402R06007
SJ>
Inventory of Radiological
Methodologies
For Sites Contaminated with
Radioactive Materials
-------
EPA 402-R-06-007
www.epa.gov
October 2006
Inventory of Radiological
Methodologies
For Sites Contaminated
With Radioactive Materials
U.S. Environmental Protection Agency
Office of Air and Radiation
Office of Radiation and Indoor Air
National Air and Radiation Environmental Laboratory
Montgomery, AL 36115
Recycled/Recyclable
Printed with Soy/Canola Ink on paper that
contains at toast 50% recycled fiber
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Inventory of Radiological Methodologies
This report was prepared for the National Air and Radiation Environmental Laboratory of the Office of
Radiation and Indoor Air, United States Environmental Protection Agency. It was prepared by Environmental
Management Support, Inc., of Silver Spring, Maryland, under contract 68-W-00-084, work assignment 46,
and contract 68-W-03-038, work assignments 10 and 26, all managed by David Garman. Mention of trade
names or specific applications does not imply endorsement or acceptance by EPA. For further information,
contact Dr. John Griggs, U.S. EPA, Office of Radiation and Indoor Air, National Air and Radiation
Environmental Laboratory, 540 South Morris Avenue, Montgomery, AL 36115-2601.
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Inventory of Radiological Methodologies
Preface
This compendium is part of a continuing effort by the Office of Radiation and Indoor Air and the
Office of Superfund Remediation and Technology Innovation to provide guidance to engineers and
scientists responsible for managing the cleanup of sites contaminated with radioactive materials.
The document focuses on the radionuclides likely to be found in soil and water at cleanup sites
contaminated with radioactive materials. However, its general principles apply also to other media
that require analysis to support cleanup activities. It is not a complete catalog of analytical method-
ologies, but rather is intended to assist project managers in understanding the concepts, require-
ments, practices, and limitations of radioanalytical laboratory analyses of environmental samples.
As with any technical endeavor, actual radioanalytical projects may require particular methods or
techniques to meet specific analytical protocol specifications and data quality objectives.
Detailed guidance on recommended radioanalytical practices may be found in current editions of
the Multi-Agency Radiological Laboratory Analytical Protocols Manual (MARLAP) and the Multi-
Agency Radiation Survey and Site Investigation Manual (MARSSIM), both referenced in this
document.
Comments on this document, or suggestions for future editions, should be addressed to:
Dr. John Griggs
U.S. Environmental Protection Agency
Office of Radiation and Indoor Air
National Air and Radiation Environmental Laboratory
540 South Morris Avenue
Montgomery, AL 36115-2601
(334) 270-3450
griggs.john@epa.gov
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Inventory of Radiological Methodologies
Acknowledgments
This manual was developed by the National Air and Radiation Environmental Laboratory (NAREL)
of EPA's Office of Radiation and Indoor Air (ORIA) in collaboration with ORIA's Radiation
Protection Division's Site Cleanup Center and with support from the Office of Superfund
Remediation and Technology Innovation.
Dr. John Griggs served as project lead for this document. Several individuals provided valuable
support and input to this document throughout its development. Special acknowledgment and
appreciation are extended to Mr. Stuart Walker, Office of Superfund Remediation and Technology
Innovation; Mr. Ronald Wilhelm, Office of Radiation and Indoor Air; Ms. Schatzi Fitz-James,
Office of Emergency Management, Homeland Security Laboratory Response Center; and Mr. David
Garman, Office of Radiation and Indoor Air, NAREL. Numerous individuals both inside and outside
of EPA provided peer review of this document, and their suggestions contributed greatly to the
quality and consistency of the final document.
Technical support was provided by Dr. N. Jay Bassin, Dr. Robert Litman, Dr. David McCurdy, and
Mr. Robert Shannon of Environmental Management Support, Inc.
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Inventory of Radiological Methodologies
Contents
List of Figures vii
List of Tables vii
Acronyms and Abbreviations ix
Radiometric Unit Conversions xii
1 Introduction 1
1.1 Scope and Purpose 2
1.2 Principles of Radioactivity 3
1.3 Radioactive Decay Chains 5
1.4 Radionuclides Covered in this Document 5
2 Overview of a Cleanup Process and Radiological Methodologies 7
2.1 Laboratory and Field Screening Methodologies 7
2.1.1 Gross Alpha and Gross Beta Methods 7
2.1.2 Gamma Analysis 9
2.2 Routine Methodologies 10
2.2.1 Gross Alpha and Gross Beta Methods 10
2.2.2 Spectrometric Methods 10
2.3 Specialized Methodologies 11
2.3.1 Mass Spectrometric Methods 11
2.3.2 Kinetic Phosphorimetry Analysis 11
2.4 Measurement Quality Objectives and Methodologies 12
3 General Analytical Considerations 12
3.1 Site Source Term 13
3.1.1 DOE Site Cleanup 13
3.1.2 Naturally Occurring Radioactive Materials Waste 14
3.2 Sample Preservation and Transport 16
3.2.1 Water 17
3.2.2 Soil 19
3.3 Parameters Affecting Quantification Using Radioactive Decay Counting Techniques . 19
3.4 Negative Results 20
3.5 Measurement Uncertainty 21
3.6 Sample Analysis Turnaround Time 22
3.6.1 Sample Receipt by the Laboratory 23
3.6.2 Sample Preparation Before Analysis 23
3.6.3 Homogeneity and Adequate Sample Preparation 24
3.6.4 Sample Digestion 25
3.6.5 Oxidation State and Speciation of Radionuclides in Environmental Samples . . 25
3.6.6 Addition of Radiotracers or Carriers 27
3.7 Chemical Separation Process 27
3.8 Sample Counting 28
3.9 Data Review and Report Generation 28
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Inventory of Radiological Methodologies
3.10 Units Used in Radioactivity Measurements 29
3.11 Measurement Quality Objectives and Performance Testing 29
3.12 Selecting a Method 30
3.12.1 Performance-Based Method Selection 30
3.12.2 Sources for Specific Method Information Available to the General Public .... 31
4 Radioanalytical Methodologies 31
4.1 Radioactive Decay Emissions Measurements 32
4.1.1 Gas Proportional Counting 32
4.1.2 Liquid Scintillation 32
4.1.2.1 Routine LSC Analysis 33
4.1.2.2 Photon-Electron Rejecting Alpha Liquid Scintillation 33
4.1.2.3 Cerenkov Counting 34
4.1.3 Gamma Spectrometry 34
4.1.4 Alpha Spectrometry 36
4.2 Atom-Counting Methods 37
4.2.1 Kinetic Phosphorimetry Analysis 37
4.2.2 Mass Spectrometry 38
4.2.2.1 Inductively Coupled Plasma-Mass Spectrometry 39
4.2.2.2 Thermal lonization Mass Spectrometry 40
4.2.2.3 Accelerator Mass Spectrometry 40
4.2.3 Summary of Analytical Methodologies, Minimum Detectable Concentrations, and
Instrument Types 41
5 Chemical and Physical Properties for Selected Radionuclides 43
5.1 Americium 43
5.2 Bismuth 44
5.3 Carbon 44
5.4 Cesium 45
5.5 Cobalt 45
5.6 Hydrogen (Tritium) 46
5.7 Iodine 47
5.8 Iridium 47
5.9 Lead 48
5.10 Nickel 49
5.11 Phosphorus 50
5.12 Plutonium 50
5.13 Radium 51
5.14 Strontium 52
5.15 Sulfur 53
5.16 Technetium 54
5.17 Thorium 55
5.18 Uranium 56
6 Reference Materials 57
6.1 Citations 57
6.2 Other Sources 60
VI
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Inventory of Radiological Methodologies
Appendix A: Glossary 62
Appendix B: Principles of Radioactive Decay and Radioactive Equilibrium 70
B. 1 Introduction 70
B.I.I Nuclides 70
B. 1.2 Radionuclides 70
B. 1.3 Radioactive Decay 71
B.I.4 Radioactive Decay Emissions 73
B.1.4.1 Alpha Particles 73
B.I.4.2Beta Particles, Positrons, and Conversion Electrons 74
B.I .4.3X-Rays, Gamma Rays, and Bremsstrahlung Radiation 74
B.I.5 Techniques for Radionuclide Detection 75
B.I.6 Radioactive Equilibrium 76
B.I.7 Useful Websites and Sources for Background Information on Radioactivity ... 77
Appendix C: Radionuclide Parameters and Characteristics 79
Appendix D: Tables of Radioanalysis Parameters 80
Appendix E: Nuclear Power Plant Decommissioning Sites 99
List of Figures
Figure 1 — Schematic example of sample process flow 2
Figure 2 — Nominal minimum detectable concentration for different radiation-detection and atom-
counting methods 41
Figure 3 — Uranium-238 decay chain 72
Figure 4 — Thorium-232 decay chain 72
Figure 5 — Uranium-235 decay chain 72
Figure 6 — Environmental and chemical factors affecting radioactive equilibrium 77
List of Tables
Table 1 — Radionuclides covered in this manual 5
Table 2 — Radionuclides with low-abundance gamma rays 9
Table 3 — Longer-lived radionuclides at DOE sites 14
Table 4 — Principal natural radionuclide decay series 15
Table 5 — Summary of preservation techniques for aqueous samples 19
Table 6 — Summary of elements and their common oxidation states 26
Table 7 — Energy range of radiochemical analyses 29
Table 8 — Possible gamma emitters that could appear in analyses due to NORM or NPP .... 35
Table 9 — Number of atoms of radionuclides with activity of 0.1 Bq 38
Table 10 — Analytical methods applicable to each radionuclide 42
Table 11 — Decommissioning status for shut-down power reactors 99
Table 12 — Important parameters associated with NPP analyses 101
vn
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Inventory of Radiological Methodologies
Acronyms and Abbreviations
(Excluding chemical symbols and formulas)
A atomic mass number, sum of protons (Z) and neutrons (N)
AA atomic absorption
AMS accelerator mass spectrometry
AMU atomic mass unit
APS analytical protocol specification
AS alpha spectrometry
ASTM American Society for Testing and Materials
ASV anodic stripping voltammetry
(3, P+ negatively and positively charged beta particles
Bq becquerel (1 dps)
BWR boiling water reactor
CERCLA .... Comprehensive Environmental Response, Compensation, and Liability Act of
1980("Superfund")
CFR Code of Federal Regulations
CIA United States Central Intelligence Agency
Ci curie
CsI(Tl) thallium-activated cesium iodide detector
d day
DCGL derived concentration guideline level
DHS United States Department of Homeland Security
DIL derived intervention level
DOD United States Department of Defense
DOE United States Department of Energy
DQO data quality objective
dpm disintegration per minute
dps disintegration per second
DTPA diethylenetriamine pentaacetic acid
DU depleted uranium
e electron
Epmax maximum energy of the beta-particle emission
EDTA ethylenediamine tetraacetate
EPA United States Environmental Protection Agency
FRMAC Federal Radiological Monitoring and Assessment Center (DOE)
FTIR Fourier transform infrared
g gram
Ge germanium semiconductor
GP gas proportional
GPC gas proportional counting
GS gamma spectrometry
Gy gray
h hour
HPGe high-purity germanium detector
HTGR high-temperature gas-cooled reactor
1C ion chromatography
viii
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Inventory of Radiological Methodologies
ICP inductively coupled plasma
ICP-MS inductively coupled plasma-mass spectrometric
IDA isotopic dilution analysis
IND improvised nuclear device (i.e., a nuclear bomb)
ISE ion-selective electrode
ISO International Organization for Standardization
IUPAC International Union for Pure and Applied Chemistry
keV thousand electron volts
KPA kinetic phosphorimetry analysis
LEGe low-energy germanium
LCS laboratory control sample
LS liquid scintillation
LSC liquid scintillation counter
MARLAP .... Multi-Agency Radiological Laboratory Analytical Protocols Manual
MARSSIM . . . Multi-Agency Radiation Survey and Site Investigation Manual
mCi millicurie (10 3 Ci)
MCL maximum contaminant level
MDA minimum detectable activity (of a radionuclide)
MDC minimum detectable concentration
MeV million electron volts
min minute
MQO measurement quality objective
MS mass spectrometry
N number of neutrons in the nucleus
Nal(Tl) thallium-activated sodium iodide detector
NCP National Oil and Hazardous Substances Contingency Plan
ng nanogram (10 9 g)
NORM naturally occurring radioactive material
NPP nuclear power plant site decommissioning
NRC United States Nuclear Regulatory Commission
PAG protective action guideline
PCB polychlorinated biphenyl
pCi picocurie (10 l2 Ci)
PERALS* .... Photon-Electron Rejecting Alpha Liquid Scintillation
PDMS post-defueling monitored storage
PMT photomultiplier tube
PWR pressurized water reactor
QA quality assurance
QC quality control
rad radiation absorbed dose
ROD radiological dispersal device (i.e., "dirty bomb")
REGe reverse-electrode germanium
rem roentgen equivalent: man
s second
Sv sievert
Si silicon semiconductor
SI International System of Units
SOW statement of work
ix
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Inventory of Radiological Methodologies
t,/2 half-life
TENORM .... technologically enhanced, naturally occurring radioactive materials
TIMS thermal ionization mass spectrometry
UV-VIS ultraviolet-visible spectrometry
VOC volatile organic compound
y year
Z atomic number: the number of protons in the nucleus
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Inventory of Radiological Methodologies
Radiometric Unit Conversions
To Convert
Years (y)
Disintegrations
per second (dps)
Bq
Bq/kg
Bq/m3
Bq/m3
Microcuries per
milliliter
(nCi/mL)
Disintegrations
per minute (dpm)
Gallons (gal)
Gray (Gy)
Roentgen
Equivalent Man
(rem)
To
Seconds (s)
Minutes (min)
Hours (h)
Becquerels (Bq)
Picocuries (pCi)
pCi/g
pCi/L
Bq/L
pCi/L
uCi
pCi
Liters (L)
rad
Sievert (Sv)
Multiply by
3.16 x 107
5.26x IO5
8.77x 103
1.00
27.0
2.70 x 10 2
2.70 x 10 2
IO3
IO9
4.50 x 10 7
4.50 x 10~!
3.78
100
IO2
To Convert
s
min
h
Bq
pCi
pCi/g
pCi/L
Bq/L
pCi/L
pCi
Liters
rad
Sv
To
y
dps
Bq
Bq/kg
Bq/m3
Bq/m3
uCi/mL
dpm
Gallons
Gy
rem
Multiply by
3.17 x 10~8
1.90 x i(r*
1.14x nr*
1,00
3.70 x 10 2
37.0
37.0
10"3
io-9
2.22
0.264
IO"2
IO2
XI
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INVENTORY OF RADIOLOGICAL METHODOLOGIES
1 Introduction
This report describes appropriate radioanalytical methodologies used to characterize environmental
samples containing radionuclides, including screening methodologies and radionuclide-specific
analyses. The document is intended for nonradioanalytical specialists, such as Remedial Project
Managers or Site Assessment Managers with backgrounds in geology, engineering, or hydrology.
Appendix A contains a glossary of terms used in this document.
This introduction briefly covers the nature and major types of radiation, natural and anthropogenic
sources of radionuclides, physical considerations unique to radiochemical analysis (such as half-
life), the general ways that different types of radiation may be measured, and an overview of the
major techniques (such as spectrometry, gross alpha and beta analysis, liquid scintillation and
proportional counting). This section also summarizes the aspects of radionuclides that differentiate
their analysis from stable and more common chemical contaminants. A more comprehensive
discussion of these topics is found in Appendix B.
Section 2 discusses the application of a long-term cleanup process with respect to radiological
methodologies described in this document and their application to the media described herein. It
provides the overview perspective of which methodologies would be applied at different stages of
a project, and how these support the measurement quality objectives (MQO) for the project. This
section puts into perspective how results of initial analyses would be used to provide more detailed
decision making regarding subsequent analyses and the methodologies to be used.
Section 3 reviews analytical considerations, such as the source term at representative types of sites
(DOE cleanup and naturally occurring radioactive materials waste sites). The section also considers
sample preservation and transport, parameters affecting quantification (such as oxidation state of
the radionuclide), measurement uncertainty, sample analysis and turnaround time, and measurement
quality objectives and performance testing.
Section 4 discusses appropriate analytical methodologies and includes tables indicating their
suitability for various environmental requirements, such as environmental media, screening, concen-
tration, typical detection limits, and any advantages or disadvantages to the methodologies for use
in mixed-waste situations. The section concludes with information on applicable analytical methods
for each radionuclide and their detection limits.
Section 5 provides methodologies and unique radioanalytical issues for 18 selected elements. For
each of the elements, a table in Appendix D summarizes the key isotopes of that element, their
radioactive emissions, achievable detection levels, and typical sample processing times for the
techniques used for analysis. Section 6 is a list of sources and web sites with reference materials that
support this document.
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Inventory of Radiological Methodologies
1.1 Scope and Purpose
The analysis of environmental samples for radionuclides requires the overlap of many different
scientific disciplines. This document provides an overview of how these disciplines mesh during the
sampling and analysis process. It does not go into the underlying scientific principles for each of
these disciplines but instead provides a summary of information, which will help to guide the user
when evaluating the process of radionuclide analysis in environmental samples.
The information presented here represents a small portion of the potential process for the
investigation and evaluation of sites that may have become radioactively contaminated. It is
important to note that this information can be used at many different stages of a site project in order
to select the appropriate methodology for the analysis results required to support the project MQOs.
Figure 1 shows the major steps for processing an environmental sample from receipt by the
laboratory to reporting. Each of these steps is described in this document, as well as the effect each
can have on final analytical results.
Receive Sample -
Homogenize/
Blend Mix or
Filter Sample
Non Destructive Testing
or
Evaporation Drying
Inspect
Sample Container
Destructive Testing
I
Add Tracer/Carrier
' I \^
or / or \ or
Furnace Acid Base
Combustion Treatment Treatment
Analytical Separations
Fusion
Sample Preparation
Physical Form
for Final Analysis
Analyze
Data Analysis and Reporting
FIGURE 1 — Schematic example of sample process flow
The scope of the document is limited to selected types of sites, samples, radionuclides, and
analytical methodologies. This document focuses on water and soil samples', and how sampling,
sample transport and preservation, and chemical analyses can determine the overall reliability of the
'Other media, including milk, meat, produce, and forage may require analysis for some site cleanup projects and during
responses at a nuclear power plant incident. Radionuclides in these media are analyzed routinely by EPA, and achievable
MDC values are available at www.epa.gov/narel/radnet/erdonline.html.
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Inventory of Radiological Methodologies
final data. Appendix C identifies characteristics and parameters for radionuclides to be found at
these sites. The types of sites that this document addresses are:
Department of Energy (DOE) site cleanup activities and
Naturally occurring radioactive materials (NORM) site cleanup activities.
For completeness, some data are provided in the appendices relevant to nuclear power plant
decommissioning.
The types of applicable water samples are ground water, surface runoff, and drinking water. This
document specifically excludes wastewater, seawater, or any water that has been chemically treated.
The three types of water samples addressed in this document have chemical characteristics that are
similar. Therefore, no distinction will be made between the way in which they are described in this
document for the purposes of radionuclide analysis. However, the water samples that are addressed
here may contain hazardous materials or hazardous wastes. For example, ground-water samples at
a DOE site may contain radionuclides like 137Cs and 3H and also volatile organic compounds (VOCs)
or lead.
The types of applicable soil samples are those expected to be found in a "clean" environment that
have been subjected to radioactive contamination. These samples may contain however materials
like polychlorinated biphenyls (PCBs) and paint residues. Thus, types of soils specifically excluded
are municipal landfill soils, sanitary waste system sludges, soils with significant contamination from
organic solvent or solid wastes, or ocean sediment.
The information provided in this document can assist individuals involved in a cleanup process for
a radioactively contaminated site. Three tiers of radioanalytical methodologies are presented that
may be used during the various phases of a cleanup process, including methodologies for soil
screening (EPA, 2000) and the determination of site-specific soil partition coefficients (Kd).
Although typical values of soil partition coefficients for radionuclides can be found in published
references (EPA, 1999), in many cases it may be desirable to determine a site-specific Kd value for
use in computer pathway analysis models in order to obtain a better estimate of the radiation risks
for existing or future radionuclide contamination and to determine acceptable remediation limits.
In most cases, in order to obtain accurate estimates of a site-specific Kd value for a radionuclide,
highly accurate (radionuclide-specific) laboratory radioanalytical methods should be used. It is
important that unique analytical protocol specifications be developed for the radioanalytical analyses
used for the determination of site-specific Kd values.
1.2 Principles of Radioactivity
A more detailed technical description of radioactivity can be found in Appendix B. The chemistry
of an element is determined by the number of protons in its nucleus. Elements are subdivided into
nuclides, defined as any species of atom having a specified number of protons and neutrons. For a
given number of protons, that element will be stable only if certain number(s) of neutrons are present
as well. Two atoms of an element with differing numbers of neutrons are referred to as isotopes.
Certain combinations of protons and neutrons lead the nucleus to be unstable and undergo
decomposition, known as radioactive decay. A nuclide that undergoes radioactive decay is referred
to as a radionuclide. The rate of radioactive decay is specific for each radionuclide and can provide
a means for distinguishing one radionuclide from another. The rate of decay is related to the number
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Inventory of Radiological Methodologies
of total radioactive atoms present at the time of measurement, or
where A is the rate of decay or "activity," measured in atoms decaying per second
X is the decay constant for the radionuclide in units of sec^' ( 0.693/t1/2), and
N is the number of atoms present at the time of the measurement.
The following formula identifies how the rate of radioactive decay changes as a function of time for
any radionuclide:
A = A0 e-xt
where A is the rate of decay at the time of measurement
A0 is the rate of decay at some time before the measurement is made, and
t is the time elapsed between the two activity measurements in the same units as >..
When the radionuclide undergoes decay, it is seeking to obtain energetic stability. In order to
achieve this stability, one or more atomic particles or photons will be emitted. This emission is
referred to as "radiation." The basic types of radiation are:
Alpha
Beta negative (equivalent to an electron)
Beta positive (a positron)
Gamma
X-rays.
The measurement of the energy, type, and number of these particles or photons emitted (per unit
time interval) can be related to the quantity of the radionuclides present in the sample. The
traditional radiochemical methods of analysis (such as gas proportional counting, liquid scintillation
and gamma-ray analyses) are able to provide specific analytical values for most radionuclides.
Some radionuclides have half-lives and particle energies that make it impossible to distinguish one
radionuclide from another with conventional techniques. Examples of these are 239Pu and 240Pu, or
243Cm and 244Cm. Their alpha particle energies are too close to be distinguished by particle counting
techniques, and their half-lives are too long to distinguish between the two isotopes by the rate-of-
decay evaluation method. Thus they are generally reported as a combined activity, such as "239/240pu
= 4.1x10 2 pCi/L," signifying that the stated value is the sum of the two radionuclide activities.
In recent years specialized methodologies (such as accelerator mass spectrometry, or inductively
coupled plasma-mass spectrometry) have been developed to analyze for such radionuclides
individually. These are discussed in sections 2, 3, and 4. These techniques look for total number of
atoms present of the radionuclides rather than examining the decay characteristics of the
radionuclides.
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Inventory of Radiological Methodologies
1.3 Radioactive Decay Chains
Many naturally occurring radionuclides undergo decay to atoms that are also radioactive. The
second generation radionuclide (referred to as first progeny) will decay to another atom, which also
may be radioactive. For a radionuclide such as 238U, this pattern continues until a stable element is
reached. The term used to describe the connection of these radionuclides is "decay chain." The 238U
decay chain has 14 progeny participants. This means that typical environmental samples containing
238U will also contain some concentration of all of its progeny as well. The amount of each will
depend on the sample history, environmental conditions and the individual chemistry of each
progeny and the parent.
1.4 Radionuclides Covered in this Document
The specific radionuclides discussed in this document are listed in Table 1, together with their
minimum detection limits and maximum allowable effluent concentrations in water according to
federal regulations. Other parameters are listed in Appendices A and B.
TABLE 1 — Radionuclides covered in this manual
Element
(Symbol)
Americium (Am)
Bismuth (Bi)
Carbon (C)
Cesium (Cs)
Cobalt (Co)
Hydrogen (H)
Iodine (I)
Indium (Ir)
Lead (Pb)
Nickel (Ni)
Phosphorus (P)
Plutonium (Pu)
Radium (Ra)
Strontium (Sr)
Sulfur (S) 1
Technetium (Tc)
Thorium (Th)
Radionuclide/
Isotope
(Mass Number)
241
243
210
I H ""
134
, 137
60
r 3
125
129
131
192
, 210
59
63
1 ~32
238
239
240
241
226
228
r ^
90
35
99
227 ^
228
230
232
Minimum Detection
Limits*
pCi/L (mg/L)
§
u §
§
§
10 (7.7x10 12)
§
1 §
1 x 103 (1.03x10-'°)
§
§
1 (8.0x10-")
§
§
§
§
§
§
§
§
o
1 (l.OxlO-9)
1 (3.7X1Q-12)
10(3.4xlO-'3)
2(1.4x10-")
§ 1
§
§
§
§
§
Maximum Contaminant Levels in
Water*
pCi/L (mg/L)
15" (4.38x10-")
15" (7.53x10-*)
_
2,000 (4.48xlO-7)
80(6.22x10-")
200(2.31x10-")
100(8.86xl012)
20,000 (N/A)
_
1 (5.68x1 0-6)
3(2.41x]0-'5)
100 (2.41 xlQ-'5)
-
300(3.77x10-")
50(8.83x10-'°)
30(1.05xlO-13)
15" (8. 87*10-'°)
15**(2.42xlO-7)
15" (2.76x10-'°)
300(2.92x10-")
51 (5.06x10-")
5; (1.8x10-")
20(6.89xlO-'3)
8(5.81x10-")
500 (inorganic only) (1.17x10-")
900(5.32xl05)
15"(4.88xlO-'3)
15" (1.83x10-")
15"(7.29xlO-7)
15" (1.37xlOM)
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Inventory of Radiological Methodologies
Element
(Symbol)
Uranium (U)1
Natural Uranium (U)TsS
Gross alpha (a)
Gross beta (P)
Radionuclide/
Isotope
(Mass Number)
234 §
235 §
238
—
—
Minimum Detection
Limits*
pCi/L (mg/L)
1.5(2.41xl(T7)
1.5(6.9x10^)
1.0(0.003)
2.0(3.0x10-')
T
J
4
Maximum Contaminant Levels in
Water*
pCi/L (mg/L)
15(2.41x10-'')
15(6.9xlO-3)
10 (0.03)
20 (0.03)
15f(N/A)
4f mrem/y (N/A)
* 40 CFR 141 (EPA, 2002)
* The MDCs for these radionuclides are 10 percent of the concentration required for an individual whole body dose of
4 mrem/y (for pYy emitters), 15 pCi/L for a emitters (except 238U), or 0.03 mg/L (for total uranium), based on a daily
intake of 2 L of water. As an example, this would be about 10 pCi/L (8.8x 10 l2 mg/L) for 60Co.
f Only radium and uranium have MCLs (EPA, 2002). Values for the other radionuclides are derived from the gross alpha
and gross beta MCL values. To avoid exceeding the MCL, the total gross alpha or gross beta radionuclide activities
should not exceed 15 pCi/L.
1 The limit for 22bRa + 228Ra is 5 pCi/L.
** Assumes that the gross alpha concentration limit applies to each isotope.
1 If uranium is determined by mass-type methods (i.e., fluorometric or laser phosphorimetry), a 0.67 pCi/ug uranium
conversion factor must be used. This conversion factor is based on the 1:1 activity ratio of 234U to 238U that is
characteristic of naturally occurring uranium in rock. The actual relationship between uranium mass concentration
(ug/L) and activity (pCi/L) varies somewhat in drinking water sources, because the relative amounts of the
radioactive isotopes that make up naturally occurring uranium (238U, 235U, and 234U) vary among drinking water
sources. The typical conversion factors that are observed in drinking water range from 0.67 up to 1.5 pCi/ug.
The drinking water regulations lists the "maximum contaminant level" (MCL) for each radionuclide
as the concentration (in pCi/L) that would result in a dose of 4 mrem/y if ingested. MCLs are often
risk-based cleanup levels. OSWER Directive 9200.4-18 (EPA, 1997) provides guidance on
establishing risk-based protective cleanup levels for Superfund sites contaminated with radiation.
For each emitter that is detected by the laboratory, the analyst must divide the pCi/L found in the
sample by the value in the conversion tables. This provides a fraction of how much the particular
beta or photon emitter is providing towards the maximum of 4 mrem/y for all of the beta photon
emitters (EPA, 2002). In order to ensure that the 4 mrem/y dose limit is not exceeded, the sum of
the individual fractions (for each radionuclide) should not exceed 1.0. Table 1 identifies the
minimum detection limit (also referred to as the "required detection limit," or RDL) that any
radioanalytical method must have in order to be acceptable for processing samples for that
radionuclide. The example below demonstrates the calculation of the sum of fractions for a sample
containing strontium and tritium:
Radionuclide
%Sr
3H
MCL
(pCi/L)
"8
20,000
Sample
(pCi/L)
6
8,000
Fraction
0.75
0.40
Sum of fractions: 1.15
Although each radionuclide individually is less than its respective MCL, the sum of the fractions is
greater than 1.0. Therefore, this would not be an acceptable water source. Facilities that discharge
radionuclides in their wastewater streams, have limits identified in 10 CFR 20 based on the radiation
dose calculated by analyzing environmental pathways. The effluent concentration values noted here
are from 10 CFR 20 (Appendix B, Table 2, Column 2), and have been converted to pCi/L. These
values are included here as a reference. Specific effluent limits for individual sites would be
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Inventory of Radiological Methodologies
established based on the requirements of the project.
2 Overview of a Cleanup Process and Radiological Methodologies
Radioactive contamination in soil and water can be determined by several different laboratory
methodologies. However, the type of site, the stage of the project that is being investigated, the
levels to which the contamination is to be determined at that site, and the specificity of the analyses
needed, will determine which of these methodologies will be appropriate. Methodologies used for
determination of radioactivity can be placed into three broad categories:
• Screening,
• Routine, and
• Specialized.
Each of these methodologies may be appropriate at different stages of a cleanup process. The
greatest selectivity for radionuclides will lie in the specialized methodologies. These generally will
be the most expensive and take the longest amount of time to perform.
2.1 Laboratory and Field Screening Methodologies
Using screening methodologies, it is possible to identify sites requiring immediate actions, as well
as areas requiring additional investigation. The screening methodologies may also allow the site
investigation team the insight into choosing which more sophisticated methodologies or analytical
techniques may be required.
Screening methodologies will generally be relatively quick (minutes to hours), are not radionuclide-
specific, require instrumentation that is not sophisticated and can be used with a minimal degree of
user training. An additional advantage is that considerable time is saved, because these techniques
do not employ chemical separations. Thus, it would be considered a limited-scope assessment
intended to determine the potential of the site for significant harm to public health or the
environment.
Site-specific action levels that are established early in the cleanup process may be adjusted as
additional data are assessed. Preliminary screening levels may initiate immediate response activities,
or may indicate that radionuclide-specific methodologies should be used for more definitive
measurements. For example, emergency response or removal could be triggered by the results of a
screening method above a certain threshold. The action levels may need to be flexible enough to
expand the scope of investigation for potential radionuclides so that the initial assessment can
accurately depict the problem. More detailed information on these detection methodologies is
provided in Section 4.
2.1.1 Gross Alpha and Gross Beta Methods
Gross screening methods are applicable when the MCL or derived concentration guideline level
(DCGL) of the radionuclide of interest is much greater than the concentrations of the total back-
ground radionuclides in the sample. These methods can identify the presence of radionuclides that
emit alpha or beta particles. The measurement made will identify the total number of particles
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Inventory of Radiological Methodologies
detected per unit time (e.g., per minute). However, it does not identify the amount or type of each
radionuclide that may be present. It allows the comparison of measurements in the suspect area to
measurements in nearby areas that are known to be free of the contamination under investigation.
Because the specific identity of the radionuclide may not be a principal concern at this point, this
analysis will identify the overall extent of the contamination in terms of gross quantity (measured
in counts per minute, cpm) and areas affected (in land area measurement units as well as depth
profile). If the gross-screening method is calibrated using a reference radionuclide, then analytical
results will be reported in disintegrations per minute.
Detection methods commonly used for making screening measurements include:
• Alpha/beta survey-type detectors (usually hand held);
• Gas flow proportional counters;
• Liquid scintillation detectors; and
• Other devices that have a thin "window" (i.e. the detector covering) that will allow the emitted
particles to interact with the detector.
These detection devices can differentiate between alpha particles and beta particles because their
energies on the detector are significantly different. However, without chemical separation, no
significant information about specific radionuclides can be gained by the gross alpha or beta count
rates.
Individual radionuclides will be either alpha or beta emitters (most of these will also emit gamma
radiation as a result of the alpha or beta decay). Alpha or beta particles emitted by different
radionuclides may not have the same energies, and this will result in different detection efficiencies.
Two examples of how these methods might be valuable will help to identify the conditions under
which they may be used.
Example 1. An old manufacturing process for luminescent dials used 226Ra. The storage area for the radium
was in the basement of the building (3 m below grade), which has since been filled in with soil. It is
necessary to determine the gross level of activity prior to site excavation to assess subsequent worker
hazards. An in situ measurement of radiation at grade using a hand-held device would most likely not yield
useful information because 226Ra is principally an alpha emitter (see Table 2), and these emissions would
not penetrate the soil. The progeny of 226Ra are all alpha and beta emitters, and their decay emissions would
also be shielded by the soil depth. However, thinly sliced segments of 3-m borings, could be measured
individually in the field with a a/[3 survey meter, or in the lab with a GP detector.
Example 2. A well located 0.5 km from the site in Example 1 may be affected by the radium in the soil.
Samples of the water may be analyzed at a laboratory without any sample preparation. A liquid scintil-
lation counter can be used for gross alpha determination, by appropriate adjustment of the instrument for
alpha response.
As shown in these examples, some types of screening methodology may not be applicable to certain
types of samples. For example an a/(3 survey meter would not be readily applicable to a screening
analysis of water samples for alpha emitters, nor would a liquid scintillation detector be applicable
for direct analysis of soils. The alpha/beta survey methods can be used in the field as well as in the
laboratory. The other methods are easily adaptable to field laboratories.
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Inventory of Radiological Methodologies
2.1.2 Gamma Analysis
Four distinct detection methods exist for screening-level gamma analysis:
• Geiger-Mueller (G-M) detector with a "beta shield";
• Cesium iodide [CsI(Tl)] detector (usually found only at research laboratories);
• Sodium iodide [Nal(Tl)] detector; and
• Germanium (HPGe) detector.
The four detection methods listed above are in order of increasing specificity and decreasing ease
of field measurement. The G-M detector with the beta shield closed will yield information regarding
gamma emitters above a certain energy threshold (~100 keV depending on the thickness of the beta
shield). The beta shield is a piece of metal (either steel or aluminum) that will absorb betas so they
do not interact with the gas-filled chamber of the counter. No information on the range of gamma
energies or the specific radionuclides would be available from this technique. The instrument is hand
held and needs no auxiliary equipment. The CsI(Tl) detector has low-energy resolution for gamma
rays in the energy range of-20 keV to 3,000 keV. It is very efficient, but it can only resolve peaks
that are on the order of 150-200 keV apart.
The Nal(Tl) detector is sensitive in the range of ~20 keV to 2,500 keV, depending on the detector
housing thickness and size of the detector. It can provide general information regarding the distribu-
tion of energies of the gamma emitters in the samples, and has a very high efficiency. However, it
most likely-cannot provide specific radionuclide identification. This is due to its limited ability to
distinguish gamma rays that are less than ~50 keV apart. Newer instruments can be hand held, but
older ones may need a high voltage power supply and cables.
The HPGe detectors can provide significant details regarding specific gamma emitting
radionuclides. It can distinguish gamma rays that are within about 1.5 keV of each other. A recent
application for this type of detection system is called ISOCS ("In Situ Objects Counting System").
This unit is field-portable, is mounted on a rolling cart, and requires a high-voltage power supply
and a supply of liquid nitrogen or an electronic cooling system.
Obviously, if the analytes in question are not gamma emitters (or weakly gamma emitting; see Table
2), then using this screening method may not provide useful information. These methods are used
routinely in the laboratory. However, several adaptations to the detection system hardware exist that
allow them to be used in the field.
TABLE 2 — Radionuclides with low-abundance gamma rays
Radionuclide
Principal Decay
Gamma, keV
Abundance, %
Radionuclide
Principal Decay
Gamma, keV
Abundance, %
89Sr
P-
909
9.5*10^
241Am
a
59.5
35.7
90Sr/90Y
p-
1761
l.lxKT2
237Np
a
86.5
12.6
241pu
P-
149
1.9*10^
232Th
a
911 (from228Ac)
27.2
2«pu
a
44.9
4.2x1 Q-2
M3Cm
a
278
14
i»!
P-
40 (32 X-ray)
7.5 (92.5)
228Th
a
84
1.21
252Cf
a
43(100)
16 (0.2)
226Ra
a
186(262)
3.3 (5* JO"3
)
Note: Several of these have additional, lower-abundance gamma rays as well
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Inventory of Radiological Methodologies
2.2 Routine Methodologies
In order to obtain radioactivity concentration for a specific radionuclide at environmental levels in
either soil or water media, chemical separations usually need to be performed. Data collected by
these routine methodologies are often used to characterize the concentration and distribution of
radionuclides; assess risk to human health and the environment; and potentially select technologies
for treatability testing to evaluate the performance and cost of the treatment technologies that are
being considered for cleanup. Because each treatment effort may be radionuclide- and matrix-
specific, a method that can differentiate the various radionuclides is important.
There are many different analytical procedures for separation of radionuclides from each other in
water and soil matrices. In each case, the chemical (i.e., elemental) characteristic of the analyte is
used for separating it from each of the other elements that may be present. Separation techniques,
such as precipitation, electroplating, or evaporation, are used to minimize the volume of the sample
fraction to be analyzed. At that point, the methods discussed in Chapter 5 (in greater detail) would
be used to quantify the activity of the radionuclide present. The routine methods are identified in the
next sections.
2.2.1 Gross Alpha and Gross Beta Methods
The analysis of radionuclides using these general methods of detection includes:
Gas proportional counting;
Liquid scintillation counting; and
Cerenkov counting (high-energy beta counting).
Each of these methods relies on effective chemical separation to determine low-level activity and
discriminate specific radionuclides (i.e., eliminate other radionuclides that might yield a positive
count rate when the radionuclide of interest is not present). Their major advantages are that these
methods generally have high detection efficiency and may minimize the sample counting time to
achieve a specific MDC. Their disadvantage is that they lack the energy discrimination necessary
to distinguish alpha or beta particles of different energies.
2.2.2 Spectrometric Methods
The methods that can be considered spectrometric are:
• Alpha spectrometry;
• Gamma spectrometry [either HPGe or Nal(Tl)]; and
• Photon-Electron Rejecting Alpha Liquid Scintillation (PERALS®).
The most discriminating of these analyses is alpha and gamma (HPGe) spectrometry because of the
high resolution of the solid state detectors they use. Thus, the identifying photon energies from 134Cs
and 137Cs can be separated using gamma spectrometry, and the identifying alpha energies from
241 Am and 243Am can be separated using alpha spectrometry. PERALS* can be used instead of alpha
spectrometry, or a Nal(Tl) detector can be used instead of an HPGe when effective chemical
separations are performed. They can be used to distinguish alpha particle energies that are ~ 150 ke V
10
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Inventory of Radiological Methodologies
different, and gamma ray energies as close as 50 keV, respectively. All of these methods are
described in detail in Section 4.
2.3 Specialized Methodologies
The specialized methodologies discussed in this document are kinetic phosphorimetry analysis
(KPA) and mass spectrometry. In contrast to measuring radioactive decay emissions, these special-
ized methodologies detect and measure the number of atoms of an element or isotope in a sample
by either emission of UV radiation from an excited state or by atom counting, respectively. Mass
spectrometry is used when there is a need to distinguish isotopes of the same element from one
another. This becomes important when the contamination may be from different types of sources.
For example, naturally occurring uranium is 99.27 percent abundant (by weight) in the 238U isotope,
0.72 percent in the 235U isotope and 0.006 percent in the 234U isotope. Fuel used for nuclear power
plants will be enriched in the 235U isotope up to ~5 percent, weapons grade will be above 90 percent.
Thus, the isotopic distribution of the uranium will help identify where it came from.
2.3.1 Mass Spectrometric Methods
Conventional techniques for radiochemical analysis are based on the chemical properties of
radionuclides that allow them to be separated from all other stable elements in the mixture of the
sample. At times it is extremely important to identify the specific isotopic mixture of some
radionuclides (e.g., U, Pu, Np, and Am) in order to determine the source of the contamination.
Three different methods that are based on the same principle, charge to mass ratio of the ionized
atom, can be used to identify the specific isotopic ratios of radionuclides. These are:
• Accelerator Mass Spectrometry (AMS);
• Thermal lonization Mass Spectrometry (TIMS); and
• Inductively Coupled Plasma-Mass Spectrometry (ICP-MS).
In each one of these methods, the sample is vaporized into its elemental constituents, the elements
ionized and passed through a mass spectrometer. The distinct advantage of these methods is that the
separation is based on the mass of the isotopes involved and not on their chemical nature. Thus,
analysis of several different radionuclides, as well as different isotopes of a single element can be
performed simultaneously. This type of analysis would most likely not be used in the initial phases
of a site evaluation due to the specific nature of the analysis. However, during later phases, these
methods could be used to collect site-specific data sufficient to characterize site conditions. They
might also be used after remediation activities have been implemented to assess whether or not
speciation of uranium or plutonium isotopes is necessary.
Currently, ICP-MS techniques are best suited for radionuclides with half-lives greater than about
10,000 years, when more sensitive analyses are required (such as for environmental levels of 239Pu)
or when isotopic analyses are required to separate isotopes whose decay emissions prevent separate
quantification (such as 240Pu from 239Pu). Methods employing specialized radiochemical separations
and the most sensitive mass spectrometers are currently being developed for radionuclides with
shorter half-lives, such as 90Sr.
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Inventory of Radiological Methodologies
2.3.2 Kinetic Phosphorimetry Analysis
KPA is a rapid method used primarily for the analysis of elemental uranium and thorium. This
method relies on the electronic structure of the uranium and thorium ions in solution to establish
valence orbitals that yield phosphorescent states. These states can be used to distinguish the uranium
and thorium emissions from many other elements. Thus this method does not use the radioactive
properties of these ions at all in determining their presence. The disadvantages are that—without
chemical processing of the sample—the minimum detectable concentration is higher than by
conventional radiation detection methods, and the measurement quality for these two elements is
compromised because KPA does not distinguish isotopes.
2.4 Measurement Quality Objectives and Methodologies
Measurement quality objectives (MQOs) are the analytical data requirements of the data quality
objectives and serve as measurement performance criteria or objectives of the analytical process for
a specific project. MARLAP (2004, see Chapter 3) provides guidance on developing MQOs for
selected method performance characteristics, such as method uncertainty at an analyte concentration,
analyte detectability (minimum detectable concentration), minimum quantifiable concentration,
applicable analyte concentration range, method specificity (ability to isolate one radionuclide from
another), and method ruggedness. Each phase of the cleanup process for a site may have different
MQOs. These MQOs will drive the specificity of the method or analysis to be used.
Referring to the example earlier in this chapter, suppose one MQO for the initial characterization
was:
Samples shall be analyzed to 15 pCi/g beta and 20 pCi/g alpha with a measurement
uncertainty of 2.2 and 3.0 pCi/g, respectively, at those concentrations.
It certainly would be possible to apply routine methodologies for Ra, Pb, Bi, Rn and Po analyses and
sum each of these to determine the total activity. One could also apply some of the specialized
methodologies to the analysis of 226Ra and mathematically estimate (conservatively) the activities
of the remaining radionuclides from the 226Ra decay chain. However, both of these approaches
would be time consuming and highly specific, for an MQO that is more easily determined using a
screening method. Later on during the site remediation and follow up activities, the MQOs might
become more radionuclide specific such as, "the 226Ra shall be analyzed to 1.5 pCi/g with a relative
measurement uncertainty at that level of 20 percent." In this case, the necessary method would have
to be able to eliminate the interference from all other chemically similar radionuclides, as well as
hone in on 226Ra specifically.
3 General Analytical Considerations
The information presented in this document on radioanalytical concepts takes into consideration the
major source terms of the radioactivity generated by man-made processes at various sites throughout
the country. The types of sites that this document is aimed at are:
• Department of Energy (DOE) and Department of Defense (DOD) site cleanup activities; and
• Naturally Occurring Radioactive Materials waste (NORM).
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Inventory of Radiological Methodologies
A summary of the important processes and radionuclides generated at each site will be discussed
in subsequent subsections.
3.1 Site Source Term
This section discusses DOE cleanup sites and wastes containing naturally occurring radioactive
materials. The decommissioning of commercial nuclear power facilities, and the required radionuc-
lide analyses for that specific process, are regulated by the Nuclear Regulatory Commission (NRC,
2004) and are outside the scope of this report. However, for completeness, Appendix E provides an
overview of issues associated with nuclear power plant decommissioning sites.
3.1.1 DOE Site Cleanup
Known as "legacy wastes," substantial amounts of radioactive wastes have been produced in the
nation's nuclear weapons productions program since 1942. Wastes for this program resulted from
the mining of uranium ore, extraction (milling) of uranium from the ore, 235U isotopic enrichment
of the uranium, and fabrication of uranium fuel from the enriched uranium to operate nuclear
reactors for the production of 239/24(>Pu. The generation of the fissile materials of plutonium and
uranium for the nuclear weapons program resulted in radioactive wastes at DOE sites throughout
the country and at uranium mining and milling operational sites, mainly in the western states. Many
of these facilities have had inadvertent releases that have led to environmental contamination. The
radioactive wastes from the uranium mining and milling operations will be discussed under the
subsection dealing with NORM waste.
Nuclear weapons production involves eight general groupings of activities including:
• Uranium mining, milling, and refining;
• Isotope separations (uranium enrichment);
• Fuel and target fabrication;
• Reactor operations;
• Chemical separations;
• Weapons component fabrication;
• Weapons operations; and
• Research, development, and testing.
Waste generated by chemical separations processes accounts for more than 85 percent of the
radioactivity generated in the nuclear weapons production process. Waste is created by the acid
dissolution of the spent fuel rods (and targets) from reactor operations and subsequent separation
of the plutonium and uranium using a chemical process. Chemical separations operations were
mainly conducted at the Hanford Site in Washington, Idaho National Engineering Laboratory
(INEL) Site in Idaho, and the Savannah River Site in South Carolina.
According to DOE (1997a), there are 79 million cubic meters of contaminated solid environmental
media associated with the nuclear weapons complex, of which 70 percent is contaminated with
radionuclides. In addition, there are about 1,800 million cubic meters of contaminated soil, of which
57 percent is contaminated with radionuclides.
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DOE has listed 38 sites that have more than 1,000 m3 of contaminated solid media and 17 that have
more than 100,000 m3. Of the 38 sites listed, those with the greatest volume of waste (more than
1,000,000 m3) are Fernald (Ohio), Hanford (Washington), Lawrence Livermore National Laboratory
(California), Los Alamos National laboratory (New Mexico), Nevada Test Site (Nevada), and the
Savannah River Site (South Carolina). The radionuclides in the waste and surrounding area at these
sites vary according to the type of activity or operations conducted at the site. The radionuclides
persisting at these sites depend on the amount of radioactivity produced during the operations and
the nuclide's half-life. In some cases, a radionuclide with a half-life in years, such as tritium (3H),
with t,/2 = 12.3 y, or 60Co, with t/2 = 5.27 y, will be found in environmental waste if it was produced
in significant quantities during operations.
As of 1991, the longer-lived radionuclides important for DOE site cleanup that are routinely
analyzed are provided in Table 3. Some of the nuclides listed below may not be the result of
operations but are included to be analyzed in the facility's standardized environmental monitoring
program and, thus, may represent nuclides that are or were measured from atmospheric weapons
testing conducted decades prior.
TABLE 3 — Longer-lived radionuclides at DOE sites
Facility
Fernald
Hanford
INEL
Los Alamos
National
Laboratory
Nevada Test
Site
Oak Ridge
National
Laboratory
Rocky Flats
Savannah
River Site
Soil
Uranium
137Cs
137Cs, 60Co, 23S''2MPU, 90Sr
241Am, I37Cs, 3H,
238/m'240Pu, 90Sr, Th, U
241Am*, 60Co, 1MEu*,
J37CS, 238,<239/240pu*5 ^Sr,
235/238rj
241Am, 60Co, 137Cs,
244Cm, 238/239Pu, Ra-228,
90e 232/233/234/235<'23ST j
241Am, 3H*, ^/239/240pUi
234/235/238TJ
137Cs, 3H, 129I, ^Sr
Surface Water
60Co*, 3H, '
238/239/240p #
241Am, 137Cs,
60Co, 244Cm,
%Sr, 3H
238/239/240p
137Cs*, 60Co*,
3H, I29I*, 90Sr*,
234/235/238TJ
Ground
Water
137Cs, 237Np, 90Sr, 232Th, U
'37Cs, 3H, 1291, 239/240Pu, 90Sr,
Ra
3H, I291, 23s'2«Pu, 90Sr
137Cs, 3H, ««^2«>pu, u
'37CS, ""CO, 3H, 2^/239/240pu^
""Sr
137Cs*, 3H*, "°Co*, 154Eu,
238/239Pu, 9l)Sr*, "Tc, 232Th,
232/233/234/235/23 8rj
137CS*, 3H*, 9°Sr*, 23«35/238u*
137Cs*, ""Co*, 3H, 238/239Pu,
226/228Ra, 90Sr, 234-235''238U
Sediment
99Tc, U
[ 137Cs, 60Co, 90Sr
239-240pu
l37Cs, 23*-40Pu*
241Am, "°Co, l37Cs,
244Cm, 238;239Pu, 91)Sr,
232,'233/234/235/238Tj 154£u
137^ 230/239pu
3H, 243/244Cm, 137Cs,
129I*, 90Sr*, 228Th,
235/238| j
* Potential contamination not fully determined.
Source: OTA, 1991
3.1.2 Naturally Occurring Radioactive Materials Waste
Naturally occurring radioactive materials (NORM) are defined as those containing naturally
occurring radionuclides—not produced by humans—in sufficient quantities or concentrations that
require control for purposes of radiological protection of the public or the environment. In most
cases, NORM may have been technologically enhanced in composition, concentration, availability,
or proximity to people. NORM does not include source, by-product, or special nuclear material
(related to the source term and products of the nuclear fuel cycle), commercial products containing
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Inventory of Radiological Methodologies
small quantities of natural radioactive materials, or natural radon in buildings (Health Physics
Society, www.HPS.org). The radioactive isotopes of uranium, thorium, carbon, potassium,
polonium, lead, and radon are the principal radionuclides considered under NORM (Table 4).
TABLE 4 — Principal natural radionuclide decay series
Nuclide
Uranium-238 Series
Thorium-234
Protactini um-2 34m
Uranium-234
Thorium-230
Radium-226
Radon-222
Polonium-2 1 8
Lead-214
Bismuth-214
Polonium-2 14
Lead-210
Bismuth-210
Polonium-2 10
Lead-206
Thorium-232 Series
Radium-228
Actinium-228
Thorium-228
Radium-224
Radon-220
Polonium-2 16
Lead-212
Bismuth-212
Polonium-2 12
Thallium-208
Lead-208
Non-Series Radionuclides
Potassium-40
Half-Life
4.47 x 109 years
24.1 days
1.17 minutes
245,000 years
77,000 years
1 ,600 years
3.83 days
3.05 minutes
26.8 minutes
19.7 minutes
164 microseconds
22.2 years
5.01 days
138 days
stable
14.1 x 10" years
5.75 years
6.13 hours
1.91 years
3.66 days
55.6 seconds
0.15 seconds
10.64 hours
60.6 minutes
0.305 microseconds
3.07 minutes
stable
1.28 * 109 years
Major Radiations
alpha, X-rays
beta, gamma, X-rays
beta, gamma
alpha, X-rays
alpha, X-rays
alpha, gamma
alpha
alpha
beta, gamma, X-rays
beta, gamma
alpha
beta, gamma, X-rays
beta
alpha
alpha, X-rays
beta
beta, gamma, X-rays
alpha, gamma, X-rays
alpha, gamma
alpha
alpha
beta, gamma, X-rays
alpha, beta, gamma, X-rays
alpha
beta, gamma
beta, gamma
These radionuclides, and more than a dozen other radioactive elements, are present in rocks, soils,
building materials, consumer products, foods, and industrial wastes generated from mining, oil and
gas extraction, mineral extraction, and geothermal wells. Commercial and consumer products, such
as lawn fertilizers, watch dials, smoke detectors, gas lantern mantles, ceramic glazes, and air filters,
may contain the long-lived radionuclides of uranium, thorium, radium, and polonium.
Regulators are most interested in the large amount of NORM waste generated from industries
conducting metal mining and processing and oil and gas extraction processes. On an annual basis,
these industries generate nearly a billion metric tons of NORM waste. More recently, programs have
been established by the state regulators and EPA to address the technologically enhanced, naturally
occurring radioactive materials (TENORM) wastes from these industries. (See www.epa.gov/
radiation/tenorm/about. htm).
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Inventory of Radiological Methodologies
The TENORM waste matrices that are evaluated include surface and ground water, produced waters
(effluents), soil, sediments, sludge, and mineral (barite) scale from pipes or conduits. The concentra-
tions of the NORM radionuclides vary according to geographical location and chemical processing
and extraction practices. For example, the 226Ra concentration in produced water from the oil and
gas extraction industries in Texas, New Mexico, Louisiana, and Mississippi typically ranges
between about 1 and 1,000 pCi/L. Additional information on TENORM can be found at the
following websites:
• www.tenorm.com/bkgrnd.htm
• pubs.usgs.gov/fs/fs-0142-99/
• pubs.usgs.gov/fs/fs-0142-99/fs-0142-99.pdf (concentration of NORM in oil and gas industry)
With two exceptions, TENORM and NORM are regulated primarily by individual state radiation
control programs and not by federal agencies. Exceptions include the transportation of NORM-
containing wastes (subject to U.S. Department of Transportation regulations) and NORM
management activities (may be subject to regulations promulgated by the Occupational Safety and
Health Administration, e.g., www.rrc.state.tx.us/divisions/og/key-programs/norm.html). The state
regulatory requirements applicable to TENORM or NORM-containing wastes can be reviewed on
the State Regulations and Guidelines page of the website (www.tenorm.com/regs2.htm#States).
Several organizations have been actively developing guidance on the regulation of NORM. The
Conference of Radiation Control Program Directors maintains suggested state regulations for control
of radiation, available at www.crcpd.org/SSRCRs/TOC_4-2004-on-line.pdf.
The principal radionuclides of concern for TENORM are from the three naturally occurring decay
series of 238U, 235U, and 232Th, and the long-lived radionuclide, 40K. Table 4 lists components of the
uranium and thorium series, along with 4<)K. Generally, the 235U (known as the actinium series) series
does not play a significant role in industrial TENORM due to its very low presence (1/20 of the
radioactivity concentration of 238U) in the natural environment. The radionuclides in the decay series
attain a state of secular radioactive equilibrium (see Appendix B) if not subjected to chemical or
physical separation. Technological enhancement of NORM as well as natural, physical, and
chemical reactions in the environment often interfere with this equilibrium balance.
3.2 Sample Preservation and Transport
The entire process of transporting water and soil samples from the sample site to the laboratory
should be carefully planned. Project planners should discuss with the contract laboratory specifics
about sample container types, sample volumes or masses required for each analysis and matrix, and
preservation techniques to be used for each matrix/radionuclide combination. Container or sample
integrity can be compromised if the sample temperature becomes too high or too low. In either case,
the sample may be damaged if temperature variations cause too much stress. The sample integrity
must be carefully considered prior to performing an analysis. The sample preservation requirements
should be part of the project's analytical protocol specifications (APSs). General information
regarding this aspect of sample handling can be found in MARLAP (2004), DOE (1997b), 40 CFR
136 Table II, and ASTM Volume 11.02 (requirements specified for each radionuclide within its
procedure).
In addition, when a container is broken, other samples can be affected because shipping labels
(sample identification) are obscured or because the other sample's integrity is compromised by
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contamination from the sample that leaked. Personnel who collect the samples should ensure that
the sample containers are firmly sealed, and that the samples will not experience extremes of heat
or cold during the transport based on the type of vehicle, the route, and the estimated time of the trip.
Simply shipping samples in ice packs, or insulation will not ensure that they will be protected from
temperature extremes.
3.2.1 Water
The chemical concentration of radionuclides in water samples is extremely small. For non-
radioactive materials, trace quantities are measured in the part-per-million (ppm) to part-per-billion
(ppb) range. Radionuclides at environmental concentrations are 6 to 12 orders of magnitude lower
in mass concentration than this. At these very low mass concentrations, oxidation-reduction,
complexation, and volatilization reactions can occur, which can change the chemical identity of a
species in solution. These reactions can lead to irreversible deposition of radionuclides on the
container wall. Small mass losses of radionuclides to the container walls during transport and
storage can significantly affect their measured concentration. It is extremely important, therefore,
that appropriate preservation techniques be specified in the sampling documents for the project.
For most radionuclides identified in this document (with the exception of carbon, hydrogen, and
iodine), preservation of the water sample at the sample site will include some form of acid
preservation using HC1 or HNO, to less than pH 2.0. There are three different possible points at
which to acidify the samples:
Acid is added to the sample vessel prior to the introduction of the sample;
Acid is added to the sample after filtration at the sample site; and
Acid is added to the sample after filtration in the lab (this requires a very short transit time from
the field to the laboratory, usually only a few hours).
The process to be used for preserving samples generally is stated in the project statement of work
(SOW) and the APS. The decision as to when to filter or preserve must be based on the project
specific measurement quality objectives.
In addition to acidification, other sampling requirements such as the type of container, the storage
temperature, and the storage period may be specified. These requirements will depend on the
expected chemical nature of the radionuclide and the chemical nature of the sample medium. Storage
containers are generally Teflon or high-density polyethylene. The composition of the sampling
container is also important because:
Some containers are more susceptible to radionuclide adsorption;
Glass presents breakage concerns during shipping and handling;
Glass containers also contain NORM which may leach in the acid environment and raise sample
background counts; and
Some containers (e.g., polystyrene culture flasks) are not stable with the concentrations of added
acid necessary for preservation.
When required and specified, a typical storage temperature is usually 4 C. This is usually only
necessary when biological activity may alter the chemical species of the radionuclide or when
volatile radionuclides (such as 14C) or any radioiodines are present.
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Additional sample preservation requirements may be necessary for certain radionuclides (elements),
depending on the nature of the sample and the specific radionuclide being sampled. Some of these
considerations are:
Addition of carrier or tracer;
Addition of oxidizing or reducing agents; and
Elimination of air space in sample bottle.
This may be important for the isotopes of S, P, Tc, U, C, I, and Pu in certain matrices. There are four
exceptions to the preservation described above. When sampling and analyzing for these
radionuclides in particular, the laboratory and the field-sampling personnel must communicate the
exact methods being used by each so that there is continuity in the sample-preservation process. This
is usually done in the APS or the SOW.
Hydrogen (specifically tritium, designated as T) in environmental water samples will almost
certainly be present as H-O-T. The only preservation methodology recommended for samples
that are to be analyzed for T is to reduce sample temperature to 4 C as soon as possible.
Addition of acids to the sample may interfere with subsequent laboratory analysis. Plastic
containers should not be used for tritium samples with very high specific activity (curie levels
and above).
Analysis for I4C in environmental water samples can deal with several different chemical carbon
forms. The two most prevalent are carbonate and bicarbonate. In both cases addition of acid to
preserve the sample will result in these species being transformed to CO2 and the expulsion of
the formed carbon dioxide gas from the sample. This will cause a loss of analyte. Presence of
14C in organic molecules may be oxidized to carbon dioxide by addition of acid, also causing
loss of the analyte. Here again the only recommended technique for preservation would be to
reduce sample temperature to 4 C as soon as possible. However, some projects have used a
mildly alkaline solution of NaOH or NH3 to prevent losses of 14C by maintaining the carbon in
its carbonate (CO3 2) form.
Iodine analysis in environmental water samples presents a significant challenge because it may
exist in as many as six different oxidation states. Iodine is also subject to conversion to volatile
I2 in acidic solutions containing oxygen. For these reasons, it is advisable to add iodide carrier
and thiosulfate (or an equivalent reducing agent) to minimize loss of iodine during sample
preservation and storage. Consideration should be given to collecting samples for iodine analysis
in glass versus plastic containers. Reduction of sample temperature to 4 C is also
recommended. A summary of preservation techniques that have been successfully employed for
water samples is shown in Table 5. This is a general summary and specific preservation
techniques should be based on project-specific data quality objectives or APSs.
Polonium-210 should be preserved only with HC1 at a pH less than 2.0.
It is also important to note that the amount of added acid or reagent may contribute to the overall
sample volume. This should be taken into account when determining the sample volume so that an
appropriate correction may be made.
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TABLE 5 — Summary of preservation techniques for aqueous samples
Element*
Americium
Bismuth
Carbon
Cesium
Cobalt
Hydrogen
Iodine
Iridiumf
Lead
Nickel
Phosphorus
Polonium
Plutonium
Radium
Strontium
Sulfur
Technetium
Thorium
Uranium
Acid
pH<2
(HO) HNO,
(HC1) HNO,
(HC1) HNO3
(HC1) HNO,
—
HN03
(HC1) HNO,
(HC1) HNO3
(HC1)
(HC1) HNO3
(HC1) HNO3
(HC1) HNO3
(HC1) HNO,
(HC1) HNO,
(HC1) HNO3
Base Reducing Oxidizing
Temperature pH > 9 Agent Agent
4 C
4 C
4 C NH3
4 C
4 C ~ ~ -----
4 C
4 C NaOH S:0.r2
4 C HNO,
4 C
4 C
4 C NaNO,
4 C
4 C
4 C NaOH
4 C
4 C
4 C
* Preservation techniques are generally specified to maintain the element in its most commonly occurring
oxidation state as found in the environment. Project-specific APSs must be developed for each project,
radionuclide, and matrix. This would include the concentration of the preservative, and (for example) the type
of acid to be used.
f Iridium, because of its chemical inertness, will be in the zero valence state, and no specific preservation is
better than any other.
* Depending upon the type of sulfur compounds expected, basic solution may be the best preservative to prevent
volatilization of sulfur as H2S or SO2.
3.2.2 Soil
Generally, there are no specific requirements for sample preservation for soil samples. However, two
items should be considered before the start of any project. The first is to minimize the amount of air
space that is in the sample container. This will minimize the potential for volatilization/oxidation
of certain species. The second is to reduce the sample temperature to 4 C as soon as possible to
minimize any biological activity participating in elemental oxidation-reduction.
3.3 Parameters Affecting Quantification Using Radioactive Decay Counting Techniques
In order to quantify the activity of a particular radionuclide, several sample- and instrument-related
parameters or factors are used:
• Sample size (mass or volume);
• Branching fraction (ratio) of the particle emission being counted (B). This is the fraction of all
decays that result in emission of the characteristic radiation (alpha, beta or gamma);
• Counting interval (t), with the same counting interval for sample and background;
• Number of accumulated sample counts (Csample);
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• Number of background counts for the equivalent sample count interval (Cbg);
• Chemical yield of the analysis (Y);
• Detector efficiency (E) for the particular emission of the radionuclide [this is also affected by
the detector and detection methodology];
• Decay constant of the radioisotope (X = 0.693/t,/2);
• Time intervals between sampling and beginning the sample count (T);
• Correction factor for radioactive decay of the radionuclide or its progeny during the counting
interval (to / [1- e^']); and
• Correction factor for the ingrowth of progeny used to calculate the activity of a parent (I).
The concentration of a radionuclide in a sample (in units of activity per unit mass or volume) can
be estimated through the following general formula and the specific analysis parameter or factor:
A,->,r-/T^ anTeg
Activity (pCi / L) = - - - - - j- - ( 1 )
-Xt
In Equation 1, CF represents a units conversion factor, and all other symbols are identified above.
A different equation would be used when the instrument background is counted longer than the
sample.
Although all of these parameters or factors affect the smallest amount of radioactive material that
can be quantified (i.e., MDC), the two that the analyst can change to lower the MDC are the sample
size and the counting interval. The sample size will have a one-for-one affect on the MDC, but not
so with the counting time, because the counting time is related to the net decays determined. The
term [Csampie-Cbg] begins to approach zero when Csampie is only slightly greater than Cbg when the
sample and background are counted for the same time. Due to the nature of radioactive decay, a
statistical distribution (estimated by a Poisson Distribution) defines the possible counts that can be
recorded in a certain time. In some instances, the background may have higher counts than the
sample for the same counting interval. For more detailed information, review MARLAP (2004,
Chapter 19).
3.4 Negative Results
The decay of radioactive atoms is a random phenomenon. The number of observed decays in a given
time is characterized by Poisson statistics. The mathematical conclusion of this statistical function
is that if we were to count the same sample for a limited number of successive intervals ( e.g., less
than 25), we would get a different number of counts each time. The range of values that we would
observe would be Csamplc ± t(Csampie)>/2, where t is the parameter representing the degree of confidence
in the measurement result. This relationship is true for both sample and background measurements.
As the counting time increases, the number of observed detector events will increase, but the average
count rate (counts/unit time) remains approximately the same. However, the relative uncertainty of
the measurement — [Csamplef / [Csample] — will decrease.
If the background were counted for two different time periods, two different results would be
expected. Although the background has not changed, the measurement results would vary because
they are affected by measurement uncertainty and the random nature of radioactive decay.
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If a sample's radionuclide concentration is very close to background, it is possible to have fewer
counts in the sample than in the background, even when counted for an equal time period. In this
case, the final sample value would be negative. (If the background and the sample are both counted
several times, on some occasions the sample might have larger counts than the background. In this
instance the sample activity would be positive.) Atom-counting techniques experience the same
difficulties in measuring amounts of radionuclides close to the background level. The net signal
detected from the sample (number of atoms) can be less than the measured background from blanks
(or the instrument). This will also lead to the occurrence of a negative value for the analyte.
Two conclusions can be drawn about negative sample values. First, when analytical results yield
negative values, the radionuclide concentration will be very small—approaching that of background.
Second, to minimize the possibility of reporting that no activity is present when some exists (a
"Type II" decision error, sometimes referred to as a "false negative"), the count time or sample size
may need to be increased (i.e., more atoms are present) to improve the statistics and reduce the
relative uncertainty of each measurement. For more detailed information, review MARLAP (2004,
Chapter 19).
3.5 Measurement Uncertainty
The term "uncertainty" refers to a lack of complete knowledge about something of interest. The
radioanalytical process requires several different measurements to be made. Each laboratory
measurement involves uncertainty, which must be considered when analytical results are used as
part of a basis for making decisions. Every measured value obtained by a radioanalytical procedure
should be accompanied by an explicit uncertainty estimate. It is often stated that field sampling
uncertainties are so large that laboratory measurement uncertainties contribute insignificantly to the
total uncertainty. These claims may be true in some cases, however that is not a reason for failing
to perform a full evaluation of the laboratory measurement uncertainty. A realistic estimate of the
measurement uncertainty is one of the most useful quality indicators for a result.
Measurement uncertainty will be caused by random effects and systematic effects in the measure-
ment process. Random effects cause the measured result to vary randomly when the measurement
is repeated. Systematic effects cause the result to differ from the measured value by an absolute or
relative amount. A systematic error is often referred to as "bias." Systematic effects may also cause
the results to vary in a nonrandom manner. Generally, both random and systematic effects are
present in the laboratory measurement process.
The measurement uncertainty of a sample result should not be confused with the error of a sample
measurement. Error of the sample measurement is a theoretical concept that refers to the difference
between the "true" value and the measured value. As the "true" value can only be estimated by
repeated measurements, and because each measurement has its own uncertainty, the error cannot
really be known or measured.
Some measurement errors are spurious errors, such as those caused by analyst blunders or instru-
ment malfunctions. Spurious errors cannot be taken into account in the statistical evaluation of
measurement uncertainty. They need to be avoided by the use of good laboratory practices. Such
practices would be part of the analytical laboratory's protocols or procedures, which would be
written. Such documents should also have a method for detecting such errors and a means through
which they are corrected by appropriate quality assurance (QA) and quality control (QC) activities.
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For example, consider a laboratory analysis that yields a value of 100 pCi/Liter for I37Cs. Assume
that we "know" the true value to be 110 pCi/L. The error would be -10 pCi/L. However, we do not
know exactly the true value or the measured value. We can ascertain how uncertain we are of both
values by the uncertainty in the measurements. Measurement uncertainty is the parameter that
analysts use to judge the precision of the analysis. A statistical parameter associated with the
uncertainty is the confidence level. The confidence level tells the analyst how sure he is of the
measured value. It is based on the standard deviation of the analysis and is constant. This uncertainty
is often expressed as a ± value after the analytical result and stated to be at a certain confidence
level.
For the same example, assume that the value was reported as 100 ± 25 pCi/L, the uncertainty is at
the 95 percent confidence level, and there is no measurement bias. The "true" radionuclide
concentration value of the sample would be within the 95 percent confidence interval (75 to 125
pCi/L) that has been established for the measurement. In addition, if the sample were to be
repeatedly re-analyzed using the same method, 95 percent of the measured concentration values
would be within the confidence interval. The reported measurement uncertainty for an individual
analysis should be consistent (same magnitude or less) with the required method uncertainty for the
radioanalytical method and sample matrix as defined in the measurement quality objectives (MQOs).
Several different measurements may be made on a sample in the laboratory, all of which contribute
to the measurement uncertainty. (Uncertainties associated with sampling are very complex and are
not within the scope of this report.) The following is a list of some of these sources:
• Mass or volume of the sample;
• Sample counts;
• Background counts;
• Tracer (counts) or carrier (mass);
• Decay correction; and
• Chemical yield.
In addition to these, some of the indirect contributors to the measurement uncertainty are half-life,
detector efficiency, and the branching fraction of the radioactive particle.
The total measurement uncertainty of a radioactivity measurement may be expressed mathematically
as the partial derivative of the radioactivity value with respect to all the input parameters that
determine it. It is unnecessary to pursue this exact mathematical derivation in this document
(MARLAP, 2004, Chapter 19). However, it is important that full consideration be given to each of
the input parameters to equations like Equation 1 on page 20 and how they impact the total
measurement uncertainty. The project planning document should identify how the measurement
uncertainty will be calculated.
3.6 Sample Analysis Turnaround Time
Turnaround time is an important aspect of the overall analytical process that is often overlooked in
the planning phases of a project. The elements of this part of the process are:
• Sample receipt by the laboratory;
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• Sample preparation before analysis;
• Analytical separation process;
• Sample counting; and
• Data review and report generation.
Depending upon the specific analysis, these elements can take a significant period of time: a week
or more is a common turnaround time for these analyses. Each of these elements is explained in the
subsections that follow. The time involved in determining the mass of a sample, or precipitate is
usually between 5 and 20 minutes and is not included in the discussion below.
The term "constant weight" is used in many protocols. This is a repetitive process requiring, at a
minimum, two cycles of drying, cooling, and weighing. This process will take a minimum of 2'/2
hours to as long as 8 hours, depending on the nature of the sample and its water content.
An estimate of the amount of time for single-sample analysis for each element for specific method-
ologies is provided in the tables in Appendix D. These times can be affected by the skill of the
analyst, the complexity of the matrix, and the detection sensitivity desired. These times also
represent no delays between sample cataloging, digestion, separation, and counting in the laboratory.
(Note that the analysis times in these tables do not include data verification/validation or report
generation and approval. Routine turnaround times for final reporting of sample results is usually
30 days; "expedited" is two weeks, and "rush" reporting is one week.) Specific methodologies that
change these times and detection capabilities are currently being developed.
3.6.1 Sample Receipt by the Laboratory
In every instance of sample transfer to a contract laboratory, sample receipt is critical, because it
establishes the sample integrity, identity, and suitability to be analyzed for the radionuclides in
question. The receiver must verify the number of sample bottles, their identity and container
integrity as compared to the chain-of-custody form that accompanies the samples. For certain
samples, a radiation survey of the shipping and sample containers may have to be performed. In
addition, any preservation requirements must be verified as acceptable. All anomalies must be noted
by the laboratory and should be verified with the remedial project manager or on-scene coordinator
(or equivalent) before any laboratory processing occurs. Once accepted, the samples are entered into
the laboratory's data management system. The total time that this step takes can be several hours,
depending upon the number of samples being transferred to the laboratory.
3.6.2 Sample Preparation Before Analysis
Most samples require preparation prior to performing the separation of the radionuclides of interest
from all the other elements in the sample matrix. Two separate examples identify the types of sample
preparation that may be needed. These examples focus on the laboratory aspect of sample
processing. Other sample constituents can affect sample holding time, preparation, and separation.
The presence of paints, VOCs, PCBs, chromium, or lead may significantly affect sample holding
times (required for nonradioactive analytes in the sample) as well as sample preparation prior to
processing. The manner in which the samples are handled by field and laboratory personnel will
need to be considered if these types of hazardous materials may be present. Thus, it is important that
planning documents effectively communicate these facts to personnel handling and processing these
samples in the field as well as in the laboratory.
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Example 1: Tritium Analysis in Water and Soil
Analyzing tritium in water requires elimination of as much chemical interference as possible in the sample
by distilling the water before liquid scintillation analysis. The distillation process should take between 30
minutes and 1 hour for laboratories that are set up to perform this analysis.
In the instance of performing tritium analysis on a soil sample, the sample must be passed through a sieve
of uniform size as determined by the APSs of the project (this may have been done in the field or may be
done in the laboratory, where it takes from 20 minutes to 1 hour). The soil must be weighed as received,
then a measured amount of "clean" water, and acid or oxidant, added. A parallel sample must be dried at
105 C to achieve constant weight, thus allowing the determination of moisture content of the soil sample
as received. The sample with "clean" water and additives is then allowed to equilibrate for up to 12 hours
(dependent upon the APSs), before distilling the water from the sample.
Example 2: Americium Analysis in Soil
Soil samples containing americium require the same sieving steps as tritium to ensure that the particle
size meets the APSs. The sample will then be dried to constant weight and then may either undergo
combustion in an oven (3-8 hours) or wet acid digestion (2-6 hours). In both cases, the purpose is to
remove the extraneous organic material in the sample and solubilize the americium (the oven
combustion is followed by acid dissolution).
Inherent to any sample preparation process is ensuring that all ions of the analytes are in the same
oxidation state or chemical form, and that any tracers or carriers have been added. This part of the
sample preparation can take up to one hour to complete, depending on the number of possible different
oxidation states or species of the analyte that may be present.
3.6.3 Homogeneity and Adequate Sample Preparation
This aspect of the sample needs to be defined in the project APSs and SOW. It identifies how to
assess if the sample is homogeneous to start, or if some physical adaptation must be performed.
If river water was sampled for the analysis of 60Co, what are the sample homogeneity criteria we
would be looking for? Cobalt can exist in both soluble and insoluble forms in the environment.
Thus, an important consideration would be to determine if the sample had suspended matter, and
what was the composition of the suspended matter. Some of the decisions that need to be made prior
to taking the sample are:
• Should the sample be filtered?
• If the sample is filtered, should the suspended matter be analyzed?
• If the water and suspended matter are analyzed separately, should the final result be combined?
• If the sample is not filtered, what measures are taken to assure that the suspended matter is the
appropriate fraction of the water taken for analysis?
A similar set of decisions needs to be made for soil samples:
• Is plant material removed from the sample? Analyzed separately?
• Does the soil need to be ground to a uniform size (and what is that size)?
• Should stones above a certain size be removed?
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• Should the soil be weighed as is, or dried at a certain temperature?
The APS also should identify the sequence for drying, mixing, and removing a portion of the soil
for analysis. For example, "The whole sample as received is to be dried at 110 C, then sieved
through an 8-mesh (2.38 mm) screen. The resultant material should then be blended for 15 minutes
in a ball mill. A separate portion of approximately 10 percent of that final mass is removed for
analysis."
Sample homogeneity and representative subsampling are extremely important when relating the final
results of analytical techniques that use different masses of sample for analysis. For example, gamma
spectrometry typically requires a large sample (100 to 4,000 g), while only 1 to 10 g is needed for
alpha spectrometry. Inadequate sample homogenization or ineffective subsampling can result in
misleading comparisons. Sample preparation and laboratory subsampling are discussed in detail in
MARLAP (2004, Chapter 12, Laboratory Sample Preparation, and Appendix F, Laboratory
Subsampling).
3.6.4 Sample Digestion
Once a homogeneous sample has been selected, digestion assures that all of the sample can be
dissolved in one solution. The objective of sample digestion is to dissolve a solid sample
quantitatively in water to produce a solution (homogeneous mixture), so that subsequent chemical
separation and analysis may be performed. Because very few natural or organic materials are readily
soluble in water, these materials routinely require the use of acids or fusion salts to bring the
radionuclides into solution. These reagents typically achieve dissolution through an oxidation-
reduction process that leaves the constituent elements in a more soluble form. In addition, each
radionuclide to be analyzed, should be in a stable oxidation state prior to performing any chemical
separations.
The three main methods of sample digestion for solids are wet digestion (using concentrated acids),
salt fusion (using a solid flux melt and forming a single molten, nonaqueous phase with the sample)
and combustion (using a stream of air in a high temperature furnace).
3.6.5 Oxidation State and Speciation of Radionuclides in Environmental Samples
Generally, analysis of environmental samples requires the total amount of a radionuclide present,
regardless of what oxidation or speciation state it is in, to be determined. Certain elements can exist
in more than one oxidation state. This means that before sample analysis begins, any carriers/tracers,
and all species of an element are brought to the same oxidation state prior to any chemical separa-
tions being performed. This ensures that when we use carriers or tracers to monitor the chemical
yield of the analysis, the amount of analyte and carrier/tracer recovered is the same percentage (see
Equation 1 on page 20).
In some instances, it may be necessary to know the following information about the radionuclides
as well:
Different oxidation states of the radionuclides;
Soluble versus insoluble fraction of the radionuclides;
Chemical or molecular form (i.e., ionic or covalent bonding) of the radionuclides; and
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Chelating agents present that can complex the radionuclides.
The most accurate way to assess these parameters is to use direct analytical methods like anodic
stripping voltammetry (ASV), ion chromatography (1C), ion selective electrode (ISE), Fourier
transform infrared (FTIR), or UV-visible spectrometry (UV-VIS). However, these methods, with
their conventional detectors, will require relatively large masses of the radionuclides (milligrams
to micrograms, 10 3 to 10 6 g). Environmental samples typically have only picogram (10 12 g) to
attogram (10~15 g) quantities of radionuclides.
Using conventional methods would require performing analysis on a split sample: one analysis for
the total mass of the radionuclide, the other for a specific oxidation state that will remain unchanged
by the procedure, such as mild acid dissolution or chelate leaching. This would be further
complicated if several different oxidation states of the radionuclide are possible. (Such a case exists
with plutonium, where as many as four different states (+3, +4, V, and VI) can exist simultaneously.)
Thus, indirect methods, which require chemical separation and radiochemical analysis, may provide
the most suitable method for determining chemical speciation.
Recent work in this area has coupled ion chromatography with 1CP-MS instruments. The enhanced
sensitivity using the ICP-MS technique allowed the eluent of the ion exchange column to be
monitored continuously for samples whose transuranic concentration were in the range of pCi/L.
Rollin and Eklund (2000) were successful in separating and quantifying IT4 and U(VI) in laboratory
standards. Truscott et al. (2001) identified an unexpected change in oxidation state of uranium from
VI to (+4) by using a reducing agent (Rongalite*) for plutonium. In these analyses of ocean water,
the ion exchange columns were able to separate different oxidation states of neptunium, plutonium,
and uranium.
Chemical speciation also can be performed by sequential aqueous extraction techniques that do not
affect the oxidation state of the radionuclides during the extraction process (Schultz et al., 1998).
Although the oxidation state of the transuranics are not identified specifically, the geological fraction
of sediment that the radionuclides are associated with can be determined. This identifies the mobility
of the radionuclides in the sediment environment.
There are other elements that also can be in multiple oxidation states in the environment in addition
to the specific examples cited here. Table 6 summarizes the possible oxidation states of the radio-
nuclides identified in this document. It is important to note that these radionuclides are "ultra-trace"
components of the sample mixture (on a mass or molar basis), and the oxidation states of these ions
can be affected significantly by the major sample ionic content. How rapidly changes can occur
depends on several factors, including time, temperature of the medium sampled, temperature at
which the sample is preserved, presence or absence of oxygen in the sample environment and its
stored container, presence of bacteria, and sample degassing after being extricated from its matrix.
TABLE 6 — Summary of elements and their common oxidation states
Element
Americium
Bismuth
Carbon
Oxidation State
-2
-1
— — -J
+1 -J
+2
o
+3
•
•
+4
LJ-L^
+5
0
+6
+7
1
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Element
Cesium
Cobalt
Hydrogen
Iodine*
Indium^
Lead
Nickel
Phosphorus
Plutonium
Radium
Strontium
Sulfur
Technetium
-2
-1
Oxidation State
| +2 I +3 F+4
+6
+7
o
o
•
•
o
Thorium
Uranium
o
o
•
o
r r t-
o Allowable state • Most common state
* The oxidation state of iodine depends significantly on the presence of other oxidizing or reducing materials.
3.6.6 Addition of Radiotracers or Carriers
A carrier is a stable (non-radioactive) isotope of an element that is chemically identical to the radio-
nuclide of interest. A radiotracer is a radioisotope, not found in the type of sample being processed,
which is chemically the same as the radionuclide of interest. Carriers or radiotracers may be added
to monitor for the loss of a radionuclide during chemical processing. In some instances (e.g.,
technetium) neither a radiotracer nor a carrier is possible, and a surrogate is used (for technetium,
it is usually rhenium).
The addition of carriers and radiotracers should be made as early on in the chemical analysis as
possible, but before any chemical separations to the sample have occurred.
3.7 Chemical Separation Process
The chemical separation of the analyte from other chemical elements or compounds in the sample
mixture is achieved through methods such as:
Precipitation/filtration/centrifugation;
Ion exchange;
Complex formation;
Solvent extraction;
Oxidation-reduction; and
Electroplating.
In many analyses, these methods are used in combination several times to achieve separation. Each
of these methods individually can take several hours to complete. The longer times will be required
when there are significant concentrations of interfering radionuclides.
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In several different methods of analysis (wSr, 226Ra, and 228Ra are noteworthy), once a certain degree
of separation has been achieved, the progeny of the radionuclide of interest are allowed to "grow
in" so that the parent nuclide can be indirectly determined. This ingrowth period can take several
hours to weeks, depending upon the half-life of the progeny.
A specific example of this type of method is used in the determination of 228Ra. The particle
emission from 228Ra (5.8 y half-life) is a very low-energy beta that is poorly detected using gas-
proportional counting. The first progeny of 228Ra (228Ac) has a short half-life (6 hours) and emits a
beta particle of higher energy compared to 228Ra, allowing better detection (quantification
capability). Because actinium and radium are chemically different, they may not be in radioactive
equilibrium in the environmental sample attained (see Appendix B). A separation of the radium is
performed using a barium sulfate precipitation method coupled with a complex formation reaction
to chemically isolate the radium from the actinium. This portion of the method will take 6-9 hours.
At that point, the actinium is allowed to "grow in" in a matrix containing only radium. This process
of ingrowth can take up to 36 hours, depending on the minimum detectable concentration desired.
The actinium is separated from the parent radium through solvent extraction, ion exchange, or
precipitation and counted.
3.8 Sample Counting
The length of time that a sample is counted will depend on two principal factors: the radionuclide's
half-life and the minimum detectable concentration to be achieved. The previous section provides
an example (Ra-Ac analysis) where the count time not only needs to take place immediately after
the separation of the actinium from the radium parent, but counting for more than about 10 hours
will not yield significantly better or more precise measurements. After a certain length of time, the
activity of the short-lived 228Ac will begin to approach the background activity (for low-activity
samples).
Radionuclides with long half-lives (weeks to years) can be counted for as much as two days to help
achieve the required minimum detectable concentration. Counting a sample longer than two days
is not advisable, because changes in the background count rate may occur. Application of a
background determined by a shorter counting time also may bias an analysis because it may not be
representative of the background in a longer counting interval.
3.9 Data Review and Report Generation
The raw data must be converted to a final analytical value in the appropriate units (i.e., pCi/L or
pCi/g), and a total uncertainty calculated based on the test parameters. A laboratory quality system
will have certain requirements for data review, verification, and validation. This process ensures that
there are no transcription errors, the calculations have been performed correctly, QC samples (splits,
spikes, duplicates, etc.) are satisfactory, and the entire process of sample analysis meets the MQOs
of the project. It usually also requires a manual calculation of the results for a small percentage of
the data to ensure any computational errors have been fixed.
The length of this process will depend on the number of samples and the types of analyses that have
been performed. However, for an individual radionuclide and one sample, the process can take as
long as 20 minutes. The sum of the times for each of the individual sections stated here will yield
the total turnaround time for just the laboratory portion of the process.
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3.10 Units Used in Radioactivity Measurements
The traditional unit for measurement of radioactivity is the curie (Ci). This unit is equivalent to
3.7 x io'° disintegrations per second (dps). This is the disintegration rate of 1 g of 226Ra. The
measurement of radioactivity in environmental samples is very small compared to this traditional
unit, and frequently the unit used is picocuries (pCi), equivalent to 10 12 Ci. For water samples, the
most commonly used concentration expression is pCi/L, for soil samples pCi/kg. It should be noted
that some projects are now using units of pCi/g for reporting purposes. Other fractional units for the
curie (such as "milli" and "micro") are also in common use. In recent years, the international
community has switched to the becquerel (Bq) as the unit of radioactivity measurement. This unit
is equivalent to 1.0 dps (see Unit Conversion Table on page xii).
The energy of radioactive particles is measured either in millions of electron volts (MeV) or
thousands of electron volts (keV). The energies of both alpha and beta emitters are usually referred
to in units of MeV, while gamma emitters are generally cited in keV. The range of energies
generally examined in radiochemical analyses are listed in Table 7.
TABLE 7 — Energy range of radiochemical analyses
Alpha (a) 3 to 10 MeV
Beta (P) 0.005 to 4 MeV
Gamma (y) 60 to 2,000 keV
Low-energy photon or X-ray 3 to 60 keV
The half-life of a radionuclide is the amount of time it takes for one-half of the initial number of
radionuclide atoms to decay, leaving one-half of the initial radionuclide atoms remaining.. The unit
for the measurement of half-life is variable, and there are not strict guidelines. Half-lives less than
one hour generally are measured in minutes, those less than one day in hours, and those less than
a year in days. Appendix B, Section B. 1.3 (page 71) provides more details about half-life and decay.
3.11 Measurement Quality Objectives and Performance Testing
The measurement of radionuclides in water and soil samples can present significant challenges to
the analyst because of the variety of matrix elements and compounds and the range of possible
radionuclide concentrations. An MQO, for the processes covered by this document, is a statement
that defines the radionuclide to be determined, the uncertainty of the measurement of that nuclide
at a certain target concentration, the minimum detectable concentration (MDC) to be achieved for
a particular radionuclide, and under what circumstances the radionuclide should be determined (see
MARLAP, 2004, Chapter 3). As an example, consider the following statements as part of the
APSs/MQOs for analysis of radium in ground water at a hypothetical remediation site:
Radium-226 and 228Ra are to be determined separately.
Analysis can be performed in the presence of concentrations of up to 1,000 ppm calcium.
At a concentration of 3.0 pCi/L, the method uncertainty at the 95 percent confidence level shall
be 0.6 pCi/L.
The presence of organic solvents at less than 100 ppm will not interfere with the analytical
process.
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These APS/MQO statements are both qualitative and quantitative. They show that the developer of
the MQO has a basic knowledge of the materials to be analyzed, the site characteristics and the
levels at which decisions will be made based on measurement uncertainties. Such statements (and
perhaps more) would be required for each analyte.
Demonstration of the MQOs is usually a requirement of the project. Performance testing is a
mechanism whereby the analysts are routinely presented with the project analytes in matrices that
challenge the MQOs. These samples may be artificial or spiked, and can be prepared by an
independent, outside laboratory or an independent branch of the analytical laboratory. Performance
testing samples are different from the QC samples that will be measured as part of the overall QA
process for the project, in that they provide evidence that the MQOs have been achieved. For the
MQOs cited above, a performance testing sample might contain both isotopes of radium at a
concentration of 1.0 pCi/L, with 500 ppm of calcium as a contaminant in the aqueous sample.
3.12 Selecting a Method
3.12.1 Performance-Based Method Selection
Typically, a laboratory will have developed and validated various methods to address the radionuc-
lides, radionuclide concentration levels (environmental or effluents), and matrices expected from
their customers and markets. However, a laboratory normally will select a particular radioanalytical
method that will meet APSs contained in a statement of work or contract written by a client. The
APSs include MQOs required for the laboratory's sample analyses, i.e., method uncertainty at a
radionuclide concentration, MDC, minimum quantifiable concentration, method selectivity, etc.
(MARLAP, 2004, Chapter 3). This type of method selection is referred to as "a performance-based
approach to method selection." Performance-based method selection allows the laboratory to choose
a method for processing samples as long as it can meet the required APSs and MQOs. Method
performance for a project is demonstrated in the form of method validation documentation for the
MQO requirements. During a project, ongoing method performance is monitored through perfor-
mance evaluation programs, project-specific performance-testing samples or internal batch quality
control samples. Additional information on laboratory method selection, project method validation
and ongoing method evaluation can be found in MARLAP (2004, Chapters 6 and 7).
For purposes of this document, a "laboratory method" includes all physical, chemical, radiometric,
and spectrometric processes conducted at a laboratory to provide an analytical result. Each method
addresses a particular radionuclide in a specified matrix or, in some cases, a group of radionuclides
having the same decay emission category (a, P, y) that can be identified through spectrometric
means. Depending on the category, a method may involve any or all of the following processes:
sample preparation or dissolution, chemical separations, mounting the resultant product for counting,
nuclear instrumentation counting, and analytical calculations. Multiple radionuclides in a sample
may require different analytical detection techniques for which a laboratory may use a sequential
separation method that addresses multiple radionuclides or stand-alone individual methods for each
radionuclide. The APSs should ensure that certain parameters that affect method selection, such as
sample preservation for each radionuclide and the sample size, are addressed.
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3.12.2 Sources for Specific Method Information Available to the General Public
Major civilian laboratories and nuclear facilities include: Los Alamos National Laboratory,
Lawrence Livermore National Laboratory, Brookhaven National Laboratory, Argonne National
Laboratory, Pacific Northwest National Laboratory, Oak Ridge National Laboratories, Savannah
River Site, and Hanford (all with DOE); DHS's Environmental Measurements Laboratory; and
EPA's National Air and Radiation Environmental Laboratory. Certain departments or organizations
within these laboratories have radiochemistry methods in the form of stand-alone standard operating
procedures or within a manual. Each laboratory or specific department may have its own policy on
the distribution of radiochemical methods employed for environmental matrices. In some cases, it
may be easier to obtain an individual method rather than a manual compilation. The most direct way
of obtaining methods is to contact the manager of the chemistry or environmental surveillance
department.
4 Radioanalytical Methodologies
As discussed in Section 2, three general methodologies are considered important to the cleanup
process: screening, routine radionuclide-specific, and specialized. The methodology selected for
sample analysis in a particular phase of the cleanup process is related to the analytical protocol
specifications/MQOs for the cleanup phase being conducted. This section addresses the typical
methodologies to detect and quantify radionuclides in various matrices. Two modes of detection are
discussed: radioactive decay emission measurements and atom counting measurements. Radioactive
decay emissions measurements detect and quantify the a, P , and p^ particles, electrons, X-rays, or
y rays emitted during the radioactive decay process. Because radioactivity is measured in terms of
activity (becquerels, or disintegrations per second), measuring the detection rate for each type of
emission (detections measured per unit time), together with information on emission probability of
the type of emission, is the most direct way to quantify radioactivity. Radioactive decay emissions
measurements come under the screening and radionuclide-specific methodologies. Atom-counting
methods (Section 4.2) are the specialized methodologies that measure the number of radionuclide
atoms directly or measure the light emissions from all stimulated atoms in an element. Given the
number of atoms or mass of the radionuclide and its half-life, the radionuclide's radioactivity can
be calculated (Appendix B, Section B. 1.3, on page 71). Atom counting methodologies include mass
spectrometry and kinetic phosphorimetry analysis.
The method selected depends upon the type of sample and the MQOs for the particular project, types
of interferences that may be present, cost, and available equipment. Methods associated with routine
radionuclide-specific and specialized methodologies may require some chemical separation prior
to the final analysis to minimize interferences from other radionuclides and to concentrate the
analyte into a smaller analytical sample. With the exception of drinking water, there are no
"government-approved" methods for chemical separations used for the determination of
radionuclides. However, the analytical techniques presented here are well established. Tables in
Appendix D are set up for each element. Each table summarizes the detection techniques that are
appropriate for each radionuclide, whether or not chemical separation is necessary, the routinely
achievable MDC values, and the amount of time required to perform the chemical and data analysis.
Important considerations affecting MDCs are explained in the box preceding the tables in Appendix
D (page 80). These tables should be used as a general guide to selecting the methodology
appropriate to the DQOs of the project.
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4.1 Radioactive Decay Emissions Measurements
4.1.1 Gas Proportional Counting
Gas proportional counting (GPC) is capable of quantifying radionuclides emitting alpha and beta
particles (with energies greater than about 150 keV) in small, dry test sources. Although this
radiation detection method can differentiate between alpha and beta particles striking the detector,
it does not have the resolution necessary to discern individual alpha or beta particle energies.
Because of this, GPC is useful only for gross alpha and beta screening applications. The most
common GPC configuration for evaporated water, soil, or air-filter samples of small residual mass
is counting in a metal planchet between 1 and 5 cm in diameter and 0.3 and 0.6 cm in height.
Test-source masses are kept between 25 and 200 mg to minimize the self-absorption effects of alpha
and beta particles in the source matrix. When there is a possibility of variable test-source mass, a
detector-efficiency curve for a specific radionuclide is generated as a function of test-source mass.
For gross alpha and beta counting applications, the accuracy of a result depends on matching the
target nuclide with the nuclide used for calibration and the number of other alpha- and beta-emitting
nuclides present in the sample. Measurement accuracies for gross alpha- and beta-particle counting
are obtainable as low as 10 to 15 percent for single nuclides, but inaccuracies of 100 to 200 percent
are not uncommon for mixtures of nuclides or heavy test sources. Data analysts should not expect
that the gross alpha or beta activity in a sample will be equivalent to the summation of the individual
activities of the alpha- or beta-emitting nuclides in the sample.
GPC also may be used for specific radionuclide analysis following radiochemical processing of a
sample during the early investigation or remediation phases. GPC normally is applied to the
measurement of 90Sr, 89Sr, 1311,210Pb, 210Po, 21()Bi, 228Ra, and total (alpha) radium following chemical
purification.
The typical GP detector backgrounds for alpha and beta particles are < 0.1 cpm and < 1 cpm,
respectively. For most applications and nominal measurement times and sample sizes, the
quantification capability is typically 1 pCi for alpha or beta measurements. With proper detector
calibration, chemical-yield determination, and chemical isolation of the target nuclide, GPC can be
very accurate for specific nuclides (a relative standard deviation of about 3 to 5 percent) when
sufficient activity is present at levels greater than 100 times the detection limit.
4.1.2 Liquid Scintillation
Liquid scintillation counting (LSC) involves the detection of light generated by the interaction of
charged particles with an aqueous solution containing organic molecules (i.e., a scintillator as a
solute) that convert the absorbed energy into light photons. However, the detection of Cerenkov
radiation, because of its production mechanism, does not require the use of an organic scintillator.
A LSC is a low-resolution energy spectrometer that can distinguish between wide-banded alpha or
beta energy regions. As such, most LSC analyses involve the measurement of a single radionuclide
when possible, avoiding spectral interferences from other radionuclides. Analytical methods have
been developed to process samples and provide a final test source matrix required for LS counting.
This detection methodology is used for beta measurements involving very-low (18 keV) to high-
energy (2,200 keV) beta-emitting radionuclides and for Cerenkov counting of high energy (> 1,000
keV) beta particle measurements. The typical applications of LSC are presented below.
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Sample analysis by liquid scintillation counting methods may occur in all phases of the cleanup
process, but its use as a screening methodology for a, )3 and P* particles is somewhat limited
primarily to a clear water matrix having a minimum of chemical interferences. Application of the
LSC as a radionuclide-specific methodology will be principally in the early investigation and
remediation phases when the radionuclide has been identified. Because LSC is not a non-destruction
sample processing method and is not a high-resolution spectrometer, sample analysis will require
sample (non-aqueous) digestion and chemical processing for the radionuclide of interest.
4.1.2.1 Routine LSC Analysis
In routine LSC applications, a small-volume (1-10 mL) aqueous test source is combined with a
commercially available organic scintillation cocktail (10-15 mL) and counted in a ~ 25 mL low-
background plastic vial for a reasonable counting interval (e.g., 100 - 400 minutes). The aqueous
test sources may include distilled water for tritium analysis to highly acid nitrate solutions for 90Sr
analysis. In some cases, a dry test source is added to the liquid or gel scintillation cocktail. Examples
of these include the insertion of an air particulate filter paper into a liquid scintillation cocktail and
the dispersion of dry BaCO3 precipitate containing 14C into a scintillation gel.
In order to prepare a test source for counting, a sample must be processed so that contaminants are
removed or the radionuclide (element) is isolated from the sample and chemically purified. Solid
samples must undergo a digestion or an acid leaching process to make the radionuclide available for
chemical purification. Care must be taken to ensure that the chemical solution containing the
purified radionuclide does not cause enhancement or degradation of the light output from the LS
cocktail used. Typically, techniques for the measurement of changes in detector response due to
chemiluminescence or phosphorescence (light enhancements) or quenching (light degradation from
chemical agents or color) are incorporated in the instrument measurement protocols for the
radionuclide method.
LSC is not as sensitive as other detection techniques for alpha and beta particle quantification.
However, many of the detrimental physical parameters affecting other detection techniques are
avoided with this detection technique, including test-source preparation problems and self-
absorption and backscatter effects that cause variability in detector efficiency. The beta-emitting
radionuclides important to environmental surveillance, effluent analysis, and site decommissioning
and decontamination commonly analyzed by LSC include 3H, 14C, 55Fe, 63Ni, "Tc, 89Sr, 90Sr, 129I, and
241Pu. For intermediate levels of contamination, when the detection limit for the alpha emitting
nuclides is higher than for low-level environmental levels, LSC can be used for the analysis of a
single alpha-emitting radionuclide in a sample, such as 234U, 235U,238U, 223Ra, 224Ra, 226Ra, 23SPu, 239Pu,
242Cm, 243Cm, 244Cm, 230Th, 232Th, 241Am, and 237Np. Because of the poor alpha resolution of the LS
process (>300 keV), it is not readily used for isotopic analysis of multiple isotopes (e.g., 234U, 235U
and 238U). For the cleanup process, the LSC method can be used in the early investigation and the
remediation phases depending on the detection limit requirements.
4.1.2.2 Photon-Electron Rejecting Alpha Liquid Scintillation
The PERALS* spectrometer combines liquid scintillation counting with electronic discrimination
to reduce the background from X- and gamma-ray photons and to eliminate interferences from beta
emitters in the test source. PERALS is used in conjunction with specially manufactured cocktails
that combine an organic extractant (for the element of interest) with an alpha particle scintillator.
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The test source must be prepared in a similar fashion as routine LSC applications; the element or
radionuclide must be put into an aqueous solution quantitatively. Once into solution, the extractant
scintillator extracts the radionuclide or element from the solution nearly quantitatively. An isotopic
tracer of the same oxidation state as the sample can be used to verify the quantitative recovery of
the target radionuclide from the sample digestion and extraction processes. Currently, extractant
scintillators have been developed that permit analysis of 226Ra, 230/232Th, 234/238U, 237Np, 238/239/2^
241/243Am, and 244Cm.
The PERALS spectrometer has better alpha-particle resolution capability compared to a standard
LSC. An alpha peak resolution of 300 keV is obtainable for most extractant scintillators and
radionuclides. Because the alpha background (2 x 10 5 counts per second) for this system is much
lower than the standard LSC, its detection capability for the alpha-emitting radionuclides is similar
to that obtained from alpha spectrometry using solid state detectors. Typical detection limits for
aqueous samples range from 0.0005 to 0.024 Bq/L, depending on sample volume, interferences, and
counting time.
For the cleanup process, the PERALS method can be used in the early investigation and the
remediation phases depending on the detection limit requirements.
4.1.2.3 Cerenkov Counting
When charged particles pass through a dielectric medium (such as water) at speeds greater than the
speed of light in that medium, they will emit Cerenkov photon radiation in the direction of travel.
Cerenkov radiation is emitted in the ultraviolet wavelength region. On a practical basis, Cerenkov
counting is applied to radionuclides emitting beta particles having an Epmax greater than 1,000 keV.
The detector counting efficiency for nuclides in water increases as the Epmax increases greater than
1,000 keV, ranging from about 7 percent at 1,000 keV to 70 percent at 3,520 keV.
There are certain unique advantages to using the Cerenkov radiation detection technique for the
analysis of high-energy beta-emitting radionuclides. In particular, there is discrimination between
detected high-energy beta particles and non-detected low-energy beta emissions. This advantage has
been used to analyze 89Sr (Epmax = 1,488 keV and detection efficiency of about 28 percent) in the
presence of 90Sr (Epmax = 546 keV and detector efficiency of < 1 percent). Another advantage is the
avoidance of using an organic scintillator and its disposal as a mixed waste and the ability to recover
unaltered test sources for other purposes. In addition to water, Cerenkov radiation is produced in
very acidic and alkaline solutions, solutions that may not be compatible with scintillation cocktails.
Normally, an analytical method is developed so that the aqueous test source solution is prepared to
avoid color quenching of Cerenkov light emissions.
The application of Cerenkov counting to environmental samples has been limited and not fully
investigated. Currently, the detection methodology has been mainly used for 89Sr, 90Sr/Y, and 32P in
effluents and environmental media. For the cleanup process, the Cerenkov LSC method can be used
in the early investigation and the remediation phases depending on the detection limit requirements.
4.1.3 Gamma Spectrometry
Gamma spectrometry is a sensitive method of analysis that can yield analytical data for several
different nuclides in a single sample analysis. Gamma-ray emission from a radionuclide is usually
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preceded by the particle emissions from radioactive beta decay (either (3" or (3+) and sometimes by
alpha decay. The decay leaves the nucleus in either a ground or excited state. If the nucleus is in an
excited state, the decay to ground state typically is achieved by gamma emission. A nucleus may
have many different energy levels through which it must pass before attaining a ground state
configuration. This means that there can be one or more gamma rays emitted from an excited
nucleus. Not all transitions have the same probability. If a nuclide emits a gamma ray of a specified
energy each time it decays, its transition probability will be 1.0. Cobalt-60 has two gamma rays
(1,173 and 1,332 keV) that are emitted, and each transition has a probability of at least 0.99.
Technicum-99 emits a gamma ray at 90 keV with a probability of <0.001. Thus, it is much easier
(and more practical) to detect the 6l)Co by gamma spectrometry than the "Tc when present at very
low concentrations in the environment.
Although gamma rays interact with a HPGe detector through three major mechanisms, the most
important mechanism for gamma spectrometry is the photoelectric effect interaction, in which all
the photon's energy is absorbed by the detector in a single event. Particularly in samples where the
radionuclide concentration is very low, each gamma ray will be easily identified from other gamma
rays. Each radionuclide emits gamma ray(s) at one or more energies characteristic to that nuclide,
enabling the spectroscopist to identify radionuclides present in the sample uniquely. The intensity
of the gamma radiation per unit time can be used to quantify the number of radionuclide atoms that
have undergone decay. From this measurement, the concentration of the radionuclide (i.e., pCi/g or
pCi/L) present in the sample being analyzed can be calculated.
Of the radionuclides listed in Section 1.5, the following can be determined routinely by gamma
spectrometry.
Americium-241
Cesium-134 and 137
Cobalt-60
Iodine-131
Iridium-192
It is important to note that due to the manner in which gamma-ray spectrometry is performed,
"other" gamma emitters (e.g., 40K, 7Be, 22SAc, 125Sb, etc.) that are outside the scope of this document
may be detected in the spectrum. These radionuclides could be from NORM or nuclear power plant
(NPP) decommissioning sites. Those present from facility decommissioning will depend upon the
length of time between when the plant was operating and when the samples are taken (due to half-
life considerations). Some of these are listed in Table 8.
NORM
Half-life
NPP*
Half-life
1 40K
1.27 x 10'y
108nV110m A
418y
250 d
228Ac
6.15H
i_J_7/S8Co
271 d
70.9 d
7Be
53.3d
54Mn
3I2d
212/2,4pb
10.6 h
26.8 min
152/154'155g
13.5 y
8.59 y
4.76 y
21M,4Bi
60.6 min
19.9 min
I 45Ca
163d
222Rn
3.82d
mSb
2.76 y
234Th
24.1 d
Also see Appendix E, Nuclear Power Plant Decommissioning Sites
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Some of the other radionuclides may emit gamma rays upon decay, but the probability of gamma
emission is very low. This means that other methodologies would be more applicable for very low
concentrations of the other gamma ray-emitting isotopes.
As a nondestructive method of sample analysis, gamma spectrometry is very applicable as a
screening and a radionuclide-specific methodology that can be used during all phases of the cleanup
process. In most instances for screening applications, a medium-resolution, high-detection efficiency
probe as part of a gamma survey unit can be used in the early investigation phase as a limited
spectrometer. A common gamma probe for surveys is a Nal(Tl), with a resolution >70 keV and a
dimension of 2.5 cm length by 2.5 cm diameter (or 5.1 cm long by 5.1 cm across). The response of
the Nal(Tl) probe is calibrated to the radionuclide (or mixture of radionuclides) of interest and the
physical dimensions (geometry) of the source of the radioactivity. The typical geometries for
surveys include walls, equipment, and the ground. When evaluating a single nuclide, or two nuclides
having gamma energies differing by 200 keV, survey measurements using this type of probe will
quantify the gamma-emitting radionuclides in survey units (areal concentration) of a contaminated
site. When there is a mixture of gamma ray-emitting radionuclides, survey measurements can be
used to compare the gamma flux (total detector response over the entire energy range) from one
survey area to another or to a reference background. Information on Nal detector calibrations can
be found in NRC (1997).
For high-resolution, radionuclide-specific gamma spectrometry, high-purity germanium HPGe
detectors are most frequently used for identifying and quantifying the gamma radiations. This type
of detector, when properly shielded and collimated, also can be used as part of a portable gamma
spectrometry system for performing in situ field surveys. In situ gamma-ray spectrometry has been
employed by the Department of Energy for more than thirty years (Beck et al., 1972; Shebell, 2003)
for measuring large areas of contaminated soil and applying computer algorithms to correlate the
measured gamma spectral response to specific radionuclide soil concentrations (areal and volumetric
contamination). However, soil core samples typically are collected (in the same measurement area)
and analyzed to verify the soil depth profile (of the radionuclide contamination) that is used in the
in situ software algorithms. In many cases, in situ gamma spectrometry has been found to be an
effective field measurement tool that is quick and reduces the number of laboratory analyses that
must be taken. More recently, one manufacturer has designed a portable gamma spectrometry
system for measuring the average surface contamination of building structures.
Within most laboratories, a highly shielded HPGe-detector gamma-ray spectrometry system is used
as a non-destructive, radionuclide-specific method. Samples of any matrix can be analyzed by this
method as long as the detector is calibrated for the sample geometry and density (Z value) and
radionuclide gamma energy. Typical sample volumes include 500 grams for solid matrices and one
or 3.5 liters for liquid samples. Commonly used counting (measurement) times range from 6,000 to
60,000 seconds, depending on the required MDC value. In some cases, mobile laboratories have
been constructed to house a highly shielded HPGe-detector gamma-ray spectrometry system for field
analyses during the assessment, site inspection, and remediation phases.
4.1.4 Alpha Spectrometry
Alpha spectrometry is a radionuclide-specific method used in the laboratory to identify and quantify
pure alpha-emitting radionuclides. Most laboratories employ an alpha spectrometry system as a
routine detection method for the difficult-to-measure alpha-emitting radionuclides. A high-resolution
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alpha spectrometry system used in a laboratory consists of a semiconductor detector in a vacuum
chamber electronically coupled to a multichannel analyzer operating over an energy range between
4 MeV and 8 MeV. In general, ion-implanted silicon or silicon surface barrier detectors having a
diameter of ~ 25 mm and a very thin sensitive depth (typically <400 urn) are used for alpha
spectrometry applications. Because the energy of the alpha particle is severely attenuated by matter,
a sample must be chemically processed and the radionuclide deposited (electroplated or micro-
precipitation) without interferences on a metal disk or filter paper mount. The final mount is inserted
into a vacuum chamber containing the semiconductor detector and analyzed in a near vacuum to
avoid degradation of the alpha particle energy and alpha spectrum. Spectral resolution of alpha-
particle energies more than 50 keV apart can be obtained with electrodeposition- and microprecipita-
tion-mounting techniques.
Alpha spectrometry as a radionuclide-specific method can be used during the early investigation and
remediation phases. In most cases, alpha spectrometry is chosen when the historical source term
information indicates the likely presence of the alpha-emitting radionuclides or when alpha
screening has indicated elevated alpha levels. For routine low-level environmental radionuclide
analyses, the typical sample processing time for most methods is one day for sample processing and
one day for counting. The typical minimum detectable activity obtained in a 60,000 second
measurement is ~ 0.03 pCi or 0.001 Bq per sample for water and soil samples. The method is used
for isotopic analysis of 234U, 23?U, and 238U; 210Po, 223Ra, 224Ra, and 226Ra; 237Np, 238Pu, and 239Pu;
241Am, 242Cm, and 244Cm; and 228Th, 230Th, and 232Th.
4.2 Atom-Counting Methods
Atom-counting methods are grouped within the special methodologies (Section 2.3) and are used
in the analysis of certain longer-lived radionuclides (e.g., 232Th, 235U, and 23SU) when very low
activity levels are encountered or when isotopic mass ratios are required. Atom-counting methods
are confined to laboratory operations and are not typically used in the field. The application of the
atom-counting methods would be for characterizing the radioactive source by isotope or element
during the characterization and remediation phases.
The two-atom counting methods discussed in this document include kinetic phosphorimetry analysis
(KPA) and mass spectrometry. Mass spectrometric methods can be used in the characterization
phase to determine if the isotopic ratio (e.g., 240Pu/239Pu mass ratio) is a signature of the source-term
contamination. Highly sensitive mass-spectrometric measurement of the ratio of 238U:235U is used
routinely to determine whether uranium is of natural origin or if it may be contaminated with
depleted uranium or enriched uranium. In some cases, a highly sensitive elemental analysis (such
as uranium and thorium) rather than an isotopic analysis would be more applicable, e.g., the non-
mass spectrometric atom-counting method of KPA. Sample-processing time usually is longer and
much more expensive for mass spectrometric analyses compared to KPA. Therefore, the sample
analysis by mass spectrometry would only be used in those phases when isotopic identification or
low-activity measurements for very long-lived radionuclides are required.
4.2.1 Kinetic Phosphorimetry Analysis
Kinetic phosphorimetry analysis is based on the measurement of ionic phosphorescence of a species
taken at selected time intervals after excitation. The intensity of the phosphorescence is related to
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the concentration of the analyte. KPA does not measure radioactive emissions but UV-V as light
emitted from a sample solution containing certain molecular species.
The analyte in the sample solution is excited by using a laser (commonly a nitrogen laser is used)
of energy equal to or greater than the excitation transition energy. A short laser pulse (on the order
of nanoseconds) will initiate a measurement cycle. Phosphorescence emission is measured at right
angles to the excitation wavelength, and delayed between 0.0001 and 10 seconds, from the incident
excitation.
Because KPA is an outer electronic orbital phenomenon (that is, it involves valence shell electron
orbitals and higher energy orbitals), the valence state of the analyte can have a significant effect on
the analysis. It is also important to note that the phosphorescent light emission is independent of the
specific isotopes of the element present in the sample. All isotopes of the element will yield the same
phosphorescence as long as they are in the same oxidation state. For example, U+4 is not sensitive
to the process, but U(VI) is sensitive. Thus, a sample to be analyzed by KPA for uranium would
need to have all the uranium oxidized to U(VI) using an oxidant such as nitric or perchloric acid.
KPA has been applied to uranium and lanthanide analyses in the range of 0.01 ppb (~ 0.2 mBq/L)
to percent by weight composition of materials. The method lends itself to the analysis of samples
with significant uranium content (ores, mill tailings, soils contaminated with spilled uranium
solutions, etc.) as opposed to background uranium measurements (seawater, river sediments etc.).
4.2.2 Mass Spectrometry
Detection of elements by mass spectrometry (MS) does not depend on the atoms' radioactive or
chemical properties. It depends only on the mass of the nucleus and the ionic charge of the atom
when introduced into the mass spectrometer. There are a variety of methods by which samples may
be introduced into the detection system. These methods become part of the hyphenated name with
MS.
Generally, MS techniques have better quantification capabilities than radioactive decay-emission
detection techniques for low-activity (< 0.1 Bq) samples of radionuclides with half-lives greater than
about 100 years. Decay-emission measurement techniques have trouble distinguishing background
decay emissions per unit time from low-activity samples. Table 9 identifies, for a given
concentration, the number of atoms present for radionuclides with a wide range of half-lives. Note
that the same activity has vastly differing numbers of atoms, but the activity concentrations are the
same.
TABLE 9 — Number of atoms of radionuclides with activity of 0.1 Bq
Radionuclide
2,0B;
90Sr
243 Am
"Tc
232Th
Half-life (years)^
1.37x 1(T2
2.91 x 10'
7.37 x JO3
2.13 x 105
1.4 x io'°
Atoms
6.23 x 104
1.33 x 108
3.35 x 10'°
9.68 x 10"
6.36 x 1016
Concentration
DCi/L
2.7
2.7
2.7
2.7
2.7
Concentration
moles/L
1.03 x 1(T19
2.21 x l(T16
5.56 x 1()-M
1.60x 1(T12
1.06x 1CT7
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Inventory of Radiological Methodologies
As with most highly sensitive analyses, mass spectrometry methods require sample preparation/
digestion and chemical isolation and purification prior to injecting the test source into the mass
spectrometer. In addition, special highly purified reagents (e.g., nitric acid) and benchware (beakers,
vials, etc.) must be used to avoid contamination of the sample with minute trace quantities of the
target element or radionuclide. Depending on the element or target radionuclide, the sample prepara-
tion and chemical processing may be conducted in a clean room to prevent contamination from
ambient airborne contaminants. A few of the more commonly used mass spectrometric methods are
identified below.
4.2.2.1 Inductively Coupled Plasma-Mass Spectrometry
ICP-MS is a hybrid technique for elemental analysis. It is the connection of an inductively coupled
plasma (ICP) unit for measuring emission lines of excited atoms with a mass spectrometer (MS).
The method uses the ICP portion to introduce samples as ionized gasses into the mass spectrometer,
which sorts out these ions based on their charge to mass ratio. The integrated instrument has the
following basic components:
• Sample introduction system
• Torch
• Interface
• Vacuum system
• Lens
• Quadrupole
• Detector
Most samples that are analyzed by ICP-MS are liquids. These samples would have undergone
digestion in aqueous media in exactly the same way as any sample prepared for radioactivity
measurements but with less emphasis on major elemental interferences. The sample is introduced
to an argon plasma torch using a nebulizer spray chamber (analogous to the type used in an atomic
absorption spectrometer). The argon plasma transforms all constituents to ionized elements. The ions
are passed through a vacuum interface through a focusing lens and into the quadrupole mass
separator. The ions are focused onto a detector (similar to a PMT) that counts individual events at
a particular charge-to-mass ratio. Commercial instruments have the capability of scanning the mass
range from 1 to 240 atomic mass units (amu) in a few tenths of a second and achieving detection
limits in the 0.1 to 1 ppb range during that time. Solid and gaseous samples can also be analyzed
directly by altering the sample introduction format. As with all other methods of analysis that require
sample preparation, this method can be affected by incomplete sample dissolution.
The benefit of this technique is that it counts atoms present in the sample as opposed to waiting for
decay events to occur. Thus it has a specific advantage over decay-particle-detection techniques for
long-lived isotopes, i.e., signal accumulation time is much less. Another advantage is that for
isotopes like 239Pu and 240Pu (which have alpha particle energies that are almost exactly the same),
the mass separation can be used effectively to identify and quantify these isotopes separately.
This technique has potential isobaric interferences resulting from combinations of abundant ions in
the mass spectrometer. An instance of isobaric interference comes from a combination of 58Ni and
'H (noted as "Ni-58:H" in the Appendix D table) as a combined ion yielding a signal at mass number
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Inventory of Radiological Methodologies
59. For example, if 59Ni were being analyzed from reactor-coolant piping, the 58Ni would be present
in large mass amounts from the steel, and the 'H would come from the water matrix. Thus, an
interference correction must be applied.
This technique also has great utility in assessing the isotopic ratios of certain elements that can
determine what the sample history has been. This technique of isotopic ratios can also be used for
a trace element technique known as isotopic dilution analysis (IDA).
4.2.2.2 Thermal lonization Mass Spectrometry
Thermal ionization mass spectrometry (TIMS) ionizes an element by heating a metal filament on
which the target nuclide has been electroplated. TIMS has been used to analyze 235U, 238U, 239Pu, and
240Pu in a variety of environmental and bioassay matrices. A detection limit of about 6 [oBq per
sample is typical for 239Pu. TIMS and quadrupole ICP-MS have similar detection limits for
uranium—about 0.1 pg for total uranium (based on 238U) and about 15 pg for a 238U/235U ratio of 138
(natural abundance). TIMS is able to measure 238u/235U ratios in ranges between 138 and 220 for
levels between 25 to more than 350 ng/kg.
4.2.2.3 Accelerator Mass Spectrometry
Accelerator mass spectrometry (AMS) is a sensitive analytical technique that uses an ion accelerator
and a beam transport system to provide different levels of mass and charge analysis, ultimately
counting individual ionized atoms. The low range sensitivity of AMS is not encumbered by the half-
life of the isotope being measured, because the atoms, not their radioactive emissions, are counted.
Isobaric identification is possible because AMS is unaffected by most background mass peaks,
because molecular ions are destroyed in the transport of the ions through the instrument. A basic
system is composed of the following:
• A sample holder;
• An ionizing source projected onto the sample;
• An injection system that includes beam transport, and beam analysis equipment;
• A tandem accelerators; and
• A detector (gas ionization counters are commonly used).
The sample holder is a metal cup (aluminum and copper have been used) in which the solid sample
is held. An ion beam is then directed at the sample to cause it to sputter. Sputter sources (e.g., heated
cesium metal producing Cs+) cause the sample to form negative ions. Ions produced in the sample
from the sputter source impact undergo energy and mass analysis before being injected into the
accelerator. The accelerator can have low and high energy tubes with a thin foil or gas stripper
placed in the high-voltage terminal between the low- and high-energy tubes to convert negative ions
to positive ions. The positive ions are then put through a second mass analyzer before being focused
on a gas ionization-type detector. The measured pulse height from the detector is directly related to
the number of produced electrons in the detector. The number of electrons is a measure of the energy
the ion lost inside the active detector space. These detectors have two advantages: they are not
subject to radiation damage and can be adjusted for varying atomic units.
The benefit of AMS analysis for long-lived isotopes is that instead of counting random events from
large samples over the course of days, milligram samples can be analyzed in several minutes. The
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Inventory of Radiological Methodologies
sensitivity of AMS is five to six orders of magnitude below radioactivity measurements for these
long-lived isotopes. Among the radioisotopes that can be analyzed by this method are 129I, I4C,
59/63Ni, 3H, 7/IOBe, 4ICa, 36C1,90Sr, 99Tc, I291,239Pu, 24()Pu, and 236U. Some disadvantages of this method
are:
• Not all atoms can be analyzed because they do not all produce significantly long-lived negative
ions;
• The final analyte form must be a solid that is formed after sample treatment;
• The instrumentation is currently very expensive;
• The equipment takes up a considerable amount of floor space (9 - 185 m2, depending upon the
number and types of isotopes being analyzed); and
• AMS can suffer from isobaric interferences similar to that of ICP-MS.
4.2.3 Summary of Analytical Methodologies, Minimum Detectable Concentrations, and
Instrument Types
Figure 2 displays the range of concentrations that the different radioanalytical methods described
above generally are capable of achieving. Note that each methodology will have a specific MDC for
each of the different radionuclides.
Water
pCs/iite: W- 10 1C 10 1CF-
j
t
Gioss vJ\)
Alpha SpscWonipt^Y (~~*'^JPu)
____^^
_J*&^£Z™E2^EEi£2HnS!S£Sl_»
___ ^i££££SSLM3S2,^^£££!S^ILL
10- 10" 10'
i\j :i"pu)
ICP-NIS
:3ijti#r )Jiar*
iruicated
t Without sample preparation.
FIGURE 2 — Nominal minimum detectable concentration for different
radiation-detection and atom-counting methods
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Inventory of Radiological Methodologies
Table 10 summarizes the applicability of the analytical methodologies described in this section to
various radionuclides.
TABLE 10 — Analytical methods applicable to each radionuclide
Notes: o Applicable technique • Most common technique
GPC: gas proportional counting; LS: liquid scintillation counting; GG: gross gamma counting using Nal(Tl) and Ge
detectors; GS: gamma spectrometry; AS: alpha spectrometry; LS: liquid scintillation; KPA: kinetic phosphorimetry
analysis; ICP-MS: inductively coupled plasma mass spectrometry; TIMS: thermal ionization mass spectrometry; AMS:
accelerator mass spectrometry.
* 239/240pu cannot be resolved by this technique, and the reported results are the sum of the activities of the two isotopes.
t GS also includes low-energy gamma- and X-ray analysis
§ 226Ra is commonly analyzed by radon emanation (see Section 5.13)
tf Gross gamma screening for environmental levels of 226Ra, 228Ra, 210Pb, U, Th, and transuranics applies only to solid
samples.
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5 Chemical and Physical Properties for Selected Radionuclides
The radionuclides in this document represent the most common or significant (in terms of radiation-
health effects) likely to be encountered at a large cleanup site. For example, the radionuclides found
at NORM sites are radium, uranium, thorium, and their decay products. If wastes from processing
ores containing these materials are causing elevated radioactivity, it is likely that the isotopes listed
here as NORM would be responsible for that elevated activity. Similarly, a DOE site decom-
missioning may contain the radionuclides in the transuranic family (e.g., plutonium and americium).
Other radionuclides may be present (e.g., 40K, 7Be, 228Ac, etc.), but their quantity, concentration, or
dose consequence will be negligible compared to those described here.
This section provides a brief description of the chemical separation and analytical techniques for
each radionuclide. Appendix D contains tables for each element that provide technical information
regarding radionuclide detection limits by specific methodologies (page 80).
5.1 Americium
Americium has no naturally occurring isotopes. It is produced synthetically by neutron
bombardment of 238U or 239Pu followed by beta decay of the unstable intermediates. Americium-241
(t,/2 = 432 y) is found in military wastes and can be extracted from reactor wastes. Some industrial
ionization sources also contain americium. Kilogram quantities of 24lAm are available, but only 10-
to 100-g quantities of 243Am (t,/2 7,371 y) are prepared. Low-energy gamma emission from 24'Am
is used to measure the thickness of metal sheets and metal coatings, the degree of soil compaction,
and sediment concentration in streams and to induce X-ray fluorescence in chemical analysis. As
an alpha emitter, it is mixed with beryllium to produce a neutron source for oil-well logging and to
measure water content in soils and industrial process streams. The alpha source is also used to
eliminate static electricity and as an ionization source in smoke detectors.
Airf3 is the oxidation state that would be found in environmental samples. Although other oxidation
states exist, they are not chemically stable and are reduced or oxidized to the +3 state in solution.
Free radicals produced by radiolysis of water by alpha particles reduce the higher states
spontaneously to Am"3. The +3 oxidation state exists as Am(OH)3 in alkaline solution. Simple
tetravalent americium is unstable in mineral acid solutions, disproportionating rapidly to produce
Am*3 and AmO2+1 [Am(V)] in nitric and perchloric acid solutions. Conversely, dissociation of
Am(OH)4 or AmOz (both Amf4) in sulfuric acid solutions produces solutions containing Am+3 and
AmOz*2. Stability is provided by complexation with fluoride ions and oxygen-containing ligands
such as carbonate and phosphate ions.
Americium is generally thought to be adsorbed by soils at pH values found in the environment.
Complexation of Am13 by naturally occurring ligands (humic and fulvic acids), however, would be
expected to strongly reduce its adsorption.
Laboratory analysis of americium involves separation from other transuranic elements by methods
of ion exchange, solvent extraction/extraction chromotography, or precipitation. Gamma spectro-
metry can be used for analysis of241 Am when in sufficient quantity, while both241 Am and 243Am can
be determined by alpha spectrometry.
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Inventory of Radiological Methodologies
Am-243 has been used as a monitor for 241Am yield when it is known that no 243Am is present in the
sample. Cm-243 has been used as a surrogate yield monitor as well. No other radionuclides are
routinely used as yield monitors. Gravimetric separation of americium for alpha analysis is achieved
using either neodymium or lanthanum fluoride as a carrier (actually a co-precipitant).
5.2 Bismuth
Bismuth has the highest atomic mass of any stable element. It has only one stable isotope, 209Bi.
Bi-210 (t,/2 5.0 d) is part of the decay chain of 238U, as is its immediate precursor, 210Pb, which has
a half-life of 22.2 years. In many types of environmental samples, these radionuclides may be found
in secular equilibrium with each other. However, due to some differences in solubility and
complexation, the secular equilibrium connection may be broken. This means that some or all of the
210Bi present may be unsupported (see Appendix B). Thus, the sampling conditions, time to start
chemical analysis, and time to complete the analysis all become important in the determination of
Because 210Bi is a beta emitter but not a strong gamma emitter, it is most frequently measured either
by GP counting or by liquid scintillation. In either case, chemical separation is required first. This
is routinely accomplished through ion exchange and precipitation. Bismuth has only one oxidation
state (+3), making its sample processing relatively straightforward.
Chemical yield of bismuth can be monitored using stable bismuth carrier and determining it either
gravimetrically as bismuth oxychloride or spectrophotometrically using atomic absorption or
colorimetric techniques.
5.3 Carbon
The chemistry of carbon compounds and their occurrence are too extensive to be summarized here.
Fortunately, only one isotope of carbon, 14C (t,/2 5,720 y, beta emission), is significant for analysis
in environmental samples. However, 14C is incorporated into many organic compounds as a tracer
for research. Once the 14C is covalently bound in a molecule, its chemistry follows that of the
molecule and not of carbon, unless the organic molecule is destroyed. In those instances it would
most likely be converted to carbon dioxide. Therefore, in those instances in which it is suspected that
organic compounds may be present, sampling methods should not be employed that could possibly
exclude any 14C compounds. As mentioned in Section 3.2.1, samples to be analyzed for I4C should
not be preserved in acid. Addition of acid could cause oxidation of any organic material containing
14C, which would be subsequently expelled as CO2 gas. Additionally, the sample analysis regime
should include oxidation of the parent molecule to carbon dioxide. This will depend on whether or
not multiple compounds may be present that contain 14C. Where more than one type of compound
may be present, sample oxidation is required. The CO2 is captured subsequently and prepared for
liquid scintillation analysis. The liquid sample prepared in this fashion may also be used for ICP-MS
analysis. AMS has become a feasible technique for carbon, especially for solid samples.
No other significantly long-lived radionuclides of 14C exist. Thus, a radiotracer yield monitor is not
available, and 100 percent recovery would be assumed. Certain methods that use a carbon carrier
and determine the original carbon content of the sample can realize specific recovery data. This is
generally done using sample oxidation and subsequent BaCO3 gravimetry.
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5.4 Cesium
Cesium has two principal isotopes that are discussed in this document, l37Cs (t,/3 30 y) and L34Cs
(t,/3 2.1 y). Cesium is in the 1A group of the Periodic Table, which means that it is present in
samples either as the metal or in the +1 oxidation state. The metal has a melting point of 28 C and
oxidizes rapidly in air to yield Cs2O. The chemistry of cesium is relatively simple. It forms weak
complex ions in aqueous media and can be separated/concentrated by ion exchange chromatography
using a cation resin. Cesium does not form any anionic complexes, and this can be used as an
effective separation tool if other radionuclides that do form anionic complexes are present. Cesium
can move very rapidly in ground water. Cesium is still found in a variety of environmental matrices
as a result of nuclear fallout and nuclear power plant discharges. The concentrations at which these
isotopes are being found is decreasing overall.
Cesium-137 is used as a check source for a variety of different instruments and is readily available
as a radioisotope. Although present as a solid material in such sources, if the source is damaged,
leakage of the cesium is likely due to its solubility and volatility.
In most cases chemical separation from other radionuclides is not performed. The two radionuclides
of cesium are usually measured directly by gamma ray spectrometry, whether the sample is soil or
water. There is no significant concern for decay correction because of the long half-lives of the two
isotopes.
One significant precaution should be noted in the analysis of 134Cs. Results may be biased low due
to gamma-ray coincidence summing effects when using gamma-ray spectrometry. This effect may
be accounted for by calibration correction, increasing sample-to-detector distance, or direct
calibration with a 134Cs source.
A chemical yield monitor for cesium is not generally used because it is almost always determined
without chemical separation by gamma spectrometry.
5.5 Cobalt
The principal radioisotopes of cobalt (with their half-lives) are "Co (t,/3 272 d), 58Co (t,/3 71 d),
and 60Co (t,/3 5.27 y). All these isotopes may be found in effluents and components of nuclear
power plants. The 60Co isotope is used to sterilize food by irradiation and in cancer treatments as a
radiation source. Thus there are significant quantities of 60Co available. Isotopes 57 and 58 can be
determined by X-ray as well as gamma spectrometry. The 60Co isotope is easily determined by
gamma spectrometry because no significant decay of the isotope occurs during sampling and
analysis, it has two gamma rays with energies high enough that they are not attenuated by sample
density, and each decay of the isotope leads to each of the gamma rays being produced.
Cobalt only has one oxidation state (+2) to be concerned with in environmental samples. It is easily
solubilized by either hydrochloric or nitric acid and will form both positive and negative complexes
in aqueous solutions with a variety of anions. For this reason, it is easily separated from other metal
ions by ion-exchange chromatography using either a cation or anion resin. Cobalt forms very
insoluble CoS in environments where sulfide ions are present. Because some water samples will
have sulfide ions present due to the presence of decaying organic materials, some cobalt can be lost
to container adsorption or inadvertent decantation. Potentially high bias can occur if sedimentation
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occurs while the sample is being counted directly on a gamma ray spectrometer. Care must be taken
with these samples. In addition, if the sample is processed so that the cobalt is chemically separated,
special techniques to dissolve the CoS may be required.
All three isotopes of cobalt decay by gamma emission. For this reason, these nuclides are generally
determined without chemical separation when they are present in significant activity. A chemical
yield monitor is not generally used, as no analyte separation is involved using gamma ray spectro-
metry.
5.6 Hydrogen (Tritium)
Tritium (3H; t,/2 12.3 y) is found most commonly in water. The only radioactive isotope of
hydrogen, its chemistry is that of the hydrogen ion. Once in the environment, most compounds that
contain tritium will undergo oxidation to water. Tritium has been incorporated into a variety of
compounds in which it is covalently bound. It has a great utility as a chemical tracer on organic and
specific bio-molecules when it is incorporated into a non-labile portion of the molecule. Tritium
containing compounds are used in liquid crystal devices (LCDs) and for illumination in certain types
of signs.
The beta particle emitted by the tritium atom is of very low energy. Liquid scintillation is by far the
most commonly used technique of analysis for tritium in water or solid samples. Both atomic mass
spectrometry and ICP-MS have been used for its analysis (Chiarappa-Zucca, 2002; Demange, 2002).
One of the interesting characteristics of tritium in the environment is that it will migrate easily.
Because it is chemically identical to hydrogen, it can exchange freely with hydrogen atoms in water
molecules. This means that tritium can have countercurrent flow in aquifers and other ground
waters. It also means that it will diffuse rapidly.
Its characteristic of being easily exchangeable with water is also a positive aspect because it can be
easily separated from other materials based on the physical properties of water. Thus, if tritium
analysis of a soil sample is necessary, the water can be separated by filtration, distillation, or freeze-
drying, and the resultant water (free of everything else) can be analyzed directly for tritium.
Tritium naturally exists in the environment as a result of cosmic ray interaction with atoms of the
upper atmosphere. It also exists as a result of atmospheric testing of nuclear weapons and discharges
from nuclear power plants and other facilities where tritium is produced. The concentration in the
environment due to natural sources is less than 50 pCi/L (1.8 Bq/L).
There are underground aquifers that have been isolated from the environment for very long periods
of time. Water taken from such a location will have much lower concentrations of tritium (some-
times referred to as "dead water") than those water sources that can exchange with the environment,
because of tritium's relatively short half-life.
Analysis for tritium does not involve the use of a chemical yield monitor. Because the tritium in the
samples is part of a water molecule, water is the "preservative": ensuring that no tritium is lost in
processing.
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5.7 Iodine
Iodine belongs to the halogen family (Periodic Table Group VII) of elements and can exist in seven
different oxidation states. Its most common states are -1, +1, (V), and (VII). Iodine does not exist
in the environment in its elemental form. Elemental iodine sublimes at ambient temperatures.
All iodine radionuclides are produced as a result of nuclear fission (e.g., I29I, t,/2 1.57 * 107 y and
131I, t,/2 8.1 d) or cyclotron production (e.g., I25I, t,/2 59.4 d) of specific isotopes. Very low levels
of 129I exist in the environment as a result of spontaneous fission. However, this concentration is well
below that which would be determined by routine radiochemical analysis (Cecil et al., 2003).
Isotopes of I25I and I3I1 are routinely produced for radio-therapeutic purposes, and are commonly
found as contaminants in medical wastes and wastewater. Iodine-129 is a fission product. Its low-
energy beta and gamma emissions make it difficult to determine in most matrices without some form
of chemical separation.
The chemistry of iodine can create significant challenges to the sampler and analyst. The multivalent
nature of iodine can create problems with sample storage and transit prior to analysis. Although the
elemental state does not exist in the environment, it can be formed as a result of other chemicals in
the sample (e.g., oxygen). Thus, some iodine may be lost as a result of volatilization unless steps are
taken to ensure all iodine is converted to the I ion immediately following sampling.
Analysis of iodine is somewhat different than with most other radionuclides, because it is the
complex former (i.e., the ligand) rather than the central ion (like the metallic radionuclides, sulfur
or phosphorus) of a molecule. Anion exchange resin is commonly used to concentrate 1311 (iodide)
from water and milk samples. Solvent extraction of iodine as I2 has been used successfully to
separate iodine from other radionuclides. However, this method means that there is a likelihood of
loss of iodine as a result of volatilization. Thus, the most effective means of separating iodine from
other radionuclides generally is through use of an iodide carrier followed by oxidation reduction and
precipitation reactions specific to iodine.
Each nuclide of iodine may be analyzed by a different method. Iodine-131 can be determined in
liquid samples, directly, by its characteristic gamma ray at 364 keV. Analysis of environmental
samples is very time dependant due to the 8-day half-life of m I. It is important for analysis of this
isotope to know the time period of sample collection (start to stop), as well as the times to final
separation of iodine (if performed), and of the total sample counting interval. All these factor into
the calculation of activity.
Iodine-125 decays by electron capture and emits characteristic X-rays at 28.6 keV (usually analyzed
with a low-energy germanium detector). Because of its long half-life and low emission energies, 129I
is most easily analyzed by liquid scintillation. Chemical yield for iodine can be determined gravi-
metrically using iodine carrier and precipitating quantitatively as PdI4, Agl, and Cut.
5.8 Iridium
Iridium is one of the noble metals. It is in Group VIII of the Periodic Table and has a very low
natural abundance in the Earth's crust. Heating any iridium compounds above 200 C in air will
yield the metal (the melting point of the metal is 2,443 C). Iridium can form halogenated com-
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Inventory of Radiological Methodologies
pounds in the +1, +3, and +4 oxidation states. However, the most stable form of this element is as
the metal.
Iridium has two stable isotopes, 191Ir and I93Ir. Iridium-192 (t,/2 73.8 d) is formed as a result of
neutron irradiation of the 191Ir isotope. It undergoes radioactive decay by both p~(95%) and ft (5%).
It is principally a low-energy gamma and X-ray emitter. These characteristics make it easily
identifiable without any chemical separation.
Iridium-192 is used principally for radiography of steel components and brachytherapy (implanting
radioisotope seeds within or very close to tumors). The iridium, used as a point source, is in the
shape of a small needle (sometimes called a "seed") and is only several millimeters in each
dimension. These sources are on the order of 1 -500 Ci each. The seeds are shipped in individual
containers for shielding as the metal. It is unlikely for the seed to disperse easily in the environment
due to the extreme inertness of the iridium metal. Dispersion of powdered material by an explosive
device would yield contamination over a large area, that would settle rapidly (due to its high density
of 22.5 g/cm3) and remain relatively fixed in place due to its inertness.
The most effective technique of analysis would be by HPGe (high-purity germanium) detection.
However because the emitted gamma rays are of low energy, precautions should be taken with
sample thickness to avoid self-shielding. Dissolution of a sample containing iridium, using normal
acid digestion, would leave the iridium behind in the residue. This might be one method of
separating the iridium from almost all other radionuclides.
5.9 Lead
Lead has several naturally occurring radionuclides because it forms part of the naturally occurring
decay chains of all the thorium and uranium isotopes. The isotope of interest in NORM waste is
2l°Pb (tVi 22.2 y), which decays principally by low-energy beta-gamma emission. The two other
isotopes commonly associated with this type of sample would be 212Pb (t,/2 11 h) and 214Pb (t,/2 27
min). These isotopes are usually determined in conjunction with radium/radon radioactive equilibria
because their activity builds up so quickly (due to their short half-lives) after separation of these
radionuclides.
Lead may be found in one of three oxidation states: 0, +2, or +4. The +2 state is more commonly
encountered in water and soil samples. Lead nitrates, perchlorates, fluorides, chlorides (in hot
water), and acetates are all soluble. Lead forms very stable complexes with chelates such as
ethylenediamine tetraacetate (EDTA) and amines, but it is only weakly associated in complexes with
inorganic ligands. Thus in solutions of concentrated acids, it is present as a cation and can be easily
removed by cation exchange.
Lead forms very insoluble salts with hydroxide, sulfate, and sulfide. However, it does form
extremely stable compounds in organic solvents with sulfur-based organic ligands such as dithio-
carbamate and diphenylthiocarbazone.
In most samples that are analyzed for lead radionuclides, the amount of stable lead is very small and
lead carrier is often added to determine the yield. However, it may be necessary to assess the
samples' stable lead concentration prior to performing radiochemical lead analysis.
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It should be noted that freshly prepared lead and lead salts from ore may have measurable quantities
of 21()Pb in it. Thus the material used as carrier for lead should be evaluated for its 2l()Pb content. For
low-level detection of gamma rays with germanium detectors, the preferred type of lead shielding
to use is "old lead" (usually more than 100 years from when it was produced from an ore). The 21()Pb
has undergone about four half-lives at that time and will yield low background radiation.
The relatively long half-life for 2l()Pb, and the low energy of its decay particles makes it difficult to
determine at very low levels. One method of analysis uses the in-growth of the first progeny of lead
21()Bi (t,/2 5.0 d). Lead is then determined based on the activity of the shorter lived bismuth isotope
determined at a fixed time after separation of lead from bismuth in HC1 solution. Bismuth
precipitates as an insoluble oxychloride in hot water and lead chloride remains in solution.
5.10 Nickel
The two isotopes of nickel addressed in this document, 59Ni (t,/2 76,400 y) and 63Ni (t,/2 100 y) are
both formed as a consequence of neutron activation of elemental nickel. Nickel is used as an
alloying element in stainless steel, Inconel®, and other components used in nuclear reactors. The
radionuclides can be formed as a result of direct irradiation of reactor components by neutrons, or
corrosion products transported through the reactor core can become radioactive.
Neither radioisotope of nickel produces a gamma ray when it undergoes decay. The electron capture
decay of 59Ni yields a low-energy X-ray from cobalt of 6.93 keV, while the energy of the p decay
of 63Ni is of very low energy (0.06 MeV). Both of these circumstances necessitate the chemical
separation of nickel from other radionuclides before they can be analytically determined.
Nickel has only one oxidation state that is seen under normal aqueous chemistry conditions; +2. It
can be oxidized to the +3 or +4 state by very strong oxidants. Both of these are unstable in solution
and revert to the +2 oxidation state. The soluble salts of nickel are the chlorides, fluorides, sulfates,
nitrates, perchlorates, and iodides. Nickel sulfide and nickel hydroxide are very insoluble
compounds of nickel. The sulfide, upon extended exposure to an aerated, basic solution, will form
Ni(OH)S (one of the few, stable, +3 compounds), which is extremely difficult to redissolve. The
hydroxide is a light-green gelatinous precipitate that can act as a scavenger for other radionuclides.
However, its gelatinous nature makes it extremely difficult to filter. It is therefore seldom used, and
care should be taken to avoid its formation in aqueous solutions.
Nickel analysis is aided by its favorable complexation with ammonia and amines. This feature
provides the principal means of chemical separation of nickel from its other transition metal
counterparts, as well as the transuranics. In ammoniacal solution between pH 6-9, nickel is very
soluble, while most other metals precipitate as the hydroxide. Nickel also will form complexes with
amines in organic phases making solvent extraction an attractive means of separation.
Nickel forms very weak complexes with chloride and fluoride, which can be used to separate it from
other transition metals by anion exchange chromatography. Chemical yield determination for nickel
can be performed gravimetrically using the nickel dimethylglyoxime precipitate or by atomic
absorption analysis.
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5.11 Phosphorus
Phosphorus has two radionuclides that are used routinely, 32P (t,/; 14 d) and 33P (t,/2 25 d). Both
isotopes usually are produced by a particle accelerator nuclear reaction on a sulfur target. Both
nuclides emit only beta particles, so the two most common methodologies of analysis are liquid
scintillation and gas proportional counting. All other isotopes of phosphorus are much shorter lived
(t,/0 < 3 min) and not commonly used.
The radiochemistry of phosphorus is somewhat different from the other radionuclides. Phosphorus
is found in the environment, principally in the orthophosphate (PO43~) form. Phosphorus, like carbon,
is non-metallic and is usually found covalently bound into many different types of compounds. In
these forms, it does not react as orthophosphate but as the molecule of which it is a part. As with
carbon, phosphorus must be determined either from the chemistry of the molecule it is contained in,
or the material must be digested so that phosphorus converts to its principal inorganic form,
orthophosphate. If chemical separation is performed, the yield for phosphorus analysis would be
determined gravimetrically using a precipitate such as barium phosphate. Analysis for 32P can be
done directly from many types of biological matrices if no other radionuclides are present, because
of the high beta particle energy (1.71 MeV) it emits.
5.12 Plutonium
Plutonium has no naturally occurring radionuclides. Its presence in the environment is due almost
entirely to anthropogenic activities (a very small quantity is present as a result of naturally occurring
spontaneous fission). Plutonium isotopes discussed in this document are formed as a result of
neutron capture of uranium isotopes that are in the vicinity of other, fissioning, uranium isotopes.
The fuel in nuclear reactors can produce several different isotopes of plutonium due to multiple
neutron capture by the same nuclide. Thus the activation of 238U leads to the formation of 239U, which
decays through 239Np to 239Pu. Because the half-life of 239Pu is 2.4xl04 years, it can capture
additional neutrons while in the reactor core. In this manner of multiple neutron captures, 240Pu, and
241Pu, can be formed. Some of the 235U also undergoes similar multiple neutron capture and 238Pu can
be formed.
Other radionuclides, like 236/237pUj are accelerator produced and are used as tracers in the analysis
of the reactor produced plutonium isotopes.
Plutonium can have oxidation states of+3, +4, (V), and (VI). The roman numeral notations for
oxidation state identify that the plutonium is the central atom of an oxo-complex in water. Thus, the
species in water, which corresponds to Pu(VI) is PuO2+2, and for Pu(V) is PuO2+1. The chemistry of
plutonium is quite complex. A solution of plutonium initially of one oxidation state will undergo
several different disproportionation and oxidation reduction reactions until all four of the above
oxidation states are present. This peculiar chemistry for plutonium requires sample storage and
analytical separations to have significant types of chemical additives to ensure that plutonium is
maintained in the proper oxidation state for analysis and separation. Plutonium also has the ability
to form long polymeric type chains, where the molecular weight of the chain can reach several
thousand daltons. This occurs when storage of solutions is allowed for long time periods (greater
than six months). These chains are not easily solubilized nor broken down, thus the analytical result
for plutonium in these samples will be biased low.
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The ability to exist in multiple oxidation states makes separation schemes for plutonium somewhat
interesting. Plutonium can react with inorganic ions like nitrates, chlorides and fluorides to form
anionic complexes in the +3 or +4 oxidation state. However, these complexes are not formed in the
(V) or (VI) oxidation state due to steric interference from the oxygen atoms. The differences in these
chemistries can be advantageously used to separate the different oxidation states of plutonium (i.e.,
chemical speciation) in an individual sample, or it can be used to separate all plutonium isotopes
from other transuranics that behave as cations (e.g., Th, Am, Cm). In a specific application of this
behavior, Kim et al. (2000) used a TRU* resin to concentrate all the cationic transuranic ions. The
Pu was present as the +4 ion due to oxidation with acidic nitrite. The americium was eluted in dilute
HC1, and then the plutonium was reduced back to the +3 oxidation state in HC1, causing the anionic
chloro- complex to form, releasing the plutonium from the column.
Separation techniques for plutonium also include solvent extraction and precipitation methods. In
every case, the separation of this element requires several layers of analytical techniques. First to
remove the bulk of the elements in the first row transition series, then to separate out each of the
transuranics individually. The final step in plutonium separation prior to analytical determination
is either precipitation or electroplating. In the former, the Pu*4 will be separated via coprecipitation
with neodymium, cerium, or lanthanum fluoride. In the latter, the plutonium will be plated onto a
platinum, stainless steel, or nickel disc in an infinitely thin film.
The analytical separation of plutonium from other transuranics is not the final hurdle in plutonium
analysis. Five different isotopes of plutonium, 238, 239, 240, 241, and 242 all may be found in
environmental samples. Plutonium-241 is easily distinguishable because it is the only beta emitter;
the rest are alpha emitters. Isotopes 238 and 242 emit distinctly different alpha particle energies from
239 and 240, and each other and are also readily determined via alpha spectrometry. However, 239Pu
has alpha particles at 5.156 and 5.144 MeV and 240Pu has alpha particles at 5.168 and 5.124 MeV.
These alpha particle energies are not significantly different, and cannot be resolved via alpha
spectrometric techniques. The half-lives of these two isotopes are sufficiently long so that neither
significantly decays during the sampling and analysis time frame. Thus it is common to report the
results for these two isotopes together, as a single value.
If the analytical value for each of these isotopes is necessary, then techniques such as ICP-MS,
TIMS, or AMS are required. These techniques will be able to separate these two isotopes based on
their mass so that individual values may be obtained, however the current cost of such analyses are
very high compared to conventional analytical methodologies.
5.13 Radium
Radium has no stable isotopes. It is a member of the uranium and thorium natural decay chains. The
isotopes that are normally encountered in environmental samples are 223Ra (t,/2 11.4 d), 226Ra (from
235U and 238U decay), and 224Ra (t,/2 3.66 d) and 228Ra (from 232Th decay). Radium-226 (t,/2
1.60 x 103 y) is the most abundant isotopic form, decaying by emission of an alpha particle to
produce 222Rn. The next most abundant isotope is 228Ra (t,/2 5.76 y), which decays by P emission.
Radium is most closely associated with uranium and thorium ore deposits. Interaction with the soil
and ground water will cause some of the radium to become separated from the parent ore due to
differences in chemical solubility. When this occurs, and the radium is found "free" in soil or water,
it is said to be "unsupported."
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Historically, radium has been extracted from ores through barium sulfate precipitation. The radium
isotopes have been used to produce luminous paints and for radiation therapy. While neither of these
have current application, there are many sources that were made in the early Twentieth Century that
remain uncontrolled. Radium sources are used for measuring metal or material thicknesses, as a
source of actinium and polonium (used to produce anti-static devices), and as a neutron source
(when mixed with beryllium).
Radium is in the same group in the Periodic Table as barium and calcium. Its chemical properties
are very closely related to these two elements. Its only oxidation state is +2. Radium salts that are
soluble are chloride, bromide nitrate, and hydroxide. Carbonate, phosphate, and fluoride are
sparingly soluble, while sulfate is the most insoluble. Procedures for the separation of radium almost
universally rely on barium as the means to coprecipitate radium as the sulfate.
Radium is not soluble in organic solvents or solvents combined with many chelating agents. This
provides a convenient means of separation of radium from many other radionuclides, especially the
transuranics. It forms weak complexes with EDTA and most inorganic complexing agents. However,
it is very strongly complexed by diethylenetriamine pentaacetic acid (DTPA), as a -3 anion.
In dilute acid solution, radium is present as the divalent cation. Because many other radionuclides
form anionic complexes in dilute HC1, radium is easily separated from many other radionuclides
using a cation exchange resin. Additionally, newly developed ion-exchange filters that contain
radium-selective chelants have been used successfully to concentrate radium directly from environ-
mental waters.
Ironically, the two major isotopes of radium may not be measured directly when trying to assess low
level concentrations. The radium is concentrated from a large volume of water, and its progeny 222Rn
is allowed to in-grow for up to 21 days. The radon gas is sparged into a closed container, allowed
to equilibrate with its progeny (total of about 10 hours), and then counted with a special device
known as a "Lucas Cell" (alpha scintillation cell) using a photomultiplier tube. This technique is
known as "radon emanation." It is very effective for 226Ra analysis because of the physical
separation of its first progeny, 222Rn (a noble gas), by expulsion into the evacuated Lucas Cell. The
Lucas Cell is calibrated with a known 226Ra source using radon emanation. The calibration is
therefore specific for 222Rn and all its progeny, which come into secular equilibrium with 222Rn (see
Section B.I.6, "Radioactive Equilibrium," on page 76).
Radium-228 is a very low-energy beta emitter (0.039 MeV) and does not lend itself to low MDCs
using gas proportional counting. However the first progeny of 228Ra is 228Ac (t,/2 6.2 h), which
achieves equilibrium with the radium in about 36 hours. It can be measured by either gas propor-
tional counting or by gamma spectrometry.
5.14 Strontium
Strontium has four stable isotopes. Its principal radioisotopes are 89Sr and 90Sr (both a result of
fission of uranium or plutonium), 85Sr (used principally as a radiotracer), and 82Sr. Radiostrontium
sources are used as depth measurement devices, calibration sources, environmental and biological
tracers, and in the treatment of some cancers.
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Strontium is a member of Group II of the Periodic Table and is chemically related to both barium
and radium. It has only one oxidation state, +2, thus making its chemistry very straightforward. The
soluble salts of strontium are chloride, fluoride, acetate, nitrate, chlorate, and permanganate. The
hydroxide and the carbonate are slightly soluble. Strontium oxalate and sulfate are fairly insoluble.
Both have been used to separate strontium gravimetrically. The nitrate can be made insoluble in
fuming nitric acid, and this technique has been used as a means of chemical separation.
Strontium does not form strong complexes. The most significant one is with EDTA, which is used
in many separation schemes for isolation of strontium from other radionuclides. Because of its poor
ability to complex, it is present as a cation in most solutions. This can be used advantageously to
separate it from other metals that can form anionic complexes. Thus, complexing transition metals
like cobalt, nickel, or iron with chlorides, and using an anion-exchange resin, will bind the anionic
complexes to the resin allowing strontium be removed. Alternatively, the complexed solution may
be passed through a cation resin, which will retain the strontium, while the other complexed
radionuclides pass through the column.
The two principal long-lived isotopes of strontium produced from fission are 89Sr (t,/2 50.5 d) and
9l)Sr (t,, 28.8 y). Both are beta emitters, and because they are the same element, they cannot be
separated chemically. Their p-particle energies are not sufficiently different to be easily
distinguished using gas proportional or liquid scintillation counting techniques.
Several techniques have been devised to deal with this problem. A popular indirect method can be
used to analyze both strontium radionuclides. It initially counts the separated strontium isotopes. The
separated strontium is allowed to build up 90Y (t/2 64 h) over a defined period of up to about two
weeks. The 90Y is then separated chemically from the strontium radionuclides, and analyzed. Due
to the laws of radioactive equilibrium (see Appendix B), the amount of 90Sr that produced the 90Y
can be calculated. This can be subtracted from the initial total strontium activity to yield an activity
of 89Sr. This limits the MDCs that can be achieved and also increases the analytical uncertainty close
to the MDC.
Samples of soil or water from areas not directly impacted by an operating nuclear facility or recent
weapons testing are not likely to contain 89Sr, due to its short half-life. However, in effluents from
nuclear facilities and some wastes, both radionuclides will be present. (It should be noted that 140Ba
may also be present in these types of samples.) Because the chemistry of barium and strontium are
so similar, the analytical separations process should specifically eliminate barium. This is usually
performed through a BaCrO4 precipitation (the strontium salt is soluble).
Yield for strontium analysis is determined either gravimetrically by using stable strontium carrier
or by using a 85Sr radiotracer. When a strontium carrier is employed, the carbonate or oxalate is
precipitated, dried, and weighed. The amount also may be determined by atomic absorption spectro-
metry. Using 85Sr radiotracer, the decay is by electron capture and gamma emission, thus allowing
an independent method (gamma spectrometry) of determining its yield without interfering with the
beta analysis.
5.15 Sulfur
Sulfur is similar to phosphorus and carbon in that it forms many chemically stable organic
compounds through covalent bonding. In environmental water samples, sulfur mainly exists as
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sulfate (SO4 2). Other inorganic forms of sulfur are sulfide (S 2), thiosulfate (S2O, 2), sulfite (SCV2),
and sulfur dioxide (SO2). Sulfur has oxidation states -2,+2, +4, and (VI), and they can be present in
both organic and inorganic compounds.
Sulfur has one long-lived radioisotope (35S, t,/2 87 d), which when incorporated into organic
materials, is a radiotracer for the specific characteristics of the organic material. This radionuclide
is a beta-only emitter (Epmax = 0.167 MeV) and can be detected using either liquid scintillation or
GPC.
Environmental samples that contain sulfur are subject to attack by microorganisms, which can
change the oxidation state of the sulfur. Desulfovibrio desulfuricans is a sulfate-reducing bacterium,
ubiquitous in the soil sample, which can change oxidized sulfur species into hydrogen sulfide. Thus,
it is important to know the condition of the sampling so that loss of this isotope as a result of this
bacteria can be addressed.
As with phosphorus, if sulfur may be present as part of an organic compound, then sampling and
analytical protocols need to address that particular compound. One means of separation from other
materials is that sulfur can be oxidized to sulfate and easily separated by gravimetric analysis. Acid
digestion or sample combustion with stable sulfate as a carrier can be successfully employed for
yield determination of the sample digestion process.
5.16 Technetium
Technetium is an oddity in the middle of the Periodic Table; it has no stable isotopes. Any
primordial technetium has decayed away because its longest-lived isotope, 98Tc, has a half-life of
only 4.2 x 106 years. The most significant isotope produced as a result of nuclear fission, 99Tc, has
a half-life of 2.1 * 105 years. It decays by emission of a beta particle (Epmax = 0.29 MeV). In the
environment, very small quantities of this isotope can be ascribed to the natural fission process of
uranium ores.
Technetium-99 is the most significant technetium isotope present in wastes from nuclear power
plants, especially in spent fuel. Medical wastes are an additional source of "Tc, because 99mTc (the
"m" is for "metastable") is used as a radio-imaging isotope for oncological assessments. The
isomeric isotope 99mTc has a half-life of only six hours, and decays directly to the ground state, 99Tc
through gamma emission.
The chemistry of technetium is very similar to that of rhenium. The most common oxidation states
of technetium are (+4) and (VII). In an oxidative environment, technetium will be present as the
pertechnetate ion, TcO 4, which has significant mobility in ground water (i.e., not well retained by
soils). In reducing environments, technetium will form partially soluble TcO2.
Technetium forms complexes with organic and inorganic ligands under many different conditions
and can be easily separated from other radionuclides using ion chromatography. Radiochemical
analysis for 99Tc can be performed by GPC, using the gamma emitter 99mTc (t,/2 6 h) to monitor
yield. In ICP-MS and some gravimetric analyses, rhenium is used as a yield monitor for technetium.
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5.17 Thorium
Thorium is the second member of the actinide series. It has as its principal isotope 232Th, which has
a half-life of 1.4 x 10'° years. Thorium is naturally occurring and is a normal radioactive constituent
of cement and concrete. Thorium has five additional naturally occurring radioisotopes (227, 228,
230, 231, and 234, with half-lives of 18.7 d, 1.91 y, 7.54 x I04y, 1-06 d, and 24.1 d, respectively)
that result from the uranium and thorium decay chains.
The presence of thorium is often not discovered directly, but through the radioactive emissions of
its progeny radium, actinium, polonium, bismuth, and lead. Thorium is a refractory material with
a very high melting point.
The chemistry of thorium in solution is relatively simple because it is difficult to reduce to the metal,
and it only has one oxidation state, +4. Although thorium is more abundant in the Earth's crust than
uranium by an order of magnitude, it is much more insoluble than uranium and is less commonly
encountered in surface and ground water. The soluble compounds of thorium include the nitrate,
sulfate, chloride and perchlorate. Most other thorium compounds (particularly hydroxide, fluoride,
and phosphate) are insoluble in water. Therefore, the pH of the environment in which the thorium
radionuclides exist will determine its mobility.
Thorium is most likely present as a hydrated cation below a pH of 3.0. Above pH 3.0 the thorium
most likely exists as a colloid. This property makes it easily amenable to separation from other trace
constituents by flocculation (like using a ferric or aluminum hydroxide precipitate). Thus it is
important to maintain a low pH and avoid precipitates (even at the low pH) so that thorium will not
be dissipated into different phases as a result of this colloidal behavior.
Soil samples analyzed for thorium should be completely dissolved. Acid leaching of the soil may
not be sufficient to solubilize all the thorium. Fusion using sodium carbonate, potassium fluoride,
and potassium bisulfate generally will provide the best means of bringing the thorium into the melt
and successfully solubilizing it in subsequent steps.
Many inorganic and organic thorium compounds and complexes are soluble in organic solvents.
This is due to the large size of the thorium ion, which results in a relatively low charge density of
the ion and its complexes and compounds. This property forms the basis of several different
separation schemes for thorium. Thorium also forms several different types of anionic and cationic
complexes in aqueous solutions that can be used to successfully separate thorium from other cations.
One such method is the use of concentrated nitric acid to separate thorium from other actinides and
its progeny using an anion exchange resin. The hexanitrato-thorate complex is strongly bound to the
anion resin while other cations pass through.
Analyses of 227Th, 228Th, 230Th, and 232Th are usually performed by alpha spectrometry or GPC.
Thorium-229 has been used as a yield monitor for alpha spectrometric analysis of these
radionuclides because it is not commonly encountered.
Thorium-231 (t,/2 1.1 d) and 234Th (t,/2 24 d) are both beta emitters and first progeny of 235U and
238U, respectively. Their short half-lives make them good markers for the relative amounts of these
two uranium isotopes. Thorium-234 is also a gamma emitter. However, its gamma rays are in the
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low energy end of the spectrum (<100 keV) and are generally obscured by background radiation if
measurable quantities of other gamma emitters are present.
5.18 Uranium
Uranium is the last of the naturally occurring elements in the Periodic Table. Although it has no
stable isotopes, the long half-life of 238U (t,/2 4.47 x l O9 y) and 235U (t,/2 7.0 x 108 y) makes their
presence in the environment possible. Long before uranium was associated with radioactivity, it was
known as a ceramic glaze. The brilliant orange color that its oxide imparts to pottery made it popular
through the 1930s. Although identified on the chart of the nuclides as a naturally occurring isotope,
234U is present as a result of being the third progeny of the 238U decay chain. Its natural abundance
of 0.0055 is due solely to the 238U decay chain.
Uranium has several different oxidation states that exist in solution chemistry and several may be
stable in the environment. The most common oxidation state is (VI) as the uranyl ion, UO22+. This
oxo-complex of uranium has a significant effect on its solution chemistry. Although the uranium has
an oxidation number of (VI), the ion in solution has a +2 charge and may behave as an anion due
to the effect of the bulky, negative oxygen atoms attached to the central uranium ion. The +3, +4,
and (V) oxidation states also can be stable in solution. The U(V) ion is present as the UO2+1 ion, and
may disproportionate to yield U+4 and U(VI), if not appropriately stabilized.
Uranium has special significance because it is part of the uranium fuel cycle used for nuclear power
reactors and also used for nuclear weapons. The enrichment process (by ultracentrifugation or gas
diffusion) leaves a material behind that is depleted in the fissionable isotope, 235U. This leftover
material is designated "depleted uranium" (DU). DU has a use in conventional weapons as antitank
ordnance due to its high density. It also may be used as ballast on commercial airliners. In both
instances, these are still radioactive materials and should be handled appropriately. Although of little
value for direct fission, DU can be used as a blanketing material in a breeder reactor to absorb
neutrons and form 239Pu, which is fissile.
Uranium is soluble in water in part due to its ability to complex with the carbonate ion. Uranium
forms a myriad of carbonate complexes from pH 1 to 14. Solubility of uranium compounds is
directly dependent upon the oxidation state of the uranium. With the exception of fluoride, uranium
(+3 and +4) halide compounds are water soluble. The U(VI) compounds follow their own rule of
solubility, and the sulfate, bicarbonate, carbonate, chromate tungstate, and nitrate are all soluble.
The solution chemistry of uranium is probably more extensive than that of any other radionuclide.
It has many different organic complexes that it can form and be extracted into various solvents. It
complexes with many inorganic and organic ions to form cationic and anionic complexes. Two of
the most significant solution characteristics of uranium will be described here. Uranium as the uranyl
ion (VI), will not precipitate or coprecipitate in fluoride media. The oxygen atoms attached to the
uranium inhibit the precipitation of uranium. However if the uranium is reduced using TiCl3, to U+4,
the uranium will easily coprecipitate with either neodymium or lanthanum fluoride. The other
anomalous behavior of uranium is related to ion exchange capability. The U(VI) ion is less strongly
bound to cation resin than the +4 oxidation state, again due to the bulky, negative field established
by the two oxygen atoms on the U(VI) ion.
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U(VI) will form strong anionic complexes with halides, and these have been used as separation
techniques from other transuranics using an anion resin material.
All of the naturally occurring uranium isotopes are alpha emitters. Analysis for uranium isotopes
may use 232U (t,/2 68.9 y) as a radiotracer, because it is not part of any decay series. Uranium-232
is a long-lived alpha emitter, whose alpha particles can be easily distinguished from the other
uranium isotopes. Uranium may also be analyzed by its ability to phosphoresce chemically. This is
a very unique property of uranium based solely on its chemical structure and having nothing to do
with its being radioactive. None of the other transuranic elements possess this particular capability
thus distinguishing uranium by this property. This analytical methodology is used for concentrations
of uranium in the part-per-million range and above. It should be noted that the presence of uranium
in environmental samples means that all of its progeny will be present to a varying extent based on
solubility.
6 Reference Materials
6.1 Citations
American Society for Testing and Materials (ASTM) Cl 345, Standard Test Method for Analysis of
Total and Isotopic Uranium and Thorium in Soil by Inductively Coupled Plasma-Mass
Spectrometry, 2001 West Conshohocken, PA.
American Society for Testing and Materials (ASTM) D5673, Standard Test Method for Elements
in Water by Inductively Coupled Plasma-Mass Spectrometry, 2003 West Conshohocken, PA.
Benitez-Nelson, C.R. and K.O. Buesseler. 1998. "P-32 and P-33 Activities in Rainwater and
Seawater," Anal. Chem. 70, p. 64.
U.S. Central Intelligence Agency (CIA). 2003. Terrorist CBRN: Materials and Threats (U). CTC
2003-40058. 6 pp.
Cecil, L.D., L.F. Hall, and J.R. Green. 2003. "Reevaluation of Background Iodine-129 Concentra-
tions in Water from the Snake River Plain Aquifer, Idaho." U.S. Geological Survey Water-
Resources Investigations Report 03-4106, prepared in cooperation with the U.S. Department of
Energy, DOE/ID-22186. Available at: http://pubs.usgs.gov/wri/wri034106/.
Chiarappa-Zucca, M.L., K.H. Dingley, M.L. Roberts, C.A. Velsko, and A.M. Love. 2002. "Sample
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U.S. Department of Energy (DOE) \991b.EML Procedures Manual, Chieco, N.A., Bogen, DC., and
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402-R-99-004A&B. Available at: www.epa.gov/radiation/cleanup/partition.htm.
U.S. Environmental Protection Agency (EPA). 2000. Soil Screening Guidance for RadionucI ides:
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U.S. Environmental Protection Agency (EPA). 2002. Implementation Guidance for Radionuclides.
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Demange, D., M. Grivet, H. Pialot, and A. Chambaudet. 2002. "Indirect Tritium Determination by
an Original 3He Ingrowth Method Using a Standard Helium Leak Detector Mass Spectrometer,"
Anal. Chem.,74, p. 3183.
U.S. Food and Drug Administration (FDA). 2004. Supporting Document for Guidance Levels for
Radionuclides in Domestic and Imported Foods [Docket No. 2003D-0558]. Center for Food
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www.cfsan.fda.gov/~dms/nucleve2.html.
Friedlander, G., Kennedy, J.W., Macias, E.S., and Miller, J.M. 1981. Nuclear and Radiochemistry,
John Wiley and Sons, New York.
Health Physics Society. Online fact sheet on naturally occurring radioactive materials (NORM),
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Dispersal Devices: An Initial Study to Identify Radioactive Materials of Greatest Concern and
Approached to Their Tracking, Tagging, and Disposition. Report to the Nuclear Regulatory
Commission and the Secretary of Energy, May.
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Kim, G., W.C. Burnett, and E.P. Horwitz. 2000. "Efficient Preconcentration and Separation of
Actinide Elements from Large Soil and Sediment Samples," Anal. Chem., 72, p. 4882.
Lapp, R.E. and H.L. Andrews. 1964. Nuclear Radiation Physics, 3rd Edition. Englewood Cliffs:
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Available at www.epa.gov/radiation/marlap/manual.htm.
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NUREG 1575 Rev 1, EPA 402-R-97-016 Revl, DOE/EH-0624 Revl. August. Available at:
www.epa.gov/radiation/marssim/index.html.
U.S. Nuclear Regulatory Commission (NRC). 1984. Long-Lived Activation Products in Reactor
Materials. NUREG/CR-3474. NRC, Washington, DC.
U.S. Nuclear Regulatory Commission (NRC). 1997. Minimum Detectable Concentrations with
Typical Radiation Survey Instruments for Various Contaminants and Field Conditions..
NUREG/CR-1507. NRC, Washington, DC.
U.S. Nuclear Regulatory Commission (NRC). 2004. Fact Sheet on Decommissioning Nuclear Power
Plants. NRC, Washington, DC. Available at www.nrc.gov/reading-rm/doc-collections/fact-
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Office of Technology Assessments (OTA). 1991. Complex Cleanup: The Environmental Legacy of
Nuclear Weapons Production. Congress of the United States, Office of Technology
Assessments, OTA-O-484, NTIS #PB91-143743, February.
Ognibene, Ted J., Graham Bench, John S. Vogel, Graham F. Peaslee, and Steve Murov. 2003. "A
High Throughput Method for the Conversion of CO2 Obtained from Biochemical Samples to
Graphite in Septa-sealed Vials for Quantification of I4C Quantification via Accelerator Mass
Spectrometry," J. Anal. Chem. 75, pp. 2192-2196.
Rollin, Stefan, and Ulla-Britt Eklund. 2000. "Determination of U(IV) and U(VI) by Ion Chromato-
graphy-Inductively Coupled Plasma Mass Spectrometry and Its Application to Kinetic Studies,"
J. Chromatogr. A, 884, pp. 131-141.
Schultz, M.K., W. Burnett, K.G. W. Inn, and G. Smith. 1998. "Geochemical Partitioning of Actinides
Using Sequential Chemical Extractions: Comparison to Stable Elements," J. Radioanal. Nucl.
Chem., 234, p. 251.
Shebell, P. 2003. "An In Situ Gamma-ray Spectrometry Intercomparison," Health Physics, 85(6),
pp. 662 - 677.
Truscott, James B., Phil Jones, Ben E. Fairman, and El Hywel Evans. 2001. "Determination of
Actinides in Environmental and Biological Samples Using High Performance Chelation Ion
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Chromatography Coupled to Sector-Field Inductively Coupled Plasma Mass Spectrometry,'V.
Chromatogr. A, 928, pp. 91-98.
6.2 Other Sources
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Butterworth-Heinemann, Oxford.
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International Organization for Standardization (ISO). 1997. Capability of Detection - Part 1: Terms
and Definitions. ISO 11843-1. ISO, Geneva, Switzerland.
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International Union of Pure and Applied Chemistry (IUPAC). 1995. Nomenclature in Evaluation
of Analytical Methods Including Detection and Quantification Capabilities. Pure and Applied
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Knoll, G. F. 1989. Radiation Detection and Measurement, 2nd Edition. New York: John Wiley &
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Elaboration oja Proposed'Position for Radiological Effluent and'Environmental Measurements.
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Isotopes: Chart of the Nuclides. 15th Edition. Lockheed Martin and General Electric.
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An Emerging Method for Analysis of Long-Lived Radionuclides," Radioactivity and
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MD: Scinta Inc.
Wahl, A.C. and Bonner, N.A. 1951, Second Printing: May, 1958. Radioactivity Applied to
Chemistry, John Wiley and Sons, New York.
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Appendix A: Glossary
(Note: terms in italics within definitions contain their own entries)
activity (A), radioactive: (1) The rate of nuclear transformations of a radioactive substance, i.e., the
number of radioactive atoms undergoing nuclear transformation (nuclear decay) per unit time; (2)
The number of nuclear decays occurring in a given quantity of material in a small time interval,
divided by the time interval: A = -dN/dt.
alpha particle (a): Essentially a helium nucleus, comprised of two protons and two neutrons (Z =
2, A = 4). An a particle is the heaviest particle emitted during radioactive decay.
analytical data requirements; Measurement performance criteria used to select and decide how the
laboratory analyses will be conducted and used for the initial, ongoing, and final evaluation of the
laboratory's performance and the laboratory data. Analytical data requirements are often described
in terms of sensitivity (method detection capability), completeness, precision, and accuracy or bias.
In a performance-based approach, the project-specific analytical data requirements serve as
measurement performance criteria and decisions on how the laboratory analyses will be conducted,
e.g., method selection, etc.
analytical method: A major component of an analytical protocol that normally includes written
procedures for sample digestion, chemical separation (if required), and counting (analyte quantifica-
tion through radioactive decay emission or atom counting measurement techniques.
analytical protocol: A compilation of specific procedures/methods that are performed in succession
for a particular analytical process. With a performance-based approach, there may be a number of
appropriate analytical protocols for a particular analytical process. The analytical protocol is
generally more inclusive of the activities that make up the analytical process than is the analytical
method. See analytical method.
analytical protocol specification (APS): The output of a directed planning process that contains the
project's analytical data needs and requirements in an organized, concise form. The level of
specificity in the APS should be limited to those requirements that are considered essential to
meeting the project's analytical data requirements to allow the laboratory the flexibility of selecting
the protocols or methods that meet the analytical requirements.
atomic mass (A): The sum of an atom's protons (Z) and neutrons (N); also called "atomic weight."
Isotopes of a given element all have the same number of protons but different numbers of neutrons,
so they have different masses (see atomic number).
atomic number (Z): The number of protons in an atom's nucleus. The atomic number defines an
element's chemical properties, and hence its place in the Periodic Table.
becquerel (Bq): The SI unit of radioactivity, defined as one disintegration (decay) per second. The
more common unit is the picocurie (pCi) or 10~12 Ci, which equals 2.22 disintegrations per minute
(dpm), or 0.037 Bq. See curie.
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beta particle: Beta particles (P ) and positrons (P") are essentially electrons, but they originate in
the nucleus of an atom. A conversion electron (e ) is generated from the interaction of a gamma ray
with an orbital electron. All of these particles have the same mass and charge. Conversion electrons
are monoenergetic, having the energy of the gamma ray minus the energy needed to remove the
electron from orbit. Beta particles and positrons always have an energy distribution from zero to a
maximum.
branching decay: This occurs when a radionuclide can decay by more than one mode. Examples
of this would be 235U decaying by alpha emission or by spontaneous fission, or 214Bi decaying by [3
or a emission. Generally, for any radionuclide, one possible decay mode predominates by orders of
magnitude. The half-life denoted is the aggregate half-life of all the decay modes, proportional to
their percent abundance. However, each branching decay has its own half-life.
branching fraction: The fraction of particles or photons with a specific energy that result from the
decay of a particular radionuclide. For example, the branching fractions for the 134Cs y rays at 795
and 605 keV are 0.854 and 0.976, respectively (for every 1,000 decay events, 854 and 976 of these
Y rays, respectively would be emitted). Also referred to as "branching ratio," "emission probability,"
and "particle yield."
bremsstrahlung radiation: When an electron passes through matter, it can undergo a very large
acceleration (deceleration). The resulting loss by the electron of radiant energy (photons) is called
bremsstrahlung (from the German "bremsen," to brake, and "Strahlung") radiation.
carrier: A stable isotope of an element (usually the analyte) added to increase the total amount of
that element so that a measurable mass of the element is present.
carrier-free radiotracer: (1) A radioactive isotope tracer that is essentially free from stable (non-
radioactive) isotopes of the element in question. (2) Addition of a specific, nonradioactive isotope
of an element to change the measured isotopic abundance of the element in the sample. Such
materials are usually designated as nonisotopic material or marked with the symbol "c.f." (see
carrier, radiotracer}.
Cerenkov radiation: Cerenkov radiation is emitted in the ultraviolet spectrum when a fast charged
particle traverses a dielectric medium (like water) at a velocity exceeding the velocity of light in that
medium. It is analogous to the "sonic boom" generated by a craft exceeding the speed of sound.
check source: A sealed source used to verify the operabilitly of an installed radiation detector. The
source is shielded from the detector except during brief intervals when it is inserted in front of the
active detector surface. The response that the detector yields must be above a certain number of
counts for the detector to be considered operable.
chelate: A class of metal-organic or metal-inorganic compounds in which the metal atom or ion is
held by a pair of ligand atoms in a single molecule.
constant weight: A process by which a sample is heated in an oven at about 105 C for at least one
hour, cooled in a desiccator, then weighed. This process is performed at least twice so that two
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successive mass determinations agree to within a range determined by the analytical protocols for
the project.
conversion electron'. See beta particle.
counting efficiency, the ratio of the events detected (and registered) by a radiation detection system
to the number of particles or photons emitted from a radioactive source. The counting efficiency
may be a function of many) variables, such as radiation energy, source composition, and source or
detector geometry.
count time: The time interval for the counting of a sample or source by a radiation detector (also
referred to as the "live" time or analysis time).
critical value: In the context of analyte detection, the minimum measured value (e.g., of the
instrument signal or the analyte concentration) required to give confidence (to a given probability)
that a positive (different than background) amount of analyte is present in the material analyzed. The
critical value is sometimes called the critical level or decision level.
cross-contamination: Cross-contamination occurs when radioactive material in one sample is
inadvertently transferred to an uncontaminated sample, which can result from using contaminated
sampling equipment and chemicals, and improperly cleaned glassware, crucibles, grinders, etc.
Cross-contamination may also occur from spills, as well as airborne dusts of contaminated materials
created during grinding.
crosstalk: A phenomenon in gas proportional counting or liquid scintillation counting when an
emission of an alpha particle is recorded as a beta particle count or vice versa. This is due to the
ionization affects of the particles at different energies.
curie (Ci): The common unit of radioactivity. Originally defined as the radioactivity of 1 g of pure
radium; since 1953 defined as exactly 3.7 x 10'° disintegrations per second, or 3.7 x 10'° Bq.
Because the Ci is such a large value, the more common unit is the picocurie, or 10 12 Ci. See
becquerel.
data package: The information the laboratory should produce after processing samples so that data
verification, validation, and quality assessment can be done.
Data Quality Objective (DQO): DQOs are qualitative and quantitative statements that clarify the
study objectives, define the most appropriate type of data to collect, determine the most appropriate
conditions from which to collect the data, and specify tolerable limits on decision error rates. The
DQOs should encompass the total uncertainty resulting from all data collection activities, including
analytical and sampling activities.
decay: The decrease in the number of atoms of any radioactive material with the passage of time
due to the spontaneous emission from the nuclei of photons or alpha or beta particles, often
accompanied by gamma radiation. Eventually, all radioactive materials decay to stable elements.
See radioactive, decay chain.
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decay chain'. A decay chain or decay series begins with a parent radioisotope (also called a parent
radionuclide or parent nuclide). As a result of the radioactive decay process, one element is
transformed into another. The newly formed element, the decay product or progeny, may itself be
radioactive and eventually decay to form another nuclide. Moreover, this third decay product may
be unstable and in turn decay to form a fourth, fifth, or more generations of other radioactive decay
products. The final decay product in the series will be a stable element. Elements with extremely
long half-lives may be considered stable in most cases. Examples of important naturally occurring
decay chains include the uranium series, the thorium series, and the actinium series.
decay emissions: The emissions of alpha particles, beta particles, or gamma rays from an atomic
nucleus, which accompany a nuclear transformation from one chemical atom to another or from a
higher nuclear energy state to lower one.
derived concentration guideline level: A derived radionuclide-specific activity concentration within
a survey unit corresponding to the release criterion. DCGLs are derived from activity/dose
relationships through various exposure-pathway scenarios.
eluent: The mobile phase in chromatography. Also called "eluant." Elution is the removal, by means
of a suitable solvent, of one material from another that is insoluble in that solvent, as in chroma-
tography.
error: The difference between a measured result and the true or expected value of the analyte being
measured. The error of a measurement is primarily a theoretical concept, because its true value is
never known. See also measurement uncertainty.
extractant: An agent used to isolate or extract a substance from a mixture or combination of
substances. An extractant scintillator extracts the radionuclide or element from the solution.
gamma ray (y): After alpha or beta emission, the nucleus may still possess excess energy (i.e., they
remain unstable). The extra energy is given off in the form of gamma radiation. Gamma rays, like
X-rays, are part of the electromagnetic spectrum (beyond ultraviolet wavelengths), and their energies
correspond to the difference in the energy levels in the nucleus from which they come. These
discrete energies are used to identify the radionuclides from which they originated. Gamma rays
typically accompany a, (3~, and P+ emission but originate from the resultant nucleus of the decay
process after the particle emission. See X-rays.
gray (Gy): The SI unit for absorbed radiation dose. One gray is 1 joule of energy absorbed per
kilogram of matter, equal to 100 rad.
half-life (t,): The time required for one-half of the atoms of a particular radionuclide in a sample
to disintegrate or undergo nuclear transformation.
ingrowth: The occurrence and increase of a progeny radionuclide within a sample, initially
containing only the parent radionuclide, caused by radioactive decay of the parent.
ion-exchange chromatography: A separation method based on the reversible exchange of ions in
a mobile phase with ions bonded to a solid ionic phase. Ions that are bonded less strongly to the solid
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phase (of opposite charge) are displaced by ions that bond more strongly bonded. Separation of
analyte ions depends on the relative strength of bonding to the solid phase. Those less strongly
bonded ions are released from the solid phase earlier and eluted sooner.
isobar: Nuclides that have the same atomic mass number but a different number of protons (Z) and
neutrons (N). Isobars have different chemical properties. For example, 36C1 (Z = 17, N = 19) and 36S
(Z = 16, N = 20) are isobars because they have the same atomic mass even though they are
chemically different. As radionuclides, isobars may be related through radioactive decay by P+, (3 ,
or electron capture. For example, 90Sr (Z = 38, N = 52) decays to 90Y (Z = 39, N = 51) by (3'
emission. These two radionuclides are isobars.
isomeric transition: The transition, via gamma-ray emission, of a nucleus from a high-energy state
to a lower-energy state without accompanying particle emission, e.g., 99mTc 99Tc + y.
isotope: Nuclides having the same number of protons in their nuclei (same atomic number), but
differing in the number of neutrons (different mass number). Thus, hydrogen (Z = 1) has one proton.
Tritium (3H) is an atom of hydrogen with one proton and two neutrons, with an atomic mass of 3.
A "radioisotope" is an isotope with radioactive properties. See nuclide and radionuclide.
laboratory control sample (LCS): (Also referred to as a "QC sample.") A standard material of
known composition or an artificial sample (created by fortification of a clean material similar in
nature to the environmental sample), which is prepared and analyzed in the same manner as the
environmental sample. In an ideal situation, the result of an analysis of the laboratory control
sample should be equivalent to (give 100 percent of) the target analyte concentration or activity
known to be present in the fortified sample or standard material.
tigand: Two atoms of a single molecule holding a metal atom or ion in a chelate.
measurement quality objective (MQO): The analytical data requirements of the Data Quality
Objectives that are project- or program-specific. MQOs can be quantitative or qualitative. MQOs
serve as measurement performance criteria or objectives of the analytical process. Quantitative
MQOs are statements of required analyte detectability or the uncertainty of the analytical protocol
at a specified radionuclide concentration, such as the action level. Qualitative MQOs are statements
of the required specificity of the analytical protocol, e.g., the ability to analyze for the radionuclide
of concern given the presence of interferences.
measurement uncertainty: Uncertainty of measurement is defined as a parameter, associated with
the result of a measurement, that characterizes the dispersion of values that could reasonably be
attributed to the measurand. The uncertainty of a measured value is typically expressed as an
estimated standard deviation, called a standard uncertainty.
minimum detectable concentration (MDC):The MDC is the "true" concentration of analyte
required to give a specified high probability that the measured response will be greater than the
critical value. The International Standards Organization (ISO) refers to the MDC as the "minimum
detectable value of the net state variable." They define this as the smallest (true) value of the net
state variable that gives a specified probability that the value of the response variable will exceed
its critical value, i.e., that the material analyzed is not blank. The "minimum detectable activity
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(MDA)" is similar, but relates to the quantity (activity) of a radionuclide rather than the
concentration of a radionuclide.
mixed wastes: Regulated wastes containing both chemically hazardous and radiological materials.
monoenergetic: The quality of a particle or quantum of energy that has a discrete, well-defined
energy range. This is a characteristic of emitted alpha particles and gamma- and X-rays.
net count rate'. The value resulting from the subtraction of the background count rate, instrument
background or appropriate blank from the total (gross) count rate of a source or sample.
nuclide: A general term for an atom with a given combination of protons, neutrons, and nuclear
energy state. See radionuclide and isotope.
parent radionuclide: The initial radionuclide in a decay series that decays to form one or more
progeny
Poisson distribution: The distribution of the total radioactive counts obtained over time as a result
of fluctuations governed by the laws of probability, as is the case for the radioactive decay process.
positron: See beta particle.
progeny: One or more radionuclides that form from radioactive decay of a parent radionuclide in
a decay series.
quality assurance (QA): An integrated system of management activities involving planning,
implementation, assessment, reporting, and quality improvement to ensure that a process, item, or
service is of the type and quality needed and expected.
quality control (QC): Monitoring key laboratory performance indicators as a means of determining
if a laboratory's measurement processes are in control.
quality control samples: Samples analyzed for the purpose of assessing imprecision and bias.
quality indicators: Measurable attributes of the attainment of the necessary quality for a particular
environmental decision. Precision, bias, completeness, and sensitivity are common data quality
indicators for which quantitative MQOs could be developed during the planning process.
quality system: The quality system oversees the implementation of QC samples, documentation of
QC sample compliance or noncompliance with MQOs, audits, surveillances, performance evaluation
sample analyses, corrective actions, quality improvement, and reports to management.
radioactive: (1) the property possessed by some elements or isotopes of spontaneously emitting
radiations by the transformation of their nucleus. (2) The product of nuclear transformations
(disintegrations) in which the energy (or a fraction thereof) of the process is emitted in the form of
alpha particles, beta particles, or photons. See decay.
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radiochemical analysis: The analysis of a sample matrix for its radionudide content, both
qualitatively and quantitatively.
radiolysis: Chemical reactions, including decomposition, induced by radiation.
radionudide: A species of atom characterized by its mass number, atomic number, and nuclear
energy state, providing that the mean half-life in that state is long enough to be observable. The
majority of known nuclides are radioactive. The term "radionudide" is used when referring to a
specific radioactive nuclide without relating it to other isotopes of an element.
radiotracer: (1) A radioactive isotope of the analyte that is added to the sample to measure any
losses of the analyte during the chemical separations or other processes employed in the analysis
(the chemical yield). (2) A radioactive element that is present in only extremely minute quantities,
on the order of 1(T15 to 10" Molar.
recovery: The actual amount of material detected in a laboratory control sample (LCS) or spiked
sample, expressed in percent of the amount of material that was added. In an ideal situation, the
result of an analysis of the laboratory control sample should be equivalent to (give 100 percent of)
the target analyte concentration or activity known to be present in the fortified sample or standard
material. The result normally is expressed as percent recovery. Because most radioanalytical
methods use radiotracers or analyze a radionudide in a sample without losses, recovery is a
measure of method bias for repetitive measurements. The LCS recovery differs from the recovery
of a matrix spike in that the matrix spike is added directly to the environmental sample and the
percent recovery is determined by comparing the difference between the original and spiked samples
after accounting for the activity in the original (unspiked) sample.
rent: The common unit for the effective or "equivalent" dose of radiation received by a living
organism, equal to the actual dose (in rads) multiplied by a factor representing the danger of the
radiation. "Rem" stands for "roentgen equivalent man," meaning that it measures the biological
effects of ionizing radiation in humans. One rem is equal to 0.01 Sv. See sievert.
representativeness: (1) The term employed for the degree to which samples properly reflect their
parent populations. (2) A representative sample is a sample collected in such a manner that it reflects
one or more characteristics of interest (as defined by the project objectives) of a population from
which it was collected. (3) One of the five principal data quality indicators (i.e., precision, bias,
representativeness, comparability, and completeness).
reproducibility: A measure of laboratory precision based on each sample matrix. Duplicate or
replicate sample results are used to evaluate reproducibility of the complete laboratory sub-
sampling, preparation, and analytical process.
SAFSTOR: A method of decommissioning in which the nuclear facility is placed and maintained
in such condition that the nuclear facility can be safely stored and subsequently decontaminated to
levels that permit release for unrestricted use.
sievert (Sv): The SI unit for the effective dose of radiation received by a living organism. It is the
actual dose received ("grays'1'' in SI or "rads" in traditional units) times a factor that is larger for more
dangerous forms of radiation. One sievert is 100 rem. Radiation doses are often measured in
68
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Inventory of Radiological Methodologies
millisieverts (mSv). An effective dose of 1 Sv requires 1 gray of beta or gamma radiation but only
0.05 gray of alpha radiation or 0.1 gray of neutron radiation.
spike: (Also termed "matrix spike.) A known amount of target analyte added to the environmental
sample in order to establish if the method or procedure is appropriate for the analysis of the
particular matrix and how the target analyte responds when the environmental sample is prepared
and measured, thereby estimating the bias introduced by the sample matrix.
standard uncertainty: The estimated standard deviation associated with a measured value.
Statistically, the standard uncertainty of x is denoted by u(x).
uncertainty: The term "uncertainty" may have several shades of meaning. In general it refers to a
lack of complete knowledge about something of interest. It usually refers to "uncertainty of
measurement," which is a parameter associated with the result of a measurement that characterizes
the dispersion of the values that could reasonably be attributed to the measurand. See also, standard
uncertainty.
X-rays: First discovered in 1895, X-rays are part of the electromagnetic spectrum, with wavelengths
shorter than visible or radio waves. X-rays originate from the realignment of atomic shells (orbital
electrons) during the decay process. While they exhibit the same dual behavior as light (waves and
photons), and they can be polarized or refracted, they are capable of penetrating matter. See gamma
rays.
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Appendix B: Principles of Radioactive Decay and Radioactive Equilibrium
B.I Introduction
This discussion on radioactivity and radiation provides the basic concepts of miclides, radionuclides,
radioactive decay, and decay emissions. These concepts are important to the measurement of
radioactivity from samples. This fundamental knowledge, in addition to the historical site assess-
ment, will assist the project managers in determining the scope of work that may originate from the
various sites.
B.I.I Nuclides
Elements may be differentiated by their physical and chemical characteristics. The elements are
arranged within the Periodic Table according to the number of protons in their nucleus (atomic
number, or "Z number"); all atoms of a particular element have the same number of protons.
Individual elements may have more than one "isotope," which are atoms of an element that have the
same number of protons (Z) but a different number of neutrons (N) in their nucleus. For example,
in addition to the stable 27A1, there are 14 other known isotopes of aluminum ranging in mass
number between 22 and 35. For aluminum, these other 14 isotopes are radioactive or unstable
nuclides. Other elements, such as iron (Fe), have several stable isotopes of different abundances
(54Fe - 5.8 percent, 56Fe - 91.8 percent, 57Fe - 2.1 percent, and 58Fe - 0.3 percent) as well as
radioactive isotopes. When referring to a radioactive isotope of an element, the term "radioisotope"
often is used. Isotopes of a given element have the same chemical properties, whether they are
radioactive or not. The ratio of Z to N determines the stability of the nucleus (i.e. whether or not the
atom is radioactive).
The general term for a specific combination of Z and N is a "nuclide." The mass number (A) of the
nuclide is the sum of the number of protons and neutrons (A = Z + N). The positive charge of the
nucleus (Z4) establishes the number of electrons in the neutral atom, and determines the
configuration of the outermost electrons. This element-specific structure of the electron cloud of the
neutral atom determines how the atom will ionize, and thus its chemical properties.
When writing a specific nuclide in symbolic form, the atomic number and mass are included. For
example, the symbolic form of stable aluminum is " Al, which is the only stable nuclide (100 percent
abundance) of aluminum. Common nomenclature normally does not include the Z number in the
symbolic form because the element symbol (Al) uniquely represents the number of protons in the
nucleus for that element— 27A1.
Nuclides with the same atomic mass (Z + N) are called "isobars." For example, 36C1 and 36S,
although chemically and physically different because of their different Z numbers, are isobars
because their A values are the same.
B.I.2 Radionuclides
The majority of known nuclides are radioactive. The term "radionuclide" is used when referring to
a specific radioactive nuclide without relating it to other isotopes of an element. The radioactive
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Inventory of Radiological Methodologies
decay of each radionuclide is unique in terms of its mean time (or half-life) for decay and the nuclear
emissions during the decay process. Radionuclides can be found in nature but most are generated
by man-made nuclear reactions such as nuclear fission or activation. Naturally occurring radionuc-
lides can be delineated into two groups according to their origin, primordial and cosmogenic.
Primordial radionuclides are those nuclides that have been present since the formation of the Earth,
and whose half-lives are sufficiently long to permit detection of these nuclides today. Examples of
primordial nuclides are B8U and 232Th. In some cases, the primordial nuclides decay into a series of
other shorter lived radionuclides (referred to as a "decay chain"). Cosmogenic radionuclides are
those nuclides formed by the irradiation of stable elements, primarily in the atmosphere, by neutrons,
gamma rays, or protons from solar irradiance. Cosmogenic radionuclides have half-lives that may
be short or very long (7Be and 14C, respectively).
There are three long-lived, naturally occurring, radionuclides that are the "parents" of decay chains
with numerous members: 238U, 232Th, and 235U. An additional decay chain once existed from 237Np
(t,/2 2.1 x 106 y), which has long since "died out," because the half-lives of the parent and progeny
are much shorter than the age of the Earth (about 4.6 * 109 y). The decay chains of the existing long-
lived radionculides are depicted in Figures 3, 4, and 5.
B.I.3 Radioactive Decay
It has been recognized that a nuclide will be stable if it contains a certain combination of neutrons
and protons. Of the known elements, only elements from hydrogen (Z = 1) to bismuth (Z = 83) have
stable nuclides. Technetium (43) and promethium (61), however, are exceptions and have no stable
isotopes. If one plots the number of protons (Z) against the number of neutrons (N), it becomes
apparent that the stable nuclides form a "line of stability" with a slope of about one (or N Z) for
the first 20 elements and a slope of less than one (or N > Z) for higher Z elements. When a nuclide
has too many neutrons, the nucleus is unstable, and a neutron will be converted to a proton resulting
in (3 emission. An example of this is
60,
When a nuclide has too many protons, the nucleus is also unstable, and a proton is converted to a
neutron either through a positron emission or capture of an orbital electron (electron capture).
Examples of these changes include:
58,
and
58 Co e Capture )58Fc
27 ^-U ' 26 r L
For nuclides that have a large excess of neutrons and protons, the nucleus can approach stability by
emitting an a
nuclides are:
emitting an alpha particle (2He ). Examples of an alpha emission that result in stable or unstable
(stable)
and
2^Ra—^>2f(, Rn (unstable: radioactive)
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Inventory of Radiological Methodologies
Th-230
alpha *
75,000 y
Po-210
alpha
138 d
U-234
alpha
25x10b y
Ra-226
alpha
1,600y
Pb-206
stable
Bi-210
' beta
5d
Po-214
alpha
1 6x10" s
Pa-234m
beta
1.17 mm
Rn-222
1 alpha
3.8 d
U-238
alpha
4.5x109 y
Th-234
x beta
24 d
Pb-210
beta >
22 3 y
Bi-214
beta
19min
Po-218
alpha
3 2 mm
Pb-214
beta
27 min
FIGURE 3 — Uranium-238 decay chain
Th-228
alpha ,
Ra-224
alpha
37d
Ac-228
" beta
61 h "
Rn-220
alpha
56s
Th-232
alpha
1.41x10'°y
Ra-228
v beta
576y
Pb-208
stable
Po-212
, alpha
3x107 s
TI-208
beta
3 mm
beta
,64%
. Bi-212
1 h *
Po-216
alpha *
0.15s
Pb-212,
^ beta
101 h
FIGURE 4 — Thorium-232 decay chain
Th-227
alpha
18.7d
I *
1
Ra-223
alpha
11 4d
i"
Rn-219
alpha
4s
I
Bi-211 Po-215
Pb-207 alpha alpha
stable 21 mm 1.8x103s
/|t /
\ TI-207 / \Pb-211 /
\ beta * ^ beta *
4.8 mm 36 1 mln
Pa-231
alpha
beta 328x10"y
^6% / V Th-231 ,
\Ac-227* \ beta X
21 7 y 1 OS d
alpha
14%
\ Fr-223
\ beta
22 mm
U-235
alpha
705x10" y
/
FIGURE 5 — Uranium-235 decay chain
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Inventory of Radiological Methodologies
During radioactive decay, the number of atoms (N) of a radionuclide decreases over time according
to its own characteristic decay rate. Mathematically, the number of atoms decaying (dN) in a short
time interval (dt) can be expressed as:
dN = -AN dt
where A is the decay constant for the radionuclide.
Integrating the differential equation results in the well-known radioactive decay equation:
N = N0e-X(t-tn)
where: N is the number of radioactive atoms remaining at time t, and
N() is the initial number of atoms at time t().
There is an important relationship between the radionuclide's decay constant and its half-life. By
definition, the half-life (t,/2) of a radionuclide is the time interval needed to reduce the number of
atoms by half. Simplifying the equation for A with N = !/2N0 would result in A = [loge 2]/t,/2, or A =
0.693 l/t,/2. In most reference materials on the properties of the various radionuclides, the half-life
of the radionuclide will be specified, typically in units of years (y), days (d), hours (h), minutes (m)
or seconds (s). The A is expressed in reciprocal time units; y"', d"1, h"1, min"1, or s"1.
Most radioactive measurements deal with activity or the number of atoms decaying per unit of time.
A radionuclide's activity is calculated by the equation A = N A. The new unit of radioactivity is the
becquerel (Bq), and is defined as one disintegration (decay) per second. The more common unit is
the picocurie (pCi) or 10"12 Ci, which equals 2.22 disintegrations per minute (dpm), or 0.037 Bq. For
example, 500 Bq of 60Co will decay to 250 Bq in one half-life (t,/2 5.27 y).
B.I.4 Radioactive Decay Emissions
Unstable nuclides (radionuclides) decay randomly to stable and unstable nuclides of lower atomic
mass. The difference between the masses of the original nuclide, and the decay product (progeny)
nuclide is related to the radiation emitted during the decay process according to Einstein's famous
mass-energy equation, E = me2.
Emissions from the nucleus of an atom during radioactive decay that are important to the measure-
ment of radioactivity in samples include alpha particles, beta particles (as P or p+), gamma rays, and
X-rays (which also may be emitted as a result of electron capture and other nuclear phenomena). The
energy of these emissions is stated in terms of electron volts (eV), which is equivalent to 1.6 x 10 '2
erg. Energies of alpha and beta particles are generally expressed in MeV while that for gamma- and
X-rays are expressed in keV.
B.I.4.1 Alpha Particles
An alpha particle (a) is the heaviest particle emitted during radioactive decay (heavier particles can
occur but are rare). An a particle is essentially a helium nucleus, comprised of two protons and two
neutrons (Z = 2, A = 4). When ejected from the nucleus of a heavier unstable atom during
radioactive decay ("alpha emission"), it always has a discrete energy ("monoenergetic"). However,
the decay process may emit an alpha particle of one of several possible discrete energies, each with
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Inventory of Radiological Methodologies
a probability of emission per decay. For example, for 241Am, an alpha particle emission may have
one of three energies, each with a different probability of emission: 5.486 MeV (85.2 percent
probability), 5.443 MeV (12.8 percent), and 5.388 MeV (1.4 percent). The "signature" of an alpha
emitting radionuclide is its alpha particle energy. This energy signature, along with the nuclide's
half-life, are specific to the identification of an alpha-emitting radionuclide. For example, the alpha
energy of 2ll)Po (t,/2 138 d) is 5.305 MeV, while the alpha energy of 208Po (t,/2 2.90 y) is 5.116
MeV. Typically, the shorter the half-life, the greater the energy of the alpha particle.
When interacting with materials, alpha particles have a very short penetration range and travel in
a nearly a straight manner, i.e., with minimal scattering. This is especially important when detecting
alpha particle emissions from radionuclides isolated by radiochemical means. A 5 MeV alpha
particle has a range of about 3.5 cm in air and 0.03 mm in skin or water. As such, test sources
containing alpha-emitting radionuclides must be extremely thin for proper detection and energy
identification, typically in the micron thickness range. It should be noted that particle and photon
absorption thickness are stated in units of milligrams per square centimeter (mg/cm2), which for
particles is equivalent to the range (cm) times density of material (g/cm3).
B.1.4.2Beta Particles, Positrons, and Conversion Electrons
Beta particles (P~) and positrons (|3+) originate in the nucleus of an atom, while a conversion electron
is generated from the interaction of a gamma ray with an orbital electron. All of these particles have
the same mass, but the beta and conversion electrons (P and e ) have a negative charge while the
positron has a positive charge. The charge of a P , P+, and e is 1.602 x 10~19 Coulombs. Like a
particles, conversion electrons are monoenergetic, having the energy of the gamma ray minus the
energy needed to remove the electron from orbit. The emissions of beta particles and positrons
always have an energy distribution from zero to a maximum, Epmax, with an average of
approximately 1/s Epmax.
Because an electron has a low mass and a single charge, it is more easily scattered and less readily
absorbed in materials compared to other nuclear particles such as alphas and protons. In addition,
as a result of this scattering, an electron's path through material is nonlinear and tortuous.
Absorption of p , p+, and e in materials is relatively independent of the atomic number of the
material. However, their absorption range varies according to the density of the material. For
energies above one MeV, the range of a P^ and p4 is linear with respect to energy (Lapp and
Andrews, 1964). The range of a tritium beta particle of Epmax — 0.018 MeV is 0.6 mg/cm2 (6 jam in
water), while the range for a 32P beta particle of Epmax = 1.71 MeV is 800 mg/cm2 (8 mm in water).
Different radiation detection methodologies are used for low energy (< 0.200 MeV) p , P+, and e'
compared to those of medium to high energy.
B.1.4.3X-Rays, Gamma Rays, and Bremsstrahlung Radiation
X- and gamma (y) rays are electromagnetic radiations that have defined energies. X-rays originate
from the realignment of atomic shells (orbital electrons) during the decay process. One requirement
for an X-ray emission is the creation of an electron vacancy in an inner shell. Because there are
many electron shells for atoms of atomic number greater than 10 (neon), there is a probability that
the X-rays from a radioactive decay will have more than one energy. However, the energy of an X-
ray is always smaller than the highest electron-binding energy in atomic shells or under about 100
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Inventory of Radiological Methodologies
keV. The probability of an X-ray emission of a specific energy per atomic disintegration has been
determined and is listed with the characteristic of the radionuclide.
Gamma rays originate from the nucleus of an atom as a result of nuclear de-excitation and have
energies from about 20 keV to several MeV. Following a, (3 , or (3^ emission, the nucleus may still
have excess energy; this energy is released in the form of gamma rays. Gamma rays are more
probable with (3 and P' emissions than with a emissions. Gamma-ray emission, without
accompanying particle emission, is known as "isomeric transition" (the nucleus goes from an excited
state to a ground state). The discrete energies of the X- and y-rays are used to identify the
radionuclides from which they originated.
For a laboratory application, bremsstrahlung radiation is produced whenever electrons ((3 and (3*)
are decelerated in matter. Unlike X- and y-rays, bremsstrahlung radiation shows a continuous
spectrum of photon energy extending from zero to the maximum energy (Epmax) of the (3 or (3+. There
are only a few radioanalytical methods that use bremsstrahlung radiation detection as a means to
quantify a radionuclide.
The degree of interaction of photons, such as X-, y-, and bremsstrahlung radiations, is highly
dependent on the photon energy. Gamma-rays, which have energies typically > 100 keV, are more
penetrating and are less absorbed by matter compared to lower energy X-rays (typically less than
100 keV). This is an important characteristic when choosing a radiation detector and for shielding
detectors from photons originating from outside (external background radiations) the sample being
analyzed. For most remediation sample analyses, gamma-ray detectors are typically shielded with
a minimum of 102 mm of lead or other very dense material.
B. 1.5 Techniques for Radionuclide Detection
When there is sufficient activity, the detection and identification of a specific radionuclide is
accomplished by evaluating the radiological and chemical properties of the nuclide of interest. For
radionuclides that emit characteristic gamma rays of a specific energy, the detection and identifica-
tion of the nuclide is based on the radiological characteristics only. For nuclides that emit beta and
alpha particles, a combination of radiological and chemical characteristics may be needed to identify
and quantify the nuclide of interest. In these cases, the nuclide is isolated from the sample matrix
through chemical means and then concentrated in some final chemical form (e.g., 89SrCO3) used as
a test source. The resulting test source can be analyzed by either a beta or alpha detector depending
on the nuclide's decay scheme or particle emission. In some cases, where there may be several
isotopes of the element in the test source, a particle energy spectrometry measurement is necessary
to discern the various isotopes, e.g., 238Pu and 239Pu. Also, radioanalytical methodologies may
employ chemical separation schemes and detectors that are specific to identifying and quantifying
a radioactive decay product of the nuclide of interest. Examples of this type of methodology
application include separating and analyzing 90Y, the short lived (t,2 64.0 h) decay of 90Sr and the
collection and analysis of 222Rn (t,/2 3.82 d), the first decay product of 226Ra.
Radiation detection methodologies have been developed based on the physical interaction of the
decay emissions with special materials that have certain characteristics that may be measured
following the absorption of the radiation. Radiation detectors may be based on the following
physical principles: ionization of gases, creation of electron-hole pairs in semiconductor materials,
and the change of energy states with subsequent light emissions for certain organic and inorganic
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materials. Examples of these radiation detection methodologies include gas proportional counting
for a and (3 detection, large germanium and silicon semiconductor detectors for X- and y-ray
detection and spectrometry, silicon semiconductor detectors for a spectrometry, and organic liquid
scintillation counting for low-energy p particles and limited a spectrometry.
B. 1.6 Radioactive Equilibrium
When the decay product of a radionuclide is another radionuclide, three distinct cases—referred to
as "radioactive equilibria"—may be derived mathematically. These are based on the relationship of
the half-lives of the original and newly formed radionuclide. These cases are referred to as secular,
transient, and no equilibrium, and the relationship is referred to as "parent-progeny" (Friedlander
et al., 1981). Thus, radioactive equilibrium may be described as the relative proportion of the
activity of each of two or more radionuclides.
These relationships become complex when the progeny gives rise to a nuclide that is also radio-
active. In this case, the relationship would become, [parent] [ 1sl progeny] [2 nd progeny]. This
connection of the radionuclides is referred to as a radioactive decay chain. When the parent of the
chain is present, some number of atoms of all of the progeny in the chain will be present eventually
as the predecessor radionuclides undergo radioactive decay. Examples of these chains are:
SECULAR EQUILIBRIUM
Decay-chain nuclides: 238U 234Th 234mpa many others
Half-lives: 4.47 x 109y 24.1 d 1.2 min
TRANSIENT EQUILIBRIUM
Decay-chain nuclides: 95Zr 95Nb
Half-lives: 64 d 35 d
No EQUILIBRIUM
Decay-chain nuclides: 210Bi 21()Po 206Pb (stable)
Half-lives: 5d 1.38xlQ2d
The relationship expressing the number of atoms of each of the radionuclides present in a decay
chain after a certain period of time has elapsed can be expressed by the Batemann Equation
(Friedlander et al., 1981). If a quantity of the parent is chemically isolated, the amount of each
progeny can be calculated for any time period after the time of separation. For environmental
samples, the secular and transient equilibria are most significant because the parent radionuclide has
a long half-life, and the progeny have relatively short half-lives or a shorter half-life than the parent.
In many cases, if the progeny were present all by themselves, they would decay and might not be
detected. But because of the decay chain relationship, new progeny continue to be formed by the
parent. Thus, it appears that the half-life of the progeny is the same as that of the parent.
However, in the environment, this decay equilibrium can be upset because of the different chemical
properties of each of the radionuclides in the decay chain. Figure 6 shows an example of how this
upset to the radioactive equilibrium can occur. Initially the 232Th and 228Ra and 238U and 226Ra (from
two separate radioactive decay chains), establish a radioactive equilibrium with their respective
progeny, radium and radon. These radioactive equilibria initially occur in their respective media.
Thorium does not dissolve in water (indicated by the "X" over that arrow), while radium does. As
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Inventory of Radiological Methodologies
the radium dissolves, it is only partially "supported" in the water, because the thorium does not
dissolve.
The other decay chain has 226Ra as the fifth progeny of 238U. Because uranium is more soluble than
thorium, the decay chain in the liquid phase is fed continually by its parent. Initially, it is in radio-
active equilibrium with the radium and radon decay products in water. The 226Ra is fully supported.
However, due to the volatility of radon, it escapes the water column and is "unsupported" in air by
radium because radium is not volatile (also indicated by the "X" over that transition). When radon
is volatilized from water, but radium is not, the radon in the water is not completely supported; there
is a loss of radon to the air, but radium keeps feeding the radon to the water. In each case where the
progeny are less than fully supported, there will be an indeterminable or nonexistent radioactive
equilibrium. Samples with radionuclides that are partially or fully unsupported need special attention
when establishing the time from sampling to analysis, because in some instances the radionuclide
of interest may decay away before analysis can occur.
Air
,.'« +2
Water
Soil
"ThlQH^ -* »> -;W4 + 4 OH" :;t'RaCO3 -* f Ra*z +
FIGURE 6 — Environmental and chemical factors affecting radioactive equilibrium
Similar cases of radionuclide progeny being unsupported in an environmental medium hold true for
other radionuclides discussed in this document such as plutonium, americium, and lead.
B.I .7 Useful Websites and Sources for Background Information on Radioactivity
• Units of measure: www.physics.nist.gov/cuu/index.html
• Table of nuclides: http://atom.kaeri.re.kr/ton/
• Periodic chart of the elements: www.webelements.com
The following websites can be used to access technical reference material such as nuclide decay
schemes, half-lives, and decay emissions:
All nuclides; National Nuclear Data Center:
www.nndc.bnl.gov
www.nndc.bnl.gov/nndc/ensdf/
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Nuclides typical for natural background and environmental remediation; DHS Environment
Measurements Laboratory, EML Publications, Procedure Manual (HASL 300), Chapter 5
Radionuclide Data: www.eml.st.dhs.gov/publications/procman/.
Gamma-ray spectra and decay schemes: www.inl.gov/gammaray/catalogs/index.shtml
Radiochemical processes: library.lanl.gov/radiochemistry/elements.htm
Statistical applications to measurements including process control:
www.itl.nist.gov/div898/handbook/index2.htm
ie.lbl.gov/toi/
www. inl. go v/gammaray/links. shtml
Federal Radiological Monitoring and Assessment Center (FRMAC):
www.nv.doe.gov.nationalsecurity/homelandsecurity/frmac/default.htm
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Appendix C: Radionuclide Parameters and Characteristics
Radionuclide Decay Mode
24'Am , a, Y
143 Am l~a~ t"
2i°Bi T~p r
I4c I p
134Cs ^p, Y 1
6°Co JJ, y ^
3H __[ P _,
125I |_,Y J
I29i rp,y n
131I !p^Y
I * §
W a. A
O £ O
Half-Life Means of Production Q Z \ Z
423 y 1 Activation ,
7.37x]Q3y j Activation i •
5.0 d i Natural decay of 238U ,
5.72x]03y Cosmic Radiation, activation
2.0 y Fission
30 y Fission
5.3 y Activation
12.3 y j Cosmic radiation, fission
59.4 d Accelerator
1.6 x 107y Fission i
8.0 d Accelerator, fission '. '
ll)2Ir p, Y 73.8 d Activation
210Pb p, Y l22-6y Natural decay of 23SU
1 J I
wNi 7.6 x 104y 1 Activation j
63Ni ^p J]
32P , p T
238Pu _T a
239Pu ~T a
240Pu ^a
241Pu p, a i
22<>Ra a
228Ra ' p ^
89Sr p
90Sr p
35s p i
"Tc ^P ,
i
lOOy Activation j
14.3 d Accelerator ,
87.7 y Activation
2.4 x io4 v Activation
... .- j !
14.4 y Activation ,
1.6 x 103y _| Natural decay of 238U 1
5.8y Natural decay of 232Th
50.5 d Fission
28.8 y , Fission
87.2 d | Accelerator '
2.1 x 105y Fission, accelerator , |
227Th i a, Y ]j8.7 d Natural decay of 335U | \
228Th 1 a,Y
1.9y i Natural decay of 232Th ' i
230Th __L
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Inventory of Radiological Methodologies
Appendix D: Tables of Radioanalysis Parameters
Americium 81
Bismuth 82
Carbon 83
Cesium 84
Cobalt 85
Hydrogen (Tritium) 86
Iodine 87
Iridium 88
Lead 89
Nickel 90
Phosphorus 91
Plutonium 92
Radium 93
Strontium 94
Sulfur 95
Technetium 96
Thorium 97
Uranium 98
The following tables identify many analytical parameters for the radionuclides discussed in this
document. The column labeled "Typical MDC" refers to minimum detectable values that can
reasonably be achieved with each type of instrument based on the listed sample size and count
time. Other factors, such as instrument efficiency and detector background, play an important part
in what the lowest achievable detection level will be with a particular instrument. Note that the
values listed in these tables as "Typical MDC" are below any required MDC values that may be
listed by EPA.
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Inventory of Radiological Methodologies
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Inventory of Radiological Methodologies
Appendix E: Nuclear Power Plant Decommissioning Sites
The decommissioning of commercial nuclear power facilities, and the required radionuclide analyses
for that specific process, are regulated by the Nuclear Regulatory Commission. However, for
completeness, this appendix provides an overview of issues associated with nuclear power facilities.
The radionuclides found at these sites will be products of nuclear fission and nuclear activation.
Table 12 identifies the most commonly encountered radionuclides at these sites.
Since the 1970s, 20 major commercial nuclear power plants (NPPs) throughout the country have
shut down and are in various stages of decommissioning, including SAFSTOR. SAFSTOR is a
decommissioning process in which the nuclear facility is placed and maintained in such a condition
that the nuclear facility can be safely stored and subsequently decontaminated to levels that permit
release for unrestricted use. These nuclear power stations use boiling water reactors (BWR),
pressurized water reactors (PWR), or high-temperature gas-cooled reactors (HTGR). Table 11 lists
the NPPs currently under some stage of decommissioning.
TABLE 11 — Decommissioning status for shut-down power reactors
Reactor Type
Indian Point I
PWR
Thermal
Power
615 MW
Dresden I j BWR 700 MW
Fermi I Fast Breeder , 200 MW
GE VBWR ^BWR ^50 MW
Yankee Rowe PWR ^600 MW
CVTR
Pressure
Tube, Heavy
Water
Big Rock Point BWR
Pathfinder
Superheat
BWR
65 MW
67 MW
190MW
Humboldt Bay 3 BWR 200 MW
Peach Bottom I
San Onofre I
Haddam Neck
Fort St. Vrain
Millstone I
Zion I
Zion 2
Maine Yankee
Rancho Seco
Three Mile Island 2
HTGR hlSMW
PWR
1347 MW
PWR ]T825 MW
HTGR
842 MW
BWR H2011MW
PWR j 3250 MW
PWR
PWR
3250 MW
2772 MW
PWR \ 2772 MW
PWR ~~(~2772 MW
Saxton PWR 28 MW
t
Shoreham
BWR
Trojan j PWR
LaCrosse BWR
2436 MW
3411 MW
165 MW
Location
Buchanan, NY
Morris, IL
Monroe Co., MI
Alameda Co., CA
Franklin Co., MA
Parr, SC
Charlevoix, MI
Sioux Falls, SD
Eureka, CA
York Co., PA ~l
San Clemente, CA
Haddam Neck, CT
Platteville, CO
iWaterford, CT
Zion, IL
rZion, IL
Bath, ME
Sacramento, CA
Middletown, PA
Saxton, PA
r
Suffolk Co., NY
Portland, OR
LaCrosse, WI
Shutdown
10/31/74
10/31/78
9/22/72
12/9/63
10/1/91 ^
f "
1/67
r8/97
r "
9/16/67
7/02/76
^0/31/74
11/30/92
7/22/96
8/18/89
|_
1 1/04/95
^2/98
2/98
12/96
6/7/89
3/28/79
5/72
6/28/89
11/9/92
4/30/87
o* * Fuel
Status
Onsite
SAFSTOR Yes
SAFSTOR Yes
SAFSTOR
SAFSTOR
DECON
License
Terminated
No
No
Yes
No
DECON | Yes
DECON NRC
Part 30
No
SAFSTOR 1 Yes
SAFSTOR No
DECON J Yes
DECON Yes
License ! Yes
Terminated
DECON Yes
SAFSTOR Yes
SAFSTOR
DECON
DECON
SAFSTOR*
DECON
License
Terminated
Yes
Yes
Yes
No
No
No
DECON 1 Yes
SAFSTOR ~~ T Yes
* Post-defueling monitored storage (PDMS).
99
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Inventory of Radiological Methodologies
Since 1989, most of the NPPs undergoing active decommissioning (rather than SAFSTOR) are in
the northeast, including Shoreham in New York, Yankee Rowe in Massachusetts, Maine Yankee
in Maine, and Hadden Neck and Millstone I in Connecticut. The Indian Point INPP in New York
is in SAFSTOR, and Shoreham NPP in New York has been decommissioned and its license
terminated.
Most NPPs undergoing decommissioning will follow the guidance in the Multi-Agency Radiation
Survey and Site Investigation Manual (MARSSIM, 2000) and perform a site characterization study.
Site characterization combines the information gathered during a historical site assessment (HSA)
and radiation surveys or sampling of the various affected and unaffected areas of the site. The
purpose of a HSA is to identify:
The radionuclides generated or used at the site during its operation and any potential residual
contamination by these radionuclides;
Potentially contaminated areas; and
Potentially contaminated media, including buildings, surface and ground water, surface and
subsurface soil/media, and sediment.
The decommissioning process involves the dismantling and disposal of the NPP by component and
structure, the transfer of the spent fuel to interim storage facilities, the cleanup of residual surface
and subsurface contamination onsite and cleanup of offsite contamination from previous operations,
and the decommissioning process.
The nuclides that may be found at nuclear power stations undergoing decommissioning include the
fission and activation products generated during the operation of the plant. The nuclides found
depend on the type of reactor, fuel components, and the time interval to initiate the decommissioning
process after the plant is shut down. For example, the nuclides and their activity levels generated in
a HTGR are very different than those generated by a BWR or PWR. In addition, certain radionuc-
lides are more prevalent in PWR than BWR, and even within a reactor type, certain nuclides may
be characteristic to specific fuel components, e.g., 108mAg and 110mAg for a PWR.
In most cases, NPP personnel will have knowledge of the nuclides present onsite and in the environ-
ment as a result of power generation operations. Usually a detailed nuclide characterization of the
radioactivity onsite is determined as a result of requirements to meet 10 CFR 61 for waste disposal
of materials from various waste streams in a NPP and 10 CFR 50 for effluent monitoring
requirements. Regulations codified at 10 CFR 61 require the quantification of the most active
radionuclides as well as the hard-to-detect (difficult-to-measure), long-lived, pure alpha and beta
nuclides for each identified waste stream, e.g., primary coolant, primary cleanup components such
as filters and resins, crud, dry active waste, and metal components. The former category includes
the gamma-ray emitting nuclides having a half-life greater than 0.1 years. Table 12 provides a listing
of the nuclides requiring quantification, their physical characteristics, the required detection limits
to be met during analyses and the typical techniques for detection and chemical yield determination.
For these "Part 61" measurements, scaling factors (based on the activity ratios) are calculated
between the easier to detect gamma emitting nuclides and the hard-to-detect nuclides.
During operations and maintenance of a nuclear plant, there is a potential for the dispersion of radio-
active materials onsite, and in some cases, for subsurface dispersion from leaking tanks or piping
or spills. In addition, normal liquid effluent releases can result in the buildup of certain longer-lived
100
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Inventory of Radiological Methodologies
radionuclides in the sediment of rivers, reservoirs or impoundments. During the decommissioning
process involving the dismantlement and transfer of highly radioactive structures (component of the
reactor, reactor vessel, pressurizers, primary coolant piping and valves, spent fuel pool and fuel
transfer areas, and structural support materials), there may be a possibility that radioactive materials
may spread to other areas of the site or to the offsite environs.
TABLE 12 — Important parameters associated with NPP analyses
Half-life
Nuclide (year)
y Emitters >0.1
3H 12.3
14C I 5,730
55FeJ 2.7
59Ni 75,000
63Ni 100
90Sr P 28.6
94NbJ 20,300
"Tc T 2.13 x 105
ml 1.57xl07
237Np} 2.14 x 10"
23KPu _L 87-8
239Pu 24,100
240Pu _[ 6,570
241Pu 14.4
242Pu 3.76x 105
L
241Am 432
243Am 7,380
242CmJ _[ 0.446
243Cnr 28.5
'""Cm* L 18.1
Radiation Emitted
(keV)*
r" "
y( 100 -2000)
r
P(18.6)
,
Detection
Technique1
Ge detector - y
spectrometry
LS
MDC ^ Chemical Yield
(nCi/g) Determination
137Cs: 10,
others: 7,000
400
P(156) LS J 80
X-Ray (5.89)
f
X-Ray (6.92)
f P (65.9)
Low-energy Ge/Si,
LS
Low-energy Ge/Si,
LS
LS
7,000
2,200
35
P(546) n GP, Cerenkov - LS 0.4
P(471), y(703, 871)
[ P (294)
r ~ "
P (152), 7(39.6)
a (477 1,4788),
y(86.5, 29.4)
f_ a (5436, 5499)
Ge detector - y
spectrometry
GP, LS 30
Low-energy Ge/Si,
LS, GP
a spectrometry
"
0.8
No chemical
separation — direct
measurement
No chemical
separation — direct
measurement
Gravimetric
ICP, AA
!_
ICP, AA
ICP, AA
u Gravimetric, 85Sr
ICP
99mTc, Re (ICP-MS)
Gravimetric
1 239Np
1 i Pu or Pu
r~ a(5105, 5143, ]
-.,,, I a spectrometry
3 1 ->->) J
a(5123, 5168) a spectrometry
1
236pu or 242pu
i ">36T-» "M2T1
1 , Pu or Pu
0(20.8) LS T 35 ^
a (4856, 4901)
a (5443, 5485),
7(59)
a (5234, 5279),
7(74.7)
a spectrometry
I r J
a spectrometry, y
spectrometry
1
-
a spectrometry, y \
spectrometry
a (6069, 6113) _|_ a spectrometry 1
a (5742, 5784), a spectrometry, y
y(228, 278) _j_ spectrometry
1
a (5763, 5805) a spectrometry 1
23(,pu Qr 242pu
243Am
—
243 Am
243 Am
243Am
* For beta emitters, column refers to maximum energy.
f LS - liquid scintillation, Ge - germanium semiconductor, Si - silicon semiconductor, GP - gas proportional counting,
ICP - inductively coupled plasma analysis, ICP-MS - inductively coupled plasma-mass spectrometry, AA - atomic
absorption
|These radionuclides are included in this table for completeness, but are not discussed in this document.
The information gained from the 10 CFR 61 analyses (scaling factors) may be used to estimate the
levels of the hard-to-detect radionuclides in contaminated materials, subsurface soils or ground
101
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Inventory of Radiological Methodologies
water. If hard-to-detect radionuclides are suspected for a given waste discharge or contamination
process, the easier-to-detect gamma-emitting nuclides are quantified, and then the hard-to-detect
nuclides are estimated from applying the scaling factors or analyzed at an offsite contract laboratory
that can provide the required detection capability.
The primary gamma-ray emitting nuclides found at most NPPs undergoing decommissioning include
60Co, 134Cs, '"Cs, 152Eu, 154Eu, and 155Eu. If decommissioning is initiated within a few years after
plant shutdown, 54Mn, 65Zn, and 57Co may be present in sufficient quantities to be detected by
gamma-ray spectrometry. NRC (1978 and 1984) list the radionuclides existing in concrete, rebar,
and surface contamination.
102
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