Other important factors are
the site location (e.g., proximity to a population
center), the volume to be remediated, the radioactive
elements, the level of radioactivity, and the presence
of other hazardous substances.
This appendix briefly describes the sites on the
Superfund NPL that contain radioactive materials. In
addition, information is presented on the DOE's
Formerly Utilized Sites Remedial Action Project
(FUSRAP), its Uranium Mill Tailings Remedial Action
Project (UMTRAP), Grand Junction Remedial Action
Project (GJRAP) and Surplus Facilities Management
Program (SFMP). The sites and remediation
experiences in DOE's projects are very similar to
those of the Superfund program. In fact a few of the
DOE sites are on the NPL. Site information presented
in this Appendix is accurate as of December 1987.
Radiologically Contaminated Superfund
Sites
The information presented here has been compiled
from the various written status reports and
investigation reports obtained principally from the EPA
Regional personnel who have the responsibility for
the described sites. The descriptions are limited to
the 20 sites currently listed on or proposed for the
NPL that are known to contain man-made
radioactive waste materials. These sites are listed in
Table B1, which is followed by the site descriptions.
A distinction exists between man-made radioactive
wastes and naturally occurring and accelerator
produced radioactive material (NARM), which has
been technologically concentrated or otherwise
altered in such a way that the potential for human
exposure has been increased. The uranium and
thorium series are hallmarks of naturally occurring
radioactive materials. The majority of the listed
Superfund sites with radionuclide contamination are
presumed to be contaminated by elements in these
series. The listed sites may not be the only
Superfund sites that are radiologically contaminated.
In fact, it may be expected that, as other Superfund
sites are more fully characterized, the list will expand.
On the other hand, there are a few Superfund sites
containing radioactivity of natural origin in measurable
amounts from the bedrock in the vicinity.
Two of the 20 sites described are landfills containing
solid waste, hazardous waste, and radioactive waste.
Ten of the sites are primarily tailings from ore
processing. Four sites include radiologically
contaminated building materials. At least five of the
sites have been used as sources of fill material on
properties in their vicinities.
Contaminated site areas total more than 9,500 acres
and individually range from about one acre to 6,550
acres. The individual sites range from less than 50
cubic yards to more than 16 million cubic yards. The
largest volume sites (those containing more than one
million cubic yards) are uranium mill tailings sites.
There are five sites in New Jersey, four in Illinois, four
in Colorado, and two in New Mexico. The remaining
sites are located in Massachusetts, Pennsylvania,
Kentucky, Missouri, and Utah.
1. Radioactive Waste Superfund Site -
Description
Name and Location:
Shpack/ALI (adjacent landfills), Norton/Attleboro,
Massachusetts
EPA Contact Region I:
Robert Shatten, FTS 835-3679
Status:
NPL Final, Rank 672
Final site response assessment report, 11/21/85,
prepared by NUS Corp. for performance of
remedial activities. Monitoring program included
water samples from 10 observation wells and soil
85
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Table B1. Radioactive Waste Superfund Sites
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11
12.
13.
14.
15
16.
17.
18.
19
20.
Site Name
Shpack/ALI (Adjacent Landfills)
Maywood Chemical CoVSears Properly
U.S. Radium Corp.
W. R Grace & Co. (Wayne Plant)
Montclair, West Orange, and Glen Ridge Radium Sites
Lodi Municipal Well
Lansdowne Property
Maxey Flats Nuclear Disposal Site
West Chicago Sewage Treatment Plant
Reed-Keppler Park
Kerr-McGee Off-Site Properties
Kerr-McGee Kress Creek/West Branch of Dupage River
The Homestake Mining Co. Uranium Mill
United Nuclear Corp.
Weldon Spring Quarry
Monticello Radioactivity-Contaminated Properties
Denver Radium Superfund Sites
Lincoln Park
U.S. DOE Rocky Flats Plant
Uravan Uranium Project
City/County
Norton/Attleboro
Maywood/Bergen Co.
Orange, Essex Co.
Wayne/Passaic Co.
Essex Co.
Lodi, Bergen Co.
Lansdowne
Fleming City/Hilisboro
West Chicago
West Chicago
West Chicago
West Chicago
Cibola Co.
Church Rock
St Charles City
Monticello San Juan, Co.
Denver
Canon City
Golden
Montrose City/Uravan
State/EPA
Region
MA/I
NJ/II
NJ/II
NJ/II
NJ/II
NJ/II
PA/111
KY/IV
IL/V
IL/V
IL/V
IL/V
NMA/I
NM/VI
MO/VII
UT/VIII
COA/III
CO/VIII
COA/III
CO/VIII
samples analyzed for priority pollutants and gross
alpha, beta, and gamma radioactivity.
No Remedial Investigation/Feasibility Study
(RI/FS) available yet.
Radiation Data:
Ra-226, U-238, U-235, U-234 above natural
background levels but uneven distribution in
surface and subsurface soil. K-40, Th-228,
Th-230 present. Rn-222, 240 pCi/l in ground
water. Some measured values in soil: Ra-226,
1571 pCi/g; U-238, 16,460 pCi/g; U-235, 200
pCi/g; U-234, 4,200 pCi/g.
Matrix Characteristics:
Wetland or swamp area; sand, gravel, silt, and
clay, organic deposits. Nonradioactive
contaminants: 1,2-dichloroethylene, trichloro-
ethylene, tetrachloroethylene, chromium,
cadmium, nickel.
Source:
Unknown, possibly manufacture of luminescent
dials and former operation of nuclear submarine
contractor.
Approximate Area and Volume:
Shpack about 8 acres; All about 23 acres; 100 tons.
Environmental Impact:
10,000 residents relying on well water within 1-
mi radius. 270 residents live within 3-mi radius.
About 35 private wells within 3 mile radius of the
site serve approximately 130 people. ORNL 1982
survey revealed no migration of radionuclides into
ground water; no hydraulic gradient (vertical or
horizontal) in underlying aquifers. Rn-222 at 328
pCi/l in ground water in 1980 study by private
consultant considered suspect. Airborne
radionuclide contamination no apparent threat to
public. Based on existing data as of 11/85, no
indication of immediate public health threat.
Source of Information:
Final Site Response Assessment Report D583-
1-5-22, Revision 2; prepared by NUS Corp.,
11/21/85.
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2. Radioactive Waste Super-fund Site -
Description
Name and Location:
Maywood Chemical Co./Sears Property,
Maywood, Rochelle Park, New Jersey
EPA Contact Region II:
Pasquale Envangelista, FTS 264-2649
Status:
NPL Final, Rank 157.
Site was identified under FUSRAP, and DOE was
designated to perform remedial action related to
radioactive residues. Residential properties in
Maywood, Rochelle Park, and parts of Lodi, NJ
were remediated. Soil from old disposal areas
was removed. Temporary storage facility called
the Maywood Interim Storage Site (MISS)
developed. DOE conducting continuous
monitoring at MISS and detailed characterizations
of properties related to the Maywood site.
one residence. Elevated gamma radiation levels
on adjacent properties.
Source of Information:
"Characterization Report for Sears Property,
Maywood, New Jersey," DOE/OR/20722-140,
Oak Ridge National Laboratory, May 1987.
"Engineering Evaluation of Disposal Alternatives
for Radioactive Waste from Remedial Actions in
and around Maywood, New Jersey,"
DOE/OR/20722-79, Oak Ridge National
Laboratory, March 1986.
EPA NPL Site Status Sheet
3. Radioactive Waste Super-fund Site -
Description
Name and Location:
U.S. Radium Corp., Orange, Essex Co. New
Jersey
Radiation Data:
Elevated gamma radiation; gross alpha in water,
18.4 pCi/l. Surface soil Th-232, 70 pCi/g; Ra-
226, 10 pCi/g; U-238, 77 pCi/g. Subsurface soil
Th-232, 180 pCi/g; Ra-226, 37 pCi/g; U-238,
<232 pCi/g. Stream sediment Th-232, 93 pCi/g;
Ra-226, 9 pCi/g; U-238 <57 pCi/g. Rn-222,
0.9-300 pCi/I in ground water.
Matrix Characteristics:
Tailings, soil, clay-like tailings; used as fill
material in several residential and commercial
properties; stream sediment; water; air.
Nonradioactive contaminants in soil and tailings:
arsenic, chromium, nickel, lead, cadmium,
beryllium, pesticides, methyl chloride, xylene,
toluene, ethyl benzene, acetone, MEK.
Source:
Maywood Chemical Works; extraction of thorium.
Approximate Area and Volume:
42 acres (entire location), area of contamination
not known; 270,000 cu yd.
Environmental Impact:
36,000 residents within 4-mi radius. Radon gas
found by NRC at levels higher than background in
EPA Contact Region II:
Douglas Johnson, FTS 264-1870
Status:
NPL Final, Rank 423.
Limited site characterization done at U.S. Radium
and satellite properties by EPA and NJDEP. Final
work plan for RI/FS prepared in July 1987. Field
investigation to begin in Fall 1987.
Radiation Data:
New Jersey Department of Environmental
Protection (NJDEP) has found radon and decay
products in air in elevated concentrations and
gamma radiation levels around property
significantly above background levels. U-238,
U-234, Th-230 and Ra-226 present in soil
and concrete and Rn-222 in air.
Surface Soil:
Ra-226 3.2-670 pCi/g
U -238 minor
Subsurface Soil (2-4.5 ft):
Ra - 226 2090-3290 pCi/g
U - 238 90-12000 pCi/g
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Matrix Characteristics:
Building materials, grounds, soil, surface, and
ground water.
Source:
Former radium ore processing plant, lab and
manufacturing facility, and radium cottage
industry.
Approximate Area and Volume:
One acre; estimated 10,000 cu yd of tailing waste
on-site.
Environmental Impact:
32,000 residents within 1/2-mi radius. NJDEP
has found radon and decay products in air in
excessive concentrations; gamma radiation levels
around property greater than normal. Satellite
properties where radium dial painting and lab
work done may also be contaminated.
Source of Information:
EPA NPL Site status sheet. EPA Office of
Radiation Programs. "Final Work Plan for
Remedial Investigation and Feasibility Study, U.S.
Radium Corporation-site, City of Orange, Essex
County, New Jersey," Camp Dresser & McKee
Inc., for USEPA April 1987.
4. Radioactive Waste Superfund Site -
Description
Name and Location:
W. R. Grace & Co. (Wayne Plant), Wayne, New
Jersey
EPA Contact Region II:
Carole Peterson, FTS 264-6190
Status:
NPL Final, Rank 214
Site was partially remediated in 1986 by DOE.
Private residences along Sheffield Brook, where
thorium tailings were carried by surface runoff
cleaned in 1986. Excavations continued in
July/August 1987. Completion of excavation is
contingent upon locating a final disposal facility.
Temporary storage of thorium tailings will be at
Wayne Interim Storage Site (WISS) awaiting a
permanent disposal site in NJ. Most of the off-
site material has been removed.
Radiation Data:
Total U, 2.7 pCi/g; Th-232, 3.78 pCi/g; Ra-226,
5.1 pCi/g; Ra-228, 6.9 pCi/g; gamma radiation
and Rn-222 in 1985 were less than in 1984
findings, due to remedial activities at the site.
Matrix Characteristics:
Sand and gravel; tailings from processing
monazite ores; tailings buried on-site; surface
and ground water; air.
Source:
Thorium ore (monazite) extraction plant on-site.
Approximate Area and Volume:
6.5 acres; 120,000 cu yd.
Environmental Impact:
51,000 residents within 3-mi radius. Extensive
soil contamination. The potential for further
contamination by runoff has been abated
somewhat by work done to date at site.
Source of Information:
"Wayne Interim Storage Site Annual Site
Environmental Report Calendar Year 1985,"
DOE/OR/20722-103, Oak Ridge Operations
Office. August 1986.
5. Radioactive Waste Superfund Site -
Description
Name and Location:
Montclair/West Orange Radium Site and Glen
Ridge Radium Site, Essex County, New Jersey
EPA Contact Region II:
Robert McKnight, FTS 264-1870
Status:
NPL Final, Rank 178
EPA released a draft Remedial Investigation and
Feasibility Study (RI/FS) report 9/85. New Jersey
Department of Environmental Protection (NJDEP)
began remediation of nine residential properties
by excavating contaminated soil 6/85. EPA RI/FS
report considered remedial cleanup and disposal
alternatives. Due to the extent of radium
contamination, EPA has been conducting
additional field studies. As of 3/87, EPA has been
unable to solve the soil disposal problem and is
88
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developing a supplemental RI/FS to focus on
continuing protective action while final remedy is
developed.
Radiation Data:
Rn-222 gas in homes, 0.5-440 pCi/l before
remediation; radium in soil above background in
40% of properties; Ra-226, U-234 present.
Gamma radiation levels as high as 1300 pR/hr.
Subsurface concentration:
Ra 1 - 5386 pCi/g (maximum)
Th 1 - 4620 pCi/g(maximum)
U 1 - 248 pCi/g(maximum)
Matrix Characteristics:
Ash and cinders in discrete pockets; also
apparently mixed with soil (silt, sand, and gravel)
or used alone as fill.
6. Radioactive Waste Superfund Site -
Description
Name and Location:
Lodi Municipal Well, Lodi, Bergen County New
Jersey
EPA Contact Region II:
Richard Wice, FTS 264-1870
Status.-
NPL proposed.
Well closed 12/83.
RI/FS Work Plan being prepared. Field activities
scheduled to begin Fall 1987. RI/FS will determine
whether the source of contamination may be
attributed to either a man-made contaminant or
a naturally occurring source.
Source:
Alleged to be former radium-processing facility
nearby.
Approximate Area and Volume:
127 acres; 350,000 cu yd total in three separate
areas; over 750 properties involved.
Environmental Impact:
Approximately 750 properties in three areas.
76,000 residents within 3-mi radius. EPA,
Centers for Disease Control (CDC), Agency for
Toxic Substances and Disease Registry (ATSDR)
have determined the long-term impact on health
of residents.
Source of Information:
Superfund Program Fact Sheet 5/86; update
11/86 and 3/87.
"Radon Contamination in Montclair and Glen
Ridge New Jersey Investigation and Emergency
Response," by J.V. Czapor and K. Gigliello, and
J. Eng.
"Feasibility study for Montclair/West Orange, Glen
Ridge, New Jersey Radium Sites", Draft Final
Report, USEPA, 1985.
Radiation Data:
One well out of nine contaminated with gross
alpha radiation from U-238 decay.
Matrix Characteristics:
Ground water; VOCs present in most of nine
wells.
Source:
Possibly nearby thorium-processing facility, or
may be natural source.
Approximate Area and Volume:
One well radiologically contaminated; 2.35 sq mi.
Environmental Impact:
One well closed due to radiological contamination.
Other eight are shut down due to volatile organic
contamination. Lodi using alternate water supply.
Source of Information:
EPA NPL status sheet.
7. Radioactive Waste Superfund Site -
Description
Name and Location:
Lansdowne Property, 105-107 E. Stratford Ave.,
Lansdowne, Pennsylvania
89
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EPA Contact Region III:
Vic Janosik, FTS 597-8996
EPA Contact Region IV:
Harold Taylor, FTS 257-2234
Status:
NPL Final, Rank 703.
Based on a radiological assessment of the
property and a remedial action plan prepared by
Argonne National Laboratory in 1985, EPA has
decided to dismantle the duplex residence and
dispose of contaminated materials at a licensed
burial site (Hanford, WA).
Radiation Data:
Elevated gamma radiation levels. Soil, sewer
lines, building materials contaminated with Fta-
226, Th-230, Ac-227, and Pa-231. Rn at
0.021 - 0.309 working level (WL). Concentration
in soil: Ra-226, 797 pCi/g; TH-230, 30 pCi/g.
Matrix Characteristics:
Soil, concrete, other building materials, sewer line
waste.
Source:
Basement operation for radium purification and
packaging by former occupant.
Approximate Area and Volume:
52,000 sq ft of land; 2,000 cu yd contaminated
soil, extending to 8 ft depth.
Environmental Impact:
Severe contamination of building and surrounding
grounds. One family in area. ATSDR issued
(3/85) health advisory warning that radiation levels
in the structure were unsafe.
Source of Information:
Radiological Assessment Report and Remedial
Action Plans for the Lansdowne Property,
prepared by Argonne National Laboratory.
8. Radioactive Waste Superfund Site -
Description
Name and Location:
Maxey Flats Nuclear Disposal Site, Fleming City,
Hillsboro, Kentucky
Status:
NPL Final, Rank 612 RI/FS work plan completed
6/30/86 with focus on risk assessment and
evaluation of alternative remediation, based on
containment of waste. Consent order entered into
3/87 by EPA and site steering committee to
perform RI/FS per work plan.
Radiation Data:
Transuranic nuclides in the environment; elevated
concentrations of tritium, cobalt and strontium.
Site contains 2.4 million Ci of radioactivity
including 430 kg of special nuclear material and
64 kg of plutonium. Gamma radiation 10-32
pR/hr; 30,000 pCi/cu m activity level.
Matrix Characteristics:
Low-level radioactive waste burial facility;
leachate, soil, air; flora, fauna. Nonradioactive
contaminants: benzene, naphthalene, d-n-
oxylphthalate, 1,4-dioxane, dichlorodifluoro-
methane, 1,1-dichloroethene, pentanol, ethyl-
enediaminetetracetic acid, 2-methylpropionic
acid,2-methylbutanoic acid, 3-methylbutanoic
acid, valeric acid, isobutyric acid, 2-methyl-
butyric acid, 3-methylbutync acid, pentanoic
acid, 2-methylpentanoic acid, 3-methyl-
pentanoic acid, Cg-branched acids, phenol,
hexanoic acid, 2-methylhexanoic acid, cresol
(isomers), 2-ethylhexanoic acid, Co-branched
acid, benzoic acid, octanoic acid, phenylacetic
acid, phenylpropionic acid, phenylhexanoic acid,
toluic acid, p-dioxane, methyl isobutyl ketone,
toluene, xylene (isomers), cyclohexanol, dibutyl
ketone, fenchone, triethyl phosphate,
naphthalene, tributyl phosphate, a-terpineol.
Source:
Disposal site for various
waste sources.
low-level radioactive
Approximate Area and Volume:
280 acres (total site), 25 acres (contaminated),
178,000 cu yd.
Environmental Impact
One hundred residents live within 1-mi radius.
Leachate escaping through bedrock fractures into
underlying sandstone and trenches. Leachate
from a number of trenches contains soluble
plutonium. Evidence of migration of tritium from
90
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trench water to wells has been established but
not in high enough levels to pose a public health
hazard. Local residents are on public water
supply system, however.
Source of Information:
RI/FS Work Plan (6/86).
9. Radioactive Waste Super-fund Site -
Description
Name and Location:
West Chicago Sewage Treatment Plant, West
Chicago, Illinois
EPA Contact Region V:
Neil Meldgin, FTS 886-4726
Status.
NPL proposed. The Remedial Investigation Report
has been completed. Samples were analyzed for
metals, radon, thoron and thorium. Values were
presented for As, Ba, Cd, Cr, Fe, Pb, Hg, and Se.
Radiation Data:
The nominal concentration of Th-232 in the soil
was 4900 pCi/g; Th-232, 0.03 pCi/l; Th-230,
0.4 pCi/l; and Ra-226, 0.03 pCi/l were measured
in the ground water; gamma radiation, 2000-
3000 pR/hr.
Matrix Characteristics:
Soil; till; gravel; ground water; monazite ore.
Approximate Area and Volume:
25 acres (includes plant site and Reed-Keppler
Park and not just contaminated area); 40,000 cu
yd-
Source:
The Rare Earths Facility, an ore processing
facility that had been used to process thorium and
rare earth ores containing radioactive thorium,
uranium, and radium.
Environmental Impact:
There are several routes of potential risks to the
environment and public health, including direct
external radiation exposure; inhalation exposure;
and ingestion of contaminated soils, ground
water, and surface water. The contaminated
media at the site are wastes from the Rare Earths
Facility. The primary radionuchde present is
thorium-232.
Source of Information:
Remedial Investigation Report, Kerr-McGee
Radiation-sites, West Chicago, Illinois,
September, 1986 CH2M Hill.
10. Radioactive Waste Superfund Site -
Description
Name and Location:
Reed-Keppler Park, West Chicago, Illinois
EPA Contact Region V:
Neil Meldgin, FTS 886-4726
Status.
NPL proposed. The Remedial Investigation Report
has been completed. Samples were analyzed for
23 metals, Th-232, U-238. Ra-228, and Ra-
226 in the soil; and gross alpha, Th-232, and
Ra-226 in the ground water. Radiation Data The
concentrations of radioactivity in the ground water
samples were: Th-232, 23 pCi/l and Ra-226,
7.6 pCi/l. In the soil sample, Th-232 up to
11,000 pCi/g. Gamma exposure levels up to
16,000 pR/hr.
Matrix Characteristics:
Till, gravel, ground water, and air.
Approximate Area and Volume:
It is estimated that 20,000 cu yd of thorium-
contaminated material is located within the Park in
11,000 sq yd area.
Source:
The Rare Earths Facility, an ore processing
facility that had been used to process thorium and
rare earth ores containing radioactive thorium,
uranium, and radium.
Environmental Impact:
There are several routes of potential risks to the
environment and public health including direct
external radiation exposure; inhalation exposure;
and ingestion of contaminated soils, ground
water, and surface water. The contaminated
media at the site are wastes from the Rare Earths
Facility. The primary radionuclide present is
thorium-232.
91
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Source of Information:
Remedial Investigation Report, Kerr-McGee
Radiation-sites, West Chicago, Illinois,
September, 1986 CH2M Hill.
11. Radioactive Waste Super-fund Site -
Description
Name and Location:
Kerr-McGee Off-Site Properties, West
Chicago, Illinois
EPA Contact Region V:
Neil Meldgin, FTS 886-4726
Status:
NPL proposed. The Remedial Investigation Report
has been completed. Mitigation procedures were
carried out at 116 locations.
Radiation Data:
Contamination in excess of 2000-3000 yR/hr
was noted prior to the mitigative measures. Th-
232 up to 16,000 pCi/g in soil was measured.
Matrix Characteristics:
Till, gravel, fill, tailings.
Approximate Area and Volume:
The area consists of 117 residential lots of
various sizes. Approximately 61,000 cu yd.
Source:
The Rare Earths Facility, an ore-processing
facility that had been used to process thorium and
rare earth ores containing radioactive thorium,
uranium, and radium.
Source of Information:
Remedial Investigation Report, Kerr-McGee
Radiation-sites, West Chicago, Illinois, Septem-
ber, 1986 CH2M Hill.
12. Radioactive Waste Superfund Site -
Description
Name and Location:
Kress Creek and the West Branch of the DuPage
River, West Chicago, Illinois
EPA Contact Region V:
Neil Meldgin, FTS 886-4726
Status:
The Nuclear Regulatory Commission (NRC)
issued an order to Kerr-McGee to prepare a
cleanup plan for Kress Creek and affected
portions of the West Branch of the DuPage River.
The NRC's Atomic Safety Licensing Board upheld
Kerr-McGee's challenge. The NRC staff has
appealed this decision. Should the appeal fail,
EPA must consider using Superfund to remedy
the creek and river contamination.
Radiation Data:
About 1.5 mi of creek and river are contaminated
in the streams and along the banks. Peak total
thorium concentrations are 555 pCi/g at a depth
of 60 cm (2 ft). Thorium has been identified as
deep as 170 cm (6 ft). Peak gamma levels are
250 pR/hr along the bank.
Matrix Characteristics:
Sediment, soil, tailings.
Approximate Area and Volume:
Undetermined but substantial. Affected area is
about 1.5 miles of creek and river bed and the
adjacent banks.
Environmental Impact:
There are several routes of potential risks to the
environment and public health including direct
external radiation exposure; inhalation exposure;
and ingestion of contaminated soils, ground
water, and surface water. The contaminated
media at the site consists of wastes from the
Rare Earths Facility. The primary radionuclide
present is thorium-232.
Source.
The Rare Earths Facility, an ore processing
facility that had been used to process thorium and
rare earth ores containing radioactive thorium,
uranium, and radium.
Environmental Impact:
There are several routes for potential risks to the
environment and public health, including direct
external radiation exposure; inhalation exposure;
92
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and ingestion of contaminated soils, ground
water, and surface water. The contaminated
media at the site consists of wastes from the
Rare Earths Facility. The primary radionuclide
present is Th-232.
Source of Information:
Comprehensive Radiological Survey of Kress
Creek, West Chicago Area, Illinois, February
1984, Oak Ridge Associated Universities.
13. Radioactive Waste Superfund Site -
Description
Name and Location:
The Homestake Mining Co. Uranium Mill, Cibola
County, New Mexico, about 5.5 miles north of
Milan.
EPA Contact Region VI:
Ursula Lennox, FTS 255-6735
Status:
NPL Final, Rank 528. Homestake and EPA signed
an Administrative Order in June 1987 for
implementation of a workplan for a radon RI/FS
developed by New Mexico's contractor, Geomet.
A 15 month Rl testing program will be started by
Homestake in November 1987. Naturally
occurring dispersed tailings, ground water
contamination, and tailings piles may be
considered as to how they act as sources.
Radiation Data:
Rn-222 in the air, 0.03 WL; radium in the mill
tailings, 60-100 pCi/g; uranium in the water, 720
ppb. One year monitoring study of indoor and
outdoor radon concentrations. Outdoor radon
concentrations ranged from 0.05 pCi/l
(background) to 2.6 pCi/l.
Matrix Characteristics:
Soil, tailings, ground water, and air.
Approximate Area and Volume:
245 acres at 6,600 foot elevation; 16,500,000 cu
yd.
Source:
Potential sources are:
Homestake Mining Company uranium mill tailings,
Anaconda mill tailings, Ambrosia Lake mining
area, and areas of near-surface uranium
mineralization.
Environmental Impact:
About two hundred people depend upon the
shallow aquifer as a water supply. An alternate
water supply is in place, and aquifer restoration
by Homestake has been somewhat successful.
Radon levels indoors and outdoors in several
subdivisions near the mill may be above
background.
Source of Information:
Geomet Report Number IE-1739, March 20,
1987. "WORK PLAN FOR HOMESTAKE MINING
COMPANY STUDY AREA NEAR MILAN, NEW
MEXICO," RI/FS for E.I.D., R.P.B., State of New
Mexico.
14. Radioactive Waste Superfund Site -
Description
Wame and Location:
United Nuclear Corp., Church Rock, New Mexico.
The site is 15 miles northeast of Gallup, New
Mexico.
EPA Contact Region W.-
Alan Tavenner, FTS 255-6735
Status:
NPL Final, Rank 651 Remedial Investigation
begun January, 1985. United Nuclear is
developing a reclamation plan. The RI/FS is
scheduled for completion Spring, 1988
Radiation Data:
Measurements of ground water showed levels as
high as 12.6 pCi/l for Ra-226 and Ra-228 and
8.15 pCi/l for uranium. Th was measured at
40,000 pCi/l and Ra at 45 pCi/l. Data are shown
for As, Cr, Se, Cd, Pb, N, and S04.
Radioactive
Contaminants
U-238
Th-230
Ra-226
Rn-222
Tailings
Pile (pCi/g)
29
290
290
no data
3.9
9.3
1.3
no
Pond
x 103
x 104
x 102
data
(pCi/l)
pCi/l
pCi/l
pCi/l
93
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Matrix Characteristics:
Radiation Data:
Tailings, ground water. Nonradioactive
contaminants:
arsenic
barium
cadmium
lead
mercury
molybdenum
selenium
vanadium
zinc
Pond (mg/l)
1.22
0.29
0.11
1.56
0.5 x 10-3
2.30
0.53
46.94
7.22
Approximate Area and Volume:
The mill tailings pond covers 170 acres and is
15-20 ft thick; 4,700,000 cu yd.
Source:
The source of the radiation is a uranium mill site,
largely from the tailings ponds.
Environmental Impact:
Several people use the shallow alluvial aquifers in
the area. A break in the tailings dam in 1979 sent
93 million gallons of tailings fluid into the Rio
Puerco. The upper Gallup aquifer is contaminated
in the vicinity of the tailings pond. The alluvial
aquifer is also contaminated.
Source of Information:
Site Status Summary, May, 1987 and Technical
Memorandum, Phase I Field Study, RI/FS, United
Nuclear, Church Rock, N. Mexico, October 4,
1985, CH2M Hill.
15. Radioactive Waste Superfund Site -
Description
Wame and Location:
Weldon Spring Quarry, St. Charles City, Missouri
EPA Contact Region VII:
Katie Biggs, FTS 757-2823
Status:
NPL Final. Under an agreement with EPA (4/87),
DOE will clean up quarry and all nearby
contaminated properties and develop an
Environmental Impact Statement incorporating all
the requirements of a RI/FS.
According to results of monitoring by DOE and
the U.S. Geological Survey (USGS), radioactive
materials have been released to surface water,
ground water, and air. Thorium, uranium, and
radium residues have been placed in quarry.
Matrix Characteristics:
Drums, process equipment, building rubble,
debris, raffinate sludges and soils which range
from gravelly to clay-like and organically rich.
Soils and sludges are variably contaminated with
TNT, DNT, and other organics.
Source:
Uranium and thorium ore processing. Previously
US Army Ordnance works.
Approximate Area and Volume:
220 acre complex; quarry is 9 acres; 780,000 cu
yd radioactive material; 51,000 cu yd radioactive
residues were deposited in quarry along with
other wastes.
Environmental Impact:
Potential contamination of alluvial aquifer 0.5 mi
from quarry, serving 58,000 people. Uranium and
radium have been detected in off-site monitoring
wells, with radium concentrations exceeding
drinking water standards.
Source of Information:
Status report from EPA Region VII.
16. Radioactive Waste Superfund Site -
Description
Wame and Location:
Monticello Radioactivity-Contaminated Prop-
erties, Monticello, Utah (San Juan County)
EPA Contact Region VIII.
Lam Nguyen, FTS 564-1519
Status:
NPL Final, Rank 502. DOE has assumed
responsibility for most of the remedial action. EPA
is negotiating Memorandum of Agreement (MOA)
with DOE to better define respective roles in
clean-up activities. DOE has authorized clean-
up of 15 properties and is studying several more
94
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for inclusion in program. EPA conducted a
planned removal action of two of the most
contaminated structures in Monticello during
1983-1984.
Radiation Data:
Widely dispersed radioactive tailings; U-238, -
234, -226, Th-230, Rn-222, Ra-226.
Exposure Rates:
Ra-226 1-23,000 pCi/g
U-238 1-24,000 pCi/g
U 18,OOOpCi/g
Matrix Characteristics:
Tailings from vanadium and uranium ore
processing; radioactive tailings widely dispersed
throughout town as fill material and as aggregate
for mortar and concrete. Vanadium 1-16,532
ppm.
Source:
Uranium and Vanadium ore processing in
Monticello plant from 1942 to 1960. Some tailings
may have been brought in from another mill in
Dry Valley.
Approximate Area and Volume:
152 potentially contaminated properties; 182,000
cu yd.
Environmental Impact:
1500 residents within 1/2-mi radius. 152
potentially contaminated properties. Widely
dispersed contamination, apparently mostly in
near-surface soils.
Source of Information:
4/87 Fact Sheet. EPA Office of Radiation
Programs
17. Radioactive Waste Super-fund Site -
Description
Name and Location:
Denver Radium Superfund Sites, Denver,
Colorado
EPA Contact Region VIII:
Marilyn Null, FTS 564-1698
Status:
NPL Final, Rank 269. Feasibility Studies have
been completed for ten fund-lead operable units
and for four fund-lead operable unit ROD's are
pending. Remedial Design is underway at four
operable units. Negotiations with Potentially
Responsible Parties are underway at the
enforcement-lead operable unit.
Radiation Data:
U-234, -238, Th-230, Ra-226, Rn-222
present. Maximum gamma radiation
concentrations at properties included in the site
ranged from 57 pR/hr to 2,547 pR/hr, maximum
radium concentrations ranged from 79 pCi/g to
5,093 pCi/g, and maximum radon decay progeny
levels of 0.30 WL (grab) have been measured on
the site.
Matrix Characteristics:
Asphalt, soil, pond bottom sediment, building
debris and contents, ground water, and airborne
particulates.
Source:
Former Denver National Radium Institute and
other processors involved in radium processing
through World War I and early 1920s, generating
large quantities of radioactive residues.
Approximate Area and Volume:
Approximate volume 106,000 cu yd, covering a
total of about 40 acres in 44 locations within a
4-mi radius of downtown Denver.
Environmental Impact:
Potential risk to human health, including direct
exposure, inhalation of radon, mgestion of
radionuclides and contaminated media.
Source of Information:
Final Feasibility Study, Denver Radium site,
Operable Unit X, 6/87; Final Feasibility Study &
Responsiveness, Denver Radium Site, Operable
Units IV/V, Vols. I & II, 9/86; Remedial Alternative
Selection and Community Relations
Responsiveness Summary, Operable Unit VII,
3/86. Remedial Investigation Report April 1986.
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18. Radioactive Waste Superfund Site -
Description
Name and Location:
Lincoln Park, Canon City, Colorado
EPA Contact Region VIII:
Gene Taylor, FTS 564-1519
Status:
NPL Final, Rank 621. RI/FS submitted to EPA by
the State for review 3/86. Memorandum of
Agreement between State and EPA 4/86, the
State of Colorado has lead responsibility for
negotiations development and implementation of a
remedy.
Radiation Data:
Groundwater quality studies per 1987 USGS
report included Ra-226 between 0.05 and 1.6
pCi/l, and U-234 and -238 between 0.4 and
5,700 ng/l.
Matrix Characteristics:
Contaminated ground water derived from unlined
tailings ponds. Nonradioactive contaminants:
molybdenum and selenium.
Source:
Uranium mill (Cotter Corporation).
Approximate Area and Volume:
900 acres; 1,900,000 tons.
Environmental Impact:
386 residents within 3-mi radius. Contaminated
ground water in the vicinity and down gradient.
No permitted drinking water wells in the area.
Company's monitoring data indicate a plume of
contaminants, including molybdenum, uranium,
and selenium extending from mill and affecting
private wells that were serving 200 people.
Source of Information:
4/87 Fact Sheet. "Ground-water Flow and
Quality Near Canon City, Colorado." US
Geological Survey, WRI Report 87-4014, 1987.
EPA Office of Radiation Programs.
19. Radioactive Waste Superfund Site -
Description
Name and Location:
U.S. DOE Rocky Flats Plant, Golden, Colorado
EPA Contact Region VIII:
James Littlejohn, FTS 564-1519
Status:
NPL proposed. Compliance agreement entered
into by DOE, EPA, and Colorado Dept. of Health
7/86, defining respective roles and
responsibilities. DOE is responsible for remedial
actions. RI/FS work plans completed 2/87; results
due 7/87. DOE has done some remedial work
such as capping and removing plutomum-
contaminated soil.
Radiation Data:
Plutonium and tritium releases.
Matrix Characteristics:
Soil and sediment; wastewater impoundments.
Source:
Production of nuclear weapons triggers; plutonium
recovery; amencium research.
Approximate Area and Volume:
6,550 acres total area; 91 sites; over 1,000 waste
streams.
Environmental Impact:
Plutonium and tritium have contaminated soils
and sediments in surface water. Ground water
has been contaminated with nitrate.
Approximately 80,000 people live within 3 mi of
the facility.
Source of Information:
4/87 Fact Sheet; 7/85 NPL Fact Sheet.
20. Radioactive Waste Superfund Site -
Description
Name and Location:
Uravan Uranium Project, Montrose City, Uravan,
Colorado
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EPA Contact Region VIII:
Holly Fliniau, FTS 564-1519
Status:
NPL Final Rank 275. State of Colorado
negotiating remedy with responsible parties. EPA
and State have entered into MOA 4/86,
designating State to pursue effective remedy. The
State of Colorado has negotiated an agreement
with Responsible Parties, and the agreement has
been approved by U.S. District Court. EPA
submitted comments to State on remedial action
plan 12/86.
U-234, U-238;
Radiation Data:
Radionuclides and Rn-222,
Th-230; Ra-226.
Th 16,000 - 165,000 pCi/l
U 1,500 - 16,000 pCi/l
Ra 66 - 676 pCi/l
Matrix Characteristics:
Ground water and air, raffinate, tailings, surface
water. Selenium, nickel, ammonia, sulfates.
Source:
Uranium and vanadium recovery plant; milling
operations; little activity at present; owned and
operated by Union Carbide Corporation.
Approximate Area and Volume:
900 acres; 2,000,000 tons removed/10,000,000
tons stabilized.
Environmental Impact:
Town in remote area. 125 residents within 3-mi
radius. All residents moved December 1986; no
permanent residents. Ground water and air
contaminated with process waste, including
uranium. Discharge and disposal of large volume
of process wastes releasing radiation.
Source of Information:
4/87 Fact Sheet
Department of Energy Remediation
Programs
The DOE has four major site remediation projects
involving radioactive materials. They are the Uranium
Mill Tailings Remedial Action Project (UMTRAP), the
Formerly Utilized Sites Remedial Action Project
(FUSRAP), the Grand Junction Remedial Action
Project (GJRAP), and the Surplus Facilities
Management Program (SFMP).
Formerly Utilized Sites Remedial Action Project
(FUSRAP)
The U.S. Army Corps of Engineers, Manhattan
Engineer District (MED) and its successor, the U.S.
Atomic Energy Commission (AEC) conducted
programs during the 1940s and 1950s involving
research, development, processing, and storage of
radioactive ores and their processing residues.
Virtually all of this work was performed for the Federal
government by private contractors at sites that were
either federally, privately, or institutionally owned.
Many of these sites and nearby properties were
contaminated with radionuclides at low concentrations
and mostly of natural origin.
When the contracts for MED/AEG activities were
terminated, the sites were decontaminated according
to then-current health and safety criteria and
released for unrestricted use. However, as research
on the effects of low-level radiation progressed,
radiological criteria and guidelines for returning sites
to unrestricted use became more stringent. In 1974,
the AEC initiated a program to identify former
MED/AEC sites and to determine their radiological
status based on a review of historical records. In
1977 the AEC changed to the US DOE which
subsequently initiated FUSRAP [1,3]. Figure B1
shows the locations of the FUSRAP sites [2].
The most seriously contaminated sites, located in
New Jersey and New York, were involved in storing,
sampling, and processing very rich pitchblende ores.
As of June 1987, a total of 29 sites in 12 states were
designated for remedial action [J. Wagnor, DOE,
Personal Communication, July 2, 1987]. Preliminary
estimates are that 29 authorized sites may contain a
total volume of 1.1 million cu yd of low-level
contaminated dirt, sediment, and rubble. Of these,
remediation has been completed to the satisfaction of
the DOE at seven sites [A. Wallo, DOE, Personal
Communication, July 2, 1987]. The disposition of
these seven sites as per DOE is as follows:
Radiologically contaminated materials from
Kellex Research (Jersey City, NJ), Bayo
Canyon, and Acid Pueblo Canyon (Los
Alamos, N.M.) were excavated and removed
to an authorized disposal facility.
Radiologically contaminated material from
Middlesex Landfill (Middlesex, NJ) was
excavated and stored at an interim storage
site (above grade with a leachate collection
system).
97
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Figure B1. FUSRAP sites as of 1 982. (Reprinted from [2].)
Albany Metallurgical Research
Center, Albany, OR
University of California, Berkeley, CA
(Completed) 7
Acid/Pueblo Canyon, Los Alamos,
NM (Completed) 8
Chupadera Mesa, White Sands 9
Missile 10
Range, NM (Completed)
Hazelwood (Latty Avenue), MO 11
St Louis Airport Storage Site,
(Vicinity Prop ), St Louis, MO
St Louis Airport Storage Site,
St. Louis, MO
Mallmckrodt, Inc , St. Louis, MO 12
University of Chicago, Chicago, IL 13
(Completed)
National Guard Armory, Chicago, IL 14
General Motors, Adrian, Ml
Niagara Falls Storage Site, (Vicinity
Prop ), Lewiston, NY 15
Ashland Oil Co #1, Tonawanda, NY 16
Seaway Industrial Park, Tonawanda, 18
NY 19
Linde Air Products, Tonawanda, NY 20
Ashland Oil Co #2, Tonawanda, NY
Universal Cyclops, Allquippa, PA 21
22
W R Grace & Company, Curtis Bay,
MD
Middlesex Landfill, Middlesex, NJ
Middlesex Sampling Plant,
Middlesex, NJ
Du Pont & Company, Deepwater, NJ
Maywood, NJ
Wayne/Pequannock, NJ
Colome, NY
Seymour Speciality Wire, Seymour,
CT
Shpack Landfill, Norton, MA
Ventron, Beverly, MA
Radiologically contaminated laboratory
buildings at the University of California
(Berkeley, CA) and the University of Chicago
(Chicago, IL) were surface cleaned (washed,
scraped, chipped).
Investigation showed that the seventh site,
Chupadera Mesa (White Sands, NM),
required no cleanup.
The remaining twenty-two sites are undergoing
remediation or are awaiting remediation. Three of the
twenty-two are also Superfund sites:
1. Shpack Landfill, Norton/Attleboro, MA.
2. Maywood Chemical Company, Maywood, NJ.
3. W. R. Grace & Company, Wayne, NJ.
Remediation at vicinity properties consisted of land
disposal or burial in a land encapsulation approved for
radioactive waste. In some cases site buildings were
decontaminated and returned to use, and in other
cases they were demolished and the rubble stored or
buried.
Removal and containment of contaminated materials
has been the strategy used thus far at FUSRAP sites.
None of the other techniques described in this report
has been attempted in full-scale remediation.
Uranium Mill Tailings Remedial Action Project
(UMTRAP)
The use of uranium for weapons research and
production resulted in the generation of huge
quantities of uranium mill tailings, the waste material
remaining after uranium is extracted from the uranium
ore. The Atomic Energy Act of 1954 authorized the
AEC to license the receipt or transfer of ores that
contained 0.05% or more of uranium and/or thorium.
However, the AEC exempted any unrefined and
unprocessed ore and processed uranium mill tailings,
which were assumed to contain less than the required
percentage of uranium and thorium. Due to this
exemption, the uranium industry was not required to
isolate or even to retain control of uranium tailings.
Although most of the uranium has been removed
from the tailings, the radium remains and is a source,
through radioactive decay, of radon gas. Also,
98
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radionuclides and other trace elements present in the
tailings can be leached from the pile and contaminate
the ground water [2].
In 1978, Congress passed Public Law 95-604, the
Uranium Mill Tailings Radiation Control Act of 1978,
based on the finding that uranium mill tailings located
at mill sites posed a potential health hazard to the
public. Title I of the Act instructed the DOE to
perform remedial actions at the designated sites,
which contained a total of approximately 25 million cu
yd of tailings. The program to carry out these actions
is the Uranium Mil! Tailings Remedial Action Project
(UMTRAP).
The remediation also includes cleanup of those
contaminated properties outside the designated
boundaries of the processing sites that became
contaminated through the use of tailings for fill and/or
construction. Approximately 8000 of these "vicinity"
properties have been identified for surveying to
confirm the presence of tailings and contamination
levels requiring remedial action [2,4].
Of the 24 UMTRAP sites, one is in Pennsylvania
(Canonsburg) and 23 in the western United States
(Figure B2). The sites range in size from 10 acres to
over 500 acres and include tailings piles, evaporation
ponds, windblown contaminated areas, and former
mill buildings and associated structures. Depths of
tailings piles range from a few feet to over 275 feet in
Durango, Colorado. Many of the sites have exposed
tailings. Some sites are covered with a foot or so of
soil or sparse vegetation.
Some of the UMTRAP sites, such as Grand Junction
and Rifle, Colorado, are adjacent to river systems.
Many, such as Canonsburg, PA; Gunnison, CO; and
Shiprock, NM, are near small rivers or creeks, and
many sites have shallow water tables [5].
Remedial action began at the first site in 1983, and
cleanup of all sites is scheduled for completion in
1993 [6]. For tailings piles, remediation consists
principally of stabilization through the use of liners
and covers to prevent migration and limit radon
emanation. This approach is consistent with EPA
regulation 40 CFR 192. For vicinity properties,
remediation consists principally of excavation and
disposal of contaminated material to tailings piles,
cleaning of buildings, and, where necessary,
destruction of buildings and removal of the rubble.
Grand Junction Remedial Action Project
Between the years 1952 and 1966, several hundred
thousand tons of tailings were removed from the
Climax Uranium Company's mill tailings pile in Grand
Junction, Colorado and used locally as fill and
construction material. In 1966, when the Colorado
Department of Health and the U.S. Public Health
Service discovered this fact, the practice was
stopped, and investigations were begun to determine
the potential radiological health effects of tailings use
in residential and commercial or civic construction. In
1972, the U.S. Surgeon General issued guidelines for
determining the need for corrective action at those
locations where increased levels of radiation were
measured as a result of the presence of tailings. The
U.S. Congress passed PL 92-314 in 1972,
authorizing Federal appropriations to assist the State
of Colorado in conducting a remedial action project at
Grand Junction. The objective was to perform
corrective action at sites where radiation exposures
exceeded the Surgeon General's guidelines. The
project is a State-operated activity, with DOE
providing 75 percent of the funding and the State, 25
percent [7].
In order to obtain the benefits of the project, a
property owner had first to apply to the Colorado
Department of Health for a determination of eligibility.
The criteria for eligibility (the Surgeon General's
guidelines) were based on annual average exposures
to external gamma radiation, or inhalation of airborne
radon daughter products resulting directly from
uranium mill tailings used in the construction of a
building. Of these two modes of exposure, the
inhalation of airborne radon daughters is by far the
more important in terms of numbers of locations
exceeding the criteria and in terms of potential
population exposure [8].
The cleanup project began in 1973. The assessment
project had identified 740 structures that would
require some form of remedial action to meet the
Surgeon General's guidelines. Schools and the more
highly contaminated dwellings were given first priority.
The project was to have been completed by the end
of fiscal year 1987.
Whenever possible, the contaminated sites have been
cleaned up by excavation and removal of tailings.
Remediation has been confined to the area of the
structure and out to a distance of ten feet surrounding
it. In many cases, the structure has been shored up
and material actually excavated from beneath it. The
original tailings site was used to store the tailings
from the cleanups. That site, in turn, will be cleaned
up under UMTRAP [T. Brazley, DOE, Personal
Communication, July 23, 1987].
Where removal of the tailings is not possible, the
structures have been remediated by applying sealants
or increasing ventilation and filtration to reduce radon
gas in the structures to acceptable levels [7].
Starting in about 1975, the Colorado Department of
Health, DOE, and the USEPA conducted a survey of
approximately 40,000 properties. The survey identified
about 6,000 vicinity properties as "core sites," which
were contaminated to some degree. Some of the
99
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Figure B2. Locations of DM TRAP sites. (Reprinted from [2].)
1 Lakeview, OR (Medium Priority)
2 Lowman, ID (Low Priority)
3 Salt Lake City, UT (High Priority)
4 Grand River, UT (Low Priority)
5 Grand Junction, CO (High Priority)
6 Natunta, CO (Medium Priority)
7 Slickrock, CO (Low Priority) (2 sites)
8 Mexican Hat, UT (Medium Priority)
9 Monument, AZ (Low Priority)
10 Tuba City, AZ (Medium Priority)
11 Ambrosia Lake, NM (Medium
Priority)
12 Shiprock, NM (High Priority)
13 Durango, CO (High Priority)
14 Gunnison, CO (High Priority)
15 Rifle, CO (High Priority) (2 sites)
16 Maybell, CO (Low Priority)
17 Riverton, WY (High Priority)
18 Spook, WY (Low Priority)
19 Bowman, ND (Low Priority)
20 Belfield, ND (Low Priority)
21 Edgemont, SD (High Priority)
(Vicinity Properties Only)
22 Falls City, TX (Medium Priority)
23 Canonsburg, PA (High Priority)
properties remediated under the Grand Junction
Remedial Action project are included in UMTRAP,
e.g., where remediation is necessary beyond ten feet
from the structure. The list has been narrowed to
about 3,800 properties requiring remediation. About
2,000 have been recommended by ORNL for
inclusion in the UMTRAP cleanup. This remedial
project has been initiated.
A second part of the UMTRAP effort is remediation
(which may include relocation) of the original tailings
pile from which all of the problem tailings originated.
The actual fate of the tailings pile has not yet been
decided.
Surplus Facilities Management Program (SFMP)
The overall objective of the SFMP is to provide the
program direction, planning, and resources for the
DOE surplus facilities to (1) maintain surplus facilities
in a safe condition pending decommissioning, (2)
maximize the options for future use of real property,
and (3) dispose of all radioactive facilities and waste
in accordance with accepted practices. Other
objectives include (1) providing research and
development funding for property and equipment
decommissioning techniques and technology transfer,
and (2) conducting cooperative information
exchanges on decommissioning activities with other
countries and international organizations.
The current inventory of surplus facilities in the
program was established by review of facilities in
1977 and by subsequent addition of some facilities
from defunct programs. Thirty-five projects at 17
sites are included in the civilian portion of the SFMP.
The sites were prioritized based on (1) the
assessment of potential for exposure to the public
and workers at the site, (2) contractual commitments,
(3) reducing the cost of continuing surveillance and
maintenance, and (4) making the property available
for alternative or unrestricted use.
Decommissioning has been conducted at the Special
Power Excursion Reactor Test Area in Idaho, at
Argonne National Laboratory-East in Illinois, vicinity
properties at Monticello, Utah, and buildings at the
Santa Susana Field Laboratory, in California.
Entombment projects have been completed at the
Bonus Facility in Puerto Rico, the Hallam Facility in
Nebraska, and the Piqua Facility in Ohio. Major
activities continue at the Idaho National Engineering
Laboratory in Idaho, the Mound Laboratory in Ohio,
Santa Susana in California, Monticello in Utah, and
ANL-East in Illinois [9]. The Shippingport Station
Decommissioning Project will place the station in a
100
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long-term radiologically safe condition by dismantling
and removing the radioactive portions of the plant.
One of the purposes of the Project is to demonstrate
to the nuclear industry the practical and affordable
dismantlement of a large nuclear power plant. Actual
physical decommissioning activities were initiated in
September 1985.
Other near term activities include initiating work at the
Weldon Spring Site. This site was first used by the
Department of the Army as an ordnance works and,
later, by a DOE predecessor agency as a uranium
feed materials plant. The site is contaminated with
thorium, uranium, and decay products. Near-term
activities include further characterizing the
contamination on the site, initiating conceptual
engineering studies, establishing a project office at
the Weldon Spring site, and completing the NEPA
documentation.
Both the Weldon Spring and Monticello sites are also
Superfund sites. The Surplus Facilities Management
Program is scheduled for completion in the early
2000's.
Summary of Remediation Methods Used
to Date
Most of the remedial technologies to date have
consisted of excavation and/or removal of
contaminated materials from plant sites and from
property owned by others in the vicinity of those
properties. In some cases, the contaminated material
has been temporarily stored in above-ground,
covered piles. In others, the material has been
permanently placed in secure land encapsulations.
No extraction or solidification technology has been
applied to any of these sites. Some laboratory
experimentation on radionuclide extraction from
tailings and soils have been conducted, as described
in Chapters 5, 6, and 7.
References
1. U.S. Department of Energy. Pathways Analysis
and Radiation Dose Estimates for Radioactive
Residues at Formerly Utilized MED/AEC Sites.
ORO-832, Revised, 1983.
2. U.S. Department of Energy, Office of Remedial
Action and Waste Technology Program Summary,
DOE/NE-0075. November 1986.
3. U.S. Department of Energy. Methods for
Assessing Environmental Impacts of RAP
Property Cleanup/Interim Storage Remedial
Action. ANL/EIS-16, Argonne National
Laboratory, 1982.
4. Stassi P.J., M.A. Jackson, and A.O. Clark.
Remedial Action at Vicinity Properties.
Proceedings of the Symposium on Waste
Management, Tucson, AZ. March 24-28, 1985.
5. Meyer, H.R., D. Skinner, J. Coffman, and J.
Arthur. Environmental Protection in the UMTRA
Project. Proceedings of the Fifth DOE
Environmental Protection Information Meeting,
Albuquerque, NM., November 6-8, 1984.
6. Matthews, M.L. UMTRA Project: Implementation
of Design. Geotechnical and Geohydrological
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7. U.S. Department of Energy, Program Summary
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8. U.S. Department of Energy, Grand Junction
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DOE/EV10162-T1. Assistant Secretary for
Environment, Washington, D.C., December 1980.
9. U.S. Department of Energy. Office of Defense
Waste and Transportation Management. 1987
Program Summary Document. April 1987.
101
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111
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Abbreviations and Symbols
AEC
ATSDR
CDC
CERCLA
Ci
cm
cu ft
cu m
cu yd
DOE
EPA/USEPA
FS
ft
FUSRAP
9
hr
kg
kg/hr
kW
MED
jim
mm
NJDEP
NRC
NPL
ORNL
pCi
pCi/g
pCi/l
Rl
RI/FS
SARA
sq ft
sq m
sq yd
UMTRAP
uR
USGS
WL
U. S. Atomic Energy Commission
Agency for Toxic Substances and Disease Registry
Centers for Disease Control
Comprehensive Environmental Response, Compensation, and Liability Act of I960
(Superfund)
Curie
Centimeter (10-3 meter)
Cubic foot
Cubic meter
Cubic yard
Department of Energy
U. S. Environmental Protection Agency
Feasibility Study
Foot or feet
Formerly Utilized Sites Remedial Action Program (Department of Energy)
Gram
Hour
Kilogram (1000 grams)
Kilograms per hour
Kilowatt (1000 watts)
U. S. Army Corps of Engineers, Manhattan Engineering District
Micron (micrometer, 10-6 meter)
Millimeter (10-3 meter)
New Jersey Department of Environmental Protection
Nuclear Regulatory Commission
National Priorities List
Oak Ridge National Laboratory
Picocurie (10'12 Curie)
Picocuries per gram
Picocunes per liter
Remedial Investigation
Remedial Investigation/Feasibility Study
Superfund Amendments and Reauthorization Act of I986
Square foot
Square meter
Square yard
Uranium Mill Tailings Remedial Action Project (Department of Energy)
Microroentgen (10~6 roentgen)
U. S. Geological Survey
Working level
112
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Convers/ons
To Convert From (A)
acre
cu ft
cu yd
°F
ft
kW
mile
sq ft
tons
°C
Curies
meter
kg
mg/l
atmosphere (atm)
To(B)
hectare
cu m
cu m
°C
m
kg-calones/min
meters
sq m
kg
°F
disintegrations per minute
yd
Ib
parts per million
kilo Pascal (kPa)
Multiply (A)
0.4047
0.02832
0.7646
.BY
(°F-32)x5/9
0.3048
1.434
1609
0.0929
1016
(°Cxg/5) •»
2.2 x 1012
1.094
2.2046
1.0
101
• 32
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Key
Name
Actinium
Aluminum
Arsenic
Barium
Beryllium
Bismuth
Boron
Bromine
Cadmium
Calcium
Carbon
Chlorine
Chromium
Cobalt
Copper
Fluorine
Helium
Hydrogen
Iodine
Iron
Lead
Lithium
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Niobium
Nitrogen
Oxygen
Palladium
Phosphorus
Platinum
Plutonium
Polonium
Potassium
Radium
Radon
Selenium
Silicon
Sodium
Strontium
Sulfur
Thorium
Tin
Titanium
Tungsten
Uranium
Vanadium
Zinc
Chemical Elements
Abbreviation
Ac
Al
As
Ba
Be
Bi
B
Br
Cd
Ca
C
Cl
Cr
Co
Cu
F
He
H
1
Fe
Pb
Li
Mg
Mn
Hg
Mo
Ni
Nb
N
0
Pd
P
Pt
Pe
Po
K
Ra
Rn
Se
Si
Na
Sr
S
Th
Sn
Ti
W
U
V
Zn
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Glossary
Air Avid
Alpha particle
Alpha radiation
Background
radiation
Ball decks
Beneficiation
Beta particle
Beta radiation
Blinding
Detection level
Dose Equivalent
Entry routes
Exfiltration
External
radiation
Gamma
radiation
Grizzly screen
ground water
Half-life
Indoor air
To increase by addition of chemicals the affinity of fine particles for air bubbles.
A positively-charged subatomic particle emitted during decay of certain radioactive
elements. For example, an alpha particle is released when radon-222 decays to
polonium-218. An alpha particle is indistinguishable from a helium atom nucleus and
consists of two protons and two neutrons.
The least penetrating type of radiation. Alpha radiation can be stopped by a sheet of paper
or outer dead layer of skin.
The radioactivity in the environment, including cosmic rays from space and radiation
that exists elsewhere - in the air, in the earth, and in man-made materials. In the U.S.,
most people receive 100 to 250 millirems of background radiation per year.
A tray of rubber balls that bounce against the bottom surface of a screen, thus eliminating
blinding.
Preparation of ore for smelting
A negatively-charged subatomic particle emitted during decay of certain radioactive
elements. A beta particle is identical to an electron.
Emitted from a nucleus during fission. Beta radiation can be stopped by an inch of wood or
a thin sheet of aluminum.
Plugging of the screen apertures with slightly oversized particles.
The minimum concentration of a substance that can be measured with a 99% confidence
that the analytical concentration is greater than zero.
The product of the absorbed dose, the quality factor, and any other modifying factors. The
dose equivalent is a quantity for comparing the biological effectiveness of different kinds of
radiation on a common scale. The unit of dose equivalent is the rem. A millirem (mrem) is
one one-thousandth of a rem.
Pathways by which soil gas can flow into a house. Openings through the flooring and walls
where the house contacts the soil.
The movement of indoor air out of the house.
Radiation originating from a source outside the body, such as cosmic radiation. The source
of external radiation can be either natural or man-made.
A form of electromagnetic, high-energy radiation emitted from a nucleus. Gamma rays are
essentially the same as x-rays and require heavy shieldmgs, such as concrete or steel, to
be stopped.
Screen made of heavy fixed bars, used to remove oversized stones, tree stumps, etc.
Subsurface water that is in the pore spaces of soil and geologic units.
The length of time in which any radioactive substance will lose one-half its radioactivity.
The half-life may vary in length from a fraction of a second to thousands of years.
That air that occupies the space within the interior of a house or other building.
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Ion exchange
Internal
radiation
Isotopes
Mesh
Microrem(pR)
Microrem per
hour (uR/hr)
Millirem (mrem)
NARM
ORNL
Picocurie (pCi)
Picocurie per
liter (pCi/l)
Plutonium
Radiation
Radioactivity
Radionuclide
Radon
Radon progeny,
Radon daughter
REM
Revolving Screen
The reversible exchange of ions contained in a crystal for different ions in solution, without
destroying the crystal structure or disturbing the electrical neutrality.
Radiation originating from a source within the body as a result of the inhalation, ingestion, or
implantation of natural or man-made radionuclides in body tissues.
Different forms of the same chemical element that are distinguished by having different
numbers of neutrons in the nucleus. A single element may have many isotopes. For
example, the three isotopes of hydrogen are protium, deuterium, and tritium.
Number of wires per inch in a screen.
A unit of radiation "dose equivalent" that is equal to one one-millionth of a rem.
A unit of measure of the rate at which "dose equivalent" is being incurred as a result of
exposure to radiation.
A unit of radiation "dose equivalent" that is equal to one one-thousandth of a rem.
Naturally-occurring or accelerator-produced radioactive materials mean any radioactive
material except for material classified as source, by-products, or special nuclear material
under the Atomic Energy Act of 1954, as amended.
Oak Ridge National Laboratory
A unit of measurement of radioactivity. A curie is the amount of any radionuclide that
undergoes exactly 3.7 x 1010 radioactive disintegrations per second. A picocurie is one
trillionth (1012) of a curie, or 0.037 disintegrations per second.
A common unit of measurement of the concentration of radioactivity in a gas or liquid. A
picocurie per liter corresponds to 0.037 radioactive disintegrations per second in every liter.
A heavy, radioactive, man-made metallic element. Its most important isotope is fissionable
238pU! which is produced by the irradiation of 238(j. Routine analysis cannot distinguish
between the 239pu and 240pu isotopes, hence, the term 239,240pu.
Refers to the process of emitting energy in the form of rays or particles that are thrown off
by disintegrating atoms. The rays or particles emitted may consist of alpha, beta, or gamma
radiation.
A property possessed by some elements, such as uranium, whereby alpha, beta, or gamma
rays are spontaneously emitted.
Any naturally occurring or artificially produced radioactive element or isotope.
A colorless, odorless, naturally occurring, radioactive gaseous element formed by
radioactive decay of radium atoms. Chemical symbol is Rn, atomic weight 222, half-life
3.82 days.
A term used to refer collectively to the intermediate products in the radon decay chain.
Each "daughter" is an ultrafine radioactive particle that decays into another radioactive
"daughter" until finally a stable nonradioactive molecule of lead is formed and no further
radioactivity is produced.
An acronym for Roentgen Equivalent Man; a unit of radiation exposure that indicates the
potential impact on human cells.
A screen with a surface that revolves around an axis; the screen surface may be inclined or
vertical.
116
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Rotary sifter
Scalping
Shaking screens
Sieve bends
Soil gas
Tailings
Uranium
Vibrating screen
Working level
(WL)
Circular motion applied to a rectangular or circular screen surface.
Removal of small amounts of oversized material from feed.
Several screen surfaces in a series, usually slightly inclined, with different apertures and a
slow linear motion essentially in place of the screen.
Screens with stationary parallel bars at a right angle to the feed flow; the surface may be
straight, with a steep incline, or curved to 300°.
Those gaseous elements and compounds that occur in the small spaces between particles
of the earth or soil. Rock can contain gas also. Such gases can move through or leave the
soil or rock depending on changes in pressure. Radon is a gas that forms in the soil
wherever radioactive decay of radium occurs.
Sand-like waste resulting from uranium production, represents about 98% of the ore that
enters the mill.
A naturally radioactive element with the atomic number of 92 (number of protons in nucleus)
and an atomic weight of approximately 238. The two principal naturally occurring isotopes
are the fissionable U-235 (0.7% of natural uranium) and the fertile U-238 (99.3% of
natural uranium).
An inclined or horizontal rectangular screening surface with a high-speed vibrating motion
that lifts particles off the surface.
A unit of measure of the exposure rate to radon and radon progeny defined as the quantity
of short-lived progeny that will result in 1.3 x 1Q.5 MeV of potential alpha energy per liter of
air. Exposures are measured in working level months (WLM); e.g., an exposure to 1 WL for
1 working month (173 hours) is 1 WLM. These units were developed originally to measure
cumulative work place exposure of underground uranium miners to radon and continue to
be used today as a measurement of human exposure to radon and radon progeny.
US GOVERNMENT PRINTING OFFICE 1988-548-158/87027
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