ASTM C993-97(2003)

Standard Guide for In-Plant Performance Evaluation of Automatic Pedestrian SNM Monitors

SIGNIFICANCE AND USE
SNM monitors are an effective and unobtrusive means to search pedestrians for concealed SNM. Facility security plans use SNM monitors as one means to prevent theft or unauthorized removal of designated quantities of SNM from access areas. Daily testing of the monitors with radioactive sources guarantees only the continuity of alarm circuits. The in-plant evaluation is a way to estimate whether an acceptable level of performance for detecting chosen quantities of SNM is obtained from a monitor in routine service or after repair or calibration.
The evaluation verifies acceptable performance or discloses faults in hardware or calibration.
The evaluation uses test sources shielded only by normal source filters and encapsulation and, perhaps, by intervening portions of the transporting individual’body. The transporting individual also provides another form of shielding when the body intercepts environmental radiation that would otherwise reach the monitor’detectors. Hence, transporting individuals play an important role in the evaluation by reproducing an important condition of routine operation.
The evaluation, when applied as a routine-operational evaluation, provides evidence for continued compliance with the performance goals of security plans or regulatory guidance. It is the responsibility of the users of this evaluation to coordinate its application with the appropriate regulatory authority so that mutually agreeable evaluation frequency, test sources, way of transporting the test source, number of test-source passages, and nuisance-alarm-rate goals are used. Agreed written procedures should be used to document the coordination.
SCOPE
1.1 This guide is affiliated with Guide C1112 on special nuclear material (SNM) monitors, Guide C1169 on laboratory performance evaluation, and Guide C1189 on calibrating pedestrian SNM monitors. This guide to in-plant performance evaluation is a comparatively rapid way to verify whether a pedestrian SNM monitor performs as expected for detecting SNM or SNM-like test sources.  
1.1.1 In-plant performance evaluation should not be confused with the simple daily functional test recommended in Guide C1112. In-plant performance evaluation takes place less often than daily tests, usually at intervals ranging from weekly to once every three months. In-plant evaluations are also more extensive than daily tests and may examine both a monitor's nuisance alarm record and its detection sensitivity for a particular SNM or alternative test source.  
1.1.2 In-plant performance evaluation also should not be confused with laboratory performance evaluation. In-plant evaluation is comparatively rapid, takes place in the monitor's routine operating environment, and its results are limited to verifying that a monitor is operating as expected, or to disclosing that it is not and needs repair or recalibration.  
1.2 In-plant evaluation is one part of a program to keep SNM monitors in proper operating condition. Every monitor in a facility is evaluated. There are two applications of the in-plant evaluation: one used during routine operation and another used after calibration.  
1.2.1 Routine Operational Evaluation -In this form of the evaluation, nuisance alarm records for each monitor are examined, and each monitor's detection sensitivity is estimated during routine operation. The routine operational evaluation is intended to reassure the plant operator, and his regulatory agency, that the monitor is performing as expected during routine operation. This evaluation takes place without pretesting, recalibration, or other activity that might change the monitor's operation, and the evaluation simulates the normal use of the monitor.  
1.2.2 Post-Calibration Evaluation -This form of the evaluation is part of a maintenance procedure; it should always follow scheduled monitor recalibration, or recalibration connected with repair or relocation of the monitor, to verify that an e...

General Information

• Status: Historical
• Publication Date: 09-May-1997
• ICS: 93.080.30 - Road equipment and installations
• Technical Committee: C26 - Nuclear Fuel Cycle

Relations

• Replaces: ASTM C993-97 - Standard Guide for In-Plant Performance Evaluation of Automatic Pedestrian SNM Monitors
• Effective Date: 10-May-1997
• Referred By: ASTM C1189-11(2018) - Standard Guide to Procedures for Calibrating Automatic Pedestrian SNM Monitors
• Effective Date: 10-May-1997

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:C993–97(Reapproved2003)
Standard Guide for
In-Plant Performance Evaluation of Automatic Pedestrian
SNM Monitors
This standard is issued under the fixed designation C993; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope testing, recalibration, or other activity that might change the
monitor’s operation, and the evaluation simulates the normal
1.1 This guide is affiliated with Guide C1112 on applying
use of the monitor.
special nuclear material (SNM) monitors, Guide C1169 on
1.2.2 Post-Calibration Evaluation—This form of the evalu-
laboratory performance evaluation, Guide C1189 on calibrat-
ation is part of a maintenance procedure; it should always
ing pedestrian SNM monitors, and Guides C1236 and C1237
follow scheduled monitor recalibration, or recalibration con-
on in-plant evaluation. This guide to in-plant performance
nectedwithrepairorrelocationofthemonitor,toverifythatan
evaluation is a comparatively rapid way to verify whether a
expected detection sensitivity is achieved. Nuisance alarm data
pedestrian SNM monitor performs as expected for detecting
do not apply in this case because the monitor has just been
SNM or SNM-like test sources.
recalibrated. Also, having just been calibrated, the monitor is
1.1.1 In-plant performance evaluation should not be con-
likelytobeoperatingatitsbest,whichmaybesomewhatbetter
fused with the simple daily functional test recommended in
than its routine operation.
Guide C1112. In-plant performance evaluation takes place less
1.3 The values stated in SI units are to be regarded as
often than daily tests, usually at intervals ranging from weekly
standard.
to once every three months. In-plant evaluations are also more
1.4 This standard does not purport to address the safety
extensive than daily tests and may examine both a monitor’s
problems, if any, associated with its use. It is the responsibility
nuisance alarm record and its detection sensitivity for a
of the user of this standard to establish appropriate safety and
particular SNM or alternative test source.
health practices and determine the applicability of regulatory
1.1.2 In-plant performance evaluation also should not be
limitations prior to use.
confused with laboratory performance evaluation. In-plant
evaluation is comparatively rapid, takes place in the monitor’s
2. Referenced Documents
routine operating environment, and its results are limited to
2.1 The guide is based on ASTM standards that describe
verifying that a monitor is operating as expected, or to
application and evaluation of SNM monitors, as well as
disclosing that it is not and needs repair or recalibration.
technical publications that describe aspects of SNM monitor
1.2 In-plant evaluation is one part of a program to keep
design and use.
SNM monitors in proper operating condition. Every monitor in
2.2 ASTM Standards:
a facility is evaluated. There are two applications of the
C859 Terminology Relating to Nuclear Materials
in-plant evaluation: one used during routine operation and
C1112 Guide for Application of Radiation Monitors to the
another used after calibration.
Control and Physical Security of Special Nuclear Material
1.2.1 Routine Operational Evaluation—In this form of the
C1169 Guide for Laboratory Evaluation of Automatic Pe-
evaluation, nuisance alarm records for each monitor are exam-
destrian SNM Monitor Performance
ined, and each monitor’s detection sensitivity is estimated
C1189 Guide to Procedures for Calibrating Automatic Pe-
during routine operation. The routine operational evaluation is
destrian SNM Monitors
intended to reassure the plant operator, and his regulatory
C1236 Guide for In-Plant Performance Evaluation ofAuto-
agency, that the monitor is performing as expected during
matic Vehicle SNM Monitors
routine operation. This evaluation takes place without pre-
C1237 Guide to In-Plant Performance Evaluation of Hand-
Held SNM Monitors
This guide is under the jurisdiction ofASTM Committee C26 on Nuclear Fuel
Cycle and is the direct responsibility of Subcommittee C26.12 on Safeguard
Applications. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 10, 2003. Published February 2003. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1991. Last previous edition approved in 1997 as C993 – 97. DOI:
Standards volume information, refer to the standard’s Document Summary page on
10.1520/C0993-97R03.
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C993–97 (2003)
3. Terminology pressed in percentage. In that case, the detection probability as
a proportion can be obtained by dividing the percentage by
3.1 Definitions:
100.
3.1.1 alternative test source—although no other radioactive
3.1.7 nuisance alarm—a monitoring alarm not caused by
materials individually or collectively duplicate the radioactive
SNM but by other causes, such as statistical variation in the
emissions of uranium or plutonium, some materials have
measurement process, a background intensity variation, or an
somewhat similar attributes and are sometimes used as alter-
equipment malfunction.
native test sources.
3.1.8 process-SNM test source—an SNM test source fabri-
3.1.2 alternative gamma-ray test sources—examples of al-
cated by a facility from process material that differs in physical
ternativegamma-raysourcesareHEUor Bausedinplaceof
or isotopic form from the material recommended in 3.1.11 for
plutonium when a plutonium source is not readily available or
standard test sources.
is prohibited.
3.1.8.1 Discussion—This type of source is used when it
3.1.2.1 Discussion—Table 1 tabulates amounts of HEU
meetsplantoperatororregulatoryagencyperformancerequire-
mass, plutonium mass, and Ba source activity that produce
ments and a suitable standard source is not readily available.
equal response in two different types of monitor.
Encapsulation and filtering should follow that recommended in
3.1.3 alternative neutron test source—acommonalternative
3.1.11.
neutron source used in place of plutonium is Cf that emits
3.1.9 SNM—special nuclear material: plutonium of any
neutrons from spontaneous fission as does plutonium.
isotopic composition, U, or enriched uranium as defined in
3.1.3.1 Discussion—Alternativetestsourcesmayhaveshort
Terminology C859.
decay half-lives in comparison to SNM isotopes; for example,
133 252
3.1.9.1 Discussion—This term is used here to describe both
the half-life of Ba is 10.7 years and Cf 2.64 years. Larger
SNM and strategic SNM, which includes plutonium, U, and
source activities than initially needed are often purchased to
uranium enriched to 20 % or more in the U isotope.
obtain a longer working lifetime for the source.
3.1.10 SNM monitor—radiation detection system that mea-
3.1.4 confidence coeffıcient—the theoretical proportion of
sures ambient radiation intensity, determines an alarm thresh-
confidence intervals from an infinite number of repetitions of
old from the result, and then, when it monitors, sounds an
an evaluation that would contain the true result.
alarm if its measured radiation intensity exceeds the threshold.
3.1.4.1 Discussion—In a demonstration, if the true result
3.1.11 standard SNM test source—a metallic sphere or cube
were known the theoretical confidence coefficient would be the
of SNM having maximum self attenuation of its emitted
approximate proportion of confidence intervals, from a large
radiation and an isotopic composition listed below that mini-
number of repetitions of an evaluation, that contain the true
mizes the intensity of its radiation emission. Encapsulation and
result. Typical confidence coefficients are 0.90, 0.95 and 0.99.
filteringalsoaffectradiationintensity,andparticulardetailsare
3.1.5 Confidence Interval for a Detection Probability—An
listed for each source. This type of test source is used in
interval, based on an actual evaluation situation, so constructed
laboratoryevaluationbut,ifsuitableandreadilyavailable,may
that it contains the (true) detection probability with a stated
be used for in-plant evaluation.
confidence.
3.1.12 standard plutonium test source—a metallic sphere or
3.1.5.1 Discussion—Confidence is often expressed as 100*
cube of low-burnup plutonium containing at least 93 % Pu,
the confidence coefficient. Thus, typical confidence levels are
less than 6.5 % Pu, and less than 0.5 % impurities.
90, 95 and 99 %.
3.1.12.1 Discussion—A cadmium filter can reduce the im-
3.1.6 detection probability—the proportion of passages for
pact of Am, a plutonium decay product that will slowly
which the monitor is expected to alarm during passages of a
build up in time and emit increasing amounts of 60-keV
particular test source.
radiation. Begin use of a 0.04-cm thick cadmium filter when
3.1.6.1 Discussion—Althoughprobabilitiesareproperlyex-
three or more years have elapsed since separation of plutonium
pressedasproportions,performancerequirementsfordetection
decay products. If ten or more years have elapsed since
probability in regulatory guidance have sometimes been ex-
separation, use a cadmium filter 0.08 cm thick. The protective
encapsulation should be in as many layers as local rules
A require. A nonradioactive encapsulation material, such as,
TABLE 1 Alternative Test Source Equivalent Amounts
aluminum (#0.32 cm-thick) or thin (#0.16 cm-thick) stainless
Ba (µCi)
steel or nickel, should be used to reduce unnecessary radiation
Required in
Monitor Monitor Plutonium, Uranium,
absorption.
NaI(T1) Plastic
Category Description g g
Scintillator Scintillator
3.1.13 standard uranium test source—a metallic sphere or
Monitors Monitors
cube of highly enriched uranium (HEU) containing at least
I Standard plutonium 1 64 2.5 3.2
93 % U and less than 0.25 % impurities. Protective encap-
II Standard uranium 0.29 10 0.9 1.4
sulation should be thin plastic or thin aluminum (#0.32 cm
III Improved sensitivity 0.08 3 0.4 0.6
thick) to reduce unnecessary radiation absorption in the encap-
IV High sensitivity 0.03 1 0.2 0.3
A
sulation. No additional filter is needed.
This table combines information from Tables II and V of the report referenced
inFootnote8.Notethattheterm“category”referstoanSNMmonitorperformance
3.2 Definitions of Terms Specific to This Standard:
category used in that report and not to an SNM accountability category.Also note
133 3.2.1 post-calibration evaluation—verifies performance af-
that the Ba source strengths depend on individual differences in how the
scintillators respond to radiation from the barium isotope and plutonium. ter repair, relocation, or recalibration. Monitor is prepared for
C993–97 (2003)
best operation. Monitor is not yet in routine operation. Only 4.3.2.2 End testing when a total number of passages, se-
sensitivity is evaluated. lected beforehand, is reached.
3.2.2 routine-operational evaluation—verifies performance 4.3.2.3 Analyze the results as a binomial experiment (see
in routine operation. Simulates normal use of a monitor. Uses 8.2).
no monitor preparation procedures. Both sensitivity and nui-
5. Significance and Use
sance alarm probability or rate are evaluated.
5.1 SNM monitors are an effective and unobtrusive means
4. Summary of Guide to search pedestrians for concealed SNM. Facility security
plans use SNM monitors as one means to prevent theft or
4.1 Preliminary Steps Common to Both Forms of In-Plant
unauthorized removal of designated quantities of SNM from
Evaluation:
access areas. Daily testing of the monitors with radioactive
4.1.1 The monitor being evaluated is an automatic
sources guarantees only the continuity of alarm circuits. The
walkthrough-portal or monitoring booth.
in-plant evaluation is a way to estimate whether an acceptable
4.1.2 The monitor’s indicated background measurement
level of performance for detecting chosen quantities of SNM is
value is recorded for possible future use in troubleshooting.
obtained from a monitor in routine service or after repair or
4.1.3 Nonmandatory Information—If a gamma-ray survey
calibration.
meter (see 6.1) capable of quickly and precisely measuring
5.2 The evaluation verifies acceptable performance or dis-
environmental gamma-ray intensity is available, its use and
closes faults in hardware or calibration.
recording its measurement value may provide additional ben-
3 5.3 The evaluation uses test sources shielded only by
eficial information for future troubleshooting. Independent
normal source filters and encapsulation and, perhaps, by
knowledge of the ambient background intensity also can help
intervening portions of the transporting individual’s body. The
to interpret performance differences at different monitor loca-
transporting individual also provides another form of shielding
tions or at one location at different times.
when the body intercepts environmental radiation that would
4.2 Steps for Routine Operational Evaluation:
otherwise reach the monitor’s detectors. Hence, transporting
4.2.1 Determine nuisance alarm probability during the pe-
individuals play an important role in the evaluation by repro-
riod since the monitor was last maintained, calibrated, or
ducing an important condition of routine operation.
evaluated (see 8.1). Use recorded numbers of alarms and
5.4 The evaluation, when applied as a routine-operational
pedestrian passages from records kept during routine monitor
evaluation, provides evidence for continued compliance with
use.
theperformancegoalsofsecurityplansorregulatoryguidance.
4.2.1.1 Handwritten alarm logs or records from the moni-
It is the responsibility of the users of this evaluation to
tor’s control unit can provide total alarms (see Section 6) from
coordinate its application with the appropriate regulatory
which alarms from daily or other performance testing and
authority so that mutually agreeable evaluation frequency, test
alarms explained by radioactive material presence in follow-up
sources, way of transporting the test source, number of
searches must be subtracted.
test-source passages, and nuisance-alarm-rate goals are used.
4.2.1.2 Total pedestrian passages can be estimated from
Agreed written procedures should be used to document the
operating logs or recorded information from the monitor’s
coordination.
control unit.
4.2.2 Estimate detection probability by transporting a stan-
6. Apparatus
dard SNM, process-SNM, or alternative test source (see
6.1
...