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

United States

Environmental Protection

Agency
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
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 I-33, all managed by David Garman and 

Dan Askren. Mention of trade names or specific applications does not imply endorsement or acceptance by 

EPA.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

i

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 handheld 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

 1 Departments of Agriculture, Commerce, Defense, Energy, Health and Human Services, Homeland Security, 

Interior, Justice, and State, and the U.S. Environmental Protection Agency.

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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

ii

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).

This document2

• Radiological Laboratory Sample Analysis Guide for Incidents of National Significance –

Radionuclides in Water (EPA 402-R-07-007, January 2008) 

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 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-11/122, October 2011)

 2 All the documents in this series are available at www.epa.gov/erln/radiation.html and at

www.epa.gov/narel/incident_guides.html. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

iii

• 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
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

iv

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. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

v

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
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

vi

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 uMR ....................... 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
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

vii

Acronyms, Abbreviations, Units, and Symbols

(Excluding chemical symbols and formulas)

α ........................alpha particle

α ........................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

β ........................beta particle

β.........................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

ε.........................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

γ.........................gamma ray

g.........................gram

GIS ....................geographic information system

G-M...................Geiger-Műller [detector]

GUM .................Guide to the Expression of Uncertainty in Measurement

h.........................hour

HPGe.................high purity germanium [detector]

HVAC ...............heating, ventilation, air conditioning [system]

IC.......................Incident Commander

ICLN .................Integrated Consortium of Laboratory Networks

ICRU.................International Commission on Radiation Units and Measurements
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

viii

IEC....................International Electrotechnical Committee

IND ...................improvised nuclear device (i.e., a nuclear bomb)

ISGS..................in situ gamma spectrometry

ISO ....................International Organization for Standardization 

ISOCSTM ...........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]

MARSSIM ........Multi-Agency Radiation Survey and Site Investigation Manual

MDC .................minimum detectable concentration

MeV ..................megaelectronvolt (106 electronvolt)

μCi.....................microcurie (10−6 Ci)

μg .....................microgram (10−9 kilogram)

min ....................minute

MQO .................measurement quality objective

mrad ..................millirad (10–3 rad)

mrem .................millirem (10–3 rem)

NaI(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

pCi.....................picocurie (10–12 Ci)

PT......................proficiency testing

QA.....................quality assurance

QAPP ................quality assurance project plan

QC.....................quality control

QSAS ................Quality Systems for Analytical Services

RCRA................Resource Conservation and Recovery Act

RDD..................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
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

ix

Sv ......................sievert

TNI....................The NELAC Institute

uMR ...............................required method uncertainty

V&V .................verification and validation 

ZnS....................[silver activated] zinc sulfide [detector]
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

x

Radiometric and General Unit Conversions

To Convert To Multiply by To Convert To Multiply by

years (y)

seconds (s)

minutes (min)

hours (h)

days (d)

3.16×107

5.26×105

8.77×103

3.65×102

s

min

h

d

y

3.17×10–8

1.90×10–6

1.14×10–4

2.74×10–3

disintegrations per 

second (dps) becquerels (Bq) 1 Bq dps 1

Bq

Bq/kg

Bq/m3

Bq/m3

picocuries (pCi)

pCi/g

pCi/L

Bq/L

27.0

2.70×10–2

2.70×10–2

10–3

pCi

pCi/g

pCi/L

Bq/L

Bq

Bq/kg

Bq/m3

Bq/m3

3.70×10–2

37.0

37.0

103

microcuries per 

milliliter (μCi/mL) pCi/L 109 pCi/L μCi/mL 10–9

disintegrations per 

minute (dpm)

μCi

pCi

4.50×10–7

4.50×10–1

pCi

μCi dpm

2.22

2.22×106

cubic feet (ft3) cubic meters (m3) 2.83×10–2 m3 ft3 35.3

gallons (gal) liters (L) 3.78 L gal 0.264

Gray (Gy) rad 102 rad Gy 10–2

roentgen equivalent 

man (rem) sievert (Sv) 10–2 Sv rem 102

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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

1

1. Scope and Purpose

This document explains the importance and interrelationship of field and laboratory measurements 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

2

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

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 

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. 

 3 http://cees.tamiu.edu/covertheborder/TOOLS/NationalPlanningSen.pdf

4

The Current Gap in Environmental Radioanalytical Laboratory Capacity, prepared for EPA in March 2007, 

currently in draft.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

3

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

• Delineating the ultimate extent of contamination;

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 (IC) or designee.

Following the initial response phase of the incident, EPA, at a minimum, will be responsible for:

• 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

4

• 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 2011a).

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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

5

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/63ead7de8fd68010VgnVCM100000f932a8c0.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

6

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 radionuclides 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 selfabsorption 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).
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

7

ANSI N13.12 defines surface contamination as “[r]adioactive 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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

8

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 μR/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 lowactivity 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 radionuclidespecific 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

9

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/cm

2

).

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 nonhomogeneous, 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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

10

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 wellestablished, 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, H0, 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

 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 Significance—Radionuclides in Water, 

(EPA 2008).

By incorrectly 

deciding to reject the null hypothesis when it is indeed true we commit a Type I decision error. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

11

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 α) is specified at the AAL. The probability of 

making a Type II error (denoted β) 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:

Δ = | AAL – DL |.

3.4.2.2 Measurement Quality Objectives

MARSAME (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 (uMR) 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, uMR, to be a fundamental 

MQO. For decisions about whether a single sample exceeds the AAL, uMR can be calculated as
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

12

α β

MR

z z

u

− + −

=

1 1

Δ

where the null hypothesis (H0) is “the true sample activity is greater than the AAL,” Δ = [AAL–

Discrimination Level] and z1-α and z1–β are the respective quantiles of the standard normal 

distribution function.8

3.4.2.3 Controlling the Probability of Decision Errors with Analytical Decision Level 

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. 

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 

 8 Values of z1-α (or z1–β) for some commonly used values of α (or β), taken from tables of the cumulative normal 

distribution (MARLAP 2004, Appendix G, Table G1), are:

α or β z1-α (or z1–β) α or β z1-α (or z1–β)

0.001 3.090 0.10 1.282

0.01 2.326 0.20 0.842

0.025 1.960 0.30 0.524

0.05 1.645 0.50 0.000
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

13

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.

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).

`
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

14

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 – z1– α uMR.

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

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 (Δ) 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: 

Δ = |AAL – DL| = |1.0 – 0.5| nCi/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 consequences—and thus greater tolerance—to falsely concluding that 

activity is present, even though it may be attributable to background activity. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

15

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:

0.17 nCi/g 1.645 1.282

0.5 nCi/g

z z

Δ

1 α 1 β

MR = + = + =

− −

u

See footnote 5 for the values of z1-α and z1–β. 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 – z1– α uMR = 1.0 nCi/g – [1.645×0.17 nCi/g] = 0.72 nCi/g.

The curve centered about 1 nCi/g in Figure 1 represents the distribution of all possible measurements of a sample with a true activity equal to the AAL. In figure 2, consistent with established 

DQOs, only 5% of this distribution (α ) 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 (β) 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, 

uMR, 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

4.1 Why is Metrology Important?

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.

The International Vocabulary of Metrology (VIM; IBWM 2008) defines metrology as the 

“...science of measurement and its application. [...] Metrology includes all theoretical and 

 11See section 4.3 for a more complete discussion of quality systems.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

16

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 MaterialTM 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. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

17

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 organization’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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

18

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
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

19

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 measurement 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 document. 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:
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

20

• 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

• Utilizing independent verification contractors to ensure that the cleanup has achieved its 

stated goals.

and

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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

21

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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

22

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.” 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

23

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 al., 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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

24

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

MARSSIM 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” (MARSSIM 2000, 

Section 4.9). MARLAP (2004, Appendix B) discusses the sources and impact of uncertainty in 

the measurement process:
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

25

“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-11 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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

26

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 welldeveloped 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/.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

27

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

 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.

(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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

28

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 al., 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

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.

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. 

16

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 

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).

 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; from UNSCEAR 2000, Annex C, Table 11. Conversion from cumulative areal deposition values assumes 

deposition in the top 5 cm of soil, and a soil density of 1.6 g/cm3

.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

29

field measurements will become much more critical. Accurate and precise measurements of 

detector background activity and corrections for background activity are possible in wellcontrolled 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

 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.

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. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

30

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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

31

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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

32

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 measurements) 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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

33

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. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

34

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., μrad/h, μR/h) based on 

the particle flux at the meter.

18

• Type of the radiation

For example, gamma survey meters, such as NaI(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:

 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. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

35

• 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

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 

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, lowto-mid-energy beta emissions, and low-energy gamma and x-ray radiation.

 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

36

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 2×2-inch detector used manually 

to scan in “swing” mode, 2×2-inch shielded detector and electronics mounted on a wheeled 

frame for horizontal area coverage, and a large (5–8-inch diameter) NaI 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 NaI 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. MARSSIM (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-
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

37

absorption on detection efficiency in a manner that ensures that contaminants will be detected,

21

• Where analyte signal approaches the detection threshold of the detection technique, or 

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 wellsuited to detecting and quantifying contamination as instrument signal approaches low levels. 

Field survey measurements may not provide unequivocal results:

• 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:

[G]reat 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

38

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 [ISOCSTM] 

or [ISOTOPICSTM].

22

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, 

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.

 22ISGS should be differentiated from commercially available software packages such as ISOCSTM (Canberra 

Industries) and ISOTOPICSTM (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. ISOCSTM and ISOTOPICSTM, 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

39

measurements will be qualitative, or associated with high levels of uncertainty, such that only an 

identification of radionuclides may be possible.

23

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 

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). 

 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

40

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 selfabsorption effects when radionuclides are not deposited on the surface.

• Setup, implementation, and interpretation of data from an ISGS unit (e.g., ISOCSTM or 

ISOTOPICSTM) 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., ISOCSTM or ISOTOPICSTM), 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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

41

• “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

• 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.

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. 

27

• Confirmatory laboratory analysis is needed to unequivocally verify the accuracy of 

efficiency models. 

(See discussion of quality control in Section 4 of this document.) 

• 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 [SRMTM]). 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

42

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 laboratory 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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

43

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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

44

radionuclides based on their characteristic decay energies.28

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 

clean and well-resolved spectra for accurate determinations of alpha-emitting radionuclides

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.

29

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 

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 

emissions, particularly beta emissions such as 99Tc, 241Pu, or 3

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.

 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 μg/cm2 can degrade the resolution of the energy spectrum to a 

point where differentiation between radioisotopes of an alpha-emitting element is not possible.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

45

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 betaemitting 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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

46

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 cm2. 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

5.3 The Effect of Measurement Geometry on Detector Calibration

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.

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.

31As 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

47

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 dosemeasuring 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 quantitative 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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

48

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

 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. 

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.

MARSSIM (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, selfabsorption). 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.” 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

49

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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

50

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

5.3.3 Measurement Geometry and Laboratory Survey and Gross Activity Measurements

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.

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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

51

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 10–6 risk levels and below.34

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. 

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. 

 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. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

52

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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

53

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 measurements performed in a fixed laboratory. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

54

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.

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 realtime 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 areal 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 

Gamma or xray emitters 

of low to

medium 

energy 

Identity 

known

Similar attributes as for medium- to high-energy gamma- and x-rayemitters 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 highenergy 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 self-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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

55

Activity 

Level

Emitter 

Type Field Survey Measurements* Laboratory Screening Measurements**

Single lowto midenergy 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 surfacedeposited 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 self-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.

be able to characterize larger areas (e.g., up to 25 m2) 

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.

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.

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 assumptions 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, wellcontrolled 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 instrumentation cannot distinguish between analyte signal from 

background. The accuracy with which the “background 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

56

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 laboratory analysis is needed to provide confidence in the field 

measurements by confirming the accuracy of assumptions 

used during calibration.

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 nondetection, measurement bias, and inaccurate estimates of 

measurement uncertainty. Higher uncertainty and increased likelihood 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- tohigh-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. 

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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

57

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 nondetection 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.

Limited applicability but more sensitive and controlled measurements of gross activity are possible than in the field. Interpretation 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.

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.

* 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

58

Table 3 – Comparison of Spectrometric Field and Laboratory Measurements for Surficially 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

Gamma

emitter of 

medium- to

high-energy

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 nondetection 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.

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 realtime 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 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. Welldefined and rigorous QC provides evidence attesting to 

the quality of results. 

Gamma or xray 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 nondetection 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. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

59

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

Radionuclide 

mixtures

Gamma emitters are effectively determined in the presence of 

alpha and beta emitters. There is limited application to spectrometric 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 demonstrate 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.

In the case of gamma spectrometry, there is higher 

uncertainty and increased likelihood of false nondetection 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 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-emitter contamination will be 

similar to the number of field measurements required 

to do the same. 

Activity of the 

radionuclide(s) 

of concern at 

action level 

similar to 

background

levels

Gamma

emitters of 

medium to

high energy

Similar attributes to measurements of gamma emitters in mediumto 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. 

Similar attributes to laboratory measurements above. 

Detection capability for medium- to high-energy 

gamma emitters may be less than that possible using 

ISGS.

Alpha, beta, or 

low-energy 

photon

emitters

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). 

Similar attributes to laboratory measurements above. 

* Field spectrometry equipment includes gamma spectrometers, Field Instrument for the Detection of Low-Energy Radiation (FIDLERs

TM)

, 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. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

60

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.

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.

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 determinations of alpha and beta emitters in the field beyond qualitative hot spot identification. In many cases, similar information can be obtained using gross activity 

measurements.

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.

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 radionuclidespecific determinations. 

In contrast to gamma, spectrometric 

analysis at the laboratory may be the 

only viable option for measurements of 

pure alpha and beta emitters.

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 determinations of alpha and beta emitters in the field beyond qualitative hot spot 

identification. Similar information often may be obtained using gross activity 

measurements.

* Field spectrometry equipment includes gamma spectrometers, FIDLERs

TM, 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. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

61

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 #11-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. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

62

• 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, welldocumented, 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

63

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 mechanisms 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 measurements 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. 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

64

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.

8. References

Abbady, A. 2006. Radiological Hazard and Radiogenic Heat Production in Some Building 

Materials in Upper Egypt. Journal of Radioanalytical and Nuclear Chemistry, Vol. 268, No.2

243–246.

American National Standards Institute (ANSI). 1999. Surface and Volume Radioactivity 

Standards for Clearance. N13.12. Health Physics Society, American National Standards 

Institute Health Physics Society, American National Standards Institute (ANSI) N13.12 

Section 2. 

American National Standards Institute (ANSI). 2004a. American National Standard 

Measurement and Associated Instrument Quality Assurance for Radioassay Laboratories. 

The Institute of Electrical and Electronics Engineers, Inc. ANSI N42.23-1996 (R2004). 

Available from: http://www.ansi.org/.

American National Standards Institute (ANSI). 2004b. Quality Systems for Environmental Data 

and Technology Programs-Requirements with Guidance for Use. American Society for 

Quality (ASQ E4), Section B.4.3, ANSI. Available from: http://www.ansi.org/.

American Society for Testing and Materials (ASTM). 2008. Standard Guide for Selection and 

Use of Portable Radiological Survey Instruments for Performing In Situ Radiological 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

65

Assessments in Support of Decommissioning. ASTM D1893-08, Section 5.3. ASTM 

International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA. 

American Society for Testing and Materials (ASTM). 2007. Standard Practice for Set-up, 

Calibration, and Quality Control of Instruments Used for Radioactivity Measurements. 

ASTM D7282-06. January. Available from: www.astm.org/.

Conference of Radiation Control Program Directors (CRCPD). 2006. Handbook for Responding 

to a Radiological Dispersal Device – First Responder’s Guide—the First 12 Hours. CRCPD 

Publication 06-6. Frankfurt, Kentucky, September. Available at: 

www.crcpd.org/RDD_Handbook/RDD-Handbook-ForWeb.pdf.

U.S. Department of Defense (DOD). 2009. Quality Systems Manual for Environmental 

Laboratories (QSM). Department of Defense. QSM rev. 4.1. April. Available at: 

www.navylabs.navy.mil/QSM%20Version%204.1.pdf.

U.S. Department of Energy (DOE). 2009. Quality Systems for Analytical Services (QSAS). 

Department of Energy Consolidated Audit Program. QSAS rev. 2.5. November. Available at: 

https://doecap.oro.doe.gov/DOECAP_Public/documentsLab.aspx.

U.S. Environmental Protection Agency (EPA). 2000. Guidance on Technical Audits and Related 

Assessments for Environmental Data Operations. Washington, DC. EPA QA/G-7, EPA-240-

R-99-080. January. Reissued May 2006. Available at: www.epa.gov/quality/qa_docs.html.

U.S. Environmental Protection Agency (EPA). 2002a. Guidance for Developing Quality Systems 

for Environmental Programs. Washington, DC. EPA QA/G-1, EPA-240-R-02-008. 

November. Reissued January 2008. Available at: www.epa.gov/quality/qa_docs.html.

U.S. Environmental Protection Agency (EPA). 2002b. Guidance for Quality Assurance Project 

Plans. Washington, DC. EPA QA/G-5, EPA-240-R-02-009. December. Available at: 

www.epa.gov/quality/qa_docs.html.

U.S. Environmental Protection Agency (EPA). 2002c. Guidance for Quality Assurance Project 

Plans for Modeling. Washington, DC. EPA QA/G-5M, EPA-240-R-02-007. December. 

Available at: www.epa.gov/quality/qa_docs.html.

U.S. Environmental Protection Agency (EPA). 2003. Guidance on Assessing Quality Systems. 

Washington, DC. EPA QA/G-3, EPA-240-R-03-003. March. Available at: www.epa.gov/

quality/qa_docs.html.

U.S. Environmental Protection Agency (EPA). 2006. Guidance on Systematic Planning Using 

the Data Quality Objectives Process. Washington, DC. EPA QA/G-4, EPA-240-B-06-00. 

February. Available at: www.epa.gov/quality/qa_docs.html.

U.S. Environmental Protection Agency (EPA). 2008. Radiological Laboratory Sample Analysis 

Guide for Incidents of National Significance – Radionuclides in Water. Washington, DC.

EPA 402-R-07-007. January. Available at: www.epa.gov/narel/incident_guides.html.

U.S. Environmental Protection Agency (EPA). 2009a. Method Validation Guide for Qualifying 

Methods Used by Radioanalytical Laboratories Participating in Incident Response Activities. 

Washington, DC. EPA 402-R-09-006. June. Available at: www.epa.gov/narel/incident_

guides.html.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

66

U.S. Environmental Protection Agency (EPA). 2009b. Radiological Laboratory Sample Analysis 

Guide for Incidents of National Significance – Radionuclides in Air. Washington, DC. EPA 

402-R-09-007. June. Available at: www.epa.gov/narel/incident_guides.html.

U.S. Environmental Protection Agency (EPA). 2009c. Radiological Laboratory Sample 

Screening Analysis Guide for Incidents of National Significance. Washington, DC. EPA 402-

R-09-008. June. Available at: www.epa.gov/narel/incident_guides.html.

U.S. Environmental Protection Agency (EPA). 2010. Standardized Analytical Methods for 

Environmental Restoration Following Homeland Security Events – SAM 2010. Revision 6.0, 

Washington, DC. EPA 600/R-10/122, September. Available at: www.epa.gov/sam/

index.htm.

U.S. Environmental Protection Agency (EPA). 2011a. Policy to Assure Competency of 

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-competency-policy.pdf. 

U.S. Environmental Protection Agency (EPA). 2011b. A Performance-Based Approach to the 

Use of Swipe Samples in Response to a Radiological or Nuclear Incident. Revision 0. Office 

of Research and Development, Cincinnati, OH, and Office of Radiation and Indoor Air, 

Washington, DC. EPA 600/R-11/122, October. Available at: http://oaspub.epa.gov/eims/

eimscomm.getfile?p_download_id=504097. 

International Bureau of Weights and Measures (BIPM). 2008. International vocabulary of 

metrology — Basic and general concepts and associated terms (VIM). Joint Committee for 

Guides in Metrology 200:2008. BIPM. Available at: www.bipm.org/en/publications/guides/. 

Integrated Consortium of Laboratory Networks (ICLN). 2007. Assessment of Nationwide 

Laboratory Surge Capacity Required to Support Decontamination of Chemical, Biological 

and Radiochemical-nuclear Agents. Task 06-32, Integrated Consortium of Laboratory 

Networks (ICLN) Capability Assessment. April 30. 

International Organization for Standardization (ISO). 1988. Evaluation of Surface 

Contamination – Part 1: Beta Emitters and Alpha Emitters. ISO-7503-1 (first edition). 

Geneva, Switzerland.

International Organization for Standardization (ISO). 1993a. Statistics – Vocabulary and 

Symbols – Part 1: Probability and General Statistical Terms. ISO 3534-1. Geneva, 

Switzerland.

International Organization for Standardization (ISO). 1993b. International Vocabulary of Basic 

and General Terms in Metrology. ISO Guide 99, Geneva, Switzerland.

International Organization for Standardization (ISO) Guide 98. 1995. Guide to the Expression of 

Uncertainty in Measurement. Geneva, Switzerland. Available at: www.iso.org/iso/catalogue_

detail.htm?csnumber=45315.

International Organization for Standardization (ISO/IEC). 2005. General Requirements for the 

Competence of Testing and Calibration Laboratories. Standard 17025, International 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

67

Organization for Standardization/International Electrotechnical Commission. Geneva, 

Switzerland. Available from: www.iso.org/

Leino, R., D.C. George, B.N. Key, L. Knight, and W.D. Steele. 1994. Field Calibration 

Facilities for Environmental Measurement of Radium, Thorium, and Potassium, Technical 

Measurements Center, Grand Junction Projects Office, Grand Junction, CO, U.S. Department 

of Energy.

Multi-Agency Radiological Laboratory Analytical Protocols (MARLAP) Manual. 2004. EPA 

402-B-04-001A, July. Volume I, Chapters 6, 7, 20, Glossary; Volume II and Volume III, 

Appendix G. Available at: www.epa.gov/radiation/marlap.

Multi-Agency Radiation Survey and Assessment of Materials and Equipment (MARSAME) 

Manual. 2009. EPA 402-R-06-002. Available at: www.epa.gov/radiation/marssim/

marsame.html.

Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM). 2000. Revision 1. 

NUREG-1575 Rev 1, EPA 402-R-97-016 Rev1, DOE/EH-0624 Rev1. August. Available at: 

www.epa.gov/radiation/marssim/index.html. 

National Council on Radiation Protection and Measurements (NCRP). 1976. Environmental 

Radiation Measurements, Report No. 50, December.

National Council on Radiation Protection and Measurements (NCRP). 1991. Calibration of 

Survey Instruments Used in Radiation Protection for the Assessment of Ionizing Radiation 

Fields and Radioactive Surface Contamination. NCRP Report 112, pp. 4-5. Bethesda, MD 

20814.

National Council on Radiation Protection and Measurements (NCRP). 1992. Environmental 

Radiation Measurements. NCRP Report No. 50. 

National Environmental Laboratory Accreditation Conference (NELAC). 2003. 2003 NELAC 

Standard, EPA-600-R-04-003, June. Available at: www.nelac-institute.org/docs/2003nelac

standard.pdf.

Novak, E.F. 1998. Exposure-Rate Calibration Using Large-Area Calibration Pads. Grand 

Junction Projects Office, Grand Junction, CO, U.S. Department of Energy.

U.S. Nuclear Regulatory Commission (NRC) and Oak Ridge Associated Universities. 1992. 

Manual for Conducting Radiological Surveys in Support of License Termination, Draft 

Report for Comment. NUREG/CR-5849. Washington, DC.

U.S. Nuclear Regulatory Commission (NRC). 1997. Minimum Detectable Concentrations with 

Typical Radiation Survey Instruments for Various Contaminants and Field Conditions.

NUREG-1507. Available at: www.orau.gov/ddsc/instrument/NUREG-1507.pdf. 

U.S. Nuclear Regulatory Commission (NRC). 2006. Consolidated Decommissioning Guidance: 

Decommissioning Process for Materials Licensees. NUREG-1757 (Volume 1, Revision 2).

Available at: www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1757/. 

U.S. Nuclear Regulatory Commission (NRC). 2007. Quality Assurance for Radiological 

Monitoring Programs (Inception through Normal Operations to License Termination)—
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

68

Effluent Streams and the Environment, Regulatory Guide 4.15, Rev. 2. July. Available at: 

http://adamswebsearch2.nrc.gov/IDMWS/ViewDocByAccession.asp?AccessionNumber=M

L071790506. 

Reginatto, M., P. Shebell, and K.M. Miller. 1997. ISD97, EML-590 – A Computer Program to 

Analyze Data from a Series of In Situ Measurements on a Grid and Identify Potential 

Localized Areas of Elevated Activity, Environmental Measurements Laboratory, New York, 

NY, October.

The NELAC Institute (TNI). 2007. Volume I: General Requirements for Field Sampling and 

Measurement Organizations; and Volume II: General Requirements for Accreditation Bodies 

Accrediting Field Sampling and Measurement Organizations. The Field Sampling and

Measurement Organization Sector of The NELAC Institute. May. Available at: www.nelacinstitute.org/doclibrary.php. 

United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). 2000. 

Sources and Effects of Ionizing Radiation. Report Vol. I. Available at: www.unscear.org/

unscear/en/publications/2000_1.html.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

69

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

 35 ISOCSTM 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 ISOCSTM 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 ISOCSTM 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.

ISGS would not have played a significant

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, areal 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

70

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

• 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.

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:

• 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. 241Am, 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

71

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 

241Am 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 ISOCSTM 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 ISOCSTM) 

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 ISOCSTM 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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

72

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 postsurvey 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

73

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 (○). 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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

74

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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

75

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 wellknown, 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?
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

76

Table 5 – Applicability of Selected Field Measurement Techniques for In Situ Measurements of Surface Activity / Concentrations of Radionuclides

241Am 244Cm 238Pu 239/40Pu 238U# 235U 232Th# 210Po 226Ra# 90Sr 89Sr 32P 99Tc 3H 241Pu 125I 129I 137Cs 60Co 103Pd

1° Radiation α α α α α α α α α β β β β β

(LE)

β

(LE)

ε

(LE)

β

(LE) β β ε(LE)

2° Radiation γ

x x (ω) x x (ω) x (ω) γ x

x 

γ (ω) n/a γ (ω)x(ω) n/a n/a n/a n/a n/a n/a γ (LE)

γ 

(LE)

γ

x(ω) γ (ω) x(ω)(LE)

HPGe (ISGS – energy greater than 0.06 MeV)

Low Activity ○ ○ I ● ●

Medium Activity ● ○ ● ○ ○ ● ●

High Activity ● ● ● ○ ● ● ●

Unshielded Geiger-Műller (G-M) (thin window non-specific ionizing radiation – gross alpha/gross beta)

Low Activity

Medium Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

High Activity ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

Unshielded NaI(Tl) (Gross Gamma )

Low Activity

Medium Activity ○ ○ ○ ○ ○ ○ ○ ● ● ○

High Activity ● ● ● ● ● ● ● ● ● ●

Alpha Scintillator (large-area in situ zinc sulfide (ZnS) detector – gross alpha)‡

Low Activity ○ ○ ○ ○ ○ ○ ○ ○ ○

Medium Activity ○ ○ ○ ○ ○ ○ ○ ○ ○

High Activity ● ● ● ● ● ● ● ● ●

Unshielded Beta Scintillator (large-area in situ organic scintillator detector – gross beta, average energy greater than 500 keV) ‡

Low Activity ○ ○ ○ ○ ○

Medium Activity ● ● ● ○ ○ ○

High Activity ● ● ● ● ● ●

Gas Proportional Counter (large-area in situ detector – discriminated gross alpha/beta) ‡

Low Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Medium Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ● ● ○

High Activity ● ● ● ● ● ● ● ● ● ● ● ● ○ ● ● ○

Gas Proportional Counter (segmented large-area in situ detector – discriminated gross alpha/beta) ‡

Low Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Medium Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ● ● ● ○ ○ ○ ○

High Activity ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ○

Thin NaI(Tl) 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 ● ● ● ● ● ● ● ● ● ○ ○ ●

● – suitable for definitive (unbiased, low-uncertainty) determination; ○ – 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 betagamma; 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; α - alpha emission; β - beta emission; γ - gamma ray emission, x - x-ray emission; ε - electron capture 

decay; LE - emission less than 100 keV; ω - 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

77

Table 6 – Applicability of Selected Field Measurement Techniques for In Situ Measurements of Volumetric Activity / Concentrations of Radionuclides 

241Am 244Cm 238Pu 239/40Pu 238U# 235U 232Th# 210Po 226Ra# 90Sr 89Sr 32P 99Tc 3H 241Pu 125I 129I 137Cs 60Co 103Pd

1° Radiation α α α α α α α α α β β β β β

(LE)

β

(LE)

ε

(LE)

β

(LE) β β ε(LE)

2° Radiation γ

x x (ω) x x (ω) x (ω) γ x

x 

γ (ω) n/a γ (ω)x(ω) n/a n/a n/a n/a n/a n/a γ (LE)

γ 

(LE)

γ

x(ω) γ (ω) x(ω)(LE)

HPGe (ISGS – energy greater than 0.06 MeV)

Low Activity ○ ○ I ● ●

Medium Activity ○ ○ ● ● ● ●

High Activity ● ○ ● ● ○ ○ ● ● ○

Unshielded G-M (thin window non-specific ionizing radiation – gross alpha/gross beta) ‡

Low Activity

Medium Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

High Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Unshielded NaI(Tl) (Gross Gamma )

Low Activity

Medium Activity ○ ○ ○ ○ ○ ● ●

High Activity ○ ○ ○ ○ ○ ○ ○ ● ● ○

Alpha Scintillator (large-area in situ ZnS detector – gross alpha)

Low Activity

Medium Activity ○ ○ ○ ○ ○ ○ ○ ○ ○

High Activity ○ ○ ○ ○ ○ ○ ○ ○ ○

Unshielded Beta Scintillator (large-area in situ organic scintillator detector – gross beta, energy greater than 500 keV) ‡

Low Activity ○ ○

Medium Activity ○ ○ ○ ○ ○ ○

High Activity ○ ○ ○ ○ ○ ○

Gas Proportional Counter (large-area in situ detector – discriminated gross alpha/gross beta)‡

Low Activity ○ ○

Medium Activity ○ ○ ○ ○ ○

High Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Gas Proportional Counter (segmented large-area in situ detector – discriminated gross alpha/gross beta)‡

Low Activity ○ ○

Medium Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

High Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Thin NaI(Tl) 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 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

● – suitable for definitive (unbiased, low-uncertainty) determination; ○ – 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 betagamma; 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; α - alpha emission; β - beta emission; γ - gamma ray emission, x - x-ray emission; ε - electron capture 

decay; LE - emission less than 100 keV; ω - 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

78

Table 7 – Applicability of Selected Laboratory Measurement Techniques for Determining Activity / Concentrations of Radionuclides

241Am 244Cm 238Pu 239/40Pu 238U# 235U 232Th# 210Po 226Ra# 90Sr 89Sr 32P 99Tc 3H 241Pu 125I 129I 137Cs 60Co 103Pd

1° Radiation α α α α α α α α α β β β β β

(LE)

β

(LE)

ε

(LE)

β

(LE) β β ε(LE)

2° Radiation γ

x x (ω) x x (ω) x (ω) γ x

x 

γ (ω) n/a γ (ω)

x(ω) n/a n/a n/a n/a n/a n/a γ 

x

γ 

x

γ

x(ω) γ (ω) x(ω)

Unshielded G-M (thin window)

Low Activity ○ ○

Medium Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

High Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Unshielded NaI(Tl) (Gross Gamma)

Low Activity

Medium Activity ○ ○ ○ ○ ○ ○ ○

High Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Shielded NaI(Tl) (Gross gamma)

Low Activity ○ ○ ○ ○ ○ ○ ○ ○

Medium Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

High Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Shielded HPGe Gamma Spectrometry – energy greater than 0.06 MeV)

Low Activity ○ ○ ○ ○ ○ ● ●

Medium Activity ● ○ ● ○ ○ ● ●

High Activity ● ● ● ● ● ● ●

Low Background Gas Proportional Counting (gross alpha/gross beta screen)

Low Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Medium Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

High Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Low Background Gas Proportional Counting (chemical separation – element or radionuclide specific)

Low Activity ● ● ● ● ● ● ● ● ● ● ● ● ● ○ ● ●

Medium Activity ● ● ● ● ● ● ● ● ● ● ● ● ● ○ ● ● ● ○

High Activity ● ● ● ● ● ● ● ● ● ● ● ● ● ○ ● ● ● ●

Liquid Scintillation Counting (α/β screen – direct analysis)

Low Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Medium Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

High Activity ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

79

241Am 244Cm 238Pu 239/40Pu 238U# 235U 232Th# 210Po 226Ra# 90Sr 89Sr 32P 99Tc 3H 241Pu 125I 129I 137Cs 60Co 103Pd

1° Radiation α α α α α α α α α β β β β β

(LE)

β

(LE)

ε

(LE)

β

(LE) β β ε(LE)

2° Radiation γ

x x (ω) x x (ω) x (ω) γ x

x 

γ (ω) n/a γ (ω)

x(ω) n/a n/a n/a n/a n/a n/a γ 

x

γ 

x

γ

x(ω) γ (ω) x(ω)

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; ○ – 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 betagamma; 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; α - alpha emission; β - beta emission; γ - gamma ray emission, x - x-ray emission; ε - electron capture 

decay; LE - emission less than 100 keV; ω - 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

80

This section presents several simple 

scenarios to help show how 

radioactive emission type and 

energy, DQOs / MQOs, and the use 

of non-spectrometric versus spectrometric measurement techniques all 

have an impact on possible 

approaches to characterizing an 

area. They also provide a taste of 

how field and laboratory measurements can be used in complementary 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 mixtures 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.

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. 

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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

81

IC38 at 7100 dpm/100 cm2 and 710 dpm/100 cm2 for total and removable 60Co 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

 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.1 (Acceptable License Termination Screening Values of Common Radionuclides for Building-Surface 

Contamination). Per note a) of NUREG-1757, “[s]creening 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 2011b). 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 60

Co 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, uMR, 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).

are 3100 and 310 dpm/100 

cm

2 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 NaI(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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

82

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" NaI(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 NaI(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

Radiation 

Type

Primary 

Measurement

Secondary 

Measurement Comment

Bldg #1 

Rm 101

60Co 

Beta-gamma

1 ISGS for total;

3 swipes for 

removable beta.

n/a

Clear pending laboratory

analysis, data V&V, and 

assessment.

Bldg #1 

Rm 111

60Co 

Beta-gamma

1 swipe for 

removable beta. n/a

Clear pending laboratory

analysis, data V&V, and 

assessment.

Bldg #1 

Rm 134 

60Co 

Beta-gamma

1 swipe for 

removable beta. n/a

Clear pending laboratory

analysis, data V&V, and 

assessment.

Bldg #1

1st floor 

hallway north

60Co 

Beta-gamma

1 swipe for 

removable beta.

Area survey with 

1×1" NaI(Tl)

Clear pending laboratory

analysis, data V&V, and 

assessment.

Bldg #1

1st floor 

hallway south

60Co 

Beta-gamma

1 swipe for 

removable beta.

Area survey with 

1×1" NaI(Tl)

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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

83

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., 1/10th those for total

contamination.

40

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" NaI(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" NaI(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 

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 lowlevel 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.

 40 The incident command recognizes that the spectrometric measurement technique is of higher quality and evaluates 

uMR 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, uMR, 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).
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

84

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" NaI(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 NaI(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 
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

85

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

Radiation 

Type

Primary 

Measurement

Secondary 

Measurement Comment

Bldg #2 

Rm 101

60Co 

BetaGamma

2 ISGS for total;

3 swipes for 

removable beta.

3 static counts for gross 

beta surface activity; 

NaI(Tl) gamma survey

60Co results above ADL; source 

not localized; laboratory swipe 

data, V&V, and assessment 

pending.

Bldg #2 

Rm 111

60Co 

BetaGamma

1 swipe for 

removable beta. n/a Laboratory analysis pending.

Bldg #2 

Rm 134 

60Co 

BetaGamma

1 ISGS for total;

3 swipes for 

removable beta

n/a

60Co below ADL; laboratory

analysis, V&V, and assessment 

pending.

Bldg #2

North end of 

1st floor 

hallway

60Co 

BetaGamma

1 swipe for 

removable beta.

Area survey with 1×1"

NaI(Tl)

Laboratory swipe analysis,

V&V, and assessment pending.

Bldg #2

South end of 

1st floor 

hallway

60Co 

BetaGamma

1 swipe for 

removable beta.

Area survey with 1×1"

NaI(Tl)

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 239/240Pu. 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 cm

2 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 uMR 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, uMR, 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).
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

86

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. Even if field 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 selfabsorption 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 gammaemitting contamination from 226Ra (and progeny) on impermeable and relatively smooth 

surfaces.

42

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 

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 239/240Pu are most effectively and defensibly determined by grab sampling (e.g., scabbling or 

coring) followed by isotopic analysis for 239/240Pu 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 239/240Pu, 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 239/240Pu, data will be assessed and additional 

action taken as deemed appropriate.

 42 Personal communication with Dick Dubiel of Millennium Shonka, 2010.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

87

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

Radiation 

Type Primary Measurement

Secondary 

Measurement Comment

Bldg #3 

Rm 101

239/240Pu 

Alpha

2 static counts for gross 

alpha total surface 

activity;

1 sample taken –

“welcome mat coupon”

5 swipes for 

removable alpha 

activity

Gross alpha above action limit; 

sample taken for analysis. 

Laboratory analysis, V&V, and 

assessment pending.

Bldg #3 

Rm 111

239/240Pu

Alpha

2 static counts for gross 

alpha total surface 

activity

5 swipes for 

removable alpha

Laboratory analysis, V&V, and 

assessment pending.

Bldg #3 

Rm 134 

239/240Pu 

Alpha n/a 5 swipes for removable alpha

Laboratory analysis, V&V, and 

assessment pending.

Bldg #3

North end of 

1st floor 

hallway

239/240Pu

Alpha n/a 1 swipe for 

removable alpha

Laboratory analysis, V&V, and 

assessment pending.

Bldg #3

South end of 

1st floor 

hallway

239/240Pu 

Alpha n/a 1 swipe for 

removable alpha

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 cm

2 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, uMR and ADLs using the following parameters to evaluate uMR 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 1⁄2 the respective AAL, the Type I tolerable error, alpha = 5%, and the Type II tolerable error, 

beta = 5%. The required relative method uncertainty, uMR, 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

88

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 nonpermeable 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 

by analysis for 90Sr 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

89

Table 11 – Summary of Measurements for Scenario #4

Location

Radiation 

Type

Primary 

Measurement

Secondary 

Measurement Comment

Bldg #4 

Rm 101

90Sr 

Beta

2 static counts for 

gross alpha total 

surface activity

5 swipes for 

removable alpha 

activity

Laboratory analysis 

and V&V pending

Bldg #4 

Rm 111

90Sr 

Beta

2 static counts for 

gross alpha total 

surface activity

5 swipes for 

removable alpha

Laboratory analysis 

and V&V pending

Bldg #4 

Rm 134 

90Sr 

Beta n/a 5 swipes for removable alpha

Laboratory analysis 

and V&V pending

Bldg #4

North end of 

1st floor 

hallway

90Sr 

Beta n/a 1 swipe for 

removable alpha

Laboratory analysis 

and V&V pending

Bldg #4

South end of 

1st floor 

hallway

90Sr 

Beta n/a 1 swipe for 

removable alpha

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., MARSSIM). 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.
Uses of Field and Laboratory Measurements During a Radiological or Nuclear Incident

90

Table 12 – Summary of Number of Scenario Measurements by Nuclide, Measurement Status, and 

Detection Status and Test

Radionuclide

Radiation 

Type

Contam. 

present? ISGS

Gross 

Gamma

Gross 

Alpha

Gross 

Beta

Alpha Swipes 

for 

Laboratory 

analysis

Beta Swipe 

for 

Laboratory 

analysis

Laboratory

Nuclide 

Specific Comment 60Co

Beta-gamma

N 1 1 0 0 0 7 0 ISGS decreases 

sample load 

60Co

Beta-gamma

Y 2 2 n/a 3 n/a 7 0

Survey detects 

60Co but cannot 

localize source

239/240Pu 

Pure alpha Y n/a n/a 4 n/a 17 n/a 1

Survey detects 

alpha – sample 

to laboratory

90Sr

Pure beta Y n/a n/a n/a 4 n/a 17 1

Survey detects 

beta – sample to 

laboratory