ASTM E1893-15(2021)

Standard Guide for Selection and Use of Portable Radiological Survey Instruments for Performing In Situ Radiological Assessments to Support Unrestricted Release from Further Regulatory Controls

SIGNIFICANCE AND USE
4.1 The purpose of this standard is to provide the user information and guidance for selecting and using instrumentation that will provide measurement results that can be compared to criteria for unrestricted use.  
4.2 Use of this standard will provide greater assurance that the measurements obtained will be technically and administratively sufficient for making decisions regarding completion of decontamination and/or demolition/removal activities.  
4.3 Use of this standard will provide greater assurance that the measurements obtained will be technically and administratively sufficient to meet all applicable regulatory requirements for unrestricted release of a component for recycle or reuse, or for unrestricted release of a remaining surface or area.
SCOPE
1.1 This standard provides recommendations on the selection and use of portable instrumentation that is responsive to levels of radiation that are close to natural background. These instruments are employed to detect the presence of residual radioactivity that is at, or below, the criteria for release from further regulatory control of a component to be salvaged or reused, or a surface remaining at the conclusion of decontamination and/or decommissioning.  
1.2 The choice of these instruments, their operating characteristics and the protocols by which they are calibrated and used will provide adequate assurance that the measurements of the residual radioactivity meet the requirements established for release from further regulatory control.  
1.3 This standard is applicable to the in situ measurement of radioactive emissions that include:  
1.3.1 alpha  
1.3.2 beta (electrons)  
1.3.3 gamma  
1.3.4 characteristic x-rays  
1.3.5 The measurement of neutron emissions is not included as part of this standard.  
1.4 This standard dose not address instrumentation used to assess residual radioactivity levels contained in air samples, surface contamination smears, bulk material removals, or half/whole body personnel monitors.  
1.5 This standard does not address records retention requirements for calibration, maintenance, etc. as these topics are considered in several of the referenced documents.  
1.6 Non-SI units are used and appropriate for this guide as they are industry standard. Mathematical equivalents may be provided in parentheses.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Jan-2021
• ICS: 17.240 - Radiation measurements
• Technical Committee: E10 - Nuclear Technology and Applications
• Drafting Committee: E10.03 - Radiological Protection for Decontamination and Decommissioning of Nuclear Facilities and Components

Relations

• Refers: ASTM C1000-19 - Standard Test Method for Radiochemical Determination of Uranium Isotopes in Soil by Alpha Spectrometry
• Effective Date: 01-Nov-2019
• Refers: ASTM C1215-18 - Standard Guide for Preparing and Interpreting Precision and Bias Statements in Test Method Standards Used in the Nuclear Industry
• Effective Date: 01-Jul-2018
• Refers: ASTM E170-17 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Jun-2017
• Refers: ASTM C999-17 - Standard Practice for Soil Sample Preparation for the Determination of Radionuclides
• Effective Date: 01-Jun-2017
• Refers: ASTM C998-17 - Standard Practice for Sampling Surface Soil for Radionuclides
• Effective Date: 01-Jun-2017
• Refers: ASTM E170-16a - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Oct-2016
• Refers: ASTM E170-16 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Feb-2016
• Refers: ASTM E170-15a - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Sep-2015
• Refers: ASTM E170-15 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Mar-2015
• Refers: ASTM E170-14a - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 15-Oct-2014
• Refers: ASTM E170-14 - Standard Terminology Relating to Radiation Measurements and Dosimetry
• Effective Date: 01-Sep-2014
• Refers: ASTM C1215-92(2012)e1 - Standard Guide for Preparing and Interpreting Precision and Bias Statements in Test Method Standards Used in the Nuclear Industry
• Effective Date: 01-Jun-2012
• Refers: ASTM C1000-11 - Standard Test Method for Radiochemical Determination of Uranium Isotopes in Soil by Alpha Spectrometry
• Effective Date: 01-Feb-2011
• Refers: ASTM C999-05(2010)e1 - Standard Practice for Soil Sample Preparation for the Determination of Radionuclides
• Effective Date: 01-Jun-2010
• Refers: ASTM C998-05(2010)e1 - Standard Practice for Sampling Surface Soil for Radionuclides
• Effective Date: 01-Jun-2010

Overview

ASTM E1893-15(2021): Standard Guide for Selection and Use of Portable Radiological Survey Instruments for Performing In Situ Radiological Assessments to Support Unrestricted Release from Further Regulatory Controls provides comprehensive guidance for selecting and using portable radiation survey instruments. Developed by ASTM, this guide is crucial for ensuring valid, repeatable, and regulatory-compliant measurements during site decontamination, decommissioning, and unrestricted release activities. The standard enables users to perform in situ radiological assessments that accurately identify and quantify residual radioactivity at or below criteria for unrestricted use, supporting safe recycling, reuse, or release of materials and areas from regulatory oversight.

Key Topics

• Instrument Selection: Covers the process of choosing portable survey instruments (e.g., alpha, beta, gamma, and X-ray detectors) that have sensitivity close to natural background levels. Emphasizes compliance with regulatory sensitivity and calibration standards.
• Operating Characteristics: Specifies requirements for operating features such as minimum detectable activity (MDA), calibration protocols, and energy response, ensuring instruments are technically adequate for unrestricted release determinations.
• Measurement Protocols: Details procedures for both stationary and scanning surveys, including best practices for using ratemeters and scalers, background measurements, and ensuring detection of low-level residual radioactivity on surfaces or in media.
• Calibration & Quality Assurance: Directs users to adhere to established calibration methods and periodic verification to ensure instrument accuracy. References standards for calibration sources, detector efficiency checks, and documentation.
• Surface and Volumetric Contamination Assessment: Defines protocols for detecting and measuring alpha, beta, gamma, and X-ray emissions from contaminated components, surfaces, or areas after remediation.
• Exclusions: Notes that the standard does not apply to neutron measurements, nor to specialized sampling devices for air, smears, bulk removals, or personnel monitoring.

Applications

This ASTM standard is widely used in nuclear facility decontamination, waste management, and environmental remediation. Its practical value lies in:

• Supporting Unrestricted Release: Ensures materials or surfaces meet stringent release criteria before recycling, reuse, or removal from regulatory controls.
• Decontamination and Decommissioning Projects: Provides reliability and consistency in the radiological assessment of facilities, equipment, or land destined for unrestricted use.
• Regulatory Compliance: Assures that radiological survey methods and instrumentation meet all technical and administrative requirements set by regulatory authorities (e.g., NRC, DOE, EPA).
• On-Site Radiological Surveys: Guides health physicists and radiation protection personnel in proper instrument deployment, calibration, and data interpretation during fieldwork.
• Risk Assessment: Assists in documenting, validating, and defending decisions regarding the safety of release based on reproducible, standards-based measurements.

Related Standards

ASTM E1893-15(2021) references and aligns with several important national and international standards to ensure harmonized practices:

• ANSI N323AB: Test and calibration guidelines for portable radiation protection instruments.
• ANSI N42.17A/C: Performance specifications for health physics instrumentation.
• ASTM E170, E181: Radiological measurement terminology and detector calibration methods.
• ASTM C998, C999, C1000, C1133: Soil sampling and radiochemical determination procedures.
• ISO 4037-4, ISO 6980-2, ISO 8769, ISO 7503 Series: International reference methods for radiation source calibration and contamination monitoring.
• NCRP Reports No. 57, 58, 112: Guidance on instrumentation, monitoring, and survey instrument calibration.
• DOE G441.1-1B: U.S. Department of Energy radiation protection program guidance.

By following ASTM E1893-15(2021) and its referenced documents, organizations can ensure their radiological assessments are technically sound, regulatorily compliant, and internationally recognized, supporting safe, responsible transitions from controlled to unrestricted use.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1893 − 15 (Reapproved 2021)
Standard Guide for
Selection and Use of Portable Radiological Survey
Instruments for Performing In Situ Radiological
Assessments to Support Unrestricted Release from Further
Regulatory Controls
This standard is issued under the fixed designation E1893; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.6 Non-SI units are used and appropriate for this guide as
they are industry standard. Mathematical equivalents may be
1.1 This standard provides recommendations on the selec-
provided in parentheses.
tion and use of portable instrumentation that is responsive to
levels of radiation that are close to natural background. These 1.7 This international standard was developed in accor-
instruments are employed to detect the presence of residual
dance with internationally recognized principles on standard-
radioactivity that is at, or below, the criteria for release from ization established in the Decision on Principles for the
further regulatory control of a component to be salvaged or
Development of International Standards, Guides and Recom-
reused, or a surface remaining at the conclusion of decontami-
mendations issued by the World Trade Organization Technical
nation and/or decommissioning.
Barriers to Trade (TBT) Committee.
1.2 The choice of these instruments, their operating charac-
2. Referenced Documents
teristics and the protocols by which they are calibrated and
usedwillprovideadequateassurancethatthemeasurementsof
2.1 ASTM Standards:
theresidualradioactivitymeettherequirementsestablishedfor
C998Practice for Sampling Surface Soil for Radionuclides
release from further regulatory control.
C999Practice for Soil Sample Preparation for the Determi-
nation of Radionuclides
1.3 Thisstandardisapplicabletotheinsitumeasurementof
C1000Test Method for Radiochemical Determination of
radioactive emissions that include:
Uranium Isotopes in Soil by Alpha Spectrometry
1.3.1 alpha
C1133Test Method for Nondestructive Assay of Special
1.3.2 beta (electrons)
Nuclear Material in Low-Density Scrap and Waste by
1.3.3 gamma
Segmented Passive Gamma-Ray Scanning
1.3.4 characteristic x-rays
E170Terminology Relating to Radiation Measurements and
1.3.5 Themeasurementofneutronemissionsisnotincluded
Dosimetry
as part of this standard.
E181Test Methods for Detector Calibration andAnalysis of
Radionuclides
1.4 This standard dose not address instrumentation used to
C1215Guide for Preparing and Interpreting Precision and
assess residual radioactivity levels contained in air samples,
Bias Statements in Test Method Standards Used in the
surface contamination smears, bulk material removals, or
Nuclear Industry
half/whole body personnel monitors.
2.2 ANSI Standards:
1.5 Thisstandarddoesnotaddressrecordsretentionrequire-
ANSI N323ABAmerican National Standard for Radiation
ments for calibration, maintenance, etc. as these topics are
Protection Instrumentation Test and Calibration, Portable
considered in several of the referenced documents.
Survey Instrumentation
This guide is under the jurisdiction of ASTM Committee E10 on Nuclear
Technology and Applications and is the direct responsibility of Subcommittee For referenced ASTM standards, visit the ASTM website, www.astm.org, or
E10.03 on Radiological Protection for Decontamination and Decommissioning of contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Nuclear Facilities and Components. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Feb. 1, 2021. Published February 2021. Originally the ASTM website.
approved in 1997. Last previous edition approved in 2015 as E1893-15. DOI: Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/E1893-15R21. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1893 − 15 (2021)
ANSI N42.17AAmerican National Standard for Perfor- 3. Terminology
mance Specifications for Health Physics Instrumentation-
3.1 accuracy, n—the degree of agreement of an individual
Portable Instrumentation for Use in Normal Environmen-
measurement or average of measurements with an accepted
tal Conditions
reference value or level (ASTM E170).
ANSI N42.17CAmerican National Standard for Perfor-
3.2 calibrate, v—to adjust or determine the response or
mance Specifications for Health Physics Instrumentation-
reading of a device relative to a series of conventionally true
PortableInstrumentationforUseinExtremeEnvironmen-
values for radiation sources (ANSI N323AB).
tal Conditions
2.3 National Council on Radiation Protection and Measure-
3.3 calibration source, n—asusedinthisstandardguide,see
ments: certified reference material.
NCRPReportNo.57InstrumentationandMonitoringMeth-
3.4 certified reference material, n—a material that has been
ods for Radiation Protection, National Council on Radia-
characterizedbyarecognizedstandardortestinglaboratoryfor
tion Protection and Measurements, May 1978
someofitschemicalorphysicalorradiologicalproperties,and
NCRP Report No. 58A Handbook of Radioactivity Mea-
that is generally used for calibration of a measurement system
surement Procedures, National Council on Radiation Pro-
or for development or evaluation of a measurement method
tection and Measurements, 2nd Ed. February 1985
(ASTM E170).
NCRP Report No. 112Calibration of Survey Instruments
3.5 check source, n—a radioactive source, not necessarily
Used in Radiation Protection for the Assessment of
calibrated, that is used to confirm the continuing satisfactory
Ionizing Radiation Fields and Radioactive Surface
functionality of an instrument (ANSI N323AB).
Contamination, National Council on Radiation Protection
and Measurements, December 1991
3.6 control charts, n—A plot of the results of a quality
2.4 International Organization for Standardization (ISO): control action to record and demonstrate that control is being
ISO-4037-4: 2004 X and Gamma Reference Radiations for
maintained within expected statistical variation or to indicate
Calibrating Dosimeters and Dose-rate Meters and for when control is or will be lost without intervention (DOE
Determining their Response as a Function of Photon
G441.1-B).
Energy, International Organization for Standardization, DISCUSSION— This provides a method for tracking an instru-
ment’s operation to demonstrate that data collected is within
ISO-6980-2: 2005 Nuclear energy – Reference beta particle expected statistical variation and to ensure that potential
radiation - Part 2: Calibration fundamentals related to
failures and/or negative trends are identified early.
basic quantities characterizing the radiation field
3.7 functional check, n—a check (often qualitative) to de-
ISO-8769Reference Sources for the Calibration of Surface
termine that an instrument is operational and capable of
Contamination Monitors – Beta Emitters (Maximum Beta
performingitsintendedfunction.Suchchecksmayinclude,for
Energy Greater than 0.15 MeV) and Alpha Emitters,
example,batterycheck,zerosetting,orsourceresponsecheck.
International Organization for Standardization, 1988
(ANSI N323AB).
ISO 8769-2: 1996 Reference sources for the calibration of
DISCUSSION—such checks may include, for example, battery
surface contamination monitors-Part 2: Electrons of en-
check, high voltage check/adjustment, zero setting, audio
ergy less than 0.15 MeV and photons of energy less than
settings, alarm settings, scale checks and check source and
1.5 MeV
background response.
ISO-7503-1Evaluation of Surface Contamination - Part 1:
3.8 hot spot, n—localized areas of elevated activity that are
Beta Emitters (Maximum Beta Energy Greater than 0.15
less than 100 cm in extent and exceed the applicable average
MeV) and Alpha Emitters, International Organization for
guideline value by greater than a factor of three.
Standardization, 1988
ISO-7503-2Evaluation of Surface Contamination - Part 2:
3.9 lower limit of detection, n—the smallest amount of a
Tritium Surface Contamination, International Organiza-
measured quantity that will produce a net signal above the
tion for Standardization, 1988
system noise for a given measurement system or process that
ISO-7503-3: 2003 Evaluation of Surface Contamination -
will result in an acceptable false positive rate if nothing is
Part3:IsomericTransitionandElectronCaptureEmitters,
present and that will be correctly interpreted as “real” with a
Low Energy Beta Emitters (E <0.15 MeV), Interna-
desired probability.
βmax
tional Organization for Standardization, 1993 (draft)
DISCUSSION—the usual acceptable error rates for in situ
2.5 Department of Energy (DOE):
measurementsareafalsepositiverateof5%(TypeIerror)and
DOE G441.1-1BRadiation Protection Programs Guide for
a false negative rate of 5% (Type II error).
Use with Title 10, Code of Federal Regulations, Part 835,
3.10 minimum detectable activity (MDA), n—see lower
Occupational Radiation Protection, Chapter 9, Portable
limit of detection (for purposes of this standard, MDAwill be
Monitoring Instrument Calibration, 3/1/2007
applied to the measurement of a point source or “hot spot”
detection).
National Council on Radiation Protection and Measurement, 7910 Wodmont
3.11 minimum surface sensitivity (MSS), n—see lower limit
Ave., Bethesda, MD 20814
ofdetection(forpurposesofthisstandard,MSSwillbeapplied
Available from ANSI Sales Department, 1430 Broadway, New York, NY
10018. to measurements of distributed activity, which will incorporate
E1893 − 15 (2021)
the detector area to enable direct comparison to regulatory 4.3 Use of this standard will provide greater assurance that
guidelines for surface activity). the measurements obtained will be technically and administra-
tively sufficient to meet all applicable regulatory requirements
3.12 national standard, n—an artifact, such as a well-
for unrestricted release of a component for recycle or reuse, or
characterizedinstrumentorradiationsource,thatembodiesthe
for unrestricted release of a remaining surface or area.
international definition of primary physical measurement stan-
dardfornationaluse(ASTME170);seealsocertifiedreference
5. Instrument Selection
material.
5.1 General:
3.13 precision, n—the degree of mutual agreement among
5.1.1 Criteria for release of materials for recycling, re-use,
individual measurements (ASTM E170).
or disposal, and of surfaces or areas remaining at the comple-
DISCUSSION—Relativetoatestmethod,precisionisthedegree
tionofdecontaminationordecommissioningactivities,orboth,
of mutual agreement among individual measurements made
aresetbyregulatoryauthorities.Forsurfacecontaminationand
under prescribed like conditions. The imprecision of a mea-
selected volumetrically contaminated media, values provided
surement may be characterized as the standard deviation of
by the Nuclear Regulatory Commission (NRC) have been
errors of measurement.
generally applied to licensed facilities, both NRC and Agree-
3.14 ratemeter, n—an analog or digital electronic character-
ment State licenses (1). ANSI has published a standard for
istic of a meter which provides the number of pulses per unit
clearance of surfaces and materials that is based on pathway
time.
modeling and end-point exposures(2). The Department of
3.15 scaler, n—a digital electronic characteristic of a meter
Energy (DOE) applies standards that are essentially equivalent
which counts the distinct number of input pulses within a
to those provided by the NRC (3). The Environmental Protec-
preset period of time.
tion Agency (EPA) and NRC have developed criteria that are
3.16 scan, n—the process whereby the surveyor moves the risk-based, resulting in radionuclide and pathway specific
probeovertheareabeingsurveyedinanattempttolocateareas release values that will be applied to decommissioning activi-
with residual radioactivity. ties.
DISCUSSION—thetechniquesofthescanningprocesswillhave 5.1.2 In situ radioactive measurements related to unre-
stricted release to be treated in this standard include:
significant affect on the MSS. Important parameters include
scan speed, detector orientation, source-detector distance, 5.1.2.1 surface contamination measurements,
5.1.2.2 measurementsofradionuclideconcentrationsinme-
scanned surface condition and the background response of the
instrument. dia (gamma measurement only), and
5.1.2.3 dose-rate measurements.
3.17 traceability, n—the ability to demonstrate that a par-
ticular measurement instrument or artifact standard has been
5.2 General Selection Criteria:
calibrated at acceptable time intervals against a national or 5.2.1 The instrument to be utilized must provide an output
international standard, or against a secondary standard which
signal that can be correlated to the appropriate release criteria
has been, in turn, calibrated against a national standard or
applicable to the residual source characteristics; for example,
transfer standard (ASTM E170).
surface emission rate, specific or total activity, dose rate.
NCRP Reports Nos. 57 and 58 describe instruments and
3.18 transfer standard, n—aphysicalmeasurementstandard
protocols addressing theses issues.
that is calibrated by direct or indirect comparison to a national
5.2.2 The characteristics and performance of the measuring
standardandistypicallyameasurementinstrumentorradiation
instruments should be evaluated against the specifications
source (ASTM E170).
described in ANSI N42.17A and ANSI N42.17C. This should
3.19 unrestricted release, n—the release of a material or a
include documentation that the instrument satisfies the calibra-
surface area for use without further radiological controls.
tion requirements described in ANSI N323AB. NCRP 112
DISCUSSION—This occurs after the material or area has been
provides additional supplemental guidance on survey instru-
surveyed and the results of the survey show that residual
ment calibration.
radioactivity is below the applicable release criteria. All
5.2.3 Documentation should be available that verifies that
instrumentation and techniques used for this application must
the applicable specification requirements described in ANSI
becapableofdetectingradioactivityatlevelsbelowtherelease
N323B for the particular measurement conditions have been
criteria.
met for the instrument selected; for example, minimum
sensitivity, energy response, environmental response, etc.
4. Significance and Use
5.3 Minimum Sensitivity (minimum detectable activity).
4.1 The purpose of this standard is to provide the user
The minimum sensitivity of the instrument selected should be
information and guidance for selecting and using instrumenta-
≤ 50 percent of the applicable release criteria to which the
tion that will provide measurement results that can be com-
measurement results will be compared. (Appendix A provides
pared to criteria for unrestricted use.
further information for determining this.)
4.2 Use of this standard will provide greater assurance that
the measurements obtained will be technically and administra-
tively sufficient for making decisions regarding completion of
The boldface numbers in parentheses refer to a list of references at the end of
decontamination and/or demolition/removal activities. this standard.
E1893 − 15 (2021)
5.4 Energy Response.An instrument, selected for a particu- 5.6.2 Background reduction—The background response of
larresidualradionuclideparticleemission,shouldbecalibrated the detector may be reduced by shielding or collimation. The
for response to the energy of that emission. General guidance shielding configuration should be selected to maximize re-
for determining this is found in ANSI N323AB. sponse to the source configuration of interest, and may range
from pin-hole collimation to selective shadow shielding.
5.4.1 Photon Energy Response. In addition to the general
5.6.3 Conversion factor—A conversion factor that will re-
provisionsinANSIN323AB,descriptionsofreferencesources
late the in situ instrument response to the distributed source
for making the photon energy response determination are
must be established. This may be done directly by sampling
found in ISO-4037-4.
and analysis or by analytical modeling. The protocols for
5.4.2 Beta Energy Response. In addition to the general
performing this determination are beyond the scope of this
provisionsinANSIN323AB,descriptionsofreferencesources
standard. Additional guidance for sampling and assessing
formakingthebetaenergyresponsedeterminationarefoundin
residual activity in soil and low density scrap media are found
ISO-6980-2, ISO-8769 and ISO 8769-2.
in ASTM Standards C998, C999, C1000, and C1133.
5.5 SurfaceContaminationDetection.Residualsurfacecon-
tamination should be evaluated using either alpha or beta
6. Instrument Use
detectors. For performing “hot spot” location surveys, the
6.1 General Requirements:
detector shall be coupled to a ratemeter for performing
6.1.1 Prior to using a particular instrument to assess the
transient(scanning)surveys.Forperformingaresidualactivity
residual radioactivity, ensure that the instrument is appropriate
(stationary) assessment, the probe may be coupled to either a
for the emissions and environmental conditions present by
ratemeter or a scaler (see Section 6.3.4).
reviewing the criteria discussed in Section 5 and identified
5.5.1 When performing scan surveys, the alpha or beta
references.
probe window areas should be ≥100 cm .
6.1.2 Prior to using a particular instrument, ensure that
documentation is available that indicates that the instrument
NOTE 1—Smaller detector probes may be used to perform scan surveys
whereaccessibilitypreventsutilizationoflargerprobesizesinaccordance
has been calibrated in accordance with the requirements
with scan requirements described in Section 6.4.1.
specified inANSI N323AB, and that the interval for recalibra-
tion has not been exceeded.
5.5.2 When performing stationary assessments, the probe
6.1.3 Prior to assessing the in situ measurements of the
windowareashouldbe100cm 630%.RefertoAppendixX2
residual radioactivity, determine the natural radiological con-
discussion on the effect of probe size on minimum detection.
ditions for the site using one or more background reference
NOTE 2—The probe area that is to be used in any measurement
areas. These areas shall be measured for:
interpretation is the total window area, based on the window opening
6.1.3.1 radiological composition of media, such as air,
dimension, not the effective open window area, that includes protective
water, soil, or structural material,
screen effects.
6.1.3.2 amount of each primary radionuclide present,
5.5.2.1 Additional guidance for instrument selection to per-
6.1.3.3 total terrestrial plus cosmic radiation dose rate.
form surface contamination measurements is provided for the
6.1.3.4 These areas are defined as having similar physical,
following residual activities:
chemical,biological,andgeologicalcharacteristicsastheareas
5.5.2.2 alpha and beta (E > 0.15 MeV) emitters - ISO
to be assessed.
7503-1
6.1.4 Determine the response of the instrument to the
5.5.2.3 tritium - ISO 7503-2
natural background and any background variations. The back-
5.5.2.4 beta (E < 0.15 MeV), isometric transition, and
ground response of the instrument shall be determined at a
electron capture emitters - ISO 7503-3.
location representative of the area to be measured, but not
affected by site operations. The NRC has drafted guidance for
5.6 Specific Activity Measurements—The in situ measure-
determining the background at a particular site (4).
ment of the residual activity distributed within a volumetric
medium of interest shall be based on the photon emission rate
6.2 Calibration:
fromthatmedium.Theresultsoftheevaluationsofthisphoton
6.2.1 General Criteria:
emission rate are normally expressed in units of picocuries per
6.2.2 Acalibrationsourcewillnormallybeusedtoestablish
gram (pCi/gm) or becquerels per gram (Bq/gm). This evalua-
the conversion factor used to convert the instrument response
tion will be dependent on the background response of the
to an estimate of in situ residual radioactivity. The calibration
detectorandonaconversionfactorestablishedforthemedium
shall be performed such that an in situ measurement can be
of interest. Nonuniform distributed source geometries can
accurately converted to the 4π (total) emission rate of the
result in large interpretation errors of in situ measurements;
residual surface activity. Factors important to this conversion
therefore, caution should be used with these evaluations.
arediscussedinAppendixX5.Thecalibrationsourcesusedfor
this determination shall, as a minimum, have the following
5.6.1 Background response—The photon detector should
have a response to background at the photon energy range of characteristics:
interest that will result in a minimum detectable activity that is 6.2.2.1 have the same type of emissions (alpha, beta, or
≤50% of the applicable release criteria. Guidance on calibra- photon) as the residual radioactivity
tion and use of crystalline (germanium and sodium-iodide) 6.2.2.2 have particle or photon energy that is within 610 %
detectors is provided in ASTM E181. of the energy emitted from residual radioactivity. Alternately,
E1893 − 15 (2021)
calibration may be established from a curve generated from at 6.4.1 Residual radioactivity on surfaces may be located by
least three sources with energies that bracket the energy of transientmeasurements(scanning)andquantifiedbystationary
interest. (fixed) measurements.
6.4.2 Scanning-Surface Activity. Surfaces are scanned to
6.2.2.3 have a particle or photon emission rate that is no
identify the presence of elevated radiation which might indi-
more than 50 times the applicable standard for unrestricted
cate residual radioactivity or hot spots in excess of the levels
release
that would permit unrestricted release. Measurement protocols
6.2.3 The calibration source should also have the following
are described for performing scanning surveys in the federal
characteristics:
interagency document, MARSSIM (5). The following
6.2.3.1 physical and/or chemical composition that produces
requirements, as a minimum, should be followed when per-
similar backscatter characteristics as the residual in situ radio-
forming scan surveys for surface radioactivity:
active matrix, for example:
6.4.2.1 Alpha and/or beta emissions should be measured, as
In situ medium Source mount
applicable.
iron/steel steel 6.4.2.2 Large area detectors should be used for measuring
concrete aluminum
flat surfaces; for example, probe area ≥100 cm .
wood/plaster plastic
6.4.2.3 Thedetectorresponseshouldbeusedwitharateme-
soil aluminum
terwithashortelectronicresponsetime(timerequiredtoreach
6.2.3.2 distribution (geometry) either within or on the sur-
90% of steady state), preferably 2-4 s.
face that is similar to the residual radioactive matrix
6.4.2.4 The distance between the detector and the surface
6.2.4 Special Criteria for Beta and Alpha Detectors:
should be maintained between 0.5 cm and 1.0 cm.
6.2.4.1 In addition to the criteria described in Section 6.2.1,
6.4.2.5 The scanning velocity should not exceed 1 detector
the conversion factors for beta and alpha detectors should also
width per second.This velocity should be reduced to as low as
consider the following:
⁄5 detector width per second when the minimum response of
6.2.4.2 the distance between the calibration source and the thedetectorisneartheunrestrictedreleaseguidelinelevel.The
detector must be the same as the distance that will be used to effects of detector geometry, source geometry, and scanning
quantify the in situ field activity. velocity on detector response are shown in Appendix X2.
6.4.3 Scanning-VolumetricActivity:Forresidualradioactiv-
6.2.4.3 for quantifying a point source, a “point source
ity distributed within a matrix such that self-shielding effects
efficiency” should be used with the conversion factor.
significantlydegradeoreliminatethealphaandbetaemissions,
6.2.4.4 for quantifying a distributed area source, a“ surface
residual activity must be identified using measurements of
source efficiency” should be used. The surface source used to
gammaemissions.Thefollowingrequirements,asaminimum,
determine the conversion factor should match the size and
should be followed when performing gamma scan surveys:
shape of the detector probe window area (see Section 5.5.2),
6.4.3.1 Crystalline or solid-state (for example, sodium-
but should not be smaller than 100 cm regardless of probe
iodide, germanium) detectors should be used with a ratemeter
window area.
having a short electronic response time, preferably2-4s.
6.3 Source Checks:
6.4.3.2 The distance between the detector and the survey
6.3.1 Each instrument used to perform residual radioactive
area should not exceed 15 cm. Greater heights will reduce the
measurements shall be tested (at least daily, or before each use
sensitivity for detecting hot spots.
if it is used less often than daily) using a suitable check source
6.4.3.3 The scanning should be performed with the probe
to verify operability within the allowable parameters.
moved in a serpentine pattern approximately 1 m wide while
6.3.2 Prior to using a particular instrument to assess the advancing at a speed of approximately 0.5 meter per second.
residual radioactivity, the mean reference response and repro-
6.4.4 Audio Response. Audio output from the ratemeter is
ducibility of the instrument, as defined inASTM C1215, shall
recommendedtoaugmentobservationsofmeterfluctuationsin
be established following a specific protocol.
the ratemeter reading. The audio signal is independent of the
electronic time constant of the meter and is a more sensitive
6.3.3 The daily verification, using the same protocol and
indicatorofelevatedactivity,particularlyfortimeconstants>4
check source, is compared to the mean response. If the daily
s.
check deviates from the mean by more than 620%, the
instrument shall be removed from service for repair and/or
NOTE 4—Experiments using hidden sources (Co-57) with signal-to-
recalibration (ANSI N323B).
background ratios from 0.6-6 resulted in approximately 75% being
located based on ratemeter observation alone, compared to approximately
NOTE 3—Control charts should be used to track the daily response
90% for audio response (6).
against the mean to observe trends and take action before the instrument
6.4.5 Direct(fixed)Measurements.Theestimateofthelevel
reaches a predetermined“ failure” point.
of residual radioactivity is based on a measurement with the
6.3.4 The check source used to perform the protocol shall
source-detector geometry fixed (stationary). When making
not decay by more than 25% of the applicable response limits
these fixed measurements, the following requirements, as a
used with the control chart throughout the duration of the
minimum, should be complied with:
measurement task.
6.4.5.1 The detector should be coupled to a scaler for this
6.4 Surface Contamination Measurements: measurement.
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NOTE 5—The factor ε may be defined for either a point source or a
6.4.5.2 If a ratemeter is used with this measurement, a long
i
surface source.The point source efficiency should be used to quantify hot
response time should be used (> 20 s). The detector shall be
spots. The surface source efficiency should be used to evaluate surfaces
kept in position for at least three times the time constant of the
without hot spots.
ratemeter.
NOTE 6—Further explanation of the factor ε and its relative magnitude
i
6.4.5.3 The effects of the concavity of the surfaces being
are given in Appendix X5.
measured on instrument efficiency shall be evaluated when the
6.5.3 Gamma Emissions:
surfaceisnotflat(examplesaregiveninAppendixX5forbeta
emissions).
6.5.3.1 Gamma detection and subsequent interpretation is
6.4.5.4 For conditions where a visible layer of dirt,
normally employed to evaluate the levels of residual activity
oxidation, or other coating cannot be removed, the effect on
that are distributed within a source matrix expressed as
source-detector response shall be included for alpha and beta
pCi/gm, Bq/kg, etc. For a uniformly distributed source, the
measurements (examples are given in Appendix X5 for beta
volumetric source term is provided by the expression
emissions).
n 2n
B
S 5
6.5 Data Interpretation:
v
ε
γ
6.5.1 Alpha and Beta Emissions:
where:
6.5.2 The evaluation of surface activity for alpha or beta
emissions (in dpm/100 cm ) is given by the expression S = volumetric source term in pCi/gm
v
(ISO-7503-1) n = total count rate in cpm
n = background count rate in cpm
B
~n 2n !
B
ε = instrument efficiency for an uniformly distributed
A 5
s γ
W
gamma source in cpm per pCi/gm.
ε 3ε 3
i s
NOTE 7—The gamma efficiency will normally be composed of two
where: factors;adoseconversioninunitsofcpm/(mR/hr)measuredwithaknown
calibration source, and a source conversion factor in units of (mR/hr)/
n = total count rate in cpm
(pCi/gm)basedonshieldingtheory.Ingeneral,thedoseconversionfactor
n = background count rate in cpm
B
for a particular detector is provided for a single photon energy, whereas,
ε = instrument efficiency for alpha or beta radiation in cpm
i
the source conversion factor includes scattered photons (buildup) which
per dpm
leadstoanestimateofthegammasourcestrengththatisconservative.The
W = total physical window area of the detector in cm
response of various NaI detector geometries as a function of photon
ε = source correction factor to account for differences
s
energy is shown in Appendix X9.
betweenthecalibrationsourceandtheresidualactivity,
such as backscatter, self absorption, source protective
coatings and/or surface coatings, geometry, etc.
(unitless)
APPENDIXES
(Nonmandatory Information)
X1. MINIMUM DETECTABLE ACTIVITY (MDA)
X1.1 When measuring residual radioactivity that must be X1.2 Givenanetsignalthatisgreaterinvaluethanasimilar
within limits or guidelines that are very near to the levels that signal that has been established as defining background, has a
“real” activity above background been detected? (The “false
are present from natural background, the minimum amount of
positive” or Type I error)
radioactivitythatmaybedetectedbyaparticularmeasurement
system must be determined. With radiation measurement, the
X1.3 Given a completely specified measurement process,
physicalamountoftheresidualradiationsource(pCi,dpm,Bq,
what is the minimum “real” activity that will produce an
etc.) is not directly measurable, but is observed as a measure-
observed signal that will be detected? (The “false negative” or
ment instrument response (digital counts, voltmeter deflection,
Type II error)
etc.). Because radioactive decay follows statistical
relationships, the statistics of detection and determination
X1.4 The first aspect relates to making an a posterior (after
apply directly to the observed (or observable) signal (meter
the fact) decision based upon the net signal(s) and a defined
reading) and its associated random fluctuations.When measur- criterion for detection. This leads to the establishment of a
ing for the presence of low residual activity, one must
“criticallevel”(L )forwhichasignalexceedingthislevelwill
c
distinguish between two fundamental aspects of the detection be interpreted as a residual activity with a probability α, when
problem (6). in fact it is only background, (error of the first kind).
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Conversely, the second aspect relates to making an a priori For purposes of this discussion, MDA will be defined in
(before the fact) estimate of the detection capabilities of the units of activity expressed as dpm or pCi. This mathematical
measurement process that yields a signal exceeding the critical
relationship for MDA will be applied to point source or “hot
level that is in fact from a “real” residual source of activity.
spot” residual. The concept of detection limit for distributed
This“ detection limit” (L ) is the smallest value such that real
D activity will be expressed using the “minimum surface sensi-
residualradioactivematerialgreaterthanL willbeinterpreted
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