United States
Environmental Protection
Agency
Office of
Solid Waste and
Emergency Response
Publication 9380.MOFS
May 1992
Characterization Protocol
for Radioactive
Contaminated Soils
Office of Emergency and Remedial Response
Office of Radiation Programs. ANTR-4SK
Quick Reference Fact Sheet
The Superfund Amendments and Reauthorization Act of 1986 (SARA) mandates that remediation at
Super fund sites must utilize a permanent solution and alternative treatment technologies or resource recovery
options to the maximum extent practicable. Treatment technologies that permanently and significantly reduce
the mobility, toxicity, or volume of hazardous substances are preferred in this requirement. However, in most
remedial actions conducted to date at radioactive sites, the radioactive soil has been excavated and stored in
temporary above-ground containment facilities. To alleviate this storage situation the Office of Radiation Pro-
grams has developed an innovative soil characterization process applicable in the RI/FS stages of the Superfund
process to support the development of technologies for on-site volume reduction of radioactive soils by physical
separation1'2 technologies.
BACKGROUND
The volume reduction methods employed are based
on physical/mechanical technologies that are
common to the coal and ore processing industries.
These common technologies have been adapted,
modified, and directed toward the task of soil
restoration. This soil characterization protocol is
designed to demonstrate the suitabilitiy (or lack
thereof) of various radioactivity contaminated soils
for physical or chemical separation processes.
These could potentially remove the radioactive
fraction from the soil, thus producing a smaller
volume requiring disposal. The protocol combines
radiochemical and petrographic analysis of soil
fractions, focusing on the contaminant waste and its
particle size distribution in the host media. Soil
remediation by volume reduction takes advantage of
the fact that radionudide contaminants concentrate
generally in the smaller soil size fractions, and tend
to selectively associate with materials that possess
unique physical and/or chemical properties. The
data obtained by following this protocol are used as
the first phase of remediation assessment to
determine if volume reduction is feasible.
CHARACTERIZATION DESCRIPTION
This soil characterization protocol examines the
various size fractions of a representative sample of
radioactive soil from a Superfund site, to provide
the following information:
Grain size distribution curve which relates
weight percent versus particle size.
Relationship of radioactivity to particle size.
Identification of the mineral/material
composition and physical properties of the
radioactive contaminants for the various
size fractions.
Identification of the mineral composition
and physical properties of the host material
for the various size fractions.
Addtional information on contaminant and
host material mineralogical and physical
properties in support of feasible volume
reduction techniques, e.g., magnetic
Drooerties.
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These data are used to conceptualize a site-cpecific
volume reduction process based on one or more of
the following technologies:
screening,
classification,
gravity separation,
magnetic separation,
flotation,
chemical extraction,
washing,
scrubbing,
surface de-bonding, and
attrition.
The two-tiered soil characterization protocol, as
shown in Figure 1, consists of feasibility analyses
(Tier I), and optimization analyses (Tier II), as
necessary, to cost-effectively maximize the volume
reduction.
Pre-Tier I
Prior to Tier I laboratory tests, the representative
contaminated soil samples obtained in compliance
with EPA and DOE directives from a site'''4'5 are
radiologically screened to assure that the activity
levels are within laboratory license requirements
and that proper safety practices will be applied.
Additional chemical analyses should be performed
on a portion of each soil sample for the presence of
organic and heavy-metal constituents if that
information has not been previously collected. This
information not only identifies hazardous
constitutents (e.g., cyanide, heavy metals,
chlorinated hydrocarbons), but also contributes to
the mineralogical determination of the soil.
The remaining portions of each soil sample are
oven dried at 6CPC prior to weighing. The upper
limit of 60°C is specified in order to maintain the
mineral integrity of the soil by preventing the loss of
water of hydration associated with the mineral
structures which occur in some clays and other
minerals at low temperatures.
Tier I
Tier I begins with radioanalysis of the dry soil
samples by high-resolution gamma spectroscopy,
and if necessary, alpha and beta spectroscopy
analysis (.using standard leaching/digestion and
chemical methods6) to determine the level and type
of activity present in each sample.
Physical separation of the soil particles is
accomplished by mixing at least 250 grams of each
soil sample with water to produce a liquid-to-solid
(L/S) ratio of 5/1, agitating the mixture with a
vigorous motion for 30 minutes at ambient
temperature, and wet screening7 through a set of
nested sieves. In some site specific cases it may be
advantageous to perform a less vigorous wash
because of the nature of the constituents. The
standard sieves include at least mesh sizes 4 (4.75
mm), 50 (0.30 mm), 100 (0.15 mm), and 200 (0.075
mm). Each soil fraction is dried at 60°C, weighed,
and analyzed for radionuclide activity. From this
procedure the weight and radionuclide distribution
by particle size is determined. A similar separation
is also performed using hydroclassification methods.
The results of these tests indicate the compatability
of the soil to remediation by particle-size
hydroseparation techniques.
[NOTE: All water used must be collected and
analysed since it may contain transferred radioactive
contaminants, Target Analyte List metals, volatile
organic solvents, and/or pesticides. The analytical
results will determine if the water can be recycled,
safely disposed down a drain, or if it must be
treated as a hazardous waste.]
Petrographic analysis is conducted on each of the
size fractions to identify the mineral/material
composition and physical properties cf the
radioactive contaminants and host materials.
Petrographic procedures8'9'10 include the use of
binocular and petrographic microscopes to provide
a statistical point count of all materials larger than
silt-size to 0.038 mm (400 mesh size), and x-ray
diffraction analysis of fines less than 0.038 mm si/e.
Density separations are made on sand and sili M/C
fractions (030 to 0.045 mm) to concentrate heavy
particles greater than 3.0 specific gravity using
sodium polytungstate as the separating liquid The
heavy fractions, in many cases, provide I\VUN on
radioactive particles which tend to concentrate m
minerals or anthropogenic radioactive maicruK of
the heavy fractions. The degree of weathering.
presence of coatings, particle shape, surface u-ourc.
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Figure 1: Soil Characterization Flow Chart
[Contaminated Soil |
Sample I
TIER 1
Radiochemical
Analysis
Soil Washing
(Particle Liberation)
Wash Water
Chemical and
Radiochemical
Analysis
Treat/Dispose
Chemical
Extraction
Analysis
Classification/Screening
(Particle Separation)
Soil Sized Fractions
Petrographic
Analysis
Radiochemical
Analysis
Laboratory Tests
Particle
Liberation
Tests
Particle
Separation
Tests
Operational
Parameters
LEGEND
O
^^2
Volumetric reduction feasible?
, Additional physical and chemical data recommend?''
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hardness, magnetism, and degree of aggregation or
homogeneous nature are also physical properties
examined for interpretations that relate to
adsorption, waste form, and potential physical
separation methods.
Tier I Report
Tier I tests results are gained from the petrographic
and radiochemical analysis of the size fractions, as
depicted in Figure I, to assess the feasibility of using
volume reduction as a remediation technology. The
test results include a grain size distribution curve of
weight percent versus particle size, graphic data on
activity level versus pcm.icle size, and tables and
graphs on complete physical and mineralogic
descriptions. This data is instrumental to the
interpretation of the radioactive contaminants
concentration in specific size ranges and the physical
similarity and difference of the contaminants in
relation to host materials.
It is assumed that the petrography and
radiochemistry will be performed by personnel who
are qualified by education and experience to employ
the methodology specified and that
recommendations for additional tests to validate key
parameters for future tests will be incorporated in
the report, e.g., recommend analysis of diagnostic
elements that constitute chemical signatures to
radioactive compounds. Radiochemical data should
also be correlated with mineralogic data for
interpretations, e.g., secular equilibrium of
radionuclides to validate natural radioactive mineral
assemblages reported or in the event of non-secular
equilibrium of radionuc1ides, to reflect on
anthropogenically enhanced radioactive waste forms
in the radioactive soil. Any historic data on the ore
minerals used and chemical processes used to
convert the radionuc1ides to anthropogenic
compounds should also be reported for the forensic
data it might provide to support the list of
radioactive compounds reported in the Tier I
testing.
The Tier I report will provide an assessment of the
technical feasibility of using one or more of the
volume reduction technologies. Based on the
feasibility of the most promising alternative, the
Tier I report will also provide recommendations on
further testing (Tier II) focusing on the validation of
key factors that affect volume reduction. On the
other hand, an evaluation of the test data could lead
to the preliminary conclusion that volume reduction
is not technically feasible.
Tier II .
If the Tier I test data indicates the soil is
~atisfactory for remediation consideration Tier II
testing is conducted. Tier II tests are designed to
coUect additional data for further characterization of
contaminated soils. For example, additional soil
fractions may be tested to focus on the mineral .
phase of opaque constituents, particle coatings, or
special materials requiring more precise
instrumentation for validation of particles than was
made available for Tier I tests. Additional tests
may also be necessary to provide optimum soil
separation sizes. These tests can be performed with
small soil volumes. The results are to be used to
plan bench-scale tests that are designed to take
advantage of unique physical and chemical
characteristics of radioactive contaminants and host
soil constituents. Tier II tests to be considered are
in support of one of the foUowing general categories
of treatment technologies:
Particle separation,
Particle liberation, and
Chemical extraction.
Particle separation is the separation of a mixture of
various particles into two or more portions. For....
example, magnetic separation separates a mixture of
soil particles based on the difference in magnetic
susceptibilities.
Particle liberation is die physical de-bonding of
contaminated particles or coatings from clean
particles. For example, attrition removes friable
coatings from soil particles.
When performing chemical extraction, the soil is
immersed in a solvent that has been carefully
chosen to preferentially extract the contaminant.
Selected chemical extraction tests may be performed
in Tier II (as shown in Figure 1) to determine the
potential for remediation by simple chemical
extraction. Chemical extraction tests are designed
to remove contaminants from selected particle-size
fractions or from whole soil if it proves to be
unsuitable for remediation by physical separation
techniques. For example, the latter possibility exists
for soils with uniform radionuc1ide distribution
among the various particle sizes.
The chemical extraction tests are conducted on 100
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gratn samples of selected soil fractions or whole
soil. On a sample in which the nature of the
contaminant is poorly known, extractions are
performed at 90°C with water and each of four
extracting reagents known to be effective in
removing various radionuclides from contaminated
soils. These reagents include dilute solutions of
hydrochloric acid, nitric acid, sodium chloride with
hydrochloric acid, and sodium hexametaphosphate.
With foreknowledge of the presence of a
contaminant in a particular mineral form, one or
two other select extracting reagents specific for the
mineral are also included in these preliminary tests.
The results of these tests provide information about
the potential of chemical extraction as a
complement or alternative to remediation.
Along with Tier I results, data from the Tier II tests
can be used to select bench-scale test equipment for
conducting remediation tests of contaminated soils.
The initiation of bench-scale testing is based on the
preliminary information pr<.'vided by soil
characterization which assesses the differences in
physical properties between the waste form and host
materials. For example, for physiCal volume
reduction the applicable information relating to the
differences in the waste form from the host material
may be classified as follows:
Relationship of radioactivity to particle
SlZes.
Relationship of radioactivity to particle
densities.
Relationship of radioactivity to particle
wettabilities.
Relationship of radioactivity to particle
shapes.
Relationship of radioactivity to particle
magnetic properties.
Relationship of radioactivity to friability of
particles or of particle coatings.
Solubility of contaminants. .
The most important information is the relationship
of radioactivity to particle sizes. The information
on the other physical properties such as density is
obtained by identifying the waste form and host
matrix using" petrographic techniques. It is
important to develop this petrographic information
for various ranges of particle size. And, based on a
careful analysis of this information, a preliminary
bencl.t-')cale test can be designed using batch
applications of physical methods if a difference in
the physical properties stated exists between the.
radioactive contamination and the host materials.
Tier II Report
The Tier II report consists of the test data
generated in the categories depicted in Figure I. In
most cases, except for the chemical extraction tests,
the Tier I recommendations provided focus on
amplification of specific objectives that appear in
tables and graphs in the report. Tier II tests results,
just like Tier I tests results, are evaluated to assess
the feasibility of using volume reduction, and if so,
to what degree. The evaluation has focus on the
physical differences previously cited between the
waste form and host materials for design of bench-
scale tests that will provide more realistic
quantification of degree of separation possible by
volume reduction equipment. The nature of the site
specific soil drives the testing performed so that,
while no standard format is presented, it is assumed
that the test objectives will be governed by qualified
personnel skilled in the state of the art of quality
benefication testing. The report data can thus
generate preliminary cost and time assessments that
relate to the feasibility of volume reduction for the
particular site.
SUIiMARY
The characterization protocol desaibed above for
radioactive contaminated soils depends mainly upon
the physical, chemical, and mineralogical
characteristics of the soil and radioactive particles
with respect to grain size. The intent is to return
the "clean" soil fractions, which can be a major
portion of the soil (by volume), to the ground,
preferrably on-site.
Supplemental information concerning this protocol
may be obtained from James Neiheisel or Mike
Eagle at (202) ~9630, ANR 461, U.S.
Environmental Protection Agency, 401 M Street
SW, Washington, D.C. 20460.
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REFERENCES
1.
Neiheisel, James, Site Characterization for the
Remedial Design at National Priority List and
FUSRAP Sites, Proceedings of the
Department of Energy Environmental
Restoration Conference, ER 91, pp 439-442,
Pasco, W A. Sep 8-11, 1991.
6.
EPA. Radiochemistry Procedures Manua4
EPA 520/5-84-006, August 1984.
2.
EP A. Assessment of Technologies for the.
Remediation of Radioactivity Contaminated
Superfund Sites, EPA/540/2-90/001, January
1990.
7.
Richardson, W.S., Hudson, T.B., WooG, J.G.,
and Phillips, C.R., Characterization and
Washing Studies on Radionuclide
Contaminated Soils, Superfund 89:
Proceedings of the 10th National Conference, .
p. 198-201, Hazardous Materials Control
Research Institute, Silver Springs, MD, 1989.
3.
EP A. Soil Sampling Quality Assurance User's
Guide, Second Edition, EPA/600/8-89/046,
March 1989.
8.
ASTM, C-295-85, Standmd Practice fo,
Petrogl'tJphic Exmnination of Aggregate for
Concrete, in Annual Book of ASTM
Standards, Sect. 4, Construction, Vol. 04.02
for Concrete and Mineral Aggregates, 1986.
4.
EP A. Methods for Evaluating the Attainment
of Cleanup Standards, Vol. 1: Soils and Solid
Media, EPA 230/02-89-042, 1989.
9.
Hutchison, C.S., Laboratory Handbook of
Petrogl'tJphic Techniques, John Wiley and
Sons, New York, 1974.
5.
U.S. Department of Energy, The
Environmental Survey Manua4 DOE/EH-
0053, Vol 1-4, August 1987.
10.
Neiheisel, James, Characterization of
Contaminated Soil from the Montclair/Glen
Ridge, New :ersey Superfund Sites, U.S. EPA
Office of Radiation Programs, EPA/500/1-
89-012, 1989.
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