&EPA
United States
Environmental Protection
Agency
Office of Radiation and Indoor Air
National Air and Radiation
Environmental Laboratory
EPA 402-R-12-007
August 2012
www.epa.gov/narel
Uses of Field and Laboratory
Measurements During a
Radiological or Nuclear Incident
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EPA 402-R-12-007
www.epa.gov/narel
August 2012
Revision 0
Uses of Field and Laboratory
Measurements During a
Radiological or Nuclear Incident
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
F^nsed Ktith Ssy.i'Canola hk on papec t
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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-03-038, work
assignment 35, and EP-W-07-037, work assignments B-33 and 1-33, all managed by David Carman and
Dan Askren. Mention of trade names or specific applications does not imply endorsement or acceptance by
EPA.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
PREFACE
In the aftermath of a major release of radioactivity to the environment, such as the detonation of
multiple radiological dispersal devices ("RDDs" or "dirty bombs") or an improvised nuclear
device (IND), hundreds of thousands of environmental samples will be collected and analyzed
during the first year. In addition, a large number of field measurements will be made following a
major radiological or nuclear incident. Immediately following the initial response, many of the
cleanup and response decisions will be based on the results of measurements made with hand-
held or field-portable equipment while others will require collection of individual samples from
various media and surfaces for analysis at radiochemistry laboratories. This document describes
the interrelationship among field and laboratory radiological analytical measurements, their
respective advantages and disadvantages, and the planning and analytical considerations
necessary to obtain data of known and defensible quality for use by decisionmakers, primarily
during the recovery phase. Key to this understanding is the metrological concept of measurement
uncertainty. Both field and laboratory measurements will play significant and complementary
roles during the recovery operations and subsequent cleanup. This guide is intended to provide
decisionmakers, response and remediation managers, and field and laboratory personnel with the
necessary understanding to obtain technically adequate and defensible data in a timely and
effective manner.
The need to ensure adequate laboratory infrastructure to support response and recovery actions
following a major radiological or nuclear incident has been recognized by a number of federal
agencies. The Integrated Consortium of Laboratory Networks (ICLN), created in 2005 by 10
federal agencies,1 consists of existing laboratory networks across the federal government. The
ICLN is designed to provide a national infrastructure with a coordinated and operational system
of laboratory networks that provide timely, high-quality, and interpretable results for early
detection and effective consequence management of acts of terrorism and other events requiring
an integrated laboratory response. It also designates responsible federal agencies (RFAs) to
provide laboratory support for chemical, biological, and radiological agents across all of the
response phases. To meet its RFA responsibilities for environmental samples, the U.S.
Environmental Protection Agency (EPA) has established the Environmental Response
Laboratory Network (ERLN) to address chemical, biological, and radiological threats. For
radiological agents, EPA is the RFA for monitoring, surveillance, and remediation, and will
share responsibility for overall incident response with the U.S. Department of Energy (DOE). As
part of the ERLN, EPA's Office of Radiation and Indoor Air is leading an initiative to develop
tools and training to aide environmental radiological laboratories in the role of supporting
cleanup and remediation activities following a major radiological or nuclear incident.
EPA's responsibilities following a major radiological or nuclear incident, such as a terrorist
attack, include response and recovery actions to detect and identify radioactive substances and to
coordinate federal radiological monitoring and assessment activities. This document was
developed to provide guidance to those who will support EPA's response and recovery actions
following a radiological or nuclear incident.
1 Departments of Agriculture, Commerce, Defense, Energy, Health and Human Services, Homeland Security,
Interior, Justice, and State, and the U.S. Environmental Protection Agency.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
The use of procedures, developed in advance, for performing field and laboratory measurements
to assess radioactivity levels of samples that contain significant quantities of radioactive
materials will ensure that the radioanalytical data produced will be of known quality and
appropriate for the intended incident response decisions. This guide will provide perspectives
that may help field and laboratory personnel have confidence that their measurements of
radiation and radioactivity will be of adequate quality to support cleanup decisionmaking.
As with any technical endeavor, a radiological or nuclear incident may necessitate use of
particular methods or techniques to address specific data quality objectives and measurement
quality objectives. This document does not catalog analytical methodologies or radionuclides,
nor does it intend to prescribe or preclude the use of particular methodologies as long as
protocols selected satisfy incident-specific data quality objectives and measurement quality
objectives. A list of radionuclide-specific methods to support response and recovery actions
following a radiological or nuclear incident can be found in Standardized Analytical Methods for
Environmental Restoration Following Homeland Security Events - SAM 2010 (EPA 2010).
Detailed guidance on recommended laboratory radioanalytical practices may be found in the
Multi-Agency Radiological Laboratory Analytical Protocols Manual (MARLAP 2004), which
provides detailed radioanalytical guidance for project planners, managers, and radioanalytical
personnel based on project-specific requirements. Additional guidance may be found in the
Multi-Agency Radiation Survey and Assessment of Materials and Equipment Manual
(MARSAME 2009).
9
This document is one in a planned series designed to present radioanalytical laboratory
personnel, Incident Commanders, and other field response personnel with key laboratory
operational considerations and likely radioanalytical requirements, decision paths, and default
data quality and measurement quality objectives for samples taken after a radiological or nuclear
incident, including incidents caused by a terrorist attack. Companion guides published or in
preparation include:
Radiological Laboratory Sample Analysis Guide for Incidents of National Significance -
Radionuclides in Water (EPA 402-R-07-007, January 2008)
Radiological Laboratory Sample Analysis Guide for Incidents of National Significance -
Radionuclides in Air (EPA 402-R-09-007, June 2009)
Radiological Laboratory Sample Screening Analysis Guide for Incidents of National
Significance (EPA 402-R-09-008, June 2009)
Method Validation Guide for Qualifying Methods Used by Radiological Laboratories
Participating in Incident Response Activities (EPA 402-R-09-006, June 2009)
Guide for Laboratories - Identification, Preparation, and Implementation of Core
Operations for Radiological or Nuclear Incident Response (EPA 402-R-10-002, June 2010)
A Performance-Based Approach to the Use of Swipe Samples in Response to a Radiological
or Nuclear Incident (EPA 600/R-l 1/122, October 2011)
All the documents in this series are available at www.epa.gov/erln/radiation.html and at
www.epa. gov/narel/incident guides.html.
11
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Guide for Radiological Laboratories for the Control of Radioactive Contamination and
Radiation Exposure (EPA 402-R-12-005, August 2012)
Radiological Laboratory Sample Analysis Guide for Radiological or Nuclear Incidents -
Radionuclides in Soil (EPA 402-R-12-006, September 2012)
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
in
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
ACKNOWLEDGMENTS
This guide was developed by the National Air and Radiation Environmental Laboratory
(NAREL) of EPA's Office of Radiation and Indoor Air (ORIA). Dr. John Griggs was the 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 Ms.
Schatzi Fitz-James, Office of Emergency Management, Homeland Security Laboratory Response
Center; and Mr. David Garman, ORIA/NAREL. We also wish to acknowledge the external peer
reviews conducted by Mr. Edward Walker and other external reviewers, whose thoughtful
comments contributed greatly to the understanding and quality of the report. Numerous other
individuals inside EPA provided internal peer reviews of this document, and their suggestions
contributed greatly to the quality and consistency of the final document. Technical support was
provided by Mr. Robert Shannon , Dr. N. Jay Bassin, Dr. Anna Berne, Mr. David Burns, Dr. Carl
V. Gogolak, Dr. Robert Litman, and Dr. David McCurdy of Environmental Management
Support, Inc.
DEDICATION
This report is dedicated to the memory of our friend and colleague, David Garman. Dave
administered nearly three dozen separate contracted radiochemistry projects for EPA dating back
nearly 17 years, beginning with the Multi-Agency Radiological Laboratory Analytical Protocols
(MARLAP) in 1994. Dave put up with countless changes of prime contractors, priorities,
subcontractors, and budgets, all with good cheer, diligence, and all while keeping up with his
"day job" as counting room lead for alpha-spectrometry analysis at NAREL.
Dave started with EPA's National Air and Radiation Laboratory in 1992. He left many friends
throughout EPA and the radioanalytical community, and he will be greatly missed.
IV
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
CONTENTS
Acronyms, Abbreviations, Units, and Symbols vii
Radiometric and General Unit Conversions x
1. Scope and Purpose 1
2. Introduction 2
3. Impact of Source Term and Measurement Conditions on MQOs and Selection of
Measurement Technologies 5
3.1 The Impact of Source-Term Radionuclides on Measurement Approach 5
3.2 Key Concepts: Surface Contamination vs. Volumetric Contamination 6
3.3 Impact of Ambient and Intrinsic Background on Measurements of Radioactivity 7
3.4 Applying the Directed Planning Process to Radionuclide Measurements 9
3.4.1 Action Levels for Incident Response 9
3.4.2 Data Quality Objectives Process 10
4. Metrology, Quality Systems, and QA/QC 15
4.1 Why is Metrology Important? 15
4.2 The Principles of Metrology 16
4.3 Quality Systems 17
4.4 Quality Systems Standards - Quality Assurance and Quality Control of Measurement
Systems 17
4.4.1 Quality Systems Standards, QA and QC for Field Measurements 18
4.4.2 Quality Systems Standards, QA and QC for Laboratory Measurements 21
4.5 Quality Assurance Project Plan 24
4.6 Uncertainty Estimates and the Measurement Process 24
4.6.1 Uncertainty Estimates and Field Measurements 25
4.6.2 Uncertainty Estimates and Laboratory Measurements 26
5. Considerations on the Capabilities and Limitations of Radioanalytical Measurement
Techniques in the Field and Laboratory 27
5.1 The Impact of Background Radiation on Radioanalytical Measurements 27
5.1.1 The Impact of Background Radiation on Field Measurements 27
5.1.2 The Impact of Background Radiation on Laboratory Measurements 31
5.2 Types of Measurements of Radioactivity 32
5.2.1 General Considerations Regarding Field Measurements 33
5.2.2 General Considerations Regarding Laboratory Measurements 41
5.3 The Effect of Measurement Geometry on Detector Calibration 46
5.3.1 Measurement Geometry and Field Survey Instrument Calibrations 47
5.3.2 Measurement Geometry and Field Spectrometry Measurements 49
5.3.3 Measurement Geometry and Laboratory Survey and Gross Activity Measurements
50
5.3.4 Measurement Geometry and Laboratory Spectrometry Measurements 51
6. Comparison and Applicability of Field and Laboratory Measurements 52
7. Conclusions 61
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
7.1 Conclusions and Recommendations Generally Applicable to Field and Laboratory
Measurements 61
7.2 Conclusions and Recommendations Specific to Field Measurements 62
7.3 Conclusions and Recommendations Specific to Laboratory Measurements 63
7.4 Summary 64
8. References 64
Appendix I: Case Study on the Use of Field Spectrometry Instruments for Remediation at
Rocky Flats Environmental Technology Site (RFETS) 69
Appendix II: Applicability of Selected Field and Laboratory Measurement Techniques 73
Appendix III: Example Scenarios: Approaches to Integrating Field and Laboratory
Measurements During Response to a Radiological or Nuclear Incident 80
FIGURES
Figure 1 -Uncontrolled Decision Error at the AAL 13
Figure 2 - Controlling the Probability of Decision Errors with the ADL and WMR 14
TABLES
Table 1 - Comparison of Non-Spectrometric Field and Laboratory Measurements of
Surficially Deposited Activity 54
Table 2 - Comparison of Non-Spectrometric Field and Laboratory Measurements for
Volumetrically Deposited Activity 56
Table 3 - Comparison of Spectrometric Field and Laboratory Measurements for Surficially
Deposited Activity 58
Table 4 - Comparison of Attributes of Spectrometric Field and Laboratory Measurements for
Volumetrically Deposited Activity 60
Table 5 - Applicability of Selected Field Measurement Techniques for In Situ Measurements
of Surface Activity / Concentrations of Radionuclides 76
Table 6 - Applicability of Selected Field Measurement Techniques for In Situ Measurements
of Volumetric Activity / Concentrations of Radionuclides 77
Table 7 - Applicability of Selected Laboratory Measurement Techniques for Determining
Activity / Concentrations of Radionuclides 78
Table 8 - Summary of Measurements for Scenario #1 82
Table 9 - Summary of Measurements for Scenario #2 85
Table 10 - Summary of Measurements for Scenario #3 87
Table 11 - Summary of Measurements for Scenario #4 89
Table 12 - Summary of Number of Scenario Measurements by Nuclide, Measurement Status,
and Detection Status and Test 90
VI
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Acronyms, Abbreviations, Units, and Symbols
(Excluding chemical symbols and formulas)
a alpha particle
a probability of a Type I decision error
AAL analytical action level
ADL analytical decision level
ANSI American National Standards Institute
ASTM American Society for Testing and Materials
P beta particle
ft probability of a Type II decision error
BEGe broad energy germanium [detector]
Bq becquerel (1 dps)
CDC Centers for Disease Control and Prevention
CFR Code of Federal Regulations
Ci curie
cm centimeter
cpm counts per minute
CRCPD Conference of Radiation Control Program Directors
D&D decontamination and decommissioning
DHS United States Department of Homeland Security
DL discrimination level
DOD United States Department of Defense
DOE United States Department of Energy
DOECAP Department of Energy Consolidated Audit Program
DOT United States Department of Transportation
dpm disintegration per minute
dps disintegration per second (Bq)
DQO data quality objective
8 electron capture
EPA United States Environmental Protection Agency
ERLN Environmental Response Laboratory Network
FDA United States Food and Drug Administration
FIDLER Field Instrument for the Detection of Low-Energy Radiation
FSMO Field Sampling and Measurement Organization
y gamma ray
g gram
GIS geographic information system
G-M Geiger-Miiller [detector]
GUM Guide to the Expression of Uncertainty in Measurement
h hour
HPGe high purity germanium [detector]
HVAC heating, ventilation, air conditioning [system]
1C Incident Commander
ICLN Integrated Consortium of Laboratory Networks
ICRU International Commission on Radiation Units and Measurements
vn
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
LEG International Electrotechnical Committee
IND improvised nuclear device (i.e., a nuclear bomb)
ISGS in situ gamma spectrometry
ISO International Organization for Standardization
ISOCS In-Situ Object Counting System
k coverage factor
keV kiloelectronvolt (103 electronvolt)
L liter
LSC liquid scintillation counting/counter
m meter
MARLAP Multi-Agency Radiological Laboratory Analytical Protocols [Manual]
MARSAME Multi-Agency Radiation Survey and Assessment of Materials and Equipment
[Manual]
MARS SIM Multi-Agency Radiation Survey and Site Investigation Manual
MDC minimum detectable concentration
MeV megaelectronvolt (106 electronvolt)
uCi microcurie (10 6 Ci)
ug microgram (1CT9 kilogram)
min minute
MQO measurement quality obj ective
mrad millirad (1CT3 rad)
mrem millirem (1CT3 rem)
Nal(Tl) (thallium-activated) sodium iodide [detector]
NAREL National Air and Radiation Environmental Laboratory
nCi nanocurie (10 9 Ci)
NCRP National Council on Radiation Protection and Measurements
NELAC National Environmental Laboratory Accreditation Conference
NIST National Institute of Standards and Technology
NRC United States Nuclear Regulatory Commission
ORIA Office of Radiation and Indoor Air
PAG Protective Action Guide
1 9
pCi picocurie (10" Ci)
PT proficiency testing
QA quality assurance
QAPP quality assurance proj ect plan
QC quality control
QSAS Quality Systems for Analytical Services
RCRA Resource Conservation and Recovery Act
ROD radiological dispersal device (i.e., "dirty bomb")
rem roentgen equivalent: man
RFA responsible federal agency
RFETS Rocky Flats Environmental Technology Site
s second
SI International System of Units
SOP standard operating procedure
SRM standard reference material
Vlll
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Sv sievert
TNI The NELAC Institute
WMR required method uncertainty
V&V verification and validation
ZnS [silver activated] zinc sulfide [detector]
IX
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Radiometric and General Unit Conversions
To Convert
years (y)
disintegrations per
second (dps)
Bq
Bq/kg
Bq/m3
Bq/m3
microcuries per
milliliter ((iCi/mL)
disintegrations per
minute (dpm)
cubic feet (ft3)
gallons (gal)
Gray (Gy)
roentgen equivalent
man (rem)
To
seconds (s)
minutes (min)
hours (h)
days (d)
becquerels (Bq)
picocuries (pCi)
pCi/g
pCi/L
Bq/L
pCi/L
jiCi
pCi
cubic meters (m3)
liters (L)
rad
sievert (Sv)
Multiply by
3.16xl07
5.26xl05
8.77xl03
3.65xl02
1
27.0
2.70xl(T2
2.70xl(T2
1(T3
109
4.50xlO~7
4.50X10"1
2.83xlO~2
3.78
102
io-2
To Convert
s
min
h
d
Bq
pCi
pCi/g
pCi/L
Bq/L
pCi/L
pCi
jiCi
m3
L
rad
Sv
To
y
dps
Bq
Bq/kg
Bq/m3
Bq/m3
(iCi/mL
dpm
ft3
gal
Gy
rem
Multiply by
3.17xl(T8
1.90xl(T6
1.14x10^
2.74xlO~3
1
3.70xl(T2
37.0
37.0
IO3
io-9
2.22
2.22xl06
35.3
0.264
io-2
IO2
NOTE: Traditional units are used throughout this document instead of the International System of
Units (SI). Protective Action Guides (PAGs) and their derived concentrations appear in official
documents in the traditional units and are in common usage. Conversion to SI units will be aided
by the unit conversions in this table.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
1. Scope and Purpose
This document explains the importance and interrelationship of field and laboratory measure-
ments following a radiological or nuclear incident. Understanding and delineating the purpose of
each field or laboratory measurement process, and implementing the measurements in a
controlled, well-documented manner, are critical to ensure that data generated in response to a
radiological or nuclear incident in the field and in the laboratory are both technically and legally
defensible.
Section 2 provides a foundation for subsequent discussion of the document by discussing the
radionuclide(s) contaminants associated with a radiological or nuclear incident and the manner in
which they are deposited. These are critical elements to consider when determining which field
and lab measurement techniques (or combinations of the two) can most effectively be used to
address measurement challenges associated with an incident.
Section 3 of the document addresses key considerations for project planning. Measurement
quality objectives (MQOs) must be developed for the contaminant(s) of concern to ensure that
the measurement methods selected will be able to reliably meet project data quality objectives
(DQOs). Once the analytical requirements have been established and appropriate measurement
technologies identified, measurements can be carried out.
Section 4 addresses the importance of the fundamental principles of metrology to ensure that
measurements will be traceable to national standards and reported in association with defensible
estimates of uncertainty. It also discusses the need for a quality systems approach to ensure that
measurements are conducted in a controlled manner using validated methods, by trained,
qualified personnel, and that all analytical operations are well-documented to preserve their
defensibility over time.
Section 5 of the document identifies the respective capabilities and limitations of field and
laboratory measurement techniques and attempts to demonstrate the complementary nature of the
two during the days and months following an incident. Factors impacting calibrations and
background corrections are addressed in this section.
Section 6 contains tables that summarize and compare the respective strengths and limitations of
laboratory and field measurements for different types of radionuclides and measurement
conditions. Section 7 provides conclusions and recommendations for field and laboratory
measurements as well as an overall summary of this document.
Three appendices follow the main body of the document. Appendix I presents a case study of
how in situ gamma spectrometry (ISGS) was used during the decontamination and
decommissioning (D&D) of the Rocky Flats Environmental Technology Site. The tables in
Appendix II show the applicability of a number of different instrument types for measurement of
a list of radionuclides and activity levels. Finally, Appendix III uses several scenarios to explore
how the DQO/MQO process can be applied to field and laboratory measurements, and
demonstrates how field and laboratory measurements can be used in a complementary manner
during a response to a radiological or nuclear incident.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
While most of the material in this document applies to all phases of an incident, the primary
focus of the document will be the recovery phase, because this phase is EPA's primary
responsibility.
2. Introduction
Immediately following a radiological or nuclear incident, prompt feedback of real-time
measurement results will be crucial in supporting decisions regarding the health and safety of the
public. Field measurements used for this assessment will be invaluable because they provide
real-time data to decisionmakers for determining the presence of a general hazard, and whether
or not the radiation exposure poses an imminent danger.
During the initial phase of an incident, responsible agencies and first responders must determine
the following as rapidly as possible:
Radionuclide(s) in the source device;
Levels of gross activity present on contaminated surfaces, and in the air, water, soil, and
other potentially contaminated areas, items or media;
Extent of the areas affected by contamination;
Levels of radiation exposure; and
What actions may be required based on Protective Action Guides (PAGs).
Estimates of the number of laboratory samples required and the expected time frame to respond
to a radiological dispersal device (RDD or dirty bomb) incident have been developed based on
White House Security Council Planning Scenario #11.3 These assessments conclude that,
following a single incident in one metropolitan area with only one radionuclide (regardless of the
radiation emission type from this radionuclide), well over 350,000 measurements would be
required within a one-year period. More information on this scenario can be found in EPA's
Assessment of Nationwide Laboratory Surge Capacity Required to Support Decontamination of
Chemical, Biological and Radiochemical-nuclear Agents (ICLN 2007) and The Current Gap in
Environmental Radioanalytical Laboratory Capacity.4
The responsibilities of various federal, state, and local agencies to address the possible health and
environmental consequences of a radiological or nuclear incident properly fall at different times
in the recognized timeline of an incident. These agencies (e.g., the Department of Homeland
Security (DHS), Food and Drug Administration (FDA), Centers for Disease Control and
Prevention (CDC), Department of Energy (DOE), EPA, state and local government) must
respond with technologies that are appropriate to their missions and responsibilities.
From the radioanalytical perspective, an RDD scenario involving a single gamma-emitting
radionuclide is perhaps the simplest scenario possible. Measurements in the field and in the
laboratory become more complicated when a mixture of alpha, beta, or gamma emitters, or pure
1 http://cees.tamiu.edu/covertheborder/TOOLS/NationalPlanningSen.pdf
lThe Current Ga\
currently in draft.
4The Current Gap in Environmental Radioanalytical Laboratory Capacity, prepared for EPA in March 2007,
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
alpha- or beta-emitting radionuclides are present. The destructive capability and radiological
impact of an improvised nuclear device (IND) would be considerably greater than that from an
RDD. Despite differences in the magnitude of the event, either of these scenarios would quickly
overwhelm resources in the field and at laboratories, making optimal use of all available
resources essential.
Samples resulting from any radiological or nuclear incident will consist of a variety of matrices
and will originate from different geographic locations and environmental conditions. The data
quality objectives and measurement quality objectives5 for an incident will be tailored to the
phase of the incident and will address issues specific to the radionuclides and matrices of
concern, and the locations and environmental conditions in and beyond areas directly impacted
by the event. For example, measurements of building surfaces in the early phase would be
expected to focus primarily on detecting levels of radioactivity that could result in short-term
exposures in excess of levels stipulated by protective action guides.
As the event progresses into the intermediate and recovery phases, efforts will shift toward
identifying progressively lower levels of contamination. Large areas will need to be quickly
characterized and cleared for longer-term use and habitation. Accordingly, the DQOs and MQOs
needed to support decisionmaking will become increasingly more demanding of analytical
measurements. A number of methods may be available for measuring radionuclides and their
radioactive emissions. The methods selected must be capable of reliably meeting the established
MQOs (i.e., a performance-based approach). This includes selecting and validating appropriate
techniques for sampling and analysis.
Measurements using field instruments will likely predominate in the earlier stages of an incident
when preliminary estimates of the type of radiation and activity levels present must be rapidly
determined so that protective actions can be implemented effectively and without delay. Early
measurements may not be radionuclide-specific or even capable of reliably detecting
radionuclides with weakly penetrating radiations. Field crews also may need to gather samples
and send them to radiochemistry laboratories for rapid, unambiguous confirmation of field
measurements when these have high or unknown levels of uncertainty. Radiochemistry
laboratories also may be called on to provide sensitive and accurate measurements of specific
radionuclides in order to meet measurement quality objectives for detection capability and
uncertainty needed to support decisionmaking by the Incident Commander (1C) or designee.
Following the initial response phase of the incident, EPA, at a minimum, will be responsible for:
Delineating the ultimate extent of contamination;
Assessing potential doses from various exposure pathways where low-level radioactive
contamination persists;
5"Data quality objectives (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. ... Measurement Quality Objectives (MQOs) can be viewed
as the analytical portion of the DQOs and are therefore project-specific." [MARLAP (2004), Section 1.4.9] See also
Section 4 of this document for further discussion of the directed planning process.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Reassuring the public that facilities, property, or homes have been decontaminated
effectively;
Determining that the disposition of contaminated equipment, materials, environmental
matrices, or facilities has been correctly and safely performed; and
Conducting ongoing monitoring.
Field measurements are valuable as they will be used to guide the process of exposure control
and remediation on a timely basis, especially in the earlier phases of an incident. As the response
to the incident progresses through the intermediate and recovery phases, action levels will
become progressively lower as decisions are based on longer-term goals. There will be a need for
increasingly sensitive, accurate, and radionuclide-specific analyses, and expectations for
stringent measurement quality will increase accordingly. Laboratory determinations will be
needed to provide critically needed measurement capabilities and capacity.
Throughout the incident response, quality systems are needed to provide the framework for
quality assurance and quality control (QA/QC) programs. Properly implemented quality systems
will provide the basis for defensible and informed decisionmaking under the stressful conditions
that will be encountered during an incident response. Integrated internal QC measures and
external measurement intercomparisons will demonstrate and document that measurements meet
established MQOs. Management structures and independent internal and external quality
oversight will ensure that the quality system is being implemented consistently and adequately.
All measurement techniques will be validated, and testing will be performed only by adequately
qualified and trained analysts following documented procedures.
Quality systems for laboratories have been addressed in detail by consensus standards
development organizations. Standards include documents such as ISO 17025 (International
Organization for Standardization [ISO]/ International Electrotechnical Committee [IEC] 2005)
and The National Environmental Laboratory Accreditation Conference (NELAC) Institute (TNI)
Standard (NELAC, 2003). Although the TNI Standard theoretically applies to field sampling and
measurement organizations, quality systems and associated certification and accreditation
programs have just begun to be implemented on a limited scope for several field parameters
(TNI 2007).
In March 2011, EPA's Forum on Environmental Measurements directed that "...organizations
(e.g., laboratories, field sampling and measurement) generating environmental data through
measurement under Agency-funded acquisitions must submit documentation of their
competency, which may include participation in applicable certification and/or accreditation
programs." At present, however, this directive has yet to be generally applied to measurements
of radioactivity in the field. As such efforts proceed, however, similar levels of data quality may
be expected of measurements from laboratory and field sampling and measurement organizations
(EPA 2011 a).6
6"Laboratories that perform field sample analysis are required to comply with rigorous quality systems standards.
Compliance with such standards provides the basis for accreditation by state regulatory agencies. Yet similar
standards do not exist for all field activities. Organizations conducting these activities are not required to meet a
quality system standard, do not need an accreditation for the work being performed and rarely are subjected to
routine oversight inspections. This inconsistency jeopardizes data usability and compromises the overall objective of
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Finally, field and laboratory measurements need to be coordinated in a manner that will ensure
that appropriate decisions can be made based on the phase of the incident and the action levels
and concentrations of the radionuclides that need to be analyzed. The abilities and strengths of
the various types of field measurements coupled with laboratory measurements are explored
further in this document.
3. Impact of Source Term and Measurement Conditions on MQOs and Selection of
Measurement Technologies
The source-term radionuclides for a nuclear or radiological incident will have a significant
impact on the most effective measurement approaches used following an incident. For example,
the RDD incident described in White House Security Council Planning Scenario #11 involves a
single, medium-energy, beta-gamma-emitting radionuclide that emits gamma radiation readily
amenable to non-destructive field radioassay techniques. Medium- to high-energy gamma rays
penetrate through matrix materials to produce a characteristic gamma ray signature, thus largely
eliminating the need for extensive laboratory work for the qualitative identification of gamma
emitters that may be present. When gamma-emitting contamination is deposited on the surface of
objects, field instrumentation techniques are capable of generating data that can be used for
defensible incident response decisionmaking. Thus, 137Cs represents a best-case radionuclide
from the standpoint of rapid and reliable measurement and remediation since responders can
most effectively utilize non-destructive field radioassay techniques. In the case of pure alpha,
beta, or low-energy gamma emitters, the selection of viable field measurement alternatives is
more limited, and laboratory analysis may be needed to provide data of sufficient quality for
decisionmaking, especially for lower activity measurements in the later phases of an event.
3.1 The Impact of Source-Term Radionuclides on Measurement Approach
When planning measurement approaches that will be used to respond to an incident, it is
important to consider that other less optimal, yet likely, scenarios are possible that are not
conducive to rapid, accurate field measurements. By their very nature, in situ measurements can
detect a radiation only after it is emitted from an object. The radiation may need to penetrate an
unknown amount of matter before it reaches the surface of the object, is emitted, and can be
detected. The type of radiation impacts its transmission through matter. This, together with the
depth of penetration into the object, will significantly affect the detectability of radiation emitted
from the object. Measurements of alpha and beta particles and low-energy photons that have
very short ranges in matter will almost always be subject to significant self-absorption effects,
whereas more highly penetrating, more energetic gamma rays will be less strongly attenuated
and will be more reliably detectable until the radionuclides have penetrated deeper into the
the data generation process. [...] Regulatory agencies have become sensitive to the negative impact that the absence
of an FSMO [Field Sampling and Measurement Organization] quality system standard may have on critical data.
This includes acknowledging that the quality of samples and field data that go to the laboratory is as critical to the
process as the quality of data generated by the laboratory. In response, such agencies have initiated steps to establish
quality system requirements for field sampling and measurement organizations." From: David N. Speis, Guest
Dialog: Improving Field Sampling Quality Control Pollution Engineering; August 1, 2004; Available at:
www.pollutionengineering.com/Articles/Column/63ead7de8fd68010VgnVCM100000f932a8cO.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
surface being measured. When it is known that alpha- and beta-emitting contaminants are freshly
deposited, or that they have been deposited on hard, relatively impermeable surfaces, accurate
measurements in the field are practicable. If the radionuclides have penetrated into the surface,
field measurements of alpha or beta emitters may not be possible, while accurate measurements
of medium- to high-energy gamma-emitting radionuclides are possible even when the radionuc-
lides of concern have penetrated 1-2 cm or more into the object being measured.
The physical and chemical form of each radionuclide, the matrix material, and the manner in
which a radionuclide is distributed in the matrix material will impact measurements of radiation
and radioactivity. An RDD may be constructed using radionuclides in a very insoluble,
refractory form. Extreme temperatures, pressures, and chemical and physical interactions with
surrounding materials also will affect the physical and chemical form of radionuclide(s) resulting
from the detonation of an IND or RDD. Once contaminants are deposited in the environment,
changes in the physical and chemical form of contaminants and the matrices with which they are
associated occur as contaminants weather. The depth profile of radionuclides may change if they
migrate into the matrix. Such effects will generally be more pronounced with porous matrices
such as soil since water can readily transport contaminants into the material on which they were
deposited. Field measurements may thus be complicated, especially if assumptions about self-
absorption cannot be defended without performing secondary measurements, or if varying rates
of adsorption and differential transport of source-term radionuclides limit the use of marker
nuclides to model the distribution of source-term radionuclide mixtures.
3.2 Key Concepts: Surface Contamination vs. Volumetric Contamination
Attenuation effects may interfere with accurate, non-destructive measurements of radioactivity
when contaminants are not deposited in a regular, thin layer on a smooth surface. Once
radionuclides penetrate an object, the radiation emitted may be self-absorbed by the matrix
material before it can escape the surface and be detected. When the degree of attenuation is high
or not well-known, unbiased measurements of radioactivity and reasonable estimates of
measurement uncertainty are generally not practicable, and the feasibility of field measurement
techniques for generating definitive results for decisionmaking may be limited.
The concepts of surface versus volumetric contamination have been the topic of much
discussion. A thorough understanding of these concepts and their impact on measurements of
radioactivity is key to subsequent discussions. The Multi-Agency Radiation Survey and
Assessment of Materials and Equipment Manual (MARSAME 2009) defines the two concepts as
follows:
Surficial Radioactive Material is radioactive material distributed on any of the surfaces of a
solid object. Surficial radioactive material may be either removable by non-destructive means
(such as casual contact, wiping, brushing, or washing) or fixed to the surface.
Volumetric Radioactive Material is radioactive material that is distributed throughout or
within the materials or equipment being measured, as opposed to a Surficial distribution.
Volumetric radioactive material may be homogeneously (e.g., uniformly activated metal) or
heterogeneously (e.g., activated reinforced concrete) distributed throughout the materials and
equipment (MARSAME 2009).
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
ANSI N13.12 defines surface contamination as "[rjadioactive contamination residing on or near
the surface of an item," and volume contamination as "... contamination residing in or throughout
the volume of an item." It further differentiates between the two, stating that "[v]olume
contamination can result from neutron activation or from the penetration of radioactive
contamination into cracks or interior surfaces within the interior matrix of an item" and that
surface "...contamination can be adequately quantified in units of activity per unit area" (ANSI
1999).
In an attempt to address the issue in an operationally useful manner, this guide will address the
concepts of surficial contamination or surface contamination, and that of volumetric
contamination, pragmatically. The term "surface" is used in this document when reliable
measurements of the radioactive contaminants deposited on an object are practicable. When a
reference is made to a "surface," this refers to contamination deposited in a thickness of material
near the surface of an object for which self-absorption effects are minimal enough that they do
not impart uncorrectable bias or unknown amounts of uncertainty into the measurement of
radioactivity in that surface. In contrast to this, measurements of radioactivity that are distributed
throughout the volume of an object are considered to be volumetric contamination. Depending
on the uniformity of their distribution, accurate measurements of radioactivity in that object may
or may not be practicable.
Given strictly surficial or homogenously distributed volumetric contaminants, accurate
measurements of radioactivity and estimations of measurement uncertainty are possible.
Considering the realities of contamination in the environment, permeable and rough materials
such as soil, concrete, asphalt, fabric, and wood are the rule and not the exception, and it is
generally not known how deeply into the object the radioactive material has penetrated. This
very significantly complicates accurate measurement of contamination. As time proceeds after an
incident, processes such as weathering set in, and radionuclides further permeate the materials on
which they were deposited. The depth of penetration may be such that levels of attenuation and
self-absorption are poorly predictable and that they reach a point where radioactive emissions
cannot reliably be detected at all by field measurements.
Even when corrections are made by assuming the depth of penetration, these assumptions may
lack documented, defensible technical basis and may not lend themselves to realistic estimates of
uncertainty. Lacking the key characteristics of a defensible measurement, such results, beyond
limited applicability to scoping studies or the identification of obvious hot spots, are not of
sufficient quality to support the decisionmaking process, and can be considered only qualitative
in nature.
3.3 Impact of Ambient and Intrinsic Background on Measurements of Radioactivity
Levels of naturally occurring radioactivity intrinsic to the material being measured may be
elevated or variable and may negatively impact the reliability or the ability of low-level field
measurements to demonstrate that an area has not been impacted or that it has been adequately
decontaminated to levels that will permit reoccupation. Similarly, ambient levels of background
radiation from naturally occurring radioactivity or incident-related contaminants may interfere
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
with low-level measurements of radioactivity. For example, in one study of building materials
from a single region, background dose rates from the natural radioactivity intrinsic to the
building materials ranged from 2.5 to 14 uR/h (Abbady 2006). Significant local variations in
gamma background due to non-homogeneous areal distribution of contaminants associated with
the event itself may also interfere with reliable low-level in situ gamma measurements in
locations adjacent to contaminants. In the presence of elevated background activity, extended
count times (or even radiochemical processing at a laboratory) may be required to differentiate
between background activity and signal from contaminant radionuclide(s), especially at many of
the lower activity levels that likely will be applicable for recovery operations.
An incident involving pure alpha- or beta-emitting radionuclides such as 238Pu or 90Sr, or
mixtures of pure alpha- or beta-emitting radionuclides with other radionuclides, would present
significant challenges to field instrument measurements not envisioned by White House Security
Council Planning Scenario #11. Earlier in the incident where higher-activity DQOs apply, field
measurements may be used to guide remediation and, with laboratory confirmation of the
underlying assumptions, field measurements often may be used effectively to address certain
lower-activity late-phase DQOs. For pure alpha emitters, and less energetic beta emitters, or
where significant weathering has occurred, however, laboratory measurements generally will be
needed to obtain radionuclide measurements of sufficient sensitivity and accuracy to meet low-
activity late-phase MQOs and final survey decisions.
In contrast to field measurements, there are fewer factors that interfere with laboratory analyses
because the laboratory environment is so carefully controlled and measures are employed to
address concerns that could adversely impact a field measurement. In the laboratory, for
example, concerns about interference from ambient background are addressed by heavily
shielding potentially affected instrumentation. Concerns about the intrinsic background activity
of the matrix materials remain a common challenge to both to field and laboratory
measurements. The activity and expected variability of radionuclides present in the background
must be well-known in order to differentiate between signal from the background radioactivity
and low activities of naturally occurring radionuclide contamination.
Concerns about non-uniform distribution of alpha- and beta-emitting contaminants can be
addressed in the laboratory by homogenizing and careful subsampling to ensure the
representativeness of results. Laboratories routinely employ digestion and fusion techniques to
address intractable matrices. Chemical separation methods are used to purify and isolate
elements of concern from substances or other radionuclides that interfere with sensitive and
accurate measurements. Samples are measured in heavily shielded instrumentation with low and
stable backgrounds, which minimizes the variations in background activity that are problematic
in field measurements. When coupled with low backgrounds and spectrometric detection
techniques, physical preparation and chemical separation steps permit sensitive radionuclide-
specific measurements of individual alpha- and beta-emitting radionuclides in mixtures of
radionuclides and complex matrices. As a result, laboratories can minimize and more accurately
estimate uncertainties associated with single measurements than is generally possible in the field.
Rigorous quality programs at laboratories require extensive validation of methods and quality
control, and ensure consistent documentation of processes so that the quality of measurement
results is highly defensible.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Laboratory measurements have their limitations as well. Although laboratory turnaround times
have improved dramatically over the past decade and results often are available as quickly as
several hours or days, samples must still be taken and shipped to the laboratory. Thus, a
laboratory process can never provide real-time results, as is possible with field measurements.
Time and effort are required in the field for collecting samples of surface or volumetric
contamination to send to the laboratory. Because laboratories generally measure and report
results in terms of the massic or volumetric activity of samples (i.e., pCi/g or pCi/L),
accommodations must be made to relate these units on a "activity per sample" basis, or to the
corresponding value in terms of areal activity (e.g., pCi/cm2).
Perhaps the most significant limitation associated with laboratory analysis relates back to the
number of in situ measurements and grab samples needed to characterize an area. While for
alpha and beta emitters, there is no substantial difference between the number of in situ
measurements or grab samples needed, when medium- to high-energy gamma emitters are
concerned and when the areal distribution of the contaminant radionuclides may be non-
homogeneous, more grab samples may be needed than in situ measurements to have a high
degree of confidence that hot spots will not be overlooked. Similarly, the overall uncertainty
associated with collecting multiple grab samples, as opposed to performing a single ISGS
measurement of a larger area, may require that more samples be collected and measured. Even
so, this may still result in higher overall combined measurement and sampling uncertainties, and
in a higher risk of not detecting activity even though it may be present in detectable quantities.
3.4 Applying the Directed Planning Process to Radionuclide Measurements
As the event progresses into the intermediate and recovery phases, efforts will shift toward
identifying progressively lower levels of contamination. Large areas will need to be quickly
characterized and cleared for longer-term use and habitation. Incident-specific action levels will
be set to support the tasks of:
Reassuring the public that facilities, property, or homes have been decontaminated
effectively; and
Determining that the disposition of contaminated equipment, materials, environmental
matrices, or facilities has been correctly and safely performed.
3.4.1 Action Levels for Incident Response
Undoubtedly a key factor will be public acceptability, which may in fact be more accurately
characterized as intense public demands and expectations. In terms of reoccupancy or continued
occupancy of impacted or possibly impacted areas, including places of work, schools,
playgrounds, day care centers, hospitals, places of worship, etc., the public will very likely insist
that these places be returned to the public's perceived "radiation free" status. This may
effectively translate into public demand that action levels be set at a fraction of the ambient
background for certain radionuclides, or at zero for source-term radionuclides not originally
present in these locations. The public demand for extremely low action levels could result in
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
significant measurement challenges, ultimately requiring very low detection capability coupled
with great precision (very small uncertainties).
While the Agency will certainly need to educate the public regarding the technical challenges
involved with extremely low action levels, the public will still likely demand the most well-
established, sensitive, and precise measurements possible. In addition, while the general public
may not be familiar with the technical aspects of data verification and validation, quality
assurance, and quality control, the public will almost certainly demand a high degree of
demonstrated certainty for the data, as well as some type of rigorous technical review and
evaluation of the data prior to Agency decisions. Given these likely public demands, as well as
lessons learned from the World Trade Center recovery efforts, the Agency will need to employ
well-established measurement processes capable of precisely measuring low levels of select
radionuclides. These measurement processes will need to be supported by well-established and
robust quality control procedures and practices that will provide sufficient information and
documentation to allow for defensible data verification and validation.
3.4.2 Data Quality Objectives Process
The DQO process is used to define specific data requirements for field and laboratory
measurement programs to ensure that the analytical measurements will be of sufficient quality to
defensibly support the decisionmaking process. DQOs also are used to develop the performance
and acceptance criteria for sampling and measurement criteria activities documented in the
quality assurance project plan (QAPP). The output of the DQO process will specify the number
of measurements needed, their locations, and any specific analytical requirements. The frequency
of measurements and number of locations will depend on the degree of variability and amount of
radioactivity compared with the established action level.
3.4.2.1 Decision Rules
One essential aspect of the DQO process is the specification of a decision rule. Decision rules
may be qualitative or quantitative. They contain alternative actions to be taken depending on the
decision about whether the result indicates there is sufficient probability that the analytical action
level (AAL) has been exceeded or not. The decision that will be made is expressed in a
hypothesis test.
A null hypothesis, HO, is defined by initially assuming that the true concentration is either above
or below the AAL. We assume that the null hypothesis is true unless the result of a measurement
allows us to reject the null hypothesis. For most environmental measurements the consequences
of exceeding an action level are greater than not exceeding it. Thus, the null hypothesis most
frequently selected will protectively state that an AAL is exceeded unless data are available that
demonstrate with high probability that the activity is less than the AAL.7 By incorrectly
deciding to reject the null hypothesis when it is indeed true we commit a Type I decision error.
7 There are occasions where it would be appropriate to assume that a result is below an action level unless the
contrary can be demonstrated. For a more complete discussion of decision rules, see MARLAP or Appendix VI in
Radiological Laboratory Sample Analysis Guide for Incidents of National SignificanceRadionuclides in Water,
(EPA 2008).
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
By incorrectly failing to reject the null hypothesis when it is indeed false, we commit a Type II
decision error.
There is uncertainty associated with every measurement. When the result of a measurement is
used to make a decision, there is a probability that a decision error may occur. Given an example
where the true concentration is equal to the AAL, by definition action should be taken. A single
measurement is performed with the plan to compare that result to the AAL to decide whether the
concentration is less than the action level. Since the result of each measurement varies according
to its uncertainty, half of all possible measurements will fall below the AAL and half will be
equal to or greater than it. Using this approach to making decisions, we commit a Type I decision
error fifty percent of the time when the our measurement falsely indicates that the concentration
is less than the AAL.
The DQO process places limits on the probability of making such decision errors. The limit for
the probability of making a Type I error (denoted a) is specified at the AAL. The probability of
making a Type II error (denoted /?) is specified generally at a lower concentration called the
discrimination level (DL). The discrimination level is a concentration at which the null
hypothesis is false (i.e., a concentration below the AAL) and at the same time, a concentration
which we need to be able to reliably distinguish from the AAL. For example, suppose the
contaminant of concern is 226Ra, and we know that 226Ra is present in the background. Then by
establishing the discrimination level equal to the background concentration of 226Ra in the
sample will minimize the probability that background concentrations of radium may be falsely
identified as 226Ra present at the AAL.
The AAL and the DL together bound the "gray region" an area in which decision error
probabilities are not controlled as tightly as outside of it. When measurement results fall in the
gray region, there is a higher risk that we will commit decision errors. The width of the gray
region is defined as:
A = | AAL - DL .
3.4.2.2 Measurement Quality Objectives
MARS AME (2009) and the Multi-Agency Radiological Laboratory Analytical Protocols Manual
(MARLAP 2004) contain guidance on developing MQOs from the applicable DQOs for
measurements of radiation and radioactivity at laboratories and in the field. MQOs are generally
quantitative data requirements that evaluate the quality of the measurement against the criteria
upon which decisions will be based using those data.
By specifying the required method uncertainty (MMR) at the AAL, it is possible to ensure that
decision errors will not exceed the levels deemed appropriate by the DQOs for defensible project
decisionmaking. Ensuring that measurements are of sufficient quality for decisionmaking also
will minimize effort, time, and money spent on making measurements, all key driving factors in
an incident response situation.
MARLAP considers the required method uncertainty at the AAL, WMR, to be a fundamental
MQO. For decisions about whether a single sample exceeds the AAL, Z/MR can be calculated as
11
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
UMR ='
where the null hypothesis (Ho) is "the true sample activity is greater than the AAL," A = [AAL-
Discrimination Level] and
o
distribution function.
' l-a
and z 1 are the respective quantiles of the standard normal
Details and refinements for the determination of the required method uncertainty are given in
MARLAP Appendix C or Appendix VI of Radiological Laboratory Sample Analysis Guide for
Incidents of National Significance - Radionuclides in Water (EPA 2008).
In order to implement the use of the required method uncertainty, the laboratory must have in
place an acceptable method for estimating measurement uncertainty. MARLAP (2004)
recommends the method presented in the Guide to Expression of Uncertainty in Measurement,
also referred to as "the GUM" (ISO Guide 98, 1995). No measurement of radioactivity should
ever be determined or reported without an associated uncertainty and its associated coverage
factor, k. Simply reporting "counting uncertainty" is incomplete and for high-activity samples,
may result in significantly underestimating the combined standard uncertainty of the
measurement.
3.4.2.3 Controlling the Probability of Decision Errors with Analytical Decision Level
The AAL is the dividing point for a choice between two alternative actions. The quality of
measurements of radioactivity should be driven by the need to make informed, defensible
decisions about whether the AAL has been exceeded with acceptable limits on the probability of
a decision error. Failure to take the variability of results and the magnitude of the measurement
uncertainty into account will result in unacceptably high error rates for decisions, or in excessive
time and effort invested in performing measurements with quality that exceeds levels needed for
decisionmaking. High and uncontrolled probabilities of false decisions are not compatible with
defensible decisionmaking, will result in less effective use of analytical resources during
response, and will increase the time needed to complete recovery from the incident.
It is often important to correctly identify samples whose true activity exceeds an AAL. For
example, when prioritizing samples to be sent to a laboratory, sending low-activity samples to a
high-activity laboratory would be less problematic (for the laboratory at least) than risking
contamination of a low-activity laboratory. By selecting the null hypothesis that the true sample
activity exceeds the AAL, we protect against a Type I error of incorrectly deciding that true
sample activity is below the AAL when it is actually above the AAL. We also want to be sure
Values of zl.a (or z^) for some commonly used values of a (or /?), taken from tables of the cumulative normal
distribution (MARLAP 2004, Appendix G, Table Gl), are:
a or/?
0.001
0.01
0.025
0.05
z^Corz^)
3.090
2.326
1.960
1.645
a or/?
0.10
0.20
0.30
0.50
z^or^)
1.282
0.842
0.524
0.000
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
that if the sample activity is significantly below the AAL, it is correctly identified, avoiding a
Type II error of incorrectly deciding that the sample activity is above the AAL when it actually is
below.9
Figure 1 is a graphical representation of a smoothed distribution from an infinite number of
measurements of a sample or object where the true activity is equal to the established AAL. In
the figure, the AAL is the mean of the distribution of measurements. Variability due to
uncertainty in the measurement will cause one-half of all possible measurements to fall below
the AAL, and one-half at or above the AAL. Based on a single measurement, a decision must be
made about whether or not activity is present above the AAL.
Sample at Ambient
Background
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Concentration (nCi/g)
1.1 1.2 1.3 1.4 1.5 1.6
Figure 1 - Uncontrolled Decision Error at the AAL
If the measured result is compared directly to the AAL to decide whether the activity is equal to
or above the AAL, there is a 50% probability that the measurement will result in an incorrect
decision that the true activity is below the AAL (this case corresponds to the solid area below
the AAL).
The magnitude of the measurement uncertainty affects the ability of a method to tell the
difference between background activity and contaminant at the AAL. Without establishing a
control on the measurement uncertainty, it may not be possible to discriminate ambient
background activity from contaminant activity at or above the AAL (this case corresponds to the
cross-hatched area above the AAL).
It is possible to control the probability of decision errors by comparing measured results with
specified limits on uncertainty to an analytical decision level (ADL).
9 In a case where there would be greater consequences associated with falsely concluding that activity is present
when it indeed is not, the most appropriate null hypothesis would be, "The measured activity is below the action
level." Because this case is less frequently applied for environmental analyses, it will not be presented here. For
details, see Appendix VI of the Radiological Laboratory Sample Analysis Guide for Incidents of National
Significance - Radionuclides in Water (EPA 2008).
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Assume that the null hypothesis is that the true activity of the sample exceeds the AAL. We can
calculate an analytical decision level as ADL= AAL - Zj_a WMR.
This means that before deciding that activity is not present at or above the AAL, the result of a
measurement must fall below the AAL by a margin corresponding to the tolerable probability of
falsely rejecting the null hypothesis that the true concentration is above the AAL.
The DL is the concentration for which the null hypothesis is considered to be false but at which it
is important to be able to distinguish the concentration from that of a sample at the AAL. The
AAL and DL together bound the "gray region" in which decision error probabilities are not
controlled as tightly as outside of it.
Consider the hypothetical situation shown graphically in Figure 2. Assume that a DQO is
established that stipulates that the null hypothesis is that the true activity of the sample exceeds
the AAL, with tolerable Type I and Type II error rates of 5% and 10% respectively.10
01 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Concentration (nCi/g)
1.1 1.2 1.3 1.4 1.5 1.6
Figure 2 - Controlling the Probability of Decision Errors with the ADL and UMR
The AAL for the screening process is 1.0 nCi/g. Samples with activity above 1.0 nCi/g may not
be sent to the low-level laboratory.
A discrimination level of 0.5 nCi/g is selected since the matrix being measured contains naturally
occurring background activity of 0.5 nCi/g, and there is concern that this activity will be
mistaken for the contaminant of concern. The gray region (A) is the area between the AAL and
the discrimination level. For a sample with true activity in the gray region, there is a high
probability of a decision error. The width of the gray region, delta, is calculated as:
A = IAAL - DL = |i.o - o.5| na/g = 0.5 nci/g.
10The probability of making Type I error is chosen to protect against the greater risk associated with incorrectly
deciding that the sample activity is below the AAL when in fact it is greater than the AAL. The larger Type II
decision error means that there are lower consequencesand thus greater toleranceto falsely concluding that
activity is present, even though it may be attributable to background activity.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
The required method uncertainty ensures that the rate of Type I and Type II decision errors is
maintained within the specified limits and is calculated as follows:
A 0.5nCi/g ft1_ _..
17nCl/g
z^+Zj.p 1.645 + 1.282
See footnote 5 for the values of z^ and z^. The ADL, which is used as the decision criterion, is a
function of the uncertainty of measurements of a sample at the AAL and is calculated as:
ADL = AAL -zi-a Z/MR = 1.0 nCi/g - [1.645x0.17 nCi/g] = 0.72 nCi/g.
The curve centered about 1 nCi/g in Figure 1 represents the distribution of all possible measure-
ments of a sample with a true activity equal to the AAL. In figure 2, consistent with established
DQOs, only 5% of this distribution (a ) falls below the ADL. The curve, centered about 0.5
nCi/g, represents the distribution of all possible measurements of a sample containing only
naturally occurring background activity (equal to the discrimination level). Consistent with
DQOs, only 10% of this distribution (/3) may exceed the ADL.
Thus, only measurements that fall significantly below the AAL (I.e., less than the ADL) will lead
to rejection of the null hypothesis, and thus reliably support the conclusion that the true activity
of the sample has not exceeded the AAL. At the same time, the required method uncertainty,
MMR, is kept small enough to ensure that the AAL will be differentiated reliably from the
naturally occurring background activity at the discrimination level. In contrast to decision error
rates of 50% that may result from comparing measurements directly to the action level,
comparing a measurement to the ADL will ensure that decision errors are maintained at the rates
consistent with DQOs.
4. Metrology, Quality Systems, and QA/QC
An effective quality system is vital in assuring the quality of any radioanalytical measurement
used for incident response decisionmaking. It ensures, among other things, that all measurements
are traceable to national standards and provides defensibility against data challenges. The rigor
and detail of one aspect of the quality system,11 its QC requirements, will likely need to be
increased from the initial response and final recovery phases and be the most stringent during
final status surveys. A graded approach may be applied to reflect changing DQOs, MQOs, and
needs for analytical quality. The QA/QC protocols used should always provide clear assurance
that data is of sufficient quality to support the decisionmaking process. This section addresses
some of the fundamental concepts of metrology, quality systems, and their importance in field
and laboratory measurements for incident response.
4.1 Why is Metrology Important?
The International Vocabulary of Metrology (VIM; IBWM 2008) defines metrology as the
"...science of measurement and its application. [...] Metrology includes all theoretical and
11 See section 4.3 for a more complete discussion of quality systems.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
practical aspects of measurement, whatever the measurement uncertainty and field of
application."
Radiation and radioactivity measurements can be complex, and establishing traceability for
instrument calibrations for complex field measurements may pose technical challenges. Some
practitioners may be uncomfortable in setting up equations for the various measurement models,
or in developing them into expressions of uncertainty.
Failing to consider and apply the fundamentals of metrology, however, will result in
measurements of unknown and very possibly substandard quality. Without meaningful estimates
of measurement uncertainty, or traceability of measurements to national standards, it is not
possible to demonstrate defensibly that a measurement possesses sufficient quality to reliably
address DQOs applicable to incident response, or even to reasonably compare it to that taken by
another analyst or organization. Since this could result in potentially serious consequences to the
decisionmaking process, it is vital that the fundamental principles of metrology be understood
and adequately incorporated into measurements of radiation and radioactivity.
4.2 The Principles of Metrology
The core approach to performing any measurement, whether it is a radiological measurement
performed in a field or laboratory setting, rests on the basic principles of metrology. Every
measurement is a comparison to a standard. The degree to which reference materials provide a
universal reference depends on the quality of the link of those measurements to the applicable
reference standards. ISO 1993a and MARLAP (2004) define traceability as a "property of the
result of a measurement or the value of a standard whereby it can be related to stated references,
usually national or international standards, through an unbroken chain of comparisons all
having stated uncertainties" (ISO 1993b).
Measurements of radiation and radioactivity must be traceable to national radiation or
radioactivity standards (e.g., a Standard Reference Material from the National Institute of
Standards and Technology). The definition of traceability also recognizes that the uncertainty of
a measured value is an integral component of its traceability. This is because the uncertainty
indicates the degree of confidence that can be placed in a measurement.
It is important that measurement results be reliable, and that results from different organizations
be comparable, and objectively and confidently accepted as such among all those likely to use
that data. Not only must instrumentation be calibrated, but measurements must also be
performed, and quality control protocols that preserve, validate, and document the traceability of
each measurement to the national standard must be available. This applies equally to
measurements made in the field and to those performed in a laboratory setting.
Factors that may affect the quality of measurements include reference materials used, equipment
calibration, and chemical treatment (e.g., extraction, digestion). These measurements can be
strongly dependent on the source material or sample matrix, whose exact composition is almost
never completely known. This limits the degree to which the measurement environment can be
defined and controlled.
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Some fundamental steps of metrology that should be followed in measurements of radioactivity
are:
Develop/define DQOs and MQOs;
Choose or develop the appropriate measurement method to meet the MQOs;
Understand a method and its strengths and limitations;
Choose suitable National Institute of Standards and Technology (NIST)-traceable certified
reference materials and use them properly;
Validate the method to demonstrate that the method will meet the MQOs; demonstrate and
confirm it;
Identify the sources of uncertainty in the method;
Derive a model or an equation for the measurement that allows the combined standard
uncertainty to be determined;
Evaluate the uncertainty of each measurement using a recognized approach;
Clearly establish and document that results are traceable to a national standard; and
Report the results, the associated combined standard uncertainty with the appropriate units,
the number of significant digits, and the coverage factor.
4.3 Quality Systems
A management system for quality must precede the design of any QA program. ISO/IEC 17025
provides guidance for developing an overall management system for quality, administrative, and
technical operations. Similarly, the EPA has provided Guidance for Developing Quality Systems
for Environmental Programs (EPA QA/G-1, 2002a). The scope and purpose statement for
QA/G-1 describes a quality system as "...the means by which an organization manages its
quality aspects in a systematic, organized manner. It provides a framework for planning,
implementing, and assessing work performed by an organization and for carrying out required
quality assurance (QA) and quality control (QC) activities. It encompasses a variety of technical
and administrative elements, including policies and objectives; organizational authority;
responsibilities; accountability; and procedures and practices." The document also stresses that a
successfully implemented quality system will reduce vulnerabilities and improve an organiza-
tion's ability to make reliable, cost-effective, and defensible decisions. The quality system
approach will help ensure scientific data integrity and produce well-documented data of quality
appropriate for the purposes intended. It also will reduce the risk of embarrassing surprises and
data challenges while improving on-time delivery of data and reducing expenditures by reducing
the need to repeat measurements unnecessarily.
4.4 Quality Systems Standards - Quality Assurance and Quality Control of
Measurement Systems
Radioanalytical measurements will play a vital role in rapidly and reliably characterizing the
type and extent of contamination following a radiological or nuclear incident. They are also key
components needed to efficiently and effectively remediate any contamination identified. The
production of data of known and sufficient quality to support long-term decisionmaking requires
a well-implemented QA program containing elements stated in guidance documents from
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various quality standards organizations. The elements defined in these programs address in detail
every aspect of measurement operations, including:
Effective, consistent, and well-documented oversight of the analytical process;
Receipt, tracking, and management of samples;
The procurement of supplies and equipment;
The qualifications and training of personnel;
The setup, maintenance, and calibration of instruments and support equipment;
Quality control of all measurement processes;
Selection, validation, and proceduralization of analytical methods;
Results' traceability to national standards (e.g., NIST);
Creation, maintenance, and archiving of records and documents;
The reporting and review of results and independent QA oversight of all measurement
processes; and
Review of analytical output.
Any measurement program that will be used as the basis for key decisions also must be
supported by a substantial and robust QC program if it is to generate reliable, verifiable, and
defensible results and uncertainty estimates. An effective QC program will empirically measure,
control, and document the precision, accuracy, representativeness, and comparability of results.
Lacking a comprehensive QA/QC program, the quality of data generated may be inadequate to
support the generation of large data sets that can be validated to levels that will withstand the
scrutiny of public or legal inquiry.
4.4.1 Quality Systems Standards, QA and QC for Field Measurements
Traditionally, it has been recognized that there are limits to the detail and the quality of testing
for radioactivity that is practicable in the field. This has included requirements for the
traceability of measurements, formalized QA, maintenance of constant test conditions, and
implementation of effective QC requirements and oversight to ensure that the quality of results
will meet DQOs/MQOs. As a result, fixed laboratories have traditionally been called upon to
perform many of the most critical, complicated, and sensitive measurements. Fixed laboratories
also have been required to maintain sophisticated quality systems commensurate with the higher
quality of measurements being performed.
Over time, innovative field measurement techniques have become increasingly more available,
and increasingly more sophisticated measurements can now be performed in the field. Since
these measurements support the same decisions that traditionally required the quality of fixed
laboratory data, field programs need to consider the same quality concerns that have been
applied at fixed laboratories for many years.
Field sampling program QA/QC has not focused on addressing the analytical process, since this
role was so frequently relegated to the fixed laboratory. Rather, it tended to address areas such as
the tracking, management, and receipt of samples; preservation of samples; sampling techniques
for various matrices; and procurement of supplies and equipment. Guidance on the performance
of field measurement parameters (e.g., conductance, pH, radiation dose rate) and the operation of
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field instruments has been provided by instrument manufacturers. A limited number of standard
practices are available from standards organizations that address field measurements and
associated QA/QC in detail. Based on available guidance and best practices, standard operating
procedures are designed for use by field analysts. Thorough guidance is needed for field
programs to ensure that sufficiently detailed direction is given to designing and effectively
implementing a quality system for field measurements. This can best be accomplished by
providing detailed analytical protocol specifications in quality assurance project plans, and by
allowing for time to focus and implement QA/QC measures in advance of deployment.
Broad ranging formalized quality system standards and certification/accreditation and oversight
programs have yet to be implemented that effectively address field measurement programs.
Although two volumes of The NELAC Institute Standard apply to field sampling and
measurement organizations (TNI 2007), implementation of these quality system standards,
adopted in 2007, and associated independent accreditation is limited to field determinations of
non-radioactive lead (Pb). The scope and timing of additional implementation has not been
determined at this time. The Multi-Agency Radiation Survey and Site Investigation Manual
(MARSSIM 2000) provides only general direction on QA measures applicable to field
instruments. For example, in situ measurements, particularly those performed using efficiency
modeling techniques, generate results that are not traceable to national standards (e.g., to a NIST
Standard Reference Material). This critical fact often is overlooked and represents a huge divide
between the standards of analysis needed to create accurate and defensible data and those that are
sometimes applied in the field.
Training of field personnel is a second area that is difficult to address, especially for an incident
response. Due to the nature of an incident response, there is little if any time available to
effectively train a large number of instrument analysts and operators prior to mobilizing for the
field. Training classes would be short and provide only generalized mechanical instructions on
operating an instrument. A thorough knowledge of how matrix and geometry affect the measure-
ment process cannot be taught during the pressure of responding to an incident. Cursory
instruction cannot substitute for the expertise that results from long-term experience and
documented historical performance running an analytical technique or instrument. Once in the
field, oversight of relatively inexperienced analysts would be difficult to perform and to docu-
ment. Additionally, each incident will have specific matrix and field sample geometry issues.
A third area of concern surrounds the defensibility of the precision and accuracy of results.
Given the variability in measurement conditions and the characteristics of the objects to be
measured, innovative, empirical quality control measures are needed to provide assurance that
the measurement process and individual measurements consistently meet MQOs. Quality control
measures for field measurements are not generally as robust as those routinely used for
laboratory measurements. This is due in part to the nature of the measurement, and the challenge
of constructing QC protocols for in situ measurements that demonstrate empirical monitoring
and quality control of field measurements. One or more measures could be implemented that are
appropriate to specific concerns surrounding the type of measurement being performed. Such
measures might include:
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Routinely analyzing independent confirmatory grab samples at a laboratory to measure
and control the bias and precision of the process;
Analyzing in situ blanks to control absolute bias in each area where measurements are
conducted by repeating the measurement in the same location and rotating the instrument
180° in the horizontal plane;
Performing redundant measurements that validate the process using modified analysis
parameters, for example, by:
o Measuring the same object from different angles and distances to show adequate
implementation of efficiency modeling and to help validate estimates of uncertainty;
o Having a different person repeat the measurement;
o Using a different instrument and/or software to repeat the measurement; or
o Repeating the measurement after breaking down the equipment, leaving the area,
coming back, and setting up the equipment and instruments again.
Analyzing known reference samples to measure and control the accuracy of the process;
Participating in regular external proficiency testing programs that provide independent
empirical evidence of the accuracy and intercomparability of measurements;12 and
Utilizing independent verification contractors to ensure that the cleanup has achieved its
stated goals.
During conventional clean-up and remediation activities (for example Resource Conservation
and Recovery Act [RCRA] sites), a final status report is written at the completion of
decontamination/removal tasks that summarizes the measurement data and discusses how a
decision is made that the data are adequate to satisfy the DQOs. In the case of structures and land
areas, the database that supports this consists of in situ measurements supported by independent
confirmatory lab analysis of random and judgmental (i.e., "biased") samples. For regulated
activities (U.S. Nuclear Regulatory Commission [NRC], DOE, agreement states), confirmatory
split sampling by regulators and independent inspection and oversight are performed by an
independent verification contractor responsible to the applicable regulatory authority.
Validating the methods/procedures to be used to conduct field measurements is another
important practice that empirically demonstrates the accuracy, precision, comparability,
specificity, and robustness provided by a method. If a field measurement technique is used in
support of the decisionmaking process, validating it will help ensure that measurement biases
and uncertainties for various geometries are known and that its capabilities are empirically tested
and well-documented prior to its use.
Techniques used for determining field measurements often rely on assumptions that are difficult
or impossible to verify (e.g., self-absorption effects, the impact of background on low-level
measurements, or the assessment of complex measurement situations). Efficiency modeling
techniques rely considerably on the judgment of instrument operators and their ability to set up,
calibrate, check performance of, and use instruments and procedures to perform processes such
as scanning surveys.
12 Small demonstration programs have been carried out in the past, but there are currently no ongoing external
programs that are designed to empirically assure the intercomparability of results produced under conditions that
approximate those encountered in the field.
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During an incident, the level of oversight and number of personnel available to support
operations will presumably be stretched to the limit. Conditions in the field may vary
significantly from measurement to measurement. The level of experience available may not
guarantee that the level of documentation and review is adequate to verify all the critical
conditions and assess the impact of decisions made during the performance of an in situ
measurement. Analyst judgment, for example, is crucial in complex in situ measurements, yet
judgment is difficult to quantify and may vary depending on the knowledge, experience, and skill
of instrument operators and the specific challenges of the measurement.
Careful and complete documentation, effective prompt review, and retention of sufficient records
to assure unambiguous recreation of a result are critical elements provided under a quality
systems approach. Lacking effective technical oversight and experienced independent reviewers,
an individual may be asked to self-perform quality-related functions that should be completed
independently, a situation that would not be allowed under laboratory QA programs where
independent review and oversight are required prior to release or utilization of results.
A very effective external QC measure, confirmatory sampling, should be incorporated as a
routine QC measure into field sampling and analysis plans. Comparing field measurement results
to radiochemical analyses of samples using recognized, independent, quantitative laboratory
techniques provides empirical evidence of the effectiveness of the field measurement process.
Integrating such quality control measures into the field measurement process lends a large degree
of defensibility to field measurements as long as it is performed at intervals frequent enough to
provide meaningful statistical feedback on the adequacy and implementation of the measurement
program in all of its unique measurement situations. When the scope of the QC program is
relatively limited, or when results are received long after the field efforts are complete and the
decisionmaking is complete, the program will do little to provide meaningful controls on
measurements.
4.4.2 Quality Systems Standards, QA and QC for Laboratory Measurements
EPA's G-series QA documents provide extensive guidance on topics applicable to measurement
projects, including the development (EPA QA/G-1, 2002a) and assessment (EPA QA/G-3, 2003)
of quality systems; on systematic planning using the DQO process (EPA QA/G-4, 2006; EPA
QA/G-5M, 2002c); the development of quality assurance project plans (EPA QA/G-5, 2002b)
and standard operating procedures (EPA QA/G-6, 2007); and on audits and assessments (EPA
QA/G-7, 2000).
Laboratories and their operational systems have a history of maintaining quality systems that
allow them to comply with extensive and elaborate quality requirements. These quality systems
prescribe in detailed fashion the elements needed to generate and document usable data from the
initial procurement of an instrument, through setup and calibration to data evaluation, reporting,
and interpretation. The laboratory must maintain management structures that ensure adequate
resources and oversight are available to perform the testing required of them. The laboratory's
ability to generate analytical results must be validated for all measurements. The laboratory must
routinely perform reliable and defensible QC that demonstrates that all measurement systems are
in control and thus capable of meeting and producing data that meet MQOs. The laboratory also
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must completely and unambiguously document all activities associated with measurements such
that all results can be recreated from available records. Such programs and standards cited are
written with the laboratory process of QA/QC and instrument calibration in mind. No
comparable or comprehensive nationally accepted and nationally implemented quality systems
programs are currently available for field measurements.
Radiochemistry laboratories operate under comprehensive laboratory quality systems standards
such as the TNI Standard (NELAC 2003), Department of Energy Consolidated Audit Program's
Quality Systems for Analytical Services (DOE 2009), the Department of Defense Quality Systems
Manual (DOD, 2009), ANSI N42.23-1996 (ANSI, 2004a), and ISO/IEC 17025 (2005). One key
example of the many elements addressed by laboratory quality programs is the calibration of
detectors. Excerpts from several consensus standards regarding standardization and calibration
are cited here to provide an example of the detail and broad influence of such documents on the
overall process and the quality and defensibility of measurement results.
For example, laboratories are accredited by any number of organizations to standards such as the
TNI Standard (NELAC 2003). The TNI Standard is a comprehensive quality standard that
addresses, among other things, issues of traceability for laboratories conducting definitive
environmental measurements:
"... [T]he essential elements that shall define the procedures and documentation for
initial instrument calibration and continuing instrument calibration verification to ensure
that the data must be of known quality and be appropriate for a given regulation or
decision."
"[A]ll initial instrument calibrations must be verified with a standard obtained from a
second manufacturer or lot if the lot can be demonstrated from the manufacturer as
prepared independently from other lots. Traceability shall be to a national standard, when
commercially available."
The American Society for Quality Standard E4 (ASQ E4), Quality Systems for Environmental
Data and Technology Programs-Requirements with Guidance for Use (ANSI 2004b), states, for
example, that for measurement devices, "Traceability to nationally recognized performance
standards should be maintained when they are used for critical or sensitive items and activities."
American Society for Testing and Materials (ASTM D7282 2007), provides detailed guidance on
the setup, calibration, and quality control of instruments used for radioactivity measurements.
MARLAP (2004) Chapter 15, "Quantification of Radionuclides," provides guidance on the
importance of standardized calibration techniques using sources of known and traceable activity.
Specifically,
"The goal of calibration- or test-source preparations is to maximize detection capability
while minimizing the introduction of bias and uncertainty into the measurement process.
To achieve this goal, calibration sources should be prepared in a manner that provides
comparability to test sources with respect to geometry, composition, and distribution of
the test-source material within a container or on a source mount."
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Furthermore, it states that:
"Proper instrument calibrations are essential for the proper identification and
quantification of radionuclides in samples. It is important to initially calibrate the
instruments with calibration sources that are traceable to a national standards body. Once
calibrated, the continuing validity of calibrations should be checked on a periodic basis
(Chapter 18, Laboratory Quality Control) as specified in a laboratory's quality manual."
The QC measures taken to verify proper instrument calibration and use are another required
component of a defensible measurement process. These measures include instrument stability
and background checks, as well as quality control sample analyses that empirically demonstrate
the validity of measurements. These elements are addressed, for example, in the Nuclear
Regulatory Commission's Regulatory Guide 4.15, Quality Assurance for Radiological
Monitoring Programs (Inception through Normal Operations to License Termination)Effluent
Streams and the Environment (NRC 2007), and include routine analysis of control samples,
duplicates, blanks, and matrix spikes. Such QC samples often are not performed in an equivalent,
formalized manner when making field measurements as would be required under an accredited
laboratory's quality system.
Unlike laboratory systems, field operations are more transitory and are not as readily amenable
to formalized audits. Accrediting authorities routinely audit laboratories to ensure compliance
with the requirements of quality systems standards. Laboratories participate in routine
independent proficiency testing (PT) studies to demonstrate satisfactory performance of
laboratory methods. These PT studies are quantifiable measures of assurance that analytical
systems are working properly to produce reliable and defensible data and that offer opportunities
to make improvements when they do not.
In contrast, a field measurement team for an incident response may be made up of personnel who
have been pulled together for that specific project. They may not have been routinely audited,
nor are they as likely to have a documented record of compliance with a quality standard or
standard operating procedures (SOPs). The use of different instruments in varied settings, and
the implementation of guidance that varies from what they are accustomed to may necessitate
additional QA/QC measures to ensure that measurements are defensible.
Regular blind intercomparison programs generally are not viable options for field sampling and
measurements organizations due to practical challenges such as the preparation of test plots or
the need to transport field crews to a facility where such plots are available. The benefits of using
field calibration facilities, such as the large area calibration pads at Walker Field Airport in
Grand Junction, Colorado (Leino et a/., 1994; Novak, 1998), could be substantial because they
would allow validation of in situ measurement technologies and training of field personnel prior
to mobilization.
Quality systems standards address another parameter key to performing quality measurements in
any setting. Variability in ambient conditions such as temperature, humidity, and ambient
background could affect analyses and challenge notions of consistency and repeatability that
form the basis for setting up, maintaining, and operating analytical instrumentation in laboratory
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settings. Careful storage and control of samples generally allow reanalysis of a sample, should
problems arise that could impact the quality or integrity of analyses.
Finally, laboratories maintain detailed records and generate extensive data deliverables that allow
each individual measured parameter to be recreated in detail and the measurement data to be
independently verified and validated. Based on the documentation produced, analytical results
can be independently verified, validated, and assessed from the deliverables and from archived
records. Comparable documentation for field measurements is more challenging because of the
fluid field conditions compared to those in the more controlled laboratory environment.
4.5 Quality Assurance Project Plan
A QAPP supplements the default quality system by providing a blueprint of where, when, why,
and how a particular measurement project will achieve data of the type and quality needed and
expected. A QAPP can form the basis of a QA program (EPA QA/G-5, 2002b). This document
should address:
Personnel training and qualifications;
DQOs and MQOs;
SOPs, or schedules for the implementation of the QA program;
Acquisition and maintenance of materials and supplies;
Calibration;
QC of instrumentation (including traceability of calibration sources);
QC of routine measurements;
External intercomparison programs and internal audits;
Training of measurement personnel;
Verification and validation (V& V) of data;
Audits, corrective actions;
Control and documentation of procedure revisions;
Field logs (describing environmental conditions);
Records of measurements (e.g., the time, date, location, instruments, and procedure used;
personnel, etc.) with sufficient detail to permit results to be unambiguously recreated
from data retained; and
QC records for radiation measurement instrumentation (including the results of
instrument checks, calibrations, instrument background determinations, and maintenance
activities that could affect equipment performance).
4.6 Uncertainty Estimates and the Measurement Process
MARS SIM recognizes the importance of minimizing the uncertainty of data used for
decisionmaking and stresses that "[s]ite surveys should be performed in a manner that ensures
results are accurate and sources of uncertainty are identified and controlled" (MARSSEVI 2000,
Section 4.9). MARLAP (2004, Appendix B) discusses the sources and impact of uncertainty in
the measurement process:
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
"The uncertainty of the measurement process involves not only an instrument and its
reproducibility, but also the representativeness of the sampling. There will be sampling
uncertainty, due to spatial and temporal variability in concentrations across the site and
from one sample to the next. There will also be analytical measurement uncertainty due
to the variability in the measurement process itself. Since it is impossible to eliminate
uncertainty, basing decisions on measurement data opens the possibility of making a
decision error. Recognizing that decision errors are possible because of uncertainty is the
first step in controlling them."
It goes on to state that:
"...sampling uncertainty can be reduced by collecting a larger number of samples.
Measurement uncertainty can be reduced by analyzing individual samples several times
or using more precise laboratory methods. Which uncertainty is more effective to control
depends on their relative magnitude. For much environmental work, controlling
[reducing] the sampling uncertainty error by increasing the number of field samples is
usually more effective than controlling measurement uncertainty by repeated
radiochemical analyses." (MARLAP 2004, Appendix B, B-ll and B-14)
4.6.1 Uncertainty Estimates and Field Measurements
When using field survey instruments to perform large-scale radioactivity measurements, there
are several factors that affect representativeness of sampling. These factors include:
Non-uniform dispersion of radioactive material in the area being measured;
Variability of ambient background radiation in and adjacent to the area being measured;
Lack of knowledge about depth penetration of the radionuclide contaminant;
Resuspension of some of the surface contamination during the measurement process;
Weather conditions during and immediately prior to the measurement; and
Robustness of the sampling and analysis plan.
In the field, it can be difficult to control and estimate these uncertainties. Thus, field surveys of
structures and materials to be left in place may provide measurements of contamination with
poorly known uncertainties. Follow-up analyses using swipes (to assess lower yet significant
levels of removable and air-suspendable material), and surface and sub-surface grab samples (to
assess volumetric contamination) can be used to confirm field measurements.
Another factor affecting the uncertainty of reported field data is the correspondence between the
calibration geometry of the instrument and the actual geometric configuration of the radioactivity
in the field. Although uncertainty estimates based on sample density and shape can be
mathematically computed, there is no uniform method established for doing so. Guidance from
documents such as Guidance on Systematic Planning Using the Data Quality Objectives Process
(EPA QA/G-4, 2006), and the GUM (ISO 1995) may be applied to field measurements. The
application of these methods to field surveys of materials and equipment is treated in
MARSAME (2000). The GUM procedures for calculating uncertainties do not always presume
that definitive estimates of each component of uncertainty are available, but provide a framework
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for assessing the magnitude of such contributions given professional judgment and knowledge of
the measurement process. This allows planners to focus on those parameters that are most likely
to impact the overall uncertainty and affect decisionmaking.
The concepts of MQOs and DQOs for field measurements of radioactivity are not as well-
developed and implemented as they are for laboratory measurements. Similarly, uncertainty
analysis and its implication for the planning and decisionmaking process are not nearly as
advanced as for laboratories. While MARSAME addresses many such concerns, it has only
recently been published, and there has been little training available in its use. Promulgating these
ideas into the field setting will require significant time, validation of the methods, and training of
the analysts who will perform these measurements.
4.6.2 Uncertainty Estimates and Laboratory Measurements
MARLAP provides guidance on calculating uncertainty and measures used to minimize
uncertainty in sample measurement processes in the radioanalytical laboratory. The guidance
provided in MARLAP supports the concepts for detailed measurement uncertainty estimates. By
placing each sample in a reproducible geometry within a shielded detector, laboratories create a
controlled and predictable environment in which measurements will be performed (including
stable, low, and well-characterized backgrounds). Samples are prepared to ensure congruence
between the sample test source and the calibration geometry. While this is clearly advantageous
in terms of minimizing measurement bias, it also minimizes measurement uncertainties and
makes it easy to assess the contribution to the uncertainty from the measurement process.
The treatment of measurement uncertainties and their relationship to MQOs and DQOs have
been thoroughly addressed in MARLAP for radioanalytical chemistry measurements in the
laboratory. The basic principles underlying these methods are outlined in Guidance on
Systematic Planning Using the Data Quality Objectives Process, the GUM, and other guidance
documents. The methods for estimating measurement uncertainties are not limited to the
applications cited in these references but are equally appropriate for virtually any type of
measurement.
Determination and reporting of uncertainty for radioanalytical laboratory measurements have
been routine at laboratories for many years. There have been volumes of publications on
uncertainty in radioanalytical measurements. ISO 17025 and NIST traceability requirements
have increased the focus on determining and reporting measurement uncertainty and made
uncertainty analyses very familiar in the laboratory setting. MARLAP Chapters 19 and 20
provide detailed guidance and examples of estimating uncertainty in radioanalytical
measurements. Training in the use of these specific methods has been provided at numerous
MARLAP training classes since 2005 and at nationally recognized radiochemistry conferences
for substantially longer periods of time.13
When considering the relative merits of in situ versus laboratory measurements, it is important to
keep in mind that the overall uncertainty of an ISGS measurement of surface activity may be less
13 See program descriptions for the 52nd and 53rd Annual Radiobioassay and Radiochemical Measurements
Conference www.lanl.gov/BAER-Conference/.
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than the combined uncertainty of laboratory measurement due to the uncertainty associated with
sampling. It is for this reason that ISGS measurements are attractive options.
Nonetheless, before a program can rely on any measurement, be it from the field or from a
laboratory, the quality of the measurement must be assured. This would include a demonstration
that its estimate of measurement uncertainty is reliable and defensible and that it can satisfy
applicable MQOs. If experience, guidance, and programmatic support for this are weak or
lacking, or conditions are variable such that inputs into the uncertainty model are poorly known,
field measurements should be verified on a routine basis using confirmatory laboratory
measurements to demonstrate that MQOs have been satisfied.
5. Considerations on the Capabilities and Limitations of Radioanalytical Measurement
Techniques in the Field and Laboratory
Field and laboratory measurement techniques each have their strengths and weaknesses, but they
may be used together in a complementary fashion during the days and months following an
incident. This section addresses some of the key factors impacting the effectiveness of
measurement techniques as they are used in the field and at the laboratory for measuring
different types of radiation and radioactivity. Among the key factors are the ability to accurately
calibrate equipment for a given purpose, and to measure and apply corrections for background
such that the bias and uncertainty of the measurements are controlled at levels that are
appropriate for decisionmaking. An understanding of these factors will help Incident
Commanders identify appropriate measurement techniques and take optimal advantage of the
respective strengths of the variety of field and laboratory measurement options available to them.
5.1 The Impact of Background Radiation on Radioanalytical Measurements
Ambient radiation can have a significant impact on analytical measurements of low levels of
radioactivity. When low action levels are encountered, as would likely apply during the recovery
phase of an incident and during final status surveys, background activity must be accurately
measured and subtracted from measurements to ensure the quality and defensibility of results.
Inaccurate measurements of background activity will result in biased measurements and
underestimation of uncertainty, and may potentially lead to incorrect decisions. The following
section addresses the impact of background radiation on radioanalytical measurements in the
field and in the laboratory.
5.1.1 The Impact of Background Radiation on Field Measurements
Most radiation detection instrumentation responds to one type, or to a combination of several
types, of radiation. Field instrumentation generally provides results as gross activity14 (e.g.,
counts) or dose or exposure (e.g., mrad or roentgens) for the particular type(s) of radiation.
Because field detectors are built to be portable, they may not be heavily shielded and respond to
any source of radiation that impinges on the active volume of the detector. Significant
14 The expressions "gross activity," "gross alpha," "gross beta," and "gross gamma" will be used in this guide to
refer to non-specific measurements of alpha, beta, or gamma radiation. These will be contrasted with measurements
of radioactivity, spectrometric or otherwise, that are specific enough to be attributed to a specific radionuclide.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
contributions from the ambient background radiation beyond the area of measurement may limit
the accuracy of field measurements adjacent to other contaminated areas. According to the
International Commission on Radiation Units and Measurements (ICRU) 53, "[a]t a detector
height of 1 m, about 30% of the total fluence rate measured comes from beyond a 3-m radius for
137Cs that is uniformly distributed with depth in the soil." For a surface source distribution, about
half the fluence comes from "beyond 10 m" (Reginatto et a/., 1997). Light shielding
(collimation) often is used to reduce (but not eliminate) shine from beyond the immediate area
being measured. Unfortunately, cylindrical shielding also reduces the field of vision of the
detector and increases the number of measurements needed to characterize an area. This impact
of ambient sources of background has been reduced and the "field-of-vision" of the detector
improved by using a downward-looking bell-shaped shield with a detector mounted in the
"neck" of the bell mounted on a wheeled frame for ease of movement.15
Sources of ambient radiation, such as cosmic radiation and naturally occurring radioactivity, are
ubiquitous in the environment. Naturally occurring radioactive materials such as uranium,
thorium, their decay progeny, 40K, and others, represent significant sources of background
radiation in soil, air, water, and construction materials (e.g., concrete, stone, wood, shingles, etc).
For example, the National Council on Radiation Protection and Measurements (NCRP) lists the
mean specific activities for several key naturally occurring radionuclides in soil as: 0.67 pCi/g
238U; 10 pCi/g 40K; 0.8 pCi/g 226Ra; and 0.65 pCi/g 232Th (NCRP 1976). Uranium, radium, and
thorium decay through radon (an inert gas) into a number of radioactive decay products. As a
gas, radon and its shorter-lived progeny are transported through the air and may deposit on
surfaces and impact measurements of radioactivity on and around those surfaces in an
unpredictable manner.
In addition to naturally occurring radioactivity, anthropogenic sources of radionuclides, such as
137Cs or 90Sr, are widely present in the environment as a result of fallout from the atmospheric
testing of nuclear weapons. Typical global concentrations of 137Cs and 90Sr in surface soil
samples may range up to 0.4 pCi/g and 0.3 pCi/g, respectively.16
The observed magnitude of the ambient background varies significantly in amount from location
to location and over time. For example, background dose levels due to gamma radiation
(excluding 222Rn) can vary substantially but commonly range between 40-100 mrem/y.
Outdoors, the beta dose rate from soil one meter above the ground is about one-third of the
gamma dose. Beta/gamma exposure rate measurements, using field instruments that have only
minimal shielding, may be impacted by variations in terrestrial radionuclide concentrations and
the various effects of cosmic radiation, depending upon altitude (NCRP 1992).
If in situ measurements of alpha, beta, or gamma activity are to be considered unbiased and of
known uncertainty, they may require adjustment to correct for the contribution from the intrinsic
detector background activity, and for ambient radioactivity. As levels of residual radioactivity
and MQOs approach background levels, the impact of ambient background on the quality of
15
Personal communication with Edward Walker, 2010.
16 Based on population-weighted average cumulative deposition density values (world) for 137Cs and 90Sr for the
year 1999; fromUNSCEAR 2000, Annex C, Table 11. Conversion from cumulative area! deposition values assumes
3
deposition in the top 5 cm of soil, and a soil density of 1.6 g/cm .
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
field measurements will become much more critical. Accurate and precise measurements of
detector background activity and corrections for background activity are possible in well-
controlled environments where the detector and ambient background can be determined
separately from the object being measured.
If the ambient background radiation level cannot be characterized accurately, measurements of
radioactivity may be biased and measurement uncertainties difficult to estimate, resulting in
measurements of unknown quality. If decisions about reoccupying space are based on such
results, the amount of contaminant present in an area could be underestimated and result in a
negative impact to public health. Conversely, unreliable background measurements could result
in the overestimation of contaminant present, and the duration and costs of recovery operations
could be increased unnecessarily. No matter what approach is taken, the accuracy of background
correction factors should be established for different measurement situations and confirmed as a
periodic QC measure by periodic confirmatory sampling.
5.1.1.1 The Impact of Background Radiation on Gross Measurements of Alpha and Beta
Radioactivity in the Field
Typical hand-held survey meters, such as thin-window Geiger-Muller detectors, respond to alpha
and beta particles and gamma rays but may not be sensitive enough for reliable measurements of
alpha and beta/gamma contamination at activities close to ambient background levels. Detectors
specific to certain types of radiation, such as alpha scintillation detectors, often have
backgrounds that are low enough to perform reliable surface measurements of pure alpha
emitters at relatively low activity levels.17 When levels of radiation being measured are clearly
above ambient background levels, as may be the case during the earlier phases of an incident, the
contribution of background to the measurement may be small to negligible. As lower and lower
levels of radioactivity are measured, as will be the case as an incident response progresses,
differentiating between background and signal from the analyte becomes increasingly
challenging and techniques that played a role early in the response may no longer be effective.
Thus, it is important to account for sources of background activity when performing field
measurements of radioactivity.
Ambient background due to beta and gamma radiation will vary significantly by location and
over time when using unshielded detectors in the field. The use of counting statistics as the basis
for detection decisions may not adequately reflect this variability and could lead to an
underestimation of the overall uncertainty of a measurement. Unreliable measurement results and
underestimates of uncertainty may lead to incorrect detection decisions or a false sense of
security about the quality of data obtained. Thus, it is critical to ensure that each measurement
technique used is appropriate for conditions under which measurements will be performed. It
should take into account variability in the background and demonstrate that a technique is still
capable of meeting quantitative and qualitative MQOs.
17It should be emphasized that this statement is applicable only when the contamination is present directly on the
surface of the object being measured such that self-absorption does not decrease the effective response of the
detector and the magnitude of analyte signal relative to the background.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Matrix materials (soil, asphalt, building materials, etc.) may contain intrinsic background
radioactivity from naturally occurring radionuclides present in the matrix prior to the incident.
This intrinsic radioactivity contributes to gross activity measurements and, unless appropriate
corrections are made, may be significant enough to result in incorrect decisions about whether
contamination is present. Similar to ambient background, this effect becomes most significant as
the incident response progresses toward later stages and the activities of concern approach
background levels. The intrinsic radioactivity of a matrix material may be determined by
analyzing a representative uncontaminated sample of the materials using the technique of
interest. This information can be used to determine the expected distribution gross activity
measurements of uncontaminated background samples and thus the levels at which one can
identify, with confidence, situations that deviate from background. Depending on the natural
background, the technique involved, and DQOs, it may or may not be possible to identify when
contamination exceeds project DQOs. If action limits or corrections are derived without regard to
the variability normally encountered under measurement conditions, systematic low or high bias
may result and may lead to an unacceptably high rate of false decisions regarding the presence
and the magnitude of contaminants.
While it may be possible to derive matrix-specific background corrections and estimates of
associated uncertainty, sometimes it may be beneficial to seek out more robust detection
techniques (e.g., when the analyte signal at the action level is less than five to 10 times the
combined uncertainty of the sum of the ambient, intrinsic, and instrument backgrounds). For
example, if a radionuclide is not present in significant concentrations in the environment, a
spectrometric measurement technique such as high purity germanium (HPGe) gamma
spectrometry might discriminate quite effectively against naturally occurring radionuclides that
would interfere with the ability of a non-spectrometric technique (i.e., a gross activity
measurement) to provide meaningful measurements at lower activity levels.
When gross activity results are corrected for contributions from ambient background activity, the
accuracy and uncertainty of correction factors should be validated under differing measurement
situations. It also is recommended that field survey measurements be verified on a periodic basis
as a QC measure (e.g., grab sampling with confirmatory analysis at a fixed laboratory).
Empirically validating measurement methods prior to use under real measurement conditions
will allow defensible statements of applicability to be made about the measurement technique,
and will demonstrate that the technique is capable of effectively meeting the DQOs and MQOs
needed for incident response decisionmaking while minimizing vulnerability to future data
challenges.
5.1.1.2 The Impact of Background Radiation on Field Measurements of Gamma
Radiation
Gamma rays are the most penetrating form of radiation and have the longest range in materials
compared to the other radiations (e.g., alpha and beta) commonly measured in the environment.
Thus, concern about interference of gamma rays with the measurement is not limited just to the
radioactive materials intrinsic to objects being measured. For example, a gamma measurement of
a wall surface in a building interior will have some component contributed by sources in the area
other than those in the expected field-of-vision of the detector. When detectors are only lightly
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
shielded or collimated, gamma rays from every part of the room and beyond can impinge on the
detector and contribute to the measurement. Gamma ray sources outside the area being measured
may significantly impact readings. For example, measurements taken inside a building in the
vicinity of a nuclear facility show variations in "background" that correspond to the amount of
radioactivity emitted from that facility.
When counting with a gamma spectrometer, background corrections may not be necessary if the
radionuclide of concern is not present in the background of the area where the sample
measurement is taken. While naturally occurring radioactivity is ubiquitous, most anthropogenic
radionuclides are rarely encountered in significant concentrations in the environment. In the case
of an incident response, however, radionuclides associated with the incident will be widely
distributed in impacted areas, and may thus become a component of ambient backgrounds and
interfere with measurements prior to remedial activities.
If background subtractions are applied to low-level in situ measurements, the background and
especially its variability (i.e., uncertainty) need to be well-characterized and reflected in the
measurement results or their evaluation. Where possible, the effect of background on sample
measurements may be minimized (but not likely eliminated) by shielding the detector. The
measurement process should include a careful consideration of whether variability in background
activity is adequately reflected in the uncertainty of the background corrected result to ensure
that measurements will be capable of meeting established MQOs. If non-specific gamma
radiation (i.e., gross gamma) is being measured, local and temporal variations in background
may make it difficult, or even impossible, to accurately and reliably determine the background
activity (or its uncertainty). No matter what approach is taken, the accuracy of background
correction factors should be established for different measurement situations and confirmed as a
periodic QC measure by periodic confirmatory sampling.
5.1.2 The Impact of Background Radiation on Laboratory Measurements
By its nature, the laboratory provides an environment where factors affecting radioanalytical
processing and measurements can be very carefully managed and controlled. Laboratory
instruments are housed in permanent locations within a building with controlled operations,
structure, temperature, and humidity. The detectors used for measurements are heavily shielded.
The shielding not only reduces the levels of the ambient background radiation impinging on the
detector surface, but it also helps to ensure that detectors are exposed to consistent and
reproducible background radiation levels. As measurement requirements approach lower levels
(as is the case in the recovery phase of a radiological or nuclear incident), the highly controlled
background environment of the laboratory setting allows more sensitive and precise
measurements and ensures quality and dependability of the data.
In instances where levels of contaminant radioactivity are very high, having a controlled
background environment is less vital. In fact, analysis of large numbers of samples of very high
radioactivity levels may create problems of cross-contamination and elevated or variable
background in the laboratory (despite the available shielding). Thus, during the early phase of an
incident, the number of samples of high activity sent to a laboratory to be analyzed should be
minimized, and the purpose of the analysis focused on identifying the radionuclides that are
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
present, establishing an upper bound on their concentration, and verifying key field
measurements.
Although there is generally a high degree of confidence that results measured in the laboratory
accurately reflect concentrations in any given sample delivered to the laboratory, the size of the
sample delivered to the laboratory is generally limited to the gram to kilogram range. This is a
much smaller effective sample size than is possible with ISGS measurements and might require
that more samples be taken and analyzed to obtain a similar level of confidence that an area is
adequately characterized and hot spots have not gone undetected.
The determination of intrinsic background in the sample matrix is an issue common to both field
and laboratory measurements. The activity of the matrix results from radionuclides present in the
matrix prior to the incident. Similar to the case discussed previously for field measurements,
intrinsic levels of radioactivity in the matrix may result in incorrect decisions that contamination
is present unless appropriate corrections are made to the measurement. For example, background
activity will confound attempts to identify alpha and beta emitters at activities similar to
background when using gross activity measurement techniques. At the laboratory, in contrast,
chemical separations can be used to determine levels of radionuclides present well below the
native gross activity of the matrix.
Similar to field measurements, the intrinsic background of the matrix must be well-characterized
to determine whether an area has been impacted. Unless the signal attributable to the analyte at
the action level is less than five to 10 times the combined intrinsic backgrounds of the material
being measured and can be shown to be de minimis, empirical matrix-specific background
corrections and estimates of associated uncertainty must be established. At these lower activity
levels, however, it is generally beneficial to seek out a more robust detection technique where
such is available. For example, for radionuclides not present in significant concentrations in the
environment, spectrometric techniques may permit effective discrimination against naturally
occurring radionuclides and allow non-spectrometric techniques (i.e., gross activity measure-
ments) to provide more accurate measurements at lower activity levels.
In contrast to many field measurements, ambient backgrounds in the laboratory are quite stable
and can be well-characterized, thus minimizing bias and uncertainty in measurements.
Measurements of detector background activity and corrections for background activity are
possible in well-controlled environments where the detector and ambient background can be
determined separately from the object being measured. The accuracy of background correction
factors applied in the laboratory is established and confirmed on a routine basis as a condition of
using an instrument.
5.2 Types of Measurements of Radioactivity
The subsequent discussion of instrumentation and measurements of radioactivity will address the
strengths, weaknesses, and general considerations that affect the capabilities of field and
laboratory measurements. In the most general sense, a field survey measurement is any
measurement used to conduct a radiation survey in the field. For the sake of this discussion,
however, a distinction will be made between field survey measurements and field spectrometry
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
measurements. Measurement techniques that measure gross activity will be classified as field
survey measurements. These include measurements that measure gross alpha, beta, or gamma
radiation, but which are not capable of determining the energy of the radiation or the isotope that
emits the radiation. Field spectrometry measurements, on the other hand, refer to measurement
techniques that are capable of analyzing the energy spectrum of radiation of concern, usually
gamma radiation, and are thus capable of identifying the radionuclide(s) present.
For radiochemical analysis at laboratories, a similar distinction applies. Chemical separations
followed by non-spectrometric measurements can achieve definitive, radionuclide-specific
measurements at the lowest activity concentrations. Thus, a distinction will be made between
screening measurements and spectrometric measurements. Screening measurements will refer to
measurements of gross activity without determination of the specific radionuclide that led to the
emission of the radiation, whereas spectrometric measurements will refer to those measurements
capable of radionuclide-specific determinations.
5.2.1 General Considerations Regarding Field Measurements
Radioactive emissions from the surfaces of objects are measured using instrumentation sensitive
to the radiation of concern (alpha, beta, or gamma). A large number of factors vary from material
to material and impact the manner in which radiation is, or is not, emitted from the surface of an
object. Variability in any one of these factors may significantly affect instrument response
relative to the source of the radioactivity (for further discussion, see Section 5.3 below).
The accuracy and sensitivity of measurement are limited by knowledge about the measurement
situation and the assumptions made about the parameters that play a role in the emission of
radiation from the object being measured to the active volume of the detector. Field
measurements are, by their very nature, measurements of radiation emitted from a surface. When
contamination is deposited directly on a surface, its measurement is much easier than if it is
deposited more or less volumetrically within an object. As discussed previously, surface activity
is radioactivity deposited on or close enough to a surface that minimal self-absorption
corrections are needed to effect a precise and unbiased measurement of that radioactivity. When
the depth profile of the radioactivity is not known, or cannot be accurately accounted for during
calibration of the instrument, accurate measurements of radioactivity are not possible. Due to
alpha- and beta emitters' limited range in matter, their measurement will be significantly
impacted even following minimal penetration of contaminants into an object. In contrast, reliable
detection and quantification of medium- to high-energy gamma emitters are possible even if
contaminants have penetrated several centimeters into an object.
While spectrometric measurements are sometimes considered to be of higher quality than gross
activity measurements, depending on the specifics of the measurement situation (e.g., surface vs.
volumetric contamination), the quality of either type of measurement may range from screening
quality to an unbiased measurement of known uncertainty and may find differing levels of
applicability depending on questions at hand.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
5.2.1.1 Survey Measurements in the Field
First responders typically will use the latest technologies that rely on the detection of gamma
rays, x-rays, and beta and alpha radiation. The applicable technologies include a variety of
portable devices such as beta/gamma and alpha survey instruments in a variety of configurations.
Generally, gamma radiation above about 200 keV (medium- to high-energy gamma emissions) is
the easiest to detect and accurately quantify with field measurements, because it is subject to
significantly less attenuation than alpha, beta, and lower-energy photon emissions, and can thus
penetrate several centimeters of material and arrive at the detector with enough energy to be
registered. Field measurements frequently provide results as uncalibrated instrument response,
such as counts per minute (cpm), or in terms of dose or exposure (e.g., urad/h, uR/h) based on
1 &
the particle flux at the meter. For example, gamma survey meters, such as Nal(Tl) detectors
and micro-R meters, are frequently calibrated using 137Cs or 60Co, perhaps due to the prevalence
of these nuclides at many nuclear sites and their relatively low cost, but also since these detectors
are optimally sensitive to radioactive emissions in this energy range. More recent generations of
instruments, however, may report activity results referenced to various radionuclides. The user is
strongly cautioned against interpreting such results as accurate measurements of absolute
radioactivity (e.g., pCi or pCi/g) unless the instrument has been calibrated for the particular
measurement situation since accurate quantitation is possible only after application of corrections
for factors such as radionuclide(s) decay type and energy, matrix composition and density,
geometric distribution of the contaminant, attenuation due to surface roughness or overlaying
material, presence of multiple radionuclides, and variations in the contribution of activity from
radionuclides in the background.
Like any other instrument, field survey instruments must be calibrated prior to use if they are to
provide results that are traceable to national standards or intercomparable from instrument to
instrument. Most field instrumentation used to measure the concentration of radionuclides
(instead of dose rate) detects total particle fluence rate with minimal regard to the energy of the
radiation. Conversion of measurements of count rate or dose (e.g., mrad per hour) to surface
activity (pCi/100 cm2) or volumetric/massic activity concentration (e.g., pCi/g) requires
knowledge of how radiation has been attenuated within the volume of the source and scattered
between the source and detector. Unless calibrations are performed that reproduce the
radionuclides and geometries and take into account self-absorption effects caused by the matrix,
the potential for bias and unknown level of uncertainty in absolute measurements of activity
cannot be discounted without additional sampling and analysis.
For direct, static measurements of beta or alpha radiation on surfaces, the efficiency of a
measurement can be viewed as a composite of two quantities:
1) Instrument efficiency, which is a function of:
Type of the radiation
18 While measurements of particle flux at the meter can be used to produce accurate estimates of dose, the use of
"uncalibrated instrument response," that is instrument net count rate, cannot be related to the activity of
radionuclides present (e.g., pCi or dpm) without applying an empirically determined values for detection efficiency,
i.e., cpm/dpm, of a specified radionuclide.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Energy of the radiation
Detector type
Position of the detector relative to the surface being measured
Window size and thickness
2) Source efficiency, which is a function of:
Type of the radiation
Energy of the radiation
Size and shape of the object
Density of the object
Physical composition of the object (i.e., average atomic number of constituents)
Depth profile of radionuclides in the object
Surface texture and roughness of the object
Density of the material
Current moisture content in the object
Establishing the instrument efficiency, that is, the response of a detector to radiation incident
upon its active area, is a relatively straightforward process if radioactive sources are available
with the appropriate radionuclides in the appropriate geometry.19 Accurately measuring the
source efficiency (i.e., the fraction of radiation emitted from a surface relative to the total number
of decays taking place in that surface) for each type of object or surface to be measured,
however, is a much more complicated task and may not be practicable without making
simplifying assumptions. A number of factors determine the fraction of total radiation that will
be emitted from a surface with enough energy to be detected.20 Complex radiation transport
models and considerable technical expertise may be needed to generate accurate corrections.
Measurement geometries are usually much more complicated in reality than approximations
based on point sources or radioactivity deposited homogenously on a plane surface. Detailed
knowledge about the measurement conditions is required to derive corrections to the efficiency.
While the density, physical composition, or even the surface texture can often be reasonably
estimated for many objects encountered in the field, it is usually impossible to accurately gauge
the depth profile of radionuclide penetration into the surface of objects encountered in the field.
This single factor alone, if not properly accounted for, may seriously impact the accuracy of field
measurements. This is particularly the case for weakly penetrating radiation such as alpha, low-
to-mid-energy beta emissions, and low-energy gamma and x-ray radiation.
If radioactivity can be assumed to reside "on the surface" of an object and the depth of
penetration of the radionuclide(s) is shallow enough that radiation is not significantly attenuated
before it escapes from the object, accurate measurements with known uncertainty are possible in
the field. As discussed earlier, this definition of surface is related to the range of the radiation in
matter and the ability to make unbiased measurements of activity and associated estimates of
uncertainty. Listed in order of increasing range, alpha emissions and beta emissions have the
shortest range, followed by x-rays and then gamma rays. Gamma rays are clearly a best case in
this regard assuming there is no contribution from sources adjacent to the surface being
19 See ANSI standards N323A and N323B for calibration of portable instruments.
20 See NUREG-1507 and ASTM standard E1893 for typical correction factors for source efficiency.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
measured (e.g., a wall in another building or a storm drain beneath a sidewalk). Alpha particles,
low-energy beta particles, and x-rays, in contrast, are worst cases because they are significantly
attenuated while passing though small amounts of matter or even by the "roughness" of the
surface from which they are emitted.
Sodium iodide or HPGe detectors, or arrays of such detectors, interfaced to a geographic
information system (GIS) can be used quite effectively to produce radiation profile maps of
gamma emitters for characterization and final status surveys. When combined with confirmatory
random and judgmental grab sample analyses at a fixed laboratory, these maps may be presented
in terms of pCi/g or pCi/unit area. Typical setups incorporate a 2x2-inch detector used manually
to scan in "swing" mode, 2x2-inch shielded detector and electronics mounted on a wheeled
frame for horizontal area coverage, and a large (5-8-inch diameter) Nal detectors mounted on a
motorized vehicle or towed behind a vehicle for very large horizontal areas. This latter system
usually includes a multichannel analyzer for in situ spectrum analysis, which may reduce or
eliminate the need for lab analysis for gamma emitters. The limited resolution of Nal detectors,
however, may limit the use of such techniques at lower activity levels because gamma emissions
from many radionuclide(s) of concern overlap those in the background. Thus, the applicability of
such techniques should be evaluated and validated on a case-by-case basis.
For scanning measurements of beta or alpha radiation (where the survey meter is moved above
and across the surface), additional parameters such as the speed of the survey meter movement
and the detector time constant must be considered to ensure correct results and detection
capability. The geometric distribution of radioactivity and the efficiency with which the field
instrument can detect its radiations must be known. At a minimum, the effective duration of the
count must be estimated using assumptions about radionuclides present, source geometry, and
detector efficiency to ensure that significant amounts of radioactivity are not missed. Finally, the
technique used for scanning can be very operator-dependent, so this should be taken into account
when setting up and validating the measurement method. NRC (1997) presents Minimum
Detectable Concentrations with Typical Radiation Survey Instruments for Various Contaminants
and Field Conditions. MARSSEVI (2000, Section 6.7.2), suggests approaches that can be used for
scanning surveys, and addresses the estimation of sensitivity (detection capability) of scanning
survey measurements.
Given these concerns, it is vital that field measurement protocols be validated relative to MQOs
prior to use to ensure that survey instrument methodologies will be capable of producing data of
sufficient quality to support DQOs and decisions to protect public health and safety. Field
measurement protocols should require correlated sampling and independent laboratory analysis
to empirically derive factors that can be used to correlate raw instrument results with
radionuclide concentrations in the matrix in question. Confirmatory sampling also should be
performed as a routine quality control measure to provide evidence that field measurement
techniques are being performed as expected and that correlation factors are accurate for the
measurement situations to which they are being applied.
In the early phase of an incident, field teams may encounter higher levels of radioactive
contamination that approach or exceed PAGs. By evaluating the impact of factors such as self-
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
91
absorption on detection efficiency in a manner that ensures that contaminants will be detected,
field teams may be able to use field survey instruments to rapidly provide protective results for
highly contaminated areas and samples such as air, water, soil, contaminated surfaces of
materials and buildings, and swipes. Such results may find great utility in providing prompt,
conservative decisions regarding the health and safety of the public. At this point in an incident
response, obtaining measurement results in real-time may outweigh the need to obtain accurate
measurements of radioactivity and the potential dose it might cause.
During the intermediate and recovery phases of an incident, field survey instruments may be
used to make dose measurements and identify areas with levels of contamination marginally
above the ambient background. However, field survey measurement techniques may not be well-
suited to detecting and quantifying contamination as instrument signal approaches low levels.
Field survey measurements may not provide unequivocal results:
Where analyte signal approaches the detection threshold of the detection technique, or
Where complex physical monitoring geometries exist, or
Where mixtures of radionuclides may be involved, or
Where weathering or other processes have set in and led to volumetric contamination of
materials.
Field survey instrument measurements can, in most cases, provide general radiation information,
such as indications of the presence of radioactive contaminants, but lacking confirmatory
analysis, they generally may not provide conclusive evidence of successful remediation during
the intermediate and recovery phases of an incident.
5.2.1.2 Spectrometric Measurements in the Field
Field spectrometric measurements are capable of measuring energy spectra and using these
characteristic spectra to provide for rapid identification of radionuclides that are present. One
example of a field gamma spectrometer is a radionuclide identifier. This is generally a sodium
iodide or high purity germanium gamma detector interfaced with a multi-channel analyzer with
automated software that analyzes characteristic energy peaks of gamma emissions. The
Conference of Radiation Control Program Directors (CRCPD) (2006) warns of the potential for
misinterpretation of data:
fGJreat caution is advised, because no identifier is correct 100% of the time, and further
analyses may be necessary for proper identification of a source. Several radioisotopes
21 Deliberately biased assumptions regarding self-absorption may help improve the reliability of field survey
measurements. For example, by assuming a worst-case penetration profile for a known radionuclide contaminant,
biased correction factors for self-absorption and associated estimates of uncertainty may be generated that ensure
that concentrations of a radionuclide that exceed an action level will be identified. Alternatively, a deliberately
biased ("judgmental") approach might be able to rapidly identify areas that likely exceed action levels, but which
will require additional characterization to determine the actual concentration prior to taking action. When biased
assumptions are applied, the technical basis for these assumptions must be clearly stated. The methods must also be
validated under the conditions of measurement using samples containing known concentrations of contaminants
(and interferences) prior to use. Once a method's limitations are well-characterized, it can be incorporated into
standard operating procedures so that all measurements provide the required degree of protection.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
emit gamma rays with energies that are similar or overlapping, or the radionuclide may
not be available for comparison in the library. These are delicate instruments that are
sensitive to abrupt changes in temperature and humidity. Additionally, radionuclide
identifiers cannot identify a pure alpha or beta emitting radionuclide unless there is an
associated gamma emitter from one of its decay products. Consequently, radionuclide
identifiers may sometimes misidentify the radioisotope.
More sophisticated field spectrometry instruments have been developed for decommissioning
nuclear power plants and radionuclide processing facilities at DOE sites. Much of the above
discussion regarding the limitations of survey instrumentation also will apply to field
spectrometry detectors. Field spectrometry measurements are by their very nature measurements
of activity emitted from a surface and may be of limited benefit unless radiation is effectively
resident on the surface of the object being measured.
Alpha, beta, and low-energy gamma rays and x-rays are much more rapidly attenuated than are
gamma rays when they are emitted from material within an object's surface. Thus, alpha, beta,
and low-energy gamma- and x-ray emitters do not lend themselves in the field to accurate
spectrometric measurements of known uncertainty unless they are known to be deposited on the
contaminated surface and thus are not subject to self-absorption effects. By contrast, the most
penetrating radiation, medium- to high-energy gamma rays, is less subject to attenuation effects.
Thus, unbiased field spectrometric measurements with known levels of uncertainty are possible
as long as the deposition profile of the radionuclides of concern is predictable and can be
accurately accounted for during calibration of the instrument.
5.2.1.3 In Situ Gamma Spectrometry Measurements
The most effective field spectrometry measurements are performed using collimated ISGS
detectors operated with supporting software such as In-Situ Object Counting System [ISOCS]
or [ISOTOPICS]. ISGS units are capable of greater specificity, and depending on
measurement conditions and the analyte(s) of interest, of greater sensitivity than gamma survey
measurements. Under the appropriate conditions, ISGS can provide significantly greater
sensitivity than highly accurate laboratory gamma spectrometry measurements and decrease the
overall number of measurements needed to characterize potentially contaminated areas. This is
due to the large field-of-view and the much larger effective sample size that can be evaluated by
a single measurement. Extended road surfaces, or large surface areas of walls, ceilings, or floors,
or even entire rooms can be evaluated with a single measurement, reducing the need to collect
samples for definitive or confirmative analysis at a laboratory.
When evaluating ISGS results, it is important to keep in mind that unless detailed information
about the distribution of radionuclides in and around the objects being measured is well-known,
22ISGS should be differentiated from commercially available software packages such as ISOCS (Canberra
Industries) and ISOTOPICS (AMETEK Ortec). In this guide, ISGS refers to the overall process of gamma
spectrometry measurements performed in situ, or in other words, without the need to destructively sample or disturb
the object or matrix in question. ISOCS and ISOTOPICS' on the other hand, are proprietary techniques that
facilitate one aspect of ISGS by estimating gamma spectrometry detection efficiencies using mathematical modeling
of the counting geometries relative to a well-characterized detector.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
measurements will be qualitative, or associated with high levels of uncertainty, such that only an
identification of radionuclides may be possible.23 In situ germanium spectrometers identify
gamma-emitting radionuclides of any gamma radiation incident on the detector. Assumptions
must be made about the geometric distribution of the radionuclide activity surrounding the
detector even in cases where little knowledge about actual conditions may be available. The
simplest approximation of geometric distribution, for example, would assume that all of the
radioactivity in the field of view of the detector is concentrated at a single point source in the
most distant point in the area of measurement, say in the furthest corner of a room five meters
from the detector. The uncollided (unscattered, full energy) photon fluence rate at the detector
position can then be calculated. Combining this fluence rate with that calculated based on a point
source calibration for the detector efficiency, a screening-level approximation of activity may be
obtained. It is important that assumptions regarding the distribution of activity lead to a result
that conservatively overestimates the true amount of activity present.
In reality, more detailed analyses are required to accommodate the complex counting geometries
that will be encountered in the field. These include models of volumetric sources of varying size,
shape, and spatial distribution of the radioactivity within the source; knowledge of angular
dependence of the photon fluence rate on detector response; and shielding effects resulting from
materials between the source and the detector. While commercial products are available for
doing such calculations, they require as input detailed models of the physical characteristics of
the object being measured, including a geometric distribution of radioactivity in the object.
Determining and documenting such information for each measurement situation, and performing
the necessary modeling, are time-consuming and involve substantial technical understanding.
Considerable professional judgment generally is needed to accurately and conservatively
estimate input parameters. Thus, it is essential that these analyses be carried out by a skilled,
knowledgeable, and experienced operator/analyst.
Absent a capable analyst, errors may be made that are unlikely to be detected in a review of the
data or reflected in the reported uncertainty of the measurements. Lacking reliable estimates of
uncertainty of measurements, critical decisions may be based on data with unknown and possibly
substantial uncertainties. Decisions may not be adequately protective and could be called into
question. Because of this fact, ISGS measurements are frequently limited to real-time
applications such as guiding remediation or recovery operations where they can be used to very
rapidly identify hot spots and gauge progress during cleanup. Final status measurements and
periodic confirmatory samples are often analyzed at fixed laboratories at critical points in the
process to provide independent assurance that the results obtained are both accurate and
reasonable. It also is common for a significant proportion of final status measurements to be
produced using definitive laboratory gamma spectrometry testing (see Appendix I for a
discussion regarding the limitations and successful use of ISGS measurements at the Rocky Flats
Environmental Technology Site).
Use of an in situ gamma spectrometer to collect reliable data requires that the instrument be set
up in the area to be evaluated in a reproducible, consistent, and well-documented fashion. The
23Automated radionuclide identification routines such as those used in radionuclide identifiers can misidentify
radionuclides present. Thus, even qualitative measurements should be evaluated by an expert gamma spectrometrist
and, where necessary, confirmatory laboratory analysis performed before results are considered final.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
instrument software requires input of observed geometry parameters. Once the setup is complete
for an individual area, an instrument measurement (count) may begin. Typically when
determining whether or not an area has contamination, a count time of one hour is reasonable,
although depending on activity levels of concern, shorter or longer measurements may be
required. Once the count is completed, the instrument may be moved to the next location and the
process repeated. If the efficiency model is established prior to making the measurement,
unreviewed results are available immediately upon completion of the measurement. If modeling
is not complete prior to the measurement, the spectrum will require subsequent workup and
reporting before unreviewed results are available.
Performing routine definitive field spectrometry measurements is a relatively newer
development. In some cases, field measurements can in fact rapidly and effectively identify
contamination at levels needed to support characterization and recovery efforts. If alpha or beta
surface activity is accompanied by a unique gamma signature, it may be possible to quantify the
alpha or beta activity using in situ spectrum analysis, minimizing the need for laboratory analysis
of grab samples beyond periodic confirmatory samples. When the gamma signature is present
and detection sensitivity permits, beta and alpha scans coupled with in situ gamma spectral
measurements may allow for rapid clearance of surfaces at action levels that would be typical of
the recovery phase.
There also is real concern about the size of the pool of capable, trained operators for field
spectrometry instruments This underscores the importance of developing robust, formalized
protocols for calibrating and operating instruments and performing QC for the field
measurements.
Although ISGS units may be able to provide sensitive gamma isotopic measurements, ISGS may
not always be a practical option for accurate evaluation of beta-gamma emitters on complex,
contaminated areas or objects. Practical disadvantages and limitations of using ISGS during an
incident response in a metropolitan area include:
ISGS detectors must be operated in the field at cryogenic temperatures. This may require
field use of liquid nitrogen, or modern electrically cooled portable detectors.
Breakdown, relocation, and setup of heavily shielded collimated units can take time and
effort and will practically limit the number of areas or surfaces that can be evaluated in a
given period of time.24
The units may have relatively long per-location acquisition times for low-level
measurements, especially for lower-energy gamma-emitting radionuclides due to self-
absorption effects when radionuclides are not deposited on the surface.
Setup, implementation, and interpretation of data from an ISGS unit (e.g., ISOCS or
ISOTOPICS ) require an experienced and technically adept operator (i.e., a specially
trained spectrometrist), of which there are relatively few.25
24For certain applications, ISGS units have been very effectively implemented in a portable configuration.
25When performing an ISGS calibration (e.g., ISOCS or ISOTOPICS), the operator must develop a mathematical
model that describes or approximates the solid geometry of the object being measured. Other required input values
are the elemental composition and density of the object, as well as the depth or penetration, distribution, and
uniformity of contaminants in and on the object, all of which must be measured or estimated. Depending on the
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
"False positive" (Type I error) and "false negative" (Type II error) measurements can
result from radionuclides that are naturally present as ambient background since varying
ambient backgrounds are often difficult to predict in field settings.
Calibration methods for ISGS measurements may not meet the rigorous standards
employed at fixed laboratories.26 ISGS generally involves mathematically modeling the
counting geometry. The skill and experience of the operator/spectrometrist, and the time
and resources required to document the circumstances of the measurement, will be
reflected in the reliability and accuracy of the calibration and the magnitude of the
uncertainty.
The level of QC measurements routinely performed for in situ measurements generally
does not rise to the level of comparable practices used to perform QC at fixed
laboratories.27 (See discussion of quality control in Section 4 of this document.)
Confirmatory laboratory analysis is needed to unequivocally verify the accuracy of
efficiency models.
Units must be checked based on documented QA/QC protocols to ensure that they are
operating properly each time they are moved to evaluate a new area or surface.
5.2.2 General Considerations Regarding Laboratory Measurements
A wide variety of instruments is used for sample measurements at laboratories. This discussion
of laboratory instrumentation will address some of the strengths, weaknesses, and general
considerations that affect laboratory instrument capabilities.
Laboratories maintain instruments that, similar to field survey equipment, measure alpha and
beta emissions from samples without regard to the energy of the respective radiations. These
include low-background gas proportional (alpha-beta) counters. Laboratories also maintain
spectrometric instrumentation that performs a range of radionuclide-specific measurements.
Examples include gamma spectrometers, alpha spectrometers, and liquid scintillation counters
(LSCs).
The initial contamination resulting from a radiological or nuclear incident is expected to be
largely removable or resuspendable as opposed to fixed, surficial contamination of structures,
objects, roadways, etc. Although they cannot readily discern between fixed and removable
contamination unless a sample is removed and analyzed separately, field measurements are
capable of rapid and sensitive measurements of total surface radiation in an area. Laboratory
measurements of removable contamination may be used to complement field measurements and
complexity of the measurement, models may need to be developed specific to each measurement. While certain of
these components are based on measured values that can be documented, others must be based on estimates that may
be less well-documented.
26At fixed laboratories, all measurements are traceable to a national standard (e.g., a NIST standard reference
material [SRM]). Calibrations are performed by direct comparison of carefully prepared sample test sources to
controlled calibration sources traceable to the appropriate national standard. Prior to first use, calibrations for each
counting configuration are verified by comparison to a second independent traceable verification standard identical
to the sample test source.
27Quality controls for in situ measurements include review of documentation about the measurement and the
analysis.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
to free field personnel to perform critical measurements of total surface contamination and grab
and confirmatory sampling. The laboratory offers the advantage of high levels of sample
throughput while maintaining accurate, sensitive, and radionuclide-specific results. The labora-
tory also is clearly best suited to the analysis of bulk samples for volumetric contamination.
Careful consideration of the complementary nature of field and laboratory measurements can
thus ensure that data will meet DQOs/MQOs while meeting operational requirements for rapid
turnaround and high throughput.
5.2.2.1 Survey Measurements at the Laboratory
At a radiochemistry laboratory, survey instrumentation is differentiated from more specialized
instrumentation used to conduct accurate and sensitive radioanalytical measurements. At a
radiochemistry laboratory, survey instruments are portable pieces of equipment used to support
laboratory operations, most frequently in the area of health physics and contamination control.
These instruments are rarely, if ever, used to perform sensitive analytical measurements of
sample activity. Instead, they find relatively limited application for such applications as
Department of Transportation (DOT) radioactive material receipt surveys, or health physics and
contamination control surveys. Survey instruments can rapidly identify the presence of
significantly elevated activities of gamma emitters. They provide results of high or poorly
estimated uncertainty and are not able to reliably and accurately quantify concentrations of
radionuclides in samples, particularly at the low activity levels that are of interest in the recovery
phase.
During an incident response, vast numbers of samples or measurements will need to be taken and
analyzed at radiochemistry laboratories. Samples must be rapidly, effectively, and accurately
prioritized for subsequent handling and radionuclide analysis based on gross activity levels.
Gross activity measurements of samples in the field or immediately upon receipt, using similar
survey instrumentation, will identify and allow prioritization of samples containing the highest
levels of gamma-emitting radionuclides. The majority of the samples, however, will contain
relatively lower levels of activity that are not effectively measured with an unshielded
instrument.
5.2.2.2 Non-Spectrometric Measurements at the Laboratory
Depending on the event, the source term may be pure alpha- or beta-emitting radionuclides,
which cannot be detected by hand-held instrument surveys of the sample containers (in the field
or in the laboratory). Alpha and beta emitters, or even lower levels of gamma activity that cannot
be detected with survey meters, are of great concern in a low-level radiochemistry laboratory
where contamination control concerns in working with open samples are much greater than in
the field due to the very low levels of activity being handled and measured at the laboratory.
Radiochemistry laboratories maintain instrumentation such as low-background gas flow
proportional detectors that perform non-specific measurements of alpha and beta radiation
analogous to those that might be performed in the field. Although the instruments in the field
bear similarity to those in the laboratory, laboratory instruments are generally heavily shielded
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
with lead and actively shielded using guard detectors to minimize ambient background radiation.
The sensitive instrumentation available at a laboratory would allow the laboratory to achieve
significantly better detection capabilities relative to most field measurements with relatively
shorter count times. Since the laboratory can have many instruments, and since it can
simultaneously process many samples in parallel using batch processes, laboratories can achieve
very high levels of throughput with lower personnel demands than is generally possible in the
field.
Environmental conditions within a laboratory are designed to be optimal for measuring
radioactivity. Background radiation levels are stable, low, well-characterized, and not subject to
variation from changes in measurement locale or to significant fluctuations from changes in
environmental conditions. Power conditioners and line-voltage regulators are commonly used at
laboratories to minimize electrical supply disturbances to the detection systems. These measures
all ensure that measurements of backgrounds and samples will be optimally sensitive and that
associated uncertainties and detection levels will be accurate and reliably determined. All of
these parameters play key roles in ensuring the quality of low-level radioactivity measurements.
Laboratories also employ chemical separations to enhance the capability of various instrument
measurement techniques. Chemical separations remove interfering matrices and radionuclides
and minimize self-absorption effects that degrade instrument response and resolution.
Laboratories can isolate a single radionuclide from a mixture of radionuclides or from the
background soup of naturally occurring radionuclides present in nearly any sample. When
combined with the appropriate chemical separations, even relatively simple gas-flow
proportional alpha-beta counters are capable of a high throughput of sensitive and accurate
radionuclide-specific measurements for a broad range of radionuclides.
5.2.2.3 Spectrometric Measurements at the Laboratory
Laboratories responding to radiological incidents will have gamma spectrometers, alpha
spectrometers, and liquid scintillation detectors. Rapid screening measurements can be made
with laboratory instruments such as liquid scintillation counters and gamma spectrometers. These
measurements can help control widespread contamination interfering with measurements, and
quick evaluation of an energy spectrum may provide a first qualitative hint of the identity of the
radionuclide contaminant. While these instruments can be used for gross activity measurements,
their full benefit is gained in using them to conduct spectrometric measurements of specific
radionuclides.
In contrast to the majority of field measurement techniques, spectrometric measurement
techniques available at the laboratory are capable of unequivocal, unbiased, and low uncertainty
determinations of specific radionuclides. In fact, these techniques are sometimes the only viable
option for determining low or medium activities of certain radionuclides. Spectrometric
instrument measurements are more accurate and generally more sensitive than determinations
that are possible with corresponding field measurements. This capability stems from these
instruments' ability to measure energy spectra, and to discriminate between mixtures of
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
9R
radionuclides based on their characteristic decay energies. Laboratory spectrometers are
operated in a very stable environment and can obtain low and reliable detection limits because of
low and stable backgrounds, and because they can discriminate against background signal that
does not exhibit the characteristic energy signature of the radionuclides of concern.
When laboratories perform measurements using alpha spectrometers, they can address the whole
range of issues that prevent accurate measurement of alpha emitters in the field. Alpha particles
are significantly attenuated by sub-milligram amounts of matter (e.g., microscopic roughness of
surfaces). Most samples contain mixtures of radionuclides that emit alpha particles with
overlapping decay energies. Many alpha emitters cannot be resolved unambiguously by an alpha
spectrometer due to their overlapping energies. However, at the laboratory, chemical separations
can be used to eliminate interfering matrix constituents and radionuclides and thereby obtain
9Q
clean and well-resolved spectra for accurate determinations of alpha-emitting radionuclides at
very low detection levels.
Although the liquid scintillation counter is capable of performing a wide range of spectrometric
measurements of alpha and beta emitters, its most common use in the radiochemistry laboratory
outside of screening samples is for measurements of radionuclides that decay via low-energy
QQ r)A'\ 1 *''
emissions, particularly beta emissions such as Tc, Pu, or H or low-energy gamma or x-ray
emitters such as 125I or 103Pd. This application is possible because the radionuclide is dissolved in
a liquid that serves as a detector, effectively eliminating the self-absorption effects that interfere
with detection of radioactivity in any solid form. Similar to alpha spectrometry, chemical
separations are used to isolate the element of concern prior to measurement to ensure the
specificity of the measurement. When combined with chemical separations, liquid scintillation is
often the only viable option for determining a number of beta emitters.
The most versatile spectrometric instrument in the laboratory is the gamma spectrometer in that
it can be used for the determination of a very large number of radionuclides. Many of the same
attributes of gamma emissions that make ISGS a powerful technique in the field are reflected in
the simplicity and efficiency of gamma measurements at the laboratory. Similar to field
measurements, the penetrating nature of gamma rays allows non-destructive measurements to be
made. This allows very rapid and accurate determinations to be made in the laboratory with a
minimum of effort but under much more controlled conditions than are possible in the field.
Although ISGS is probably the most attractive option for quickly characterizing large areas for
gamma emitting contaminants due to its ability to cover large areas with a single measurement,
the discussion of field measurements in Section 5.2 points out several concerns that should be
addressed to ensure that the quality of data is defensible. The first is the impact of potentially
high or spatially variable backgrounds on measurements that may interfere with effective
operations in the immediate vicinity of areas significantly contaminated by the incident. It is
28One notable exception is in situ gamma spectrometry measurements which, due to the large effective size of
samples, can obtain high sensitivity and minimize the likelihood of not detecting radionuclides that actually are
present at levels of concern. The downside of ISGS is that it tends to deliver semi-quantitative results that, ideally,
should bias "conservatively" high.
29Even amounts of residual matter as small as 25-50 ug/cm2 can degrade the resolution of the energy spectrum to a
point where differentiation between radioisotopes of an alpha-emitting element is not possible.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
notable, however, that this will be of less concern in later phases once remedial activities have
removed larger, contiguous sources of contaminants, and thus the background associated with
them.
For freshly deposited gamma-emitting contaminants deposited over a large area, ISGS is a very
powerful technique. One significant concern with in situ measurements involves limited
traceability of ISGS measurements to national standards. Although instruments are checked with
NIST-traceable sources to demonstrate their continued performance prior to use, they are not
necessarily calibrated using reliable reference sources that match the area being measured. Thus,
the accuracy of the analysis is largely dependent on assumptions about conditions encountered in
the field. These assumptions are used to derive factors that relate the gamma-ray flux at the
detector to the activity concentration of the specific radionuclide being measured. They include
corrections for self-absorption effects related to the depth profile of contaminants in the solid
matrix and variable distribution of radionuclides. Assumptions also could also needed to address
the degree to which gamma-emitting marker nuclides are representative of pure alpha- or beta-
emitting radionuclides in the source-term mixture, especially where weathering has occurred
after deposition. Such assumptions may be readily confirmed by analyzing select random and
judgmental grab samples at the laboratory as a regular, ongoing QC measure.
At the laboratory, high backgrounds are not of concern since instruments are heavily shielded
(4"-thick lead shielding is routine). Similarly, variability of the background is a minor concern
since instruments are maintained in the same configuration used for the sample measurements,
and backgrounds are relatively constant and can be accurately measured and subtracted from
sample measurements. As an additional control, the stability of backgrounds is tracked and
trended using control charts. The second significant concern about field gamma measurements
involved concerns about the traceability of the field measurements to national standards and the
impact of assumptions that are made regarding the geometry of the source being measured.
These assumptions include the spatial distribution of gamma emitters relative to the detector and
corrections for self-absorption within the material being measured (affected by penetration
within the object and the density and average atomic mass or "Z" of the material). These issues
are routinely addressed at the laboratory by calibrating detectors for specific counting geometries
using certified radionuclide standards traceable to NIST. Prior to counting, samples received
from the field are homogenized and transferred into counting containers so that the geometry of
the sample closely matches that of the calibration standard. Since the shape, volume, density, and
radionuclide distribution in the standard can be closely matched to that of the sample, very
accurate and precise calibration of the instrument and very accurate and precise sample
measurements are possible. Once the detector is calibrated, it is common practice to verify
calibration by counting a second standard obtained from a source independent of the one used for
the calibration.
In practice, there are also disadvantages to laboratory gamma spectrometry as opposed to field
gamma spectrometry. The first has to do with the relative detection capability of field versus lab
measurements. Field gamma spectrometry measurements have to rely on assumptions about the
measurement geometry and background. They may be associated with high or unknown levels of
uncertainty, and depending upon MQOs, the energy of the radiation and deposition patterns, it
may be possible to make conservative assumptions so that the results err protectively toward
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
reliable identification of the presence of contaminants above an action level.30 If ISGS
measurements are conservatively biased (or unbiased and of known uncertainty such that they
can be used for reliable measurements), the sensitivity and effectiveness of ISGS measurements
may exceed that obtainable by measurement in the laboratory of grab samples taken from the
same area. In cases where deposition is non-uniform, ISGS can identify hot spots that would be
very difficult to find without a large number of grab samples. This is primarily a function of the
effective size of the sample because in field measurements, the sample size is effectively very
large, whereas grab samples generally represent an area of -100 cm . For example, effective
coverage of a plane has been obtained with measurements performed one meter above the
ground using a five-meter grid (Reginatto et al. 1997). As stated above, although many
laboratory samples may be spared by using ISGS, it is generally important that the integrity of
ISGS measurements and the assumptions underlying them be confirmed using correlated
laboratory measurements.31
Another disadvantage of laboratory gamma spectrometry measurements is less technical and
more practical in nature. Since samples must be taken and shipped to the laboratory, laboratory
analysis cannot offer real-time results. Laboratories do, however, offer very rapid turnaround
times for gamma spectrometric measurements, when needed, often providing results within
hours of receiving a sample (depending on MQOs). In compensation for this, laboratories can
perform large numbers of measurements in a relatively short amount of time.
Measurements made in a laboratory will determine unequivocally which radionuclides are
present in a particular sample and can be used to address concerns that widespread contamination
could have compromised field ISGS measurements.
5.3 The Effect of Measurement Geometry on Detector Calibration
When using field survey instruments for any type of measurement, the detector is generally
positioned relative to a potentially contaminated object or surface to optimize coverage of the
area. In some cases, larger areas may be measured in a single measurement, thus minimizing the
number of measurements and lowering the overall time and effort required to characterize an
area. One of the challenges that must be addressed for field measurements is ensuring that
instruments are adequately calibrated. Once an instrument is calibrated, several questions should
be addressed. Does the calibration reflect the object or surface being measured? What are the
bounds of the measurement? Given those bounds, what is the potential for bias in the
30Unless there is empirical evidence to support them, in situ gamma spectrometry measurements are generally
qualitative or associated with elevated levels of uncertainty. Nonetheless, they may be configured and effectively
used in a manner that is protective of health and environment. In this case, it is assumed that background corrections
will introduce no bias or that any bias introduced will be "conservative" (i.e., too little background will be subtracted
yielding a final result with a high bias). It is also assumed that any bias associated with assumptions made during
efficiency calibration or modeling will be "conservative" and thus produce results that always bias high. Since these
measurements should be biased, confirmatory sampling and analysis are needed to determine the extent of bias
introduced and to minimize unnecessary expenditures of resources and efforts in the recovery process.
31 As discussed above, there is a downside to the higher sensitivity of in situ measurements that also must be taken
into account. Given the large field of vision of the detector, the presence of a hot spot within the field of view of the
instrument (even if it is beyond the direct area of measurement) may bias measurements. Thus, confirming
measurements are often needed to isolate a hot spot. Nonetheless, ISGS would still outperform grab sampling
followed by laboratory analysis, which would be more likely to fail to identify a hot spot.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
measurement? Are personnel adequately experienced and trained to know how to perform the
measurements and recognize when conditions are inconsistent with assumptions underlying the
calibration? Can a reasonable yet conservative bound on the measurement uncertainty be
established that will provide needed assurance that MQOs will be met using this technique?
5.3.1 Measurement Geometry and Field Survey Instrument Calibrations
Field measurements of gamma radiation are perhaps the most powerful and useful of field
techniques available during incident response. The instruments are portable and setup is
relatively rapid. Consistent with this, minimal shielding is generally used, often limited to a thin
collimator around the detector itself. Although a portion of the detector is shielded, the detector
will respond in varying degrees to radiation from all directions. Thus, there is no way to
completely avoid, or to account and correct for, contributions from materials beyond the
intended focus of the measurement. The calibration of field survey instruments is generally
performed using single radionuclide sources in fixed geometries or by using Monte Carlo
modeling. Although both of these approaches have been frequently used, lacking the ability to
restrict the field-of-view of the instrument or to perfectly and accurately model the area within
the field of view of the detector means that there may not be a one-to-one correspondence
between the assumed calibration geometry and the area being measured. Significant
measurement bias may result, and it may be difficult to accurately assign realistic estimates of
uncertainty to the measurements.
ASTM D1893-08 (2008) speaks of challenges involved with calibration of detection systems
used for in situ measurements of contamination.
"The in situ measurement of the residual activity distributed within a volumetric medium
of interest shall be based on the photon emission rate from that medium. The results of
the evaluations of this photon emission rate are normally expressed in units of picocuries
per gram (pCi/gm) or becquerels per gram (Bq/gm). This evaluation will be dependent on
the background response of the detector and on a conversion factor established for the
medium of interest. Non-uniform distributed source geometries can result in large
interpretation errors of in situ measurements; therefore, caution should be used with these
evaluations."
NCRP Report 112 (1991) also points out shortcomings of direct measurement techniques, among
which is a "limited ability to relate the reading of a survey meter to that of an alternative dose-
measuring instrument or device." It stresses that "...proper calibration of the instrument and a
thorough understanding of its response characteristics can reduce such discrepancies" and that
"[t]he selection and use of radiation detectors and instruments require detailed knowledge of
their response characteristics as well as judgment in their application." The report also frames the
context of many in situ measurements:
"For purposes of common radiation control, routine measurements of surface
contamination are made to fulfill regulatory requirements and to provide semi quantita-
tive information on which to base further action (e.g., decontamination). Under such
circumstances, a sophisticated and time-consuming calibration of a monitoring
instrument is not justified. In some situations, e.g., the release of a previously
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
contaminated building for unrestricted use, measurements must provide sufficient
accuracy that regulators and others can make the proper decisions. In the latter instances,
it is desirable, and perhaps necessary, that inaccuracies in measurements yield
conservative results. It is, therefore, important that the variables that affect instrument
response be understood well enough to ensure that errors are in the conservative
direction."
Calibrating detectors for direct surface measurements of alpha- and beta-emitting radionuclides
in the field can be a greater challenge than for gamma. In order to physically calibrate a detector,
a calibration source is needed that is representative of the surface or object being measured. The
reality of field measurements is that there is considerable variability in surfaces being measured,
including the composition of materials comprising the surface, and their shape, roughness, and
position relative to the detector. Given the short range of alpha and beta particles, and their
susceptibility to attenuation within the surfaces being measured, the depth profile of
radionuclides within the surface will have a profound effect on attenuation of the radioactive
emissions, and thus on the general validity of the calibration and its applicability to the
measurement situation. When measuring radionuclides present on a surface, it is often assumed
that radionuclides are present at the surface of an object and that self-absorption is either
negligible or constant. The most accurate results for alpha- and beta-emitting radionuclides can
be obtained when measuring freshly deposited contamination on a smooth, non-permeable
surface. It is extraordinarily difficult to predict the penetration of alpha- and beta-emitting
radionuclides within a surface. Thus, field measurements of alpha- and beta-emitting nuclides
should be restricted to measurements of surface contamination on relatively smooth, clean,
impermeable surfaces where the activity may be assumed to be uniformly distributed and
effectively resident on the surface.32 Even in cases that approach the ideal, surface texture can
impact instrument response. It may not be possible to obtain representative, traceable calibration
sources that conservatively match conditions expected in the field. This may necessitate
application of additional correction factors, which must be determined empirically or by best
judgment. If a detector cannot be reproducibly positioned relative to the surface being measured,
calibrations might also be affected.
MARSSEVI (2000) addresses this concern:
"In many facilities, surface contamination is assessed by converting the instrument
response (in counts per minute) to surface activity using one overall total efficiency. The
total efficiency may be considered to represent the product of two factors, the instrument
(detector) efficiency, and the source efficiency. Use of the total efficiency is not a
problem provided that the calibration source exhibits characteristics similar to the surface
contamination (i.e., radiation energy, backscatter effects, source geometry, self-
absorption). In practice, this is hardly the case; more likely, instrument efficiencies are
determined with a clean, stainless steel source, and then those efficiencies are used to
determine the level of contamination on a dust-covered concrete surface."
32In the sense used here, "surface" refers to a thickness of material that will not significantly attenuate the
radioactive emissions. This varies according to the material in question and the type and energy of radioactive
emissions being measured. Clean refers to the surface being free of dust, debris, or other material that would
requiring attenuation corrections. Quantitative measurements are not possible if the penetration profile is unknown.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
MARSSIM also points to methods that can be used to minimize these effects. For example, it
refers to NRC (1997) for typical source efficiencies for common surface materials and
overlaying material. The text also lists factors that impact efficiency:
"Instrument efficiency may also be affected by detector-related factors such as detector
size (probe surface area), window density thickness, geotropism, instrument response
time, counting time (in static mode), scan rate (in scan mode), and ambient conditions
such as temperature, pressure, and humidity. Instrument efficiency also depends on solid
angle effects, which include source-to-detector distance and source geometry. Source
efficiency may be affected by source-related factors such as the type of radiation and its
energy, source uniformity, surface roughness and coverings, and surface composition
(e.g., wood, metal, concrete)" (ISO 1988).
It is critical that measurement geometries be well-characterized and well-defined. Measurement
procedures should consistently define the conditions that must apply for a calibration to be valid
and also ensure that all calibrations and measurements proceed according to these considerations.
Prior to use in the field, empirical validation should be conducted to demonstrate that a
measurement technique, as implemented in the field, will be capable of meeting pre-defined
MQOs. Periodic QC measures, such as confirmatory sampling, should then be used on an
ongoing basis to demonstrate that the measurement system is operating as planned.
Unless the bounds on such measurements are well-defined, and the methods validated and
carefully implemented, bias may result and the uncertainty of the measurement may be
underestimated or worse, not taken into account when evaluating the applicability of a technique
for the required measurements. This could provide a false sense of security regarding the quality
of the measurements being performed.
5.3.2 Measurement Geometry and Field Spectrometry Measurements
Several different types of field spectrometry instruments are commercially available. The most
powerful and commonly used instruments are high-purity gamma spectrometers similar to those
found in analytical laboratories. These instruments are ruggedly constructed to be used in harsh
environments. They do have certain disadvantages because they are used directly in the
environment they are monitoring. One such disadvantage is the concern about the introduction of
bias by ambient background from gamma emitters adjacent to areas being characterized.
A detailed discussion of one example of the use and limitations in the use of field spectrometry
measurements during the cleanup of Rocky Flats Environmental Technology Site can be found
in Appendix I. See also Tables 3, 4, and Table 5 in Section 6, which summarize the applicability
of several field instrumentation techniques for the determination of a select group of
radionuclides important to incident response.
Assuming that the absolute geometry of the measurement is known, accurate, precise, and very
sensitive, in situ measurements of gamma emitters are possible in the field. Specifically, this
requires knowledge of the areal distribution and the depth profile of radionuclide contaminants,
the elemental composition and physical makeup (e.g., density) of the matrix material, and the
ambient contribution from the contaminant of concern in the vicinity of the measurement. When
all of these factors are well-known, in situ measurements of gamma emitters are clearly the
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
fastest and most sensitive techniques available for the characterization of gamma-emitting
contaminants. The long range of gamma rays and the resultant wider field of vision for gamma
detectors allow measurement of relatively large areas. Not only does this increase the effective
size of the "sample" measured and the sensitivity of the measurement as compared with grab
sampling techniques, but ISGS techniques also are able to measure larger areas in a single
measurement. This dramatically reduces the number of measurements needed to characterize an
impacted area with confidence that hot spots will not be overlooked.
It is necessary that the limitations of ISGS measurements be carefully considered and addressed.
Questions about the geometry, the composition of matrix materials, or the impact of ambient
background on the field measurement almost always exist.33 Without regular periodic
confirmation of the assumptions that underlie the measurement, the accuracy and especially the
estimates of measurement uncertainty of the in situ measurement should be called into question.
Even when the technique is used for qualitative or approximate measurements, such as clearing
hot spots in an area, it is vital that confirmatory measures be routinely employed that
demonstrate the adequacy of the model and the competency of the operator used for the
measurement. The most effective QC measure that can be used involves routine, periodic
confirmatory measurements of grab samples under very controlled conditions in a laboratory.
5.3.3 Measurement Geometry and Laboratory Survey and Gross Activity Measurements
Laboratories utilize survey instruments that in many cases are similar or identical to those used
for field survey measurements. These portable instruments are used almost exclusively for the
least formalized laboratory measurements, such as those performed during sample receipt. The
calibration and measurement protocols for such laboratory survey instrumentation do not vary
substantially from those used for field survey measurements and do not result in substantially
different measurement quality than what is available for similar instrumentation in the field.
More elaborate screening instrumentation available at radiochemistry laboratories can be used to
perform rapid screening measurements of gross activity. Examples of screening instrumentation
used at laboratories include low-background gas proportional counters, liquid scintillation
counters, and sodium iodide gamma counters operated in gross activity mode. As used here,
screening refers to measurements of "gross" activity in a sample that are potentially biased and
have high levels of uncertainty. In other words, this measurement is not specific to a radionuclide
and cannot differentiate between a mixture of radionuclides that emit the same radiation type
(i.e., alpha, beta, or gamma). These laboratory instruments tend to be heavily shielded and can
provide much more sensitive and reliable results than do survey measurements performed with
hand-held field or laboratory instruments, especially at lower activity levels such as those that
typically would be experienced in the later phases of an event. Often these laboratory screening
measurements are preceded by a simple preparation step, such as drying, grinding, digestion, and
a source preparation step to create a sample test source geometry that very closely matches that
33Assuming mean specific activities as quoted in NCRP Report No. 50, Table 2-6 (i.e., 0.67 pCi/g 238U with seven
alpha-emitting progeny in equilibrium, and 0.65 pCi/g 232Th with five alpha-emitting progeny in equilibrium), the
mean alpha activity of geological materials would approach 10 pCi/g with higher levels routinely encountered in a
number of natural construction materials. Unless the background matrix has been very precisely characterized, it
would be inadvisable to attempt to detect contaminants using gross activity measurements until the activity
significantly exceeds these values.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
of the applicable calibration source. Stable, low, and well-quantified backgrounds, and extended
count times facilitate more sensitive measurements at lower activity levels than can be achieved
with field or laboratory survey instruments. When combined with more stringent quality
assurance and quality control measures routinely practiced in the laboratory, these techniques
reliably provide very reproducible and defensible determinations of gross alpha, beta, or gamma
radioactivity in samples received from the field. If a single radionuclide is involved, especially at
levels well above background, screening information can often provide very accurate and
reproducible estimates of the activity of the contaminant in the sample. Thus, within minutes to
hours of receiving a sample, information of high quality not otherwise available in the field can
be made available to an Incident Commander.
5.3.4 Measurement Geometry and Laboratory Spectrometry Measurements
As time progresses during the intermediate and recovery phases, an increasing proportion of
samples will require radionuclide-specific analysis at successively lower levels. This will be
necessary to satisfy DQOs and MQOs for cleanup criteria and to reassure the public that
facilities, private property, public spaces, and personal residences have not been contaminated or
that they have been successfully decontaminated.
In the laboratory, environmental conditions such as temperature, humidity, background,
electrical line voltage, and contamination are very carefully managed to ensure reliable
measurements of radioactivity, especially at the lowest activity levels. The combination of low,
stable, and well-characterized backgrounds; extended count times; robust chemical separation
methods (incorporating chemical yield carriers and tracers to substantially reduce or eliminate
measurement biases relative to direct measurements); careful source preparation; and
spectrometric detection methods all allow these techniques to unambiguously differentiate and
accurately measure very low activities of contaminant radionuclides.
For example, alpha spectrometers can, using chemical separations, routinely and very accurately
determine the activity of alpha emitters present at 0.1 pCi level and below. Liquid scintillation
and gas-flow proportional counters can accurately determine beta-only emitters following
chemical separation at concentrations commensurate with 1CT6 risk levels and below.34 Given
progress in practical chemical separation techniques over the last five to 10 years, processing
times that were previously measured in weeks have decreased to days or even hours. While there
are no real analogs to laboratory capabilities for radionuclide-specific determinations of pure
alpha and beta emitters in the field, sensitive spectroscopic measurements of gamma emitters
using high resolution gamma spectrometers are possible without chemical separations, both in
the field and in the laboratory.
While gamma ray analysis at the laboratory may not match the effectiveness and availability of
real-time results possible with in situ measurements, the more controlled conditions in the
laboratory are conducive to producing highly accurate measurements of known uncertainty. At
the laboratory, samples are carefully homogenized and sample-to-detector geometries closely
reproduced to ensure that measurements are traceable to national radionuclide standards.
34Although gas-proportional counters possess limited energy discrimination capabilities, they are not spectrometers.
They are mentioned in this section, however, since when combined with element-specific chemical separations, they
can be used to perform very accurate and reliable low-level measurements of pure beta-emitting radionuclides.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Measurement uncertainties associated with calibration, moisture, density, and sample
homogeneity can be more accurately estimated. The laboratory also can very accurately
determine and correct measurements for ambient background, thereby ensuring unambiguous
determinations of radioisotopes even in the presence of contaminant or naturally occurring
radioactivity present in the background.
Thus, with relatively limited exceptions (such as ISGS measurements in well-characterized
areas), field measurements do not provide the sensitivity, specificity, and reliability of
radionuclide-specific measurements performed at a laboratory. Significant questions regarding
the intercomparability of field data may arise, whereas the controlled environment,
standardization of radioanalytical methods and practices at radioanalytical laboratories, and
regular participation in laboratory intercomparisons and proficiency testing programs ensure the
intercomparability of results between laboratories.
Section 5 of this document compares and contrasts various aspects of field and laboratory
measurements and addresses their relative strengths and weaknesses. Section 6 contains four
tables that compare performance characteristics of several field and laboratory measurement
techniques.
6. Comparison and Applicability of Field and Laboratory Measurements
Table 1 compares performance characteristics of non-spectrometric techniques for field and
laboratory measurements of surficial contamination. Table 2 compares performance
characteristics of non-spectrometric techniques for field and laboratory measurements of
volumetrically contaminated objects. Analogous to Tables 1 and 2, Tables 3 and 4 consider
performance characteristics for spectrometric measurements of surficially and volumetrically
contaminated objects. These performance characteristics are differentiated according to the type
of radiation being measured (alpha, beta, low-energy gamma ray, medium- to high-energy
gamma rays) and the activity relative to background.
Tables 1 and 3 address surficial contamination and assume that the contaminant radionuclides
are deposited homogeneously on a surface in such a manner that self-absorption corrections are
not needed to perform unbiased measurements with well-defined and defensible estimates of
uncertainty. Tables 2 and 4 address volumetric contamination and assume that contaminant
radionuclides are deposited within the volume of an object or matrix material such that
corrections for measurement geometry and self-absorption can be effectively applied and that the
resulting measurement does not exhibit significant bias and reasonable estimates of uncertainty
can be performed.
In the case of some field measurements, it may not be practicable to perform unbiased
measurements, although measurements may be configured in such a manner that allows
measurement quality objectives to be met defensibly. This specifically includes "judgmental"
(i.e., strategically biased) measurements as long as the combined bias and uncertainty provides
defensible and conclusive evidence that MQOs have been met.
These tables also presuppose that ambient sources of background radioactivity beyond the
surface being measured (e.g., activity associated with volumetric contamination or inherent
radioactivity of the object in question) can be accurately determined and subtracted from the
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
measurements in a manner that results in minimal absolute bias and permits reasonable and
accurate estimates of measurement uncertainty.
For field measurements, the tables further differentiate between in situ measurements of surface
contamination and in situ measurements of volumetric contamination. There is only a single
table addressing laboratory measurement (Table 7 in Appendix II) because at the laboratory there
is no significant difference in how surface or volumetric measurements are conducted beyond the
units used to report results.
Note that when compared to field measurements, there are fewer permutations for laboratory
measurements. Thus, there is minimal need to differentiate between emitter types, and there is
only a single description to address lab measurements at each activity level. This is because
laboratories, by design, can homogenize samples, perform chemical separations to address
interferences, and carefully match calibration geometries to samples. By taking control of
measurement conditions, there is no need to differentiate between many situations that pose
different challenges to field measurements.
Given the variability of conditions in the field, independent confirmatory measurements of grab
samples at a laboratory should always be performed, in parallel with in situ measurements, on a
routine basis as a quality control measure to demonstrate the integrity of the measurement
systems and to validate the accuracy of assumptions underlying the measurements.
Incident-specific circumstances, such as radionuclides of concern, matrix, interfering
radioactivity, random circumstances surrounding the measurement, and DQOs and MQOs may
influence the viability of a specific technique for a given situation. Tables 1 through 4 of this
section are complemented by three tables in Appendix II, Tables 5, 6, and 7. These tables show
the applicability of specific field and laboratory measurement techniques for determinations of
different radionuclides of concern at low, medium, and high activity levels. Tables 5, 6, and 7 do
not attempt to address every possible measurement technology; rather, they serve as a
comparative tool and a starting point for selecting appropriate field and laboratory techniques for
measurements of a variety of radionuclides at different activity levels.
Finally, Appendix III presents four simple example scenarios that synthesize information
presented in this guide. They provide a simple demonstration of how the DQO/MQO process
combined with a quality systems approach could be employed during response to a radiological
or nuclear incident in an urban field setting. Several permutations are explored, ranging from the
simplest scenario of a single medium- to high-energy gamma emitter, to more challenging
scenarios with pure alpha and beta emitters, and mixtures of radionuclides. These simple
examples are not meant for specific use in the field; rather, they identify how DQOs/MQOs,
validated measurement techniques, and a quality systems approach could be applied in a field
setting, and how field and lab measurements can be used in complementary fashion to most
expeditiously characterize areas potentially impacted by a radiological event. These scenarios
should serve as starting points for developing an approach to DQO/MQO-focused field
measurements that are technically and legally defensible and as well-documented as measure-
ments performed in a fixed laboratory.
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Table 1 - Comparison of Non-Spectrometric Field and Laboratory Measurements of Surficially Deposited Activity
Activity
Level
Emitter
Type
Field Survey Measurements*
Laboratory Screening Measurements*
Gross
activity at
the action
level
significantly
greater than
background
levels
Single
gamma
emitter of
medium- to
high-energy
Identity
known
Ideally suited for rapid, real-time location of hot spots, and qualitative
or approximate measurements of single, surface-deposited radionuclide
of known identity. Risk of false non-detection is low to moderate. Large
field-of-vision may reduce sampling uncertainty and total number of
required measurements relative to grab sampling techniques.
Measurement bias and problems estimating measurement uncertainty
increase with depth of penetration of contaminant in the surface.
Confidence in measurements is significantly improved by a routine
program of confirmatory sampling and independent laboratory analysis
that validates assumptions about deposition profiles of contamination on
and in the object being measured.
Gamma or x-
ray emitters
of low to
medium
energy
Identity
known
Similar attributes as for medium- to high-energy gamma- and x-ray-
emitters except: Measurements are less rapid; risk of false non-detection
is moderate to high; rapid increase in measurement bias and problems
estimating measurement uncertainty with decreasing energy of the
radiation and increasing penetration of contaminant into the surface.
Confidence in measurements is significantly improved by a routine
program of confirmatory sampling and independent laboratory analysis
that confirms assumptions about deposition profiles of contamination on
and in the object.
Single high-
energy beta
emitter
Identity
known
Well-suited for rapid, real-time identification of hot spots and
qualitative or approximate measurements of a single surface-deposited
radionuclide. Risk of false non-detection and data quality depends on
the adequacy of assumptions about serf-absorption, surface roughness,
efficiency corrections, and estimates of measurement uncertainty.
Confidence in measurements is significantly improved by a routine
program of confirmatory sampling and independent laboratory analysis
that confirms assumptions about deposition profiles of contamination on
and in the object.
Ideally suited for rapid, high throughput screening, or
unbiased, low-uncertainty measurements of a single
radionuclide of known identity. Also well-suited for
confirmatory measurements. Additional effort is
needed in the field for grab sampling.
Laboratory measurements are not completed in real-
time since measurements follow sampling, shipping
and preparation of test sources at the laboratory.
Results reported by laboratories in terms of activity
concentration (i.e., pCi/g or pCi/mL) may not be
directly comparable to field measurements prior to
conversion to area! concentration (i.e., pCi/m2).
Analyses are performed on prepared, homogenous
aliquants representative of the sample provided to the
laboratory, minimizing the degree of concern about
false detection and non-detection. Low and stable
backgrounds, good control of calibrations, and
measurement geometries minimize introduction of
bias during preparation and analysis and allow
minimization and accurate estimation of measurement
uncertainty. Well-defined, rigorous QC protocols
provide documented evidence supporting the quality
of results.
In the case of medium- to high-energy gamma
emitters, higher levels of uncertainty and increased
likelihood of false non-detection accompany the need
to take multiple samples to characterize an area,
whereas in situ measurements of gamma emitters may
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Activity
Level
Emitter
Type
Field Survey Measurements*
Laboratory Screening Measurements*
Single low-
to mid-
energy beta
or alpha
emitter
Identity
known
Very limited applicability. Can play a supporting role in real-time
identification of hot spots and approximate measurements of surface-
deposited radionuclides. Risk of false non-detection is very significant
for alpha and low- to mid-energy beta emitters. Total number of
required measurements is similar to grab measurement techniques.
Problems with bias and uncertainty estimates increase rapidly with
surface roughness and when the contaminant may have penetrated
below the surface of the object. Data quality depends on the accuracy of
assumptions about serf-absorption and surface roughness and estimates
of measurement uncertainty. Confidence in measurements may be weak
unless a routine program of confirmatory sampling and independent
laboratory analysis confirms that contamination is present only on the
surface of objects measured.
Radionuclide
mixtures
Identity
unknown
Well-suited for rapid, real-time identification of hot spots. Applicability
is highly dependent on specific mixes; measurement conditions; ability
to make accurate assumptions about the mixture, distribution, and depth
profile of radionuclides; and ability to accurately calibrate survey
instrumentation. High levels of alpha emitters increase probability of
false detection and non-detection. Confidence in measurements may be
weak unless a routine program of confirmatory sampling and
independent laboratory analysis confirms that assumptions used during
calibration match the conditions of analysis.
be able to characterize larger areas (e.g., up to 25 m )
in a single measurement. As a result, more laboratory
gamma measurements may be needed to characterize
an area than would be required using ISGS.
In contrast to gamma emitters, due to the short range
of the radiations in matter, the number of
measurements required to characterize alpha-, beta-,
and low- to mid-energy photon-emitting contaminants
will be similar in the field and in the laboratory.
Given significantly better detection capabilities for
short-range radiations, overall higher throughput of
measurements may be possible at laboratories,
allowing more effective used of field personnel to
streamline recovery operations.
Gross
activity at
action level
similar to
background
levels
Alpha, beta,
gamma, or
x-ray
emitters
Identity
known or
unknown
Limited applicability. Low-level survey measurements with unshielded
instrumentation do not reliably or accurately detect or quantify
contaminants due to inability to distinguish signal from background.
High risk of false detection/false non-detection due to temporal and
spatial variability in background. Significant risk of false non-detection
of alpha and beta emitters with rough or porous surfaces due to assump-
tions about geometry and variable deposition profiles. Confidence in
measurements may be weak unless a routine program of confirmatory
sampling and independent laboratory analysis confirms that assumptions
used during calibration match the conditions of analysis.
Limited applicability but more sensitive, well-
controlled measurements of gross activity are possible
than in the field. Requires grab sampling, shipping
and preparation of sample prior to measurement.
Matrix is homogenized prior to measurement.
Interpretation of results is limited when instrumen-
tation cannot distinguish between analyte signal from
background. The accuracy with which the "back-
ground activity" of the matrix is known determines
usability of measurements.
Unshielded beta/gamma and alpha survey meters.
Laboratory Screening Measurements column applies to multiple emitter types. Laboratory screening includes gross alpha, beta, and gamma analyses for a variety of sample
geometries. Instruments include shielded gas-proportional counters, gamma ray detectors, and liquid scintillation counters.
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Table 2 - Comparison of Non-Spectrometric Field and Laboratory Measurements for Volumetrically Deposited Activity
Activity Level
Emitter Type
Field Survey Measurements*
Laboratory Screening Measurements*
Gross
activity at
action level
significantly
greater than
background
levels
Gamma and
x-ray emitters
Suitability ranges significantly depending upon measurement
conditions. Rapid, real-time measurements of a known single
radionuclide are possible. Can be used qualitatively in
scanning mode to quickly localize hot spots. Relating surface
activity to volumetric activity requires that assumptions
about the spatial distribution of contaminant in samples
relative to the detector be taken into account during
calibration of the instrument. Large field-of-vision may
reduce sampling uncertainty and the total number of required
measurements relative to grab sampling techniques. Risk of
false non-detection, negative bias, and problems estimating
measurement uncertainty are high. Non-homogenous
distribution of contaminants within an object will impact the
accuracy of instrument calibrations. When this technique is
used to characterize volumetric contamination, a routine
program for confirmatory sampling and independent labora-
tory analysis is needed to provide confidence in the field
measurements by confirming the accuracy of assumptions
used during calibration.
Alpha and
Beta emitters,
low-energy
photon
emitters
Poorly suited for any volumetric measurement with the
exception of qualitative identification of hot spots. Risk of
false non-detection, negative bias, and problems estimating
measurement uncertainty are extremely high due to short
range of alpha and beta particles in solids.
Ideally suited for rapid, high throughput screening, and unbiased
measurements of known uncertainty of a single radionuclide of
known identity. Well-suited for confirmatory measurements at
the laboratory.
Additional effort is needed in the field for grab sampling.
Laboratory measurements are not completed in real-time since
measurements follow sampling, shipping, and preparation of test
sources.
Low and stable backgrounds, good control of calibration and
sample measurement geometries, and rigorous, well-defined QC
protocols minimize concerns about false detection and non-
detection, measurement bias, and inaccurate estimates of
measurement uncertainty. Higher uncertainty and increased like-
lihood of false non-detection are associated with grab sampling.
The number of samples needed to address this concern is higher
than what would be required for in situ measurements of mid- to-
high-energy gamma emitters. In contrast to gamma, the overall
number of measurements required to quantify alpha-, beta-, and
low- to mid-energy photon-emitting contaminants is similar to
the number of field measurements required, but processing time
in the laboratory may be more rapid.
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Activity Level
Emitter Type
Field Survey Measurements*
Laboratory Screening Measurements*
Gross
activity at
action level
similar to
background
levels
Gamma and
x-ray emitters
Limited applicability. In most cases, low-level survey
measurements with unshielded instrumentation do not
reliably or accurately detect or quantify contaminants due to
inability to distinguish signal from background. High risk of
false non-detection and false detection due to variability in
background radioactivity. Significant risk of false non-
detection of alpha, beta, and low-energy-photon emitters
when measuring rough or porous surfaces due to
assumptions about geometry and variable depth of
contamination that underlie calibrations. When this
technique is used to characterize volumetric contamination, a
routine program for confirmatory sampling and independent
laboratory analysis is needed to provide confidence in the
field measurements by confirming the accuracy of
assumptions used during calibration.
Alpha and
Beta emitters,
low-energy
photon
emitters
Field techniques are generally poorly suited for any
volumetric measurement of alpha and beta emitters with the
exception of the qualitative identification of hot spots. Risk
of false non-detection, negative bias, and problems
estimating measurement uncertainty are extremely high due
to short range of alpha and beta particles in solids.
Limited applicability but more sensitive and controlled measure-
ments of gross activity are possible than in the field. Interpreta-
tion of results is limited when instrumentation cannot distinguish
signal from background. The accuracy with which the
"background activity" of the matrix is known determines
usability of measurements. Requires grab sampling, shipping,
and preparation of sample prior to measurement.
Unshielded beta/gamma and alpha survey meters.
Laboratory Screening Measurements column applies to multiple emitter types. Laboratory screening includes gross alpha, beta, and gamma analyses for a variety of sample
geometries. Instruments include shielded gas-proportional counters, gamma ray detectors, and liquid scintillation counters.
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Table 3 - Comparison of Spectrometric Field and Laboratory Measurements for Surficially Deposited Activity
Activity Level
Emitter Type
Field Spectrometry Measurements
Laboratory Spectrometry Measurements*
Gamma
emitter of
medium- to
high-energy
Activity of the
radionuclide(s)
of concern at
the action level
significantly
greater than
background
levels
Ideally suited for rapid, real-time determination of radionuclide
identity and for approximate measurements of surface-deposited
gamma-emitting radionuclides. Can be used qualitatively in
scanning mode to quickly localize hot spots. Risk of false non-
detection is low-to-moderate. Large field-of-vision may reduce
sampling uncertainty and the total number of measurements
required relative to grab sampling techniques. Measurement bias
and problems estimating measurement uncertainty increase with
depth of penetration of contaminant into the surface. Confidence in
measurements is significantly improved when a routine program of
confirmatory sampling and independent laboratory analysis is used
to confirm that contamination is homogenously distributed and
only present on the surface of the object.
Gamma or x-
ray emitters of
low to medium
energy
Similar attributes as for medium- to high-energy gamma and x-ray
emitters except: Measurements are less rapid; risk of false non-
detection is moderate to high; rapid increase in measurement bias
and problems estimating measurement uncertainty with
penetration of contaminant into the surface and decreasing energy
of the radiation. Confidence in measurements is significantly
improved when a routine program of confirmatory sampling and
independent laboratory analysis are used to demonstrate that
contamination is homogenously distributed and present only on the
surface of the object.
Alpha and beta
emitters
There is very limited application to spectrometric determinations
of alpha and beta emitters in the field. Similar information can be
obtained using gross activity measurements.
Laboratory analysis of alpha, beta, and gamma emitters
is ideally suited for rapid, high throughput, low-bias,
low-uncertainty measurements of radionuclides present
alone or in mixtures. Also well-suited for confirmatory
measurements at the laboratory.
Laboratory measurements are not completed in real-
time since the measurements follow sampling,
shipping, and preparation of test sources.
Additional effort is needed in the field for grab
sampling. Results reported by laboratories in terms of
activity concentration (i.e., pCi/g or pCi/mL) may not
be directly comparable to field measurements prior to
conversion to areal concentration (i.e., pCi/m2).
Analyses are performed on prepared, homogenous
aliquants representative of the sample provided to the
laboratory to minimize concerns about false detection
and non-detection. Use of tracers/carriers during
chemical separation and analysis, low and stable back-
grounds, good control of calibrations, and measure-
ment geometries minimize introduction of bias during
preparation and analysis and allow minimization and
accurate estimation of measurement uncertainty. Well-
defined and rigorous QC provides evidence attesting to
the quality of results.
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Activity Level
Activity of the
radionuclide(s)
of concern at
the action level
significantly
greater than
background
levels
Activity of the
radionuclide(s)
of concern at
action level
similar to
background
levels
Emitter Type
Radionuclide
mixtures
Gamma
emitters of
medium to
high energy
Alpha, beta, or
low-energy
photon
emitters
Field Spectrometry Measurements *
Gamma emitters are effectively determined in the presence of
alpha and beta emitters. There is limited application to spectromet-
ric determinations of alpha and beta emitters in the field (see
above for respective discussions). If the activity of gamma emitters
relative to alpha and beta emitters has been characterized, it may
be possible to assume that the ratio holds, allowing mixtures of
radionuclides to be characterized with field measurements of
gamma marker nuclides. Confidence in measurements is
significantly improved when a routine program for confirmatory
sampling and independent laboratory analysis is used to demon-
strate that contamination is homogenously distributed and present
only on the surface of the object, and to verify assumptions about
ratios for radionuclide mixtures that have been subjected to
chemical processes such as weathering.
Similar attributes to measurements of gamma emitters in medium-
to high-activity settings, especially for non-natural radionuclides.
The power of the technique diminishes when measuring radionuc-
lides present in the matrix prior to the incident, or in areas where
there is significant target analyte shine from collocated contamina-
tion.
There is limited application to spectrometric determinations of
alpha and beta emitters in the field, especially for lower level
determinations (see above for respective discussions).
Laboratory Spectrometry Measurements**
In the case of gamma Spectrometry, there is higher
uncertainty and increased likelihood of false non-
detection associated with sampling than in field
measurements of gamma, which can characterize
larger areas. As a result, a larger number of samples
may be analyzed for gamma emitters at the laboratory
and more complex statistical analysis might be
required than would be the case for in situ measure-
ments of mid- to high-energy gamma emitters.
In contrast to gamma, the overall number of measure-
ments required to quantify alpha-, beta-, and low- to
mid-energy-photon-emitter contamination will be
similar to the number of field measurements required
to do the same.
Similar attributes to laboratory measurements above.
Detection capability for medium- to high-energy
gamma emitters may be less than that possible using
ISGS.
Similar attributes to laboratory measurements above.
Field Spectrometry equipment includes gamma spectrometers, Field Instrument for the Detection of Low-Energy Radiation (FIDLERs-1, and radionuclide identifiers.
Laboratory Spectrometry measurements column applies to multiple emitter types. Laboratory Spectrometry instrumentation includes alpha and gamma spectrometers and
liquid scintillation counters, and non-spectrometric techniques that provide radionuclide-specific results when combined with chemical separations.
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Table 4 - Comparison of Attributes of Spectrometric Field and Laboratory Measurements for Volumetrically Deposited Activity
Activity Level
Emitter
Type
Field Spectrometry Measurements
Laboratory Spectrometry
Measurements**
Activity of the
radionuclide(s)
of concern at
the action level
significantly
greater than
background
levels
Medium- to
high-energy
gamma
emitters
Suitability ranges significantly depending upon conditions of the measurement.
Rapid, real-time identification of hot spots or approximate measurements of a single
radionuclide of known identity are possible. Levels of uncertainty may vary
significantly. Relationship of surface activity to volumetric activity assumes that
spatial distribution of contaminant in samples relative to the detector is well-known
and accounted for during calibration. Large field-of-vision may reduce sampling
uncertainty and the total number of required measurements relative to grab sampling
techniques. Risk of false non-detection, negative bias, and problems estimating
measurement uncertainty are high. Contaminants may be non-homogenously
distributed within objects, leading to a mismatch between calibration and sample
geometries. When this approach is used, a routine program for confirmatory
sampling and independent laboratory analysis is needed to provide confidence in the
field measurements by verifying assumptions used during calibration and analysis.
Alpha and
beta
emitters,
low-energy
photon
emitters
Surface activity measurements are poorly suited for volumetric measurement of
alpha and beta emitters. There is limited application for spectrometric determina-
tions of alpha and beta emitters in the field beyond qualitative hot spot identifica-
tion. In many cases, similar information can be obtained using gross activity
measurements.
Similar attributes to laboratory
measurements listed in the tables above
except that measurements need not be
converted to volumetric units.
Detection capability for medium- to
high-energy gamma emitters may be
poorer than that possible using ISGS.
In contrast to gamma, spectrometric
analysis at the laboratory may be the
only viable option for measurements of
pure alpha and beta emitters.
Activity of the
radionuclide(s)
of concern at
action level
similar to
background
levels
Gamma and
x-ray
emitters
Similar attributes to measurements of gamma emitters in medium- to high-activity
settings, especially for non-natural radionuclides. The power of the technique
diminishes when measuring radionuclides present in the matrix prior to the incident,
or in areas where there is significant target analyte shine from collocated
contamination.
Alpha and
beta
emitters,
low-energy
photon
emitters
Surface activity measurements are poorly suited for volumetric measurement of
alpha and beta emitters. There is limited application for spectrometric determina-
tions of alpha and beta emitters in the field beyond qualitative hot spot
identification. Similar information often may be obtained using gross activity
measurements.
Similar attributes to laboratory
measurements above except that
measurements are generally reported in
units of volumetric or massic activity.
Approach is well-suited for sensitive,
accurate, and precise radionuclide-
specific determinations.
In contrast to gamma, spectrometric
analysis at the laboratory may be the
only viable option for measurements of
pure alpha and beta emitters.
* Field Spectrometry equipment includes gamma spectrometers, FIDLERs, and radionuclide identifiers.
** Laboratory Spectrometry Measurements column applies to multiple emitter types. Laboratory Spectrometry instrumentation includes alpha and gamma spectrometers and liquid
scintillation counters, and non-spectrometric techniques that provide radionuclide-specific results when combined with chemical separations.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
7. Conclusions
7.1 Conclusions and Recommendations Generally Applicable to Field and Laboratory
Measurements
There will be an unprecedented demand for radioanalytical capabilities following a
radiological or nuclear incident. The Agency's decisions regarding re-occupancy of
places of work, schools, playgrounds, day care centers, hospitals, places of worship,
etc., must be based on defensible data of demonstrated accuracy and quality.
Much attention has been focused on planning based on the White House Security
Council Planning Scenario #11 involving a single gamma-emitting radionuclide. It is
important to recognize that a Scenario #ll-type event is one of the simplest possible
scenarios in terms of radioanalytical measurement. Planning exclusively for the
simplest case runs a significant risk of not being prepared to address more
challenging scenarios, including mixtures of radionuclides, especially those involving
pure alpha- or beta-emitting radionuclides. Such scenarios would place extensive
demands on available resources in the field and at laboratories, and would more
quickly overwhelm available resources than would Scenario #11.
Both field and laboratory radionuclide measurements will play critical roles following
a radiological or nuclear incident. There are inherent tradeoffs between laboratory and
field measurements in terms of reliability, repeatability, uncertainty, turnaround time,
cost, and throughput. If Incident Commanders, planners, and decisionmakers
understand the respective benefits and limitations of the two approaches, they will be
able to decide under which circumstances one approach is favored over another, and
where and how the two approaches may be used synergetically to increase the
effectiveness of the response while ensuring the reliability and defensibility of
measurements used for decisionmaking.
In the intermediate and the recovery phases, a gradual transition to progressively
lower action levels and more demanding analytical requirements will likely require
increased reliance on field spectrometry measurements and increased demand for
laboratory measurements.
DQOs and MQOs must be established to provide a defensible foundation for planning
and for defending the types and quality of measurements used to support
decisionmaking. They can control the levels of uncertainty and minimize decision
error rates for decisionmaking.
All radioanalytical measurements rest on the basic principles of metrology. Every
result used for critical decisionmaking should be traceable to national radionuclide
standards.
o Instrumentation must be calibrated, and measurements performed to preserve
traceability.
o Reasonable and defensible estimates of measurement uncertainty must be
determined and reported with each result to indicate the degree of confidence that
can be placed in that result.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
The credibility, and ultimately the defensibility, of data depend on data being
generated under a quality system framework.
o Quality systems, such as those envisioned by ISO 17025, or the TNI Standard, are
critical in providing a solid framework for ensuring that all measurements used to
support the decisionmaking process are accurate and of known uncertainty, well-
documented, traceable to national standards, and generally technically and legally
defensible. Several important components of a quality system include:
Accreditation by independent authorities.
Validation of measurement methods and procedures prior to use to
demonstrate that they are capable of reliably meeting MQOs.
All measurements performed by qualified and trained analysts.
Routine blind performance evaluations against traceable standards in various
matrices.
Internal quality control measures to demonstrate the ongoing quality of
measurements.
Rigorously documented programs to ensure that data can be recreated and
independently validated and thus withstand possible data challenges.
o Although the concept of quality systems for field measurements has been
considered, implementation has yet to occur. The transitory nature of many field
operations may be partially responsible for this.
o Creative, more formalized, and effective quality controls could be implemented to
support field measurements. These might range from implementing additional QC
measurements in the field, to periodic independent confirmatory analyses at the
laboratory.
Emissions from naturally occurring radionuclides in the background may interfere
with measurements of contaminant using gross activity techniques. This challenge
may be overcome by increased use of spectrometric measurement techniques for
gamma emitters that can most effectively be performed in the field.
7.2 Conclusions and Recommendations Specific to Field Measurements
Field measurements will play a predominant role in the early phase. They:
o Are ideally suited for generating real-time data for short-term protective action
decisions involving medium- to high-activity levels.
o Can provide real-time results for rapid and effective decisionmaking.
o Can provide the best estimate of average activities of gamma-emitting
radioactivity.
o Can minimize the risk of not identifying hot spots of gamma emitters.
The value of using field calibration facilities cannot be underestimated. The availability
of such a facility, if used prior to deployment for an incident, would allow field sampling
and measurement organizations to address potential weak points in their measurement
systems to ensure that:
o Measurement technologies could be validated against reliable reference sources.
o Instruments could be calibrated against reliable reference sources.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
o Analysts could be trained and qualified in a real-world environment prior to
deployment in the field.
A number of technical and practical considerations impact the viability of field
measurements in providing rapid, unbiased, low-uncertainty measurements of
radioactivity. Several of these include:
o Control of measurement geometry to ensure defensible in situ measurements.
o The impact on calibrations and measurements of deposition patterns and mechan-
isms and self-absorption effects resulting from penetration of contaminants into
solid surfaces. Gamma-emitting contaminants are the most amenable to field
measurement. Alpha- and beta-emitting contaminants may present more
challenges to field measurements and require confirmatory or primary laboratory
analysis for their determination.
o If an incident involves pure alpha and beta emitters, or mixtures containing pure
alpha and beta emitters, field measurements may be much more limited in their
ability to meet MQOs, especially in the later stages of an incident.
The effectiveness and quality of field measurements may be limited by the
availability of equipment and experienced and trained operator/analysts.
Confidence in the field data is significantly increased by grab sampling with
confirmatory analysis at a laboratory.
7.3 Conclusions and Recommendations Specific to Laboratory Measurements
Laboratory measurements will play a limited role in the early phase. They:
o Identify the complete list of contaminants.
o Perform defensible confirmatory analyses for field measurements and measure-
ments in media such as water.
o Can be used to delineate the extent of impacted areas for lower activity air
particulate and soil measurements.
A number of technical and practical considerations impact the viability of laboratory
measurements in providing, rapid, unbiased, low-uncertainty measurements of
radioactivity. Several of these include:
o Real-time measurements are not possible with laboratory measurements.
o Grab samples must be collected and shipped to the laboratory for preparation and
analysis, which leads to a delay in obtaining analysis results relative to real-time
measurements in the field.
o Laboratories can perform independent final status measurements to meet the
highest data quality requirements.
o Laboratories provide low-bias, low-uncertainty, and low-level measurements of
alpha- and beta-emitting contaminants. Measurement geometries and calibrations
are carefully matched, controlled environments provide low and stable
backgrounds, and chemical separations may be combined with non-spectrometric
and spectrometric measurement techniques to produce reliable measurements at
the lowest activity levels.
o In spite of longer turnaround times of one to several days, laboratories provide
high throughput for less time-critical, quality-assured measurements of alpha,
beta, and gamma emitters.
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
o If sufficient resources and expertise are available in the field to collect grab
samples, combining laboratory and field capacity will result in an overall increase
in analytical throughput and more rapid completion of recovery operations.
o Naturally occurring radionuclides in the matrix may interfere with measurements
of contaminant using gross activity techniques. This challenge may be overcome
by increased use of spectrometric measurement techniques for alpha, beta, and
gamma emitters, which are readily available at the laboratory. (Note that this
challenge is shared with field measurements.)
o For gamma spectrometry measurements, larger numbers of grab samples may
have to be collected and analyzed in the laboratory to obtain the same level of
confidence obtained using in situ gamma spectral measurements.
7.4 Summary
Ultimately, both laboratory and field measurements will be used in all phases of an event as part
of the recovery and remediation process. The results of all measurements from these sources
should not only support the DQOs and MQOs, but also should be complementary to each other.
This is an extremely important part of the data assessment process that will provide the basis for
a defensible decision. Whether measurements are performed in the field or the laboratory, the
data generated need to be technically defensible. Data need to be obtained using rigorous and
well-documented analytical protocols within the context of a robust and well-implemented
quality management program. Ultimately, it is the responsibility of the Incident Commanders
and their designees to ensure that all analytical data produced will be of sufficient quality to
support decisionmaking.
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U.S. Environmental Protection Agency (EPA). 2009b. Radiological Laboratory Sample Analysis
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Laboratories, Field Sampling, and Other Organizations Generating Environmental
Measurement Data under Agency-Funded Acquisitions. Agency Policy Directive Number
FEM-2011-01, March. Available at: www.epa.gov/fem/pdfs/fem-lab-competencv-policy.pdf.
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Competence of Testing and Calibration Laboratories. Standard 17025, International
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Organization for Standardization/International Electrotechnical Commission. Geneva,
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Leino, R., D.C. George, B.N. Key, L. Knight, and W.D. Steele. 1994. Field Calibration
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402-B-04-001A, July. Volume I, Chapters 6, 7, 20, Glossary; Volume II and Volume III,
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Appendix I: Case Study on the Use of Field Spectrometry Instruments for Remediation at
Rocky Flats Environmental Technology Site (RFETS)
At Rocky Flats Environmental Technology Site, in situ gamma spectrometry (ISGS) was one of
several radioanalytical techniques used to support the decontamination and decommissioning
(D&D) process. Given RFETS' historical mission, the majority of contamination at the site
resulted from plutonium processing and involved isotopes of americium and plutonium with
lesser amounts of uranium. Experience during the D&D at RFETS showed that ISGS was a
valuable tool at the radiologically contaminated site. Given the right environmental conditions
and the resources for physically characterizing objects being measured and performing data
reduction via established procedures, it was able to play vital and complementary roles in
assessment and remediation activities. At the same time, experience showed that ISGS
applications have clear limitations and that these limitations may run counter to expectations that
large amounts of definitive radioanalytical data can be quickly and easily generated in the field,
especially if more complex mixtures of pure alpha and beta emitting radionuclides are present in
the source term.
ISGS found primary application at RFETS in situations where grab sampling was impractical
(e.g., large objects or areas) and results were needed in real-time. Specific applications included:
Support of excavations of contaminated areas and landfills (e.g., 903 Pad35);
Identifying the extent of heavily contaminated areas;
Safeguarding measurements of special nuclear materials in glove-boxes (i.e., "hold up");
Tracking progress during cleanup and excavation to provide "go" and "no-go"
determinations;
Surveys of outdoor areas (soil, pads, or other potentially contaminated surfaces); and
Characterization and final status surveys in buildings and outdoor areas during
assessment.
Most critically, in order for ISGS to provide usable results, the isotope of interest must be a
gamma-emitting radionuclide. Alpha and beta emitters cannot be detected unless they also
possess a secondary gamma ray emission. At RFETS, this was nearly an insurmountable
challenge because the primary contaminant at the site, plutonium, is an alpha emitter that emits
only very weak gamma and x-rays. Thus, plutonium is not readily detectable using gamma
spectrometry unless very large amounts are present.36 ISGS would not have played a significant
35ISOCS was used at Rocky Flats in the remediation of the 903 Pad to help guide the progress of excavation in
real-time. It might be misleading, however, to say that the measurements made at the 903 Pad using ISGS were
definitive since quantitative in situ measurements of contaminants often are impossible in the presence of
confounding contaminants and the background activity associated with them. In such cases, samples must be taken
"destructively" and transported to an area where the background activity has been quantitatively determined. At the
903 Pad, for example, a fixed geometry approach was used for many of the measurements. Although ISOCS was
used, it was most frequently not applied in situ but rather in a manner more reminiscent of conventional gamma
spectrometry measurements with the exception that ISOCS measurement efficiencies were modeled and results
generated without direct comparison to a NIST standard. Although the results generated may have been reasonable,
they were not traceable to a NIST standard as would be required of quantitative measurements.
36 While absolute detection thresholds for 239Pu were typically at the nanocurie level, exact detection thresholds
depend on ambient background, composition of the material being measured, depth and profile of deposition, area!
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
role in the D&D effort at RFETS except for the fortuitous availability of accurate data on the
isotopic makeup of plutonium used at the plant. This, together with the latest date of plutonium
separation (beginning when production operations at the plant ceased), made it possible to
inferentially relate the 241Am present to the 241Pu. Despite this information about the source term,
extensive pre-survey and post-survey confirmatory sampling and radiochemical analysis at fixed
laboratories were needed to verify that the americium to plutonium ratios presumed from process
knowledge were still valid and had not been changed due to chemical processes and transport
mechanisms following deposition of the contaminants in the environment.37
Although in situ techniques played an indispensable role in the rapid pace and ultimate success
of D&D at RFETS, it would be misleading to overlook the fact that ISGS results were qualitative
in nature, or associated with unknown levels of bias and uncertainty. To perform an accurate
"calibration" for this technique, the following conditions must be met:
Ambient background must be accurately determined, particularly for environmental and
low-level measurements where incident-related contaminants may be present adjacent to
the location of the measurement.
The physical characteristics of the material or materials comprising the object being
measured must be accurately known, including their elemental composition and density.
The shape of the contaminated objects and materials of which they are composed and
their spatial relationship to the detector must be well known.
The areal and volumetric distribution of the contaminants on and in the objects being
measured must be very well known.
All of these factors must be synthesized into a mathematical model that is representative
of the measurement, which must be done by a gamma spectrometrist specially trained and
experienced in the technique.
Given the number of critical factors underlying the application of ISGS in the real world (and the
assumptions generally necessary to estimate these factors), it is not surprising that in many cases
it is extremely difficult to realistically assign uncertainty to ISGS measurements. Similarly, it
should not be overly surprising when realistic assessments of measurement uncertainty exceed
those obtained through fixed laboratory measurements.
Thus, for critical measurements requiring reliable and defensible data (as opposed to "go" and
"no-go" measurements, such as those used to guide remedial excavations), samples were taken
and radiochemical analysis performed under the carefully controlled conditions available in
radioanalytical laboratories. Fixed laboratory analysis was crucial in situations where in situ
measurements were technically or practically infeasible. This analysis also was used to develop
distribution of the contaminant, and location of the detector. 241 Am, which has a reasonably abundant gamma ray
emission, for example, would not meet the criteria specified in 10 CFR 835 Appendix D for removable surface
contamination with MDCs of -30-50 dpm/cm2 for an ideal geometry, a flat plane surface, and extended count times
between eight and 24 hours (based on personal experience and unreleased MDC data).
37 According to informal communications with several individuals, attempts to apply similar assumptions at other
DOE sites have met with limited success.
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correlation factors used to guide in situ measurements, and as a reliable and defensible
confirmatory technique (i.e., "ground truth").
Additionally, accurate measurements with ISGS are possible only when extensive and detailed
information regarding the distribution and deposition characteristics of the contaminant is
available. Even minor variations in the characteristics (e.g., variations in depth and profiles of
contaminant penetration due to porosity, or even due to surface roughness) could introduce
significant errors into measurements. The most accurate results are obtained in cases where
surface contamination was "fixed" on a flat surface by stabilizing the contaminant with paint. In
practice, though, confirmatory sampling followed by chemical separation and laboratory analysis
is necessary to validate the assumptions made during calibration of the instruments. On a number
of occasions, traditional sampling and analysis indicated that the original assumptions made to
calibrate the ISGS were inaccurate and that the inaccuracy of measurements was not covered by
the reported uncertainty.
In the field (e.g., with soils or rough or porous surfaces), it became increasingly difficult to make
defensible assumptions and more frequent, extensive, and specialized analysis of grab samples
(e.g., radionuclide penetration analysis in cored or scabbled samples) was necessary to ensure
that ISGS measurements were accurate. Given the time, effort, and cost for the fixed laboratory
analysis, the need to synthesize this information gained, and the delay in time needed to do this,
much of the perceived rapidity of analysis was lost.
Even if only 241Am is present and conditions are otherwise reasonably ideal (e.g., 241Am-free
background, with the detector -30 cm from a plane surface), the sensitivity of the technique may
not be able to reliably measure 241 Am at the levels needed to detect surface contamination at the
limits established under 10 CFR 835 Appendix D (20 dpm/100 cm2). For example, one
representative minimum detectable concentration (MDC) study performed at RFETS indicated
detection capabilities ranging from 30-50 dpm/100 cm2 for areal deposition of 241Am using a
broad energy germanium (BEGe) detector even with extended count times of eight to 24 hours.
Another limitation of ISGS encountered at RFETS involved measurements in contaminated
areas. Because the detector is only lightly shielded (using a collimator), ambient radiation in an
area cannot be reliably differentiated from analyte signal. As a result, when contamination was
present in an area of concern at RFETS, often it was not possible to determine the background
activity. This necessitated collecting grab samples for measurement under adequately controlled
conditions. For example, although many ISOCS measurements were made during the 903 Pad
excavation, a large number of these samples were removed from the area and counted away from
the main source of contamination (in a quasi fixed-geometry situation very similar to the
traditional laboratory setting).
Finally, the experience at RFETS showed that while there are distinct advantages given the right
conditions, there are just as distinct limits to sample throughput for ISGS (specifically ISOCS)
measurements. Gamma spectrometrists specially trained and experienced in ISGS techniques are
needed to produce defensible data. Based on interviews with personnel intimately involved in
performing ISOCS measurements onsite at RFETS, 15 to 60 minutes are needed to set up a
gamma "shot." A highly experienced operator is required who can very carefully document
71
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
conditions of analysis, prepare accurately dimensioned sketches of the area, determine and
document the composition of the object being analyzed, and identify conditions that could
impact very subtle (and subjective) factors in the analysis such as depth of penetration of
contaminants. Count times vary depending on the sensitivity of the measurement needed, but
even assuming a short count of 45 minutes, a single operator with a single instrument could be
expected to perform a maximum of eight measurements in a day. If extended counts (8- to 24-
hours) are needed, throughput drops precipitously. Once the spectrum and associated data have
been acquired, data reduction and analytical results are performed by an experienced
spectrometrist. At RFETS, this required approximately 20 minutes per gamma spectrum in
routine cases. Thus, optimistically, four people would be required to produce about 25
measurements per day. This does not make any allowance for confirmatory sampling or
integration of feedback from confirmatory sampling.
In summary, ISGS would not have been capable of detecting levels of plutonium low enough to
support environmental and free-release criteria at RFETS without making assumptions regarding
ratios of plutonium relative to the marker isotope, 241Am. That it was used at all is due to the
fortuitous availability of historical isotopic characterization data for the site's plutonium.
Calibrating ISGS detection systems requires extensive knowledge that was not always available
to operators in the field. Varying and unknown levels of self-absorption in weathered settings
complicated the development of ISGS calibration models. As a result, extensive pre- and post-
survey fixed-laboratory radiochemical measurements were needed to confirm and support the
assumptions used to generate the ISGS data. The ambient background activity of 241Am from site
contaminants often precluded use of in situ techniques for measurements of 241Am. Instead,
where defensible analyses were required (i.e., results traceable to NIST standards that would be
used to make decisions of record), ISGS results were not generally used; rather, grab samples
were routinely taken and sent to fixed laboratories for alpha isotopic analysis.
In the case of a radiological or nuclear incident, it is foreseeable that even if a large amount of
ISGS equipment is procured, similar circumstances could apply. Large numbers of expert,
experienced operators and spectrometrists would be needed to perform ISGS measurements, a
requirement that would very likely cause staffing shortfalls. The limitations of assumptions
needed to develop models for calibration and elevated background from co-located contaminants
or natural background would require the coordination of field and lab resources to balance the
need for large numbers of measurements with the data quality needed to support critical
decisionmaking.
72
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Appendix II: Applicability of Selected Field and Laboratory Measurement Techniques
Tables 5, 6, and 7 provide a comparative overview of the applicability of various detection
techniques for determining radionuclides at low, medium, and high activity levels in the field and
at the laboratory. The tables may help to provide perspective on the relative applicability of
specific techniques for measurements of radionuclides conducted at different activity levels.
Incident-specific parameters, such as those listed below, will all affect the viability of a specific
technique for measurement of the radionuclides of interest:
DQOs;
MQOs;
Matrices to be sampled;
Deposition profiles of radionuclides in matrices;
Interfering radionuclides or radiation;
Non-radiological interferences;
Need for rapid or even real-time measurements; and
Relative availability of needed instrumentation, skilled and experienced analyst/operators
or samplers, and laboratory capacity.
Clearly, incident-specific circumstances such as DQOs, MQOs, matrix, interfering radiation,
circumstances of the measurement, etc., will influence the viability of a technique to a given
situation. Thus, these tables should be viewed only as a comparative tool and as a starting point
for comparing field and laboratory techniques for measurements of various radionuclides.
In the tables below, cases where a technique is generally well-suited to unbiased, low-uncertainty
determinations of a radionuclide contaminant at the respective activity level are marked with a
solid dot (). Cases in which the test is deemed to be of marginal applicability, or cases where
the technique is by its nature non-definitive, or where applicability is limited over a significant
portion of the range noted are marked with an open circle (o). Where a technique is deemed to be
unsuitable for determining the radionuclide at the activity level in question, the slot is left blank.
For field measurements, the tables further differentiate between in situ measurements of surface
contamination and in situ measurements of volumetric contamination. There is only a single
table addressing laboratory measurements because there is no significant difference in how
surface or volumetric measurements are conducted beyond the units used to report results.
In general, instruments that have high or variable backgrounds, such as unshielded
instrumentation, will find limited applicability unless the levels of radioactivity of concern are
high enough that analyte signal can be unambiguously differentiated from ambient radiation
levels. This clearly limits the applicability of many field techniques at the lowest activity levels.
When an uncontaminated sample matrix contains elevated levels of background radioactivity
intrinsic to the uncontaminated matrix material, these will compete with or mask signal from the
analyte. This is commonly the case in measurements of radionuclides at low-to-medium activity
levels. Thus, techniques based on the measurement of gross activity are viable only when the
activity of the contaminant significantly exceeds the gross activity in the uncontaminated sample
73
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
matrix. In the field, and in some cases at the laboratory, this will limit the applicability of most
non-spectrometric techniques to medium- to higher-activity levels.
In some cases, the analyte of concern itself is a radionuclide encountered in the ambient
background or in the uncontaminated matrix material, such as isotopes of radium, uranium, lead,
and polonium. In such cases, the intrinsic activity and associated uncertainty of the analyte in
uncontaminated matrix material must be determined by separately analyzing representative
uncontaminated matrix material. The uncertainty with which competing background activity is
known will define the threshold for determining the presence or absence of contaminant.
Spectrometric techniques, especially gamma spectrometry, can discriminate against interfering
radiation while specifically measuring the contaminant even when significant levels of
background activity are present. Gross gamma measurements may not provide unambiguous
results at the low and medium activity levels, while gamma spectrometric measurements may
detect very low levels of radionuclides even in the presence of the ambient levels of interfering
radioactivity.
Radionuclide-specific measurements in the laboratory will nearly always produce more accurate
results and reliable estimates of uncertainty at lower levels of activity than is possible for field
measurements. Field measurements using lightly shielded or unshielded alpha, beta, or dose rate
meters, especially at low-to-medium activities, will not be able to discriminate against the
intrinsic background signal of the matrix. This concern can be addressed at the laboratory by
combining chemical separations with heavily shielded alpha and beta measurement techniques to
provide radionuclide-specific data with lower detection levels and smaller measurement
uncertainties. Controlled counting geometries, longer count times, and tighter QA/QC controls
also allow lower uncertainties and a higher degree of defensibility.
Field techniques can provide defensible results that meet MQOs given the proper conditions.
Most optimally, when radionuclide(s) of known identity are freshly deposited on smooth and
relatively impermeable surfaces, bias due to inaccurate self-absorption corrections is
significantly minimized to a point where it is non-problematic. In most cases, however,
radionuclides are deposited on permeable and irregularly shaped surfaces, where weathering may
have occurred requiring more information about measurement conditions to generate accurate
estimates of the detection efficiency and its associated uncertainty. Such information could
include the size and shape of the active source, information about the spatial distribution
(including depth of penetration for self-absorption corrections), the degree of homogeneity of
contaminants within the source, the elemental composition of the object, and the ambient
background activity in the area of the measurement.
There is one notable exception where field measurement sensitivity may be significantly greater
than the corresponding measurements at a laboratory. ISGS is a very powerful tool for real-time
field measurement of medium- to high-energy gamma emitting radionuclides. If the
measurement geometry is reproducible and well-controlled, accurate results and low
measurement uncertainties may be possible at detection limits that are much lower than may be
routinely available at the laboratory. ISGS measurements, however, often are subject to
interference from ambient background, which may introduce bias into results and increase the
74
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
uncertainty of the measurement. Laboratory gamma spectrometry measurements, on the other
hand, are made in an environment where background from ambient sources of radiation has been
effectively eliminated but tends to be limited by the size of the sample that can be measured.
Even when factors impacting instrument calibrations and background corrections are less well-
known, a conservative set of assumptions may be applied to allow ISGS measurements to be
used protectively for rapid characterization of large areas and detecting hot spots in the field with
a minimum of effort. Given the potential for mismatch between measurement conditions and the
assumptions underlying the gamma spectrometer calibrations, however, assumptions should be
carefully applied and operational controls established to ensure that measurements will
consistently err on the side of protecting human health and the environment (i.e., always have a
positive bias).
Since in situ measurements may be biased or have high or unknown levels of uncertainty, they
should be clearly qualified as such and used only very judiciously for decisionmaking. Positive
measurements that could be the result of bias in the measurement system, or for which estimates
of uncertainty may be unrealistically low, should be verified prior to taking significant action.
The validity of all field measurements also should be routinely confirmed by independent
measurement of samples at laboratories since measurement conditions and bias are much more
carefully controlled in the laboratory setting than is generally possible in the field. These
confirmatory data provide the program with high quality, traceable results and documented
evidence, thus providing solid support for decisionmaking during incident response.
Assuming there are further limiting technical issues, decisions about whether field or laboratory
measurement techniques (or both) should be used will be influenced by operational
considerations such as: Is there a need for rapid or real-time results? Are trained and experienced
sampling personnel and fixed laboratory capacity available? Are trained, experienced
operator/analysts and field instrumentation available for field analysis?
75
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Table 5 - Applicability of Selected Field Measurement Techniques for In Situ Measurements of Surface Activity / Concentrations of Radionuclides
1 ° Radiation
2° Radiation
241Am
a
7
X
244Cm
a
x(w)
238pu
a
X
239f40pu
a
X((0)
238U#
a
x(w)
235U
a
r
X
232Jh#
a
X
7 (a)
210p0
a
n/a
226Ra#
a
y(w)
x(w)
gosr
p
n/a
sssr
P
n/a
32p
P
n/a
"Tc
p
n/a
3H
p
(LE)
n/a
241pu
P
(LE)
n/a
125|
E
(LE)
7
(LE)
129|
P
(LE)
7
(LE)
13?Cs
P
7
x(w)
6°Co
P
y(o>)
103pd
E
(LE)
X((0)
(LE)
HPGe (ISGS - energy greater than 0.06 MeV)
Low Activity
Medium Activity
High Activity
o
o
o
o
o
Unshielded Geiger-Muller (G-M) (thin window non-specific ionizing radiation - gross al
Low Activity
Medium Activity
High Activity
o
o
o
o
o
o
o
I
o
oha/gross beta)
o
o
o
o
o
o
o
o
o
Unshielded Nal(TI) (Gross Gamma )
Low Activity
Medium Activity
High Activity
o
o
o
o
o
o
o
o
Alpha Scintillator (large-area in situ zinc sulfide (ZnS) detector- gross alpha)*
Low Activity
Medium Activity
High Activity
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
Unshielded Beta Scintillator (large-area in situ organic scintillator detector - gross beta, average energy greater than 500 keV) t
Low Activity
Medium Activity
High Activity
o
o
o
o
o
o
o
o
Gas Proportional Counter (large-area in situ detector- discriminated gross alpha/beta)*
Low Activity
Medium Activity
High Activity
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
Gas Proportional Counter (segmented large-area in situ detector - discriminated gross alpha/beta) t
Low Activity
Medium Activity
High Activity
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
Thin Nal(TI) Low-energy Photon Detector (e.g., FIDLER - x-ray spectrometry specificity is limited, self-absorption prevents unbiased, low-uncertainty determinations unless surface deposited)
Low Activity
Medium Activity
High Activity
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
- suitable for definitive (unbiased, low-uncertainty) determination; o - capable of screening quality measurements only;
Low activity refers to levels between -0.1- 10 pCi/g alpha or -1-100 pCi/g beta-gamma; Medium activity refers to levels between -10-500 pCi/g alpha or -100-5000 pCi/g beta-
gamma; High activity refers to levels greater than 500 pCi/g alpha and 5000 pCi/g beta-gamma (determinations with low uncertainty are possible at levels significantly above
background); * determination based on decay progeny if in equilibrium; a - alpha emission; P - beta emission; y - gamma ray emission, x - x-ray emission; & - electron capture
decay; LE - emission less than 100 keV;
-------
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Table 6 - Applicability of Selected Field Measurement Techniques for In Situ Measurements of Volumetric Activity / Concentrations of Radionuclides
1 ° Radiation
2° Radiation
241Am
a
7
X
244Cm
a
x(w)
238pu
a
X
239f40pu
a
X((0)
238U#
a
x(w)
235U
a
7
X
232Jh#
a
X
r(w)
210p0
a
n/a
226Ra#
a
y(w)
x(w)
gosr
p
n/a
89Sr
p
n/a
32p
p
n/a
"Tc
p
n/a
3H
p
(LE)
n/a
241pu
p
(LE)
n/a
125|
E
(LE)
r
(LE)
129|
P
(LE)
r
(LE)
137CS
P
J
x(w)
6°Co
p
y(co)
103pd
E
(LE)
X((0)
(LE)
HPGe (ISGS - energy greater than 0.06 MeV)
Low Activity
Medium Activity
High Activity
0
0
0
o
0
I
o
o
o
Unshielded G-M (thin window non-specific ionizing radiation - gross alpha/gross beta)*
Low Activity
Medium Activity
High Activity
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
Unshielded Nal(TI) (Gross Gamma )
Low Activity
Medium Activity
High Activity
0
o
0
o
0
o
0
o
0
o
o
o
o
Alpha Scintillator (large-area in situ ZnS detector- gross alpha)
Low Activity
Medium Activity
High Activity
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
Unshielded Beta Scintillator (large-area in situ organic scintillator detector - gross beta, energy greater than 500 keV) *
Low Activity
Medium Activity
High Activity
o
0
o
0
o
0
o
0
0
o
0
0
o
0
Gas Proportional Counter (large-area in situ detector- discriminated gross alpha/gross beta)*
Low Activity
Medium Activity
High Activity
0
0
0
0
0
0
0
0
0
o
0
o
0
o
0
0
o
0
0
o
0
Gas Proportional Counter (segmented large-area in situ detector- discriminated gross alpha/gross beta)*
Low Activity
Medium Activity
High Activity
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
0
o
o
0
o
o
Thin Nal(TI) Low-energy Photon Detector (e.g., FIDLER - x-ray spectrometry specificity is limited, self-absorption prevents unbiased, low-uncertainty determinations unless surface deposited)
Low Activity
Medium Activity
High Activity
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
0
o
- suitable for definitive (unbiased, low-uncertainty) determination; o - capable of screening quality measurements only;
Low activity refers to levels between -0.1- 10 pCi/g alpha or -1-100 pCi/g beta-gamma; Medium activity refers to levels between -10-500 pCi/g alpha or -100-5000 pCi/g beta-
gamma; High activity refers to levels greater than 500 pCi/g alpha and 5000 pCi/g beta-gamma (determinations with low uncertainty are possible at levels significantly above
background); * determination based on decay progeny if in equilibrium; a - alpha emission; P - beta emission; y - gamma ray emission, x - x-ray emission; & - electron capture
decay; LE - emission less than 100 keV;
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Table 7 - Applicability of Selected Laboratory Measurement Techniques for Determining Activity / Concentrations of Radionuclides
1 ° Radiation
2° Radiation
241Am
a
7
X
244Cm
a
x(co)
238pu
a
X
239f40pu
a
x(a>)
238y#
a
x(co)
235U
a
7
X
232Th#
a
X
y((o)
210Po
a
n/a
226Ra#
a
7(<»)
x((o)
9°Sr
P
n/a
89Sr
P
n/a
32p
P
n/a
99Tc
P
n/a
3H
P
(LE)
n/a
241pu
P
(LE)
n/a
125|
S
(LE)
7
X
129|
P
(LE)
7
X
1"Cs
P
7
x(w)
6°Co
P
y(w)
103Rd
S
(LE)
x(w)
Unshielded G-M (thin window)
Low Activity
Medium Activity
High Activity
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Unshielded Nal(TI) (Gross Gamma)
Low Activity
Medium Activity
High Activity
0
o
0
o
0
o
0
o
0
o
o
o
0
o
0
o
o
Shielded Nal(TI) (Gross gamma)
Low Activity
Medium Activity
High Activity
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
o
Shielded HPGe Gamma Spectrometry - energy greater than 0.06 MeV)
Low Activity
Medium Activity
High Activity
o
o
o
o
o
o
o
o
Low Background Gas Proportional Counting (gross alpha/gross beta screen)
Low Activity
Medium Activity
High Activity
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Low Background Gas Proportional Counting (chemical separation - element or radionuclide specific)
Low Activity
Medium Activity
High Activity
0
0
0
0
Liquid Scintillation Counting (a/p screen - direct analysis)
Low Activity
Medium Activity
High Activity
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
0
o
o
78
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
1° Radiation
2° Radiation
241Am
a
7
X
244Cm
a
x(a>)
238pu
a
X
239f40pu
a
x(a>)
238|J#
a
x(a>)
235U
a
7
X
232Th#
a
X
y((0)
210Po
a
n/a
226Ra#
a
y(a>)
X(0))
90Sr
P
n/a
sssr
P
n/a
32P
P
n/a
"Tc
P
n/a
3H
P
(LE)
n/a
241pu
P
(LE)
n/a
125|
s
(LE)
7
X
129|
P
(LE)
7
X
13?Cs
P
7
x(co)
60Co
P
y(co)
103Pd
s
(LE)
x(co)
Liquid Scintillation Counting (chemical separation - element or radionuclide specific)
Low Activity
Medium Activity
High Activity
Alpha Spectrometry(following separations)
Low Activity
Medium Activity
High Activity
> - suitable for definitive (unbiased, low-uncertainty) determination; o - capable of screening quality measurements only;
Low activity refers to levels between ~0.1- 10 pCi/g alpha or 1-100 pCi/g beta-gamma; Medium activity refers to levels between 10-500 pCi/g alpha or 100-5000 pCi/g beta-
gamma; High activity refers to levels greater than -500 pCi/g alpha and -5000 pCi/g beta-gamma (determinations with low uncertainty are possible at levels significantly above
background); * determination based on decay progeny if in equilibrium; a - alpha emission; P - beta emission; y - gamma ray emission, x - x-ray emission; & - electron capture
decay; LE - emission less than 100 keV; o> - low intensity emission (between 0.1% and 5%); I - poorly resolvable gamma-ray interference.
* Interference from crosstalk may limit the effectiveness of beta measurement techniques when high activities of alpha activity are present, and vice versa.
79
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Appendix III: Example Scenarios: Approaches to Integrating Field and Laboratory
Measurements During Response to a Radiological or Nuclear Incident
This section presents several scenarios that illustrate
some of the challenges that may be encountered, and
some of the benefits that may be gained, during an
incident response by coordinating field and laboratory
measurements to rapidly and accurately characterize the
situation while making optimal use of limited resources
at the field and laboratory.
This section presents several simple
scenarios to help show how
radioactive emission type and
energy, DQOs / MQOs, and the use
of non-spectrometric versus spectro-
metric measurement techniques all
have an impact on possible
approaches to characterizing an
area. They also provide a taste of
how field and laboratory measure-
ments can be used in complement-
ary fashion for more effective and
efficient characterization of indoor
spaces such as those in potentially
contaminated buildings.
These examples should not be
viewed as limiting. For example,
scenarios involving complex mix-
tures of alpha- and beta-emitting
radionuclides are possible and would
require more extensive use of
spectrometric techniques in the field
and heavier reliance on laboratory
measurements following chemical
separations.
Scenarios #1 and #2 demonstrate the capabilities of ISGS
measurements. When compared to grab sampling
followed by laboratory analysis, using ISGS for the
determination of gamma emitters can significantly
decrease the number of measurements needed to
characterize an area while significantly increasing the
probability that contamination, if present, will be
detected. Using ISGS, where possible, may free up
laboratory capacity to perform more sensitive and
unbiased gamma spectral measurements of known
uncertainty such as periodic, routine confirmation of
ISGS measurements. ISGS is not without drawbacks,
however. The scenario demonstrates that an unshielded
in situ detector will respond to all incident radiation,
even if it originates from beyond the presumptive
confines of the intended measurement.
Scenarios #3 and #4 involve pure alpha and beta emitters. These underscore the limitations of
alpha and beta measurements in the field. Given the very short range of this radiation, a much
larger number of samples is needed to demonstrate that an area has not been contaminated. In
these scenarios, not only are the testing techniques not sensitive enough to address the lowest
action limits for removable contamination, but pending empirical evidence of their efficacy, they
also should be recognized for what they are: screening tests. Although results are calculated
using conservatively assigned attenuation factors to address potential geometry concerns (surface
penetration and texture), a certain fraction of results will be subjected to confirmatory analysis
using a technique at the laboratory that is capable of delivering unbiased results of known
uncertainty.
Scenario #1: Following an RDD event, Building #1 is to be assessed for 60Co contamination.
The building was downwind from the incident, and there is potential for contamination since the
heating, ventilation, and air conditioning (HVAC) was running during and after the incident as
the plume passed. As is the case throughout the city, there is also the potential that people have
tracked contamination from other areas into the building. AALs have been established by the
80
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
TO a fj f:s\
1C at 7100 dpm/100 cm and 710 dpm/100 cm for total and removable Co contamination,
respectively. The MQO for required relative method uncertainty for screening measurements of
gross gamma or gross beta activity is 34% of the respective AALs of 7100 dpm/100 cm2 and 710
dpm/100 cm2. The corresponding analytical decision levels (ADLs)39 are 3100 and 310 dpm/100
cm2 respectively.
Cobalt 60 contamination will be assessed by in situ gamma counting (non-spectrometric screen)
on each floor of the building. Given the long range of gamma rays, a single gamma measurement
can characterize a relatively large area, minimize the risk of false non-detection, and minimize
the total number of measurements required relative to measurements of alpha or beta radiation.
This could minimize the need to take multiple grab samples for analysis at the laboratory. Given
the better detection capabilities for beta radiation at the laboratory and the relative ease of taking
swipes, it may be more effective to screen for higher levels of gamma and to assess removable
contamination by taking swipes and counting beta at a radiochemistry laboratory. This optimizes
limited field staff and equipment resources and significantly streamlines characterization efforts
in the field.
An unshielded in situ Nal(Tl) gamma detector is set up in an elevated position in the center of
the room and a 1-hour count is performed. The ISGS gamma measurement is evaluated using
conservative assumptions about the geometry (i.e., all contamination is assumed to be
concentrated at a distant point within the room but no more than 3 m from the detector, and that
the radiations from 60Co are attenuated by no more than 2 cm of intervening solid material).
There is no concern about "shine" from outside the building since it is known that ambient 60Co
levels outside the building are low. Therefore, no background correction will be applied,
minimizing the risk of negative bias.
38 Actual AALs established for a specific incident would vary by incident. The AALs presented are provided here
for demonstration purposes only. These values are roughly equivalent to values shown in NRC (2006) Appendix B,
Table B.I (Acceptable License Termination Screening Values of Common Radionuclides for Building-Surface
Contamination). Per note a) of NUREG-1757, "[screening levels are based on the assumption that the fraction of
removable surface contamination is equal to 0.1. For cases when the fraction of removable contamination is
undetermined or higher than 0.1, users may assume, for screening purposes, that 100 percent of surface
contamination is removable, and therefore the screening levels should be decreased by a factor of 10." Both total
and removable limits must be met separately to satisfy criteria for free release. A single measurement of total
activity less than the ADL for removable activity can be used to demonstrate compliance with the AAL for
removable activity. See Section 3.4.2 for a more detailed discussion of MQOs, AALs, required method uncertainty
and ADLs.
39 The approach for determining MQOs is described in detail in Section VI of A Performance-Based Approach to
the Use of Swipe Samples in Response to a Radiological or Nuclear Incident (EPA 201 Ib). MQOs are derived from
DQOs consistent with MARLAP principles and ensure that decisions are based on measurements of sufficient
quality to address the question at hand. The analytical decision level is the level below which the measurement
provides sufficient confidence to reject the null hypothesis that "activity present on the surface is greater than the
action level." In this case, the AAL for total 60Co contamination is established at 7100 dpm/100 cm2. For the gross
activity measurements, the DL is 0, the Type I tolerable error, alpha, 5%, and the Type II tolerable error, beta, 10%.
Thus, the required method uncertainty, MMR, is 2400 dpm/100 cm2 at the AAL and the ADL is 3,100 dpm/100 cm2.
Thus, any result greater than the ADL of 3,100 dpm/100 cm2 would trigger appropriate corrective actions (e.g., a
more precise measurement, destructive sampling followed by lab analysis, or remediation). The values for the UMR
and ADL for removable contamination using gross activity screens are proportional to the AAL (1/10 the level for
total contamination).
81
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
If 60Co is detected in the gamma screening survey above the ADL for total contamination, a
confirmatory survey will be conducted at a new location in the room to verify the initial reading.
If 60Co is detected, gross beta surface measurements will be conducted in the room in question
with a large area beta scintillation detector and a portable 1><1" Nal(Tl) gamma survey. Swipes
also will be taken in the room and analyzed at the laboratory for removable beta contamination to
provide evidence to support achievement of removable AALs and to confirm survey results. If
60Co is detected in the gamma survey, even at levels below the AALs, the default sampling
frequency of one room per floor will be expanded as appropriate to minimize the risk of missing
contaminated rooms. Finally, swipes and a portable Nal(Tl) survey will be taken in two rooms
and two locations in the hallway of each affected floor.
As the gamma screening measurement proceeds, and after the technician has completed
assembling survey documentation (including maps and QC), three random swipe samples are
taken from judgmentally biased locations in the room (e.g., dusty areas, air intakes, door knobs),
one each from two additional rooms on the floor, and one each in opposing halves of the
hallway. The gamma measurement meets all MQOs for sensitivity and uncertainty and activity
results are below the critical level. This supports the conclusion that 60Co is not present in those
locations at levels that exceed the AAL. The swipes will be sent to a laboratory for sensitive
confirmatory counting for gross beta referenced to 60Co. The swipes are quick, low-cost, and
sensitive, and provide confirming evidence that there is no indication of removable
contamination above the AAL. The technician tags the room and floor with a "survey results
pending" notice and moves on to continue the process on the next floor of the building. The
survey will be finalized in two days after all of the data from the building, including the swipe
results, have been received back from the laboratory and independently assessed and approval is
granted.
Table 8 - Summary of Measurements for Scenario #1
Location
Bldg#l
RmlOl
Bldg#l
Rmlll
Bldg#l
Rml34
Bldg#l
1st floor
hallway north
Bldg#l
1st floor
hallway south
Radiation
Type
60 r*
Co
Beta-gamma
60 f^
Co
Beta-gamma
60 f^
Co
Beta-gamma
60Co
Beta-gamma
60Co
Beta-gamma
Primary
Measurement
1ISGS for total;
3 swipes for
removable beta.
1 swipe for
removable beta.
1 swipe for
removable beta.
1 swipe for
removable beta.
1 swipe for
removable beta.
Secondary
Measurement
n/a
n/a
n/a
Area survey with
lxl"NaI(Tl)
Area survey with
lxl"NaI(Tl)
Comment
Clear pending laboratory
analysis, data V&V, and
assessment.
Clear pending laboratory
analysis, data V&V, and
assessment.
Clear pending laboratory
analysis, data V&V, and
assessment.
Clear pending laboratory
analysis, data V&V, and
assessment.
Clear pending laboratory
analysis data V&V, and
assessment.
Scenario #2: This scenario is essentially the same as Scenario 1 except the analysis will be made
using ISGS instead of in situ gamma counting. Following an RDD event, Building #2 is to be
assessed for 60Co contamination. The building was downwind from the incident, and there is a
82
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
potential for contamination since the HVAC was running during and after the incident as the
plume passed. As is the case throughout the city, there is also the potential that people have
tracked contamination from other areas into the building. The MQO specifies that a relative
method uncertainty of 30% is required at the respective AALs for total and removable
contamination of 7100 dpm/100 cm2 and 710 dpm/100 cm2. The ADL is 3600 dpm/100 cm2. The
MQO for removable contamination is proportional to the AAL, i.e., 1/10* those for total
contamination.40
60Co contamination will be assessed by ISGS in one room on each floor of the building. Given
the long range of gamma rays, a single ISGS measurement can characterize a relatively large
area and minimize the risk of false non-detection and the total number of measurements required
relative to measurements of alpha or beta radiation. This could minimize the need to take
multiple grab samples for analysis at the laboratory. On the other hand, due to the long range of
gamma rays and the wide distribution of 60Co contamination following the incident, gamma ray
activity for 60Co is present in the background, and there is concern that 60Co detected in low-
level in situ measurements may come from a source beyond the object being measured. Given
better detection capabilities for beta radiation at the laboratory, and the relative ease of taking
swipes, it will be more effective to screen for higher levels of total 60Co using ISGS and to assess
removable contamination by beta counting swipes at a radiochemistry laboratory. This optimizes
limited field staff and equipment resources and significantly streamlines characterization efforts
in the field.
An unshielded ISGS unit is set up in an elevated position above the center of the room, and a
spectrum is recorded for 3,600 seconds. The ISGS gamma measurement is evaluated using
conservative assumptions about the geometry: i.e., all contamination is assumed to be
concentrated at a distant point within the room from the detector, which can be no more than 3
meters from the detector, and 60Co is attenuated by no more than 2 cm of intervening solid
material. In this case, there is no concern about "shine" from outside the building since it is
known that ambient 60Co levels outside the building are low. Therefore, no background
correction will be applied minimizing the risk of negative bias.
If 60Co is detected in the ISGS survey above the AAL for total contamination, a second survey
will be conducted at a new location in the room to verify the reading and to ensure that detector
placement did not bias the measurement (e.g., due to shielding by furniture, etc.). If 60Co is
detected, gross beta surface measurements with a large area beta scintillation detector and a
gamma survey will be conducted in the room in question using a 1><1" Nal(Tl) detector. Swipes
also will be taken in the room and analyzed at the laboratory for removable beta contamination to
provide further support and confirmation of survey results. Finally, swipes and a 1><1" Nal(Tl)
survey will be taken in two rooms and two locations in the hallway of each affected floor. If 60Co
is detected in the ISGS survey, even at levels below the AAL, the default sampling frequency of
40 The incident command recognizes that the spectrometric measurement technique is of higher quality and evaluates
and the ADL for total contamination using the following parameters: the DL is 0, the Type I tolerable error,
alpha, is 5%, and the Type II tolerable error, beta, is 5%. The required method uncertainty, MMR, is 220 dpm/100 cm2
at the AAL and the ADL is 360 dpm/100 cm2. Any result greater than 360 dpm/100 cm2 will trigger appropriate
corrective actions (e.g., a more precise measurement, destructive sampling followed by lab analysis, or remediation).
83
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
one room per floor will be expanded as appropriate to minimize the risk of missing significant
levels of contamination.
Note: The building ventilation system was in operation during the incident, and contamination
was spread throughout the system. A hot spot exists in the HVAC system but has not yet been
identified. The building has been unoccupied since the incident so there is less concern that
routine building cleaning operations have moved contamination or that it has become fixed.
An in situ gamma spectrometer is set up in the center of the first room to be surveyed. After
performing QC checks to ensure that the instrument is operating properly, the technician starts
the count and a spectrum is recorded over the space of an hour. The ISGS gamma measurement
will be evaluated using conservative assumptions about the geometry (i.e., all contamination is
concentrated at a single point in the room, 3 m from the detector, with less than 2 cm of
intervening solid material).
As the ISGS measurement proceeds, and after the technician has completed survey
documentation (including maps and QC), three random swipe samples are taken from
judgmentally biased locations in this room (e.g., dusty areas, air intakes, door knobs), one each
from two additional rooms on the floor, and one each in opposing halves of the hallway.
The measurement indicates that 60Co levels are high enough that they do not permit rejection of
the null hypothesis that "levels of total 60Co in the room exceed the action limit." 60Co is
somewhere within the field of view of the detector, which given the high energy of the gamma
rays in question, may extend beyond the four walls of the room. As soon as the first gamma ray
measurement has been completed and initial results indicate potentially elevated levels of 60Co,
the technician moves the instrument and prepares to conduct a confirmatory count. After QC
checking the instrument, the technician initiates a second one-hour ISGS count.
As the second gamma count proceeds, the technician performs additional surveys of the room.
Based on the identification of 60Co, static counts with a 600 cm2 beta-scintillating detector are
initiated at two random locations in the room. A scanning survey for gamma radiation is also
performed with a portable 1><1" Nal(Tl) detector. Although the gamma scanning measurements
are not of sufficient sensitivity to "clear" the room, they often are useful for hot spot
identification. It is important to keep in mind that large area measurements may effectively
"average" and thus fail to identify hotspot activity. The technician notes slightly elevated
readings toward the center of the building in front of air conditioning ductwork. A note is made
in the paperwork that the floor of the room is ceramic tile and that elevated gamma activity is
observed over the tile. Based on the elevated readings in the Nal(Tl) survey in the vicinity of the
air conditioning duct, one additional static count for gross beta is taken adjacent to the AC vent
but no supporting beta activity is found. Based on available evidence, it appears that the source
of the activity may be outside the room. The technician will note this in the report and bring it to
the attention of the team leader.
The results of the second in situ gamma count support those of the first and indicate that
detectable 60Co is present. Since the field of view for the detector extends beyond the room,
however, the detector may be responding to some source of contamination outside the room. The
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
static beta measurement in front of the air conditioning duct shows slightly elevated levels that
exceed action limits for removable contamination. The results of the gas proportional beta counts
in all non-ceramic locations meet specifications for sensitivity and measurement uncertainty, and
the results are low enough to support the conclusion that 60Co is not present at those locations at
levels that exceed the AAL for removable contamination. The beta survey on the tile is
predictably very elevated, but the technician has seen this problem before and notes the concerns
about 40K in the log. Following procedure, the technician takes four random swipes from the
tiled area, and one swipe from a judgmental (i.e., worst case) location on the wood floor and
queues these to be sent to the laboratory for confirmatory gross beta counting. The room is
tagged with a note stating "survey results pending" and the process is repeated in the next room.
Table 9 - Summary of Measurements for Scenario #2
Location
Bldg #2
RmlOl
Bldg #2
Rmlll
Bldg #2
Rml34
Bldg #2
North end of
1st floor
hallway
Bldg #2
South end of
1st floor
hallway
Radiation
Type
60Co
Beta-
Gamma
6UCo
Beta-
Gamma
6UCo
Beta-
Gamma
60Co
Beta-
Gamma
60Co
Beta-
Gamma
Primary
Measurement
2ISGSfortotal;
3 swipes for
removable beta.
1 swipe for
removable beta.
1ISGS for total;
3 swipes for
removable beta
1 swipe for
removable beta.
1 swipe for
removable beta.
Secondary
Measurement
3 static counts for gross
beta surface activity;
Nal(Tl) gamma survey
n/a
n/a
Area survey with 1x1"
Nal(Tl)
Area survey with 1x1"
Nal(Tl)
Comment
60Co results above ADL; source
not localized; laboratory swipe
data, V&V, and assessment
pending.
Laboratory analysis pending.
60Co below ADL; laboratory
analysis, V&V, and assessment
pending.
Laboratory swipe analysis,
V&V, and assessment pending.
Laboratory analysis, V&V, and
assessment pending.
Scenario #3: This is essentially the same scenario as Scenarios #1 and #2 with the exception that
the RDD source term has been identified as pure alpha-emitting 239240Pu. The building was
downwind from the incident, and there is reasonable potential for contamination since the HVAC
was running during and after the incident as the plume passed. As is the case throughout the city,
there is also the potential that people have tracked contamination from other areas into the
building. AALs have been established at 50 dpm/100 cm2 and 5 dpm/100 cm2 for total and
removable contamination respectively. The MQOs specify that a required method uncertainty of
24% is required at the AAL. ADLs of 30 and 3.0 dpm/100 cm2 are specified for total and
removable contamination respectively.41
41 Incident Command has established MQOs for MMR using the following parameters. The AAL for total alpha is 50
dpm/100 cm2. The DL is 10 dpm/100 cm2, (set at an assumed native gross alpha of 10 dpm/100 cm2), the Type I
tolerable error, alpha = 5%, and the Type II tolerable error, beta = 5%. The required method uncertainty, MMR, is thus
12 dpm/100 cm2 at the AAL and the ADL is 30 dpm/100 cm2. Thus, relative low uncertainty measurements are
needed, and any result greater than 30 dpm/100 cm2 will trigger appropriate corrective actions (e.g., a more precise
measurement, destructive sampling followed by lab analysis, or remediation).
85
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
This scenario presents special challenges since field surveys for low levels of alpha-emitting
contaminants are of limited effectiveness. Ambient levels of naturally occurring alpha emitters in
building materials and interference from radon and decay progeny, for example, will prevent
MQOs for removable contamination from being determined using in situ measurements. Wipe
samples will be analyzed at the laboratory by gross alpha and, when needed, isotopically (after
chemical separation from other alpha emitters) to determine the specific concentration of
239/240pu £ven if fi^d measurements, such as those conducted with a large area ZnS counter (600
cm2), are able to provide sufficient sensitivity to differentiate between the gross alpha natural
background (assumed to be 10 dpm/100 cm2) from the 50 dpm/100 cm2 AAL for total 239/240Pu
contamination, it is important that the technician be able to identify situations where self-
absorption may be a confounding factor that undermines the defensibility of the measurements.
Laboratory analysis of grab samples will provide superior detection limits and lower
measurement uncertainties for gross alpha, and thus minimize the risk of false non-detection.
Lacking techniques with similar detection range to ISGS, incident-specific protocols for alpha
and beta detection specify that an increased number of surveys will be conducted in multiple
rooms on each floor of the building. Large-area ZnS alpha detectors have been shown to be
capable of rapidly identifying elevated levels of beta-gamma emitters, and alpha- and gamma-
emitting contamination from 226Ra (and progeny) on impermeable and relatively smooth
surfaces.42 It is important, however, to carefully evaluate the applicability of direct measurement
techniques for each surface. When rough, dirty, or porous surfaces are involved, direct alpha
measurements using a large-area ZnS detector may be "non-conservative" and thus may be
suitable only for identifying hot spots and triggering more aggressive follow-up surveys.
Similarly, porous or rough materials, and materials known to contain elevated levels of intrinsic
naturally occurring alpha emitters (such as granites and some concretes), may not be amenable to
gross alpha screening.
Where problematic surfaces predominate, or where direct measurements indicate possible
contamination, field instruments such as FIDLERs may be used to improve the reliability of
measurements, and certainly to perform real-time qualitative identification of hot spots, but they
cannot defensibly "clear" an area, at least without confirming measurements that verify the
assumptions upon which the clearance measurements are based. Instead, accurate determinations
of 239240Pu are most effectively and defensibly determined by grab sampling (e.g., scabbling or
coring) followed by isotopic analysis for 239/2 °Pu at a radiochemistry laboratory. Wipe samples
of removable contamination also can be sent to a radiochemistry laboratory for gross alpha
screening, with potential alpha isotopic determinations of 239 40Pu, as indicated. Finally,
confirmatory grab sampling at a direct measurement location will be performed as a recurring
QC measure to confirm the accuracy of the direct measurements. Since AALs are provided in
units of areal contamination, sample volumes must be recorded in terms convertible to equivalent
surface area and the laboratory instructed to calculate results in terms of activity per unit surface
area. If any of the laboratory results are positive for 239240Pu, data will be assessed and additional
action taken as deemed appropriate.
The technician enters the first room specified for surveying and sets up two large area ZnS
detectors for a 30-minute static count of the tile floor and the welcome mat. As the counters
42 Personal communication with Dick Dubiel of Millennium Shonka, 2010.
86
-------
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
acquire data, the technician proceeds to collect swipes from five locations in room 101, and one
swipe each from the north and south ends of the hallway. When acquisition is complete, the
technician notes that uncertainty requirements have been met, but that the count on the welcome
mat exceeds the action limit for total alpha. In keeping with protocol, he surveys the area, cuts a
100 cm2 coupon from the area showing the highest survey results, and packages and labels this to
be sent to the laboratory for confirmatory analysis. Once the work is complete, the technician
marks the room as "potentially contaminated pending confirmatory laboratory analysis" and
continues to room 111, where he initiates two more static counts for total alpha activity. As these
data are being acquired, he collects five wipe samples each from rooms 111 and 134. When the
static counts are finished, the technician verifies that the uncertainties will meet the MQOs and
determines that both results are low enough to conclude that the activity will not exceed the
AAL. He places a sign on the door indicating that laboratory analysis is pending and moves on to
the next floor.
Table 10 - Summary of Measurements for Scenario #3
Location
Bldg #3
RmlOl
Bldg #3
Rmlll
Bldg #3
Rml34
Bldg #3
North end of
1st floor
hallway
Bldg #3
South end of
1st floor
hallway
Radiation
Type
239/240pu
Alpha
239/240pu
Alpha
23y/24aPu
Alpha
239/240pu
Alpha
239/240pu
Alpha
Primary Measurement
2 static counts for gross
alpha total surface
activity;
1 sample taken -
"welcome mat coupon"
2 static counts for gross
alpha total surface
activity
n/a
n/a
n/a
Secondary
Measurement
5 swipes for
removable alpha
activity
5 swipes for
removable alpha
5 swipes for
removable alpha
1 swipe for
removable alpha
1 swipe for
removable alpha
Comment
Gross alpha above action limit;
sample taken for analysis.
Laboratory analysis, V&V, and
assessment pending.
Laboratory analysis, V&V, and
assessment pending.
Laboratory analysis, V&V, and
assessment pending.
Laboratory analysis, V&V, and
assessment pending.
Laboratory analysis, V&V, and
assessment pending.
Scenario #4: This is the same scenario as Scenario #2 except in this case, the RDD source term
is identified as 90Sr. AALs have been established at 87 dpm/100 cm2 and 8.7 dpm/100 cm2 for
total and removable contamination respectively. The MQO specifies that a required method
uncertainty of 15% at the AAL. The ADLs are 65 and 6.5 dpm/100 cm2 for total and removable
contamination respectively.43
43 Incident Command has established AALs, MMR and ADLs using the following parameters to evaluate MMR and the
ADL. The AALs for gross beta screening are 87 dpm/100 cm2 and 8.7 dpm/100 cm2, for total and removable
activity. The DL = is l/i the respective AAL, the Type I tolerable error, alpha = 5%, and the Type II tolerable error,
beta = 5%. The required relative method uncertainty, MMR, is 15% of the AAL, and the ADLs are 65 dpm/100 cm2
and 6.5 dpm/100 cm2 for total and removable contamination respectively. Given the low levels that would be
required to demonstrate meeting levels for removable activity, they will be analyzed by taking swipes that will be
sent to a radiochemistry laboratory for analysis on a low background proportional counter, and where necessary,
verification of radioisotopic activity following chemical separations.
87
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Given the limitations of field surveys for very low levels of beta contamination, the superior
detection capability at laboratories for gross beta, and accuracy and reliability of laboratory
analysis for 90Sr, the approach will rely more heavily on laboratory analysis of swipes for non-
permeable surfaces and on grab samples for porous or other rough surfaces. Because 90Sr does
not emit any gamma rays, ISGS is not a viable alternative. Lacking the detection range of ISGS,
protocols specify that surveys will be conducted in two rooms on each floor of the building. If
surfaces are impermeable and relatively smooth (and significant levels of naturally occurring
radionuclides are not present), large area beta scintillation detectors have been validated to
determine compliance with action limits for total 90Sr contamination on smooth and impermeable
surfaces. Due to the potential for self-absorption of beta emissions, surface measurements on
porous or rough surfaces are considered non-conservative screens and are suitable only for
identifying hot spots and triggering more aggressive follow-up surveys. Porous or rough
materials, or materials known to contain elevated levels of naturally occurring beta emitters
(such as ceramic tile, granites, and concretes), will produce high rates of false positive
determinations. Where such surfaces are predominant, or where direct measurement has
indicated possible contamination, grab sampling (e.g., coring or scabbling) is required followed
on
by analysis for Sr at a radiochemistry laboratory. Confirmatory grab sampling also is required
at one direct measurement location at a frequency of one sample per building. Since AALs are
provided in units of areal contamination, sample volumes must be recorded in equivalent surface
area and the laboratory instructed to calculate results in terms of activity per unit surface area. If
any of the laboratory results are positive for 90Sr, data will be assessed and additional action
taken as deemed appropriate.
The technician enters the first room specified for surveying and sets up both large area beta
scintillation detectors for 10-minute static counts. As the counters acquire data, the technician
proceeds to collect swipes from five locations in room 101, and one swipe each from the north
and south ends of the hallway. When acquisition is complete, the technician notes that
uncertainty requirements have been met and that both counts are low enough to conclude that the
action limit for total beta has not been exceeded. The technician marks the room as "pending
laboratory analysis" and continues to room 111 to initiate two additional static counts for total
beta activity. As these data acquire, the technician collects five wipe samples each from rooms
111 and 134. When the static counts are finished, the technician verifies that the uncertainties
will meet the MQOs and determines that both results are low enough to conclude that the activity
is not high enough to exceed the action limit and trigger laboratory confirmation. The technician
places a sign on the door indicating "laboratory analysis pending" and moves on to the next
floor.
88
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Table 11 - Summary of Measurements for Scenario #4
Location
Bldg #4
RmlOl
Bldg #4
Rmlll
Bldg #4
Rml34
Bldg #4
North end of
1st floor
hallway
Bldg #4
South end of
1st floor
hallway
Radiation
Type
90Sr
Beta
90Sr
Beta
yuSr
Beta
90Sr
Beta
90Sr
Beta
Primary
Measurement
2 static counts for
gross alpha total
surface activity
2 static counts for
gross alpha total
surface activity
n/a
n/a
n/a
Secondary
Measurement
5 swipes for
removable alpha
activity
5 swipes for
removable alpha
5 swipes for
removable alpha
1 swipe for
removable alpha
1 swipe for
removable alpha
Comment
Laboratory analysis
and V&V pending
Laboratory analysis
and V&V pending
Laboratory analysis
and V&V pending
Laboratory analysis
and V&V pending
Laboratory analysis
and V&V pending
Observations on the Four Scenarios: Table 12 summarizes the number of samples needed for
each of the above scenarios. Several general observations are noted:
Gross measurements in the field may not be capable of reliably detecting radionuclide
contamination at levels approaching background.
Instrument detection capability does not guarantee that a technique will be useful for
measuring contamination.
o Bias due to self-absorption may not permit MQOs to be met and may require
sampling and laboratory analysis.
o High background activity may interfere with measurements, or may lead to such long
measurements being required that grab sampling and laboratory analysis may be a
more effective and efficient option.
Alpha and Beta Emitters
o The risk of false non-detection of alpha or beta emitters is higher than for gamma
emitters.
o Minimizing the risk of false non-detection for alpha and beta emitters must be
accomplished using a robust sampling plan (e.g., MARSSEVI). A similar number of
measurements are needed in the field and at laboratories.
Gamma Emitters
o Gross gamma measurements may not be able to effectively or efficiently detect or
measure radionuclides at levels approaching the ambient background.
o Field measurements for gamma contaminants can significantly minimize the overall
number of samples needed to characterize an area.
o Fewer measurements are needed to characterize gamma-emitting contamination than
alpha- and beta-emitting contamination.
o ISGS can detect contamination at levels below ambient background as long as the
radionuclide of concern is not present in the background.
Strategic use of laboratory and field measurements may speed up the overall recovery
process by optimally using laboratory and field resources.
89
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Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident
Table 12 - Summary of Number of Scenario Measurements by Nuclide, Measurement Status, and
Detection Status and Test
Radionuclide
Radiation
Type
60Co
Beta-gamma
60Co
Beta-gamma
239/240pu
Pure alpha
90Sr
Pure beta
Contain.
present?
N
Y
Y
Y
ISGS
1
2
n/a
n/a
Gross
Gamma
1
2
n/a
n/a
Gross
Alpha
0
n/a
4
n/a
Gross
Beta
0
3
n/a
4
Alpha Swipes
for
Laboratory
analysis
0
n/a
17
n/a
Beta Swipe
for
Laboratory
analysis
7
7
n/a
17
Laboratory
Nuclide
Specific
0
0
1
1
Comment
ISGS decreases
sample load
Survey detects
60Co but cannot
localize source
Survey detects
alpha - sample
to laboratory
Survey detects
beta - sample to
laboratory
90
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