ASTM C993-97

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

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 expected detection sensitivity is achieved. Nuisance alarm data do not apply in this case because the monitor has just been recalibrated. Also, having just been calibrated, the monitor is likely to be operating at its best, which may be somewhat better than its routine operation.  
1.3 The values stated in SI units are to be regarded as standard.  
1.4 This standard does not purport to address the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-May-1997
• Technical Committee: C26 - Nuclear Fuel Cycle

Relations

• Replaced By: ASTM C993-97(2003) - 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 superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: C 993 – 97
Standard Guide for
In-Plant Performance Evaluation of Automatic Pedestrian
SNM Monitors
This standard is issued under the fixed designation C 993; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 1.2.2 Post-Calibration Evaluation—This form of the evalu-
ation is part of a maintenance procedure; it should always
1.1 This guide is affiliated with Guide C 1112 on applying
follow scheduled monitor recalibration, or recalibration con-
special nuclear material (SNM) monitors, Guide C 1169 on
nected with repair or relocation of the monitor, to verify that an
laboratory performance evaluation, Guide C 1189 on calibrat-
expected detection sensitivity is achieved. Nuisance alarm data
ing pedestrian SNM monitors, and Guides C 1236 and C 1237
do not apply in this case because the monitor has just been
on in-plant evaluation. This guide to in-plant performance
recalibrated. Also, having just been calibrated, the monitor is
evaluation is a comparatively rapid way to verify whether a
likely to be operating at its best, which may be somewhat better
pedestrian SNM monitor performs as expected for detecting
than its routine operation.
SNM or SNM-like test sources.
1.3 The values stated in SI units are to be regarded as
1.1.1 In-plant performance evaluation should not be con-
standard.
fused with the simple daily functional test recommended in
1.4 This standard does not purport to address the safety
Guide C 1112. In-plant performance evaluation takes place less
problems, if any, associated with its use. It is the responsibility
often than daily tests, usually at intervals ranging from weekly
of the user of this standard to establish appropriate safety and
to once every three months. In-plant evaluations are also more
health practices and determine the applicability of regulatory
extensive than daily tests and may examine both a monitor’s
limitations prior to use.
nuisance alarm record and its detection sensitivity for a
particular SNM or alternative test source.
2. Referenced Documents
1.1.2 In-plant performance evaluation also should not be
2.1 The guide is based on ASTM standards that describe
confused with laboratory performance evaluation. In-plant
application and evaluation of SNM monitors, as well as
evaluation is comparatively rapid, takes place in the monitor’s
technical publications that describe aspects of SNM monitor
routine operating environment, and its results are limited to
design and use.
verifying that a monitor is operating as expected, or to
2.2 ASTM Standards:
disclosing that it is not and needs repair or recalibration.
C 859 Terminology Relating to Nuclear Materials
1.2 In-plant evaluation is one part of a program to keep
C 1112 Guide for Application of Radiation Monitors to the
SNM monitors in proper operating condition. Every monitor in
Control and Physical Security of Special Nuclear Material
a facility is evaluated. There are two applications of the
C 1169 Guide for Laboratory Evaluation of Automatic Pe-
in-plant evaluation: one used during routine operation and
destrian SNM Monitor Performance
another used after calibration.
C 1189 Guide to Procedures for Calibrating Automatic
1.2.1 Routine Operational Evaluation—In this form of the
Pedestrian SNM Monitors
evaluation, nuisance alarm records for each monitor are exam-
C 1236 Guide for In–Plant Performance Evaluation of Au-
ined, and each monitor’s detection sensitivity is estimated
tomatic Vehicle SNM Monitors
during routine operation. The routine operational evaluation is
C 1237 Guide to In–Plant Performance Evaluation of Hand-
intended to reassure the plant operator, and his regulatory
–Held SNM Monitors
agency, that the monitor is performing as expected during
routine operation. This evaluation takes place without pre-
3. Terminology
testing, recalibration, or other activity that might change the
3.1 Definitions:
monitor’s operation, and the evaluation simulates the normal
3.1.1 alternative test source—although no other radioactive
use of the monitor.
materials individually or collectively duplicate the radioactive
emissions of uranium or plutonium, some materials have
This guide is under the jurisdiction of ASTM Committee C26 on Nuclear Fuel
Cycle and is the direct responsibility of Subcommittee C26.12 on Safeguard
Applications.
Current edition approved May 10, 1997. Published May 1998. Originally
published as C 993 – 91. Last previous edition C 993 – 92. Annual Book of ASTM Standards, Vol 12.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C 993
somewhat similar attributes and are sometimes used as alter- 3.1.8 process-SNM test source—an SNM test source fabri-
native test sources. cated by a facility from process material that differs in physical
3.1.2 alternative gamma-ray test sources—examples of al- or isotopic form from the material recommended in 3.1.11 for
ternative gamma-ray sources are HEU or Ba used in place of standard test sources.
plutonium when a plutonium source is not readily available or
3.1.8.1 Discussion—This type of source is used when it
is prohibited.
meets plant operator or regulatory agency performance require-
3.1.2.1 Discussion—Table 1 tabulates amounts of HEU
ments and a suitable standard source is not readily available.
mass, plutonium mass, and Ba source activity that produce
Encapsulation and filtering should follow that recommended in
equal response in two different types of monitor.
3.1.11.
3.1.3 alternative neutron test source—a common alternative
3.1.9 SNM—special nuclear material: plutonium of any
neutron source used in place of plutonium is Cf that emits
isotopic composition, U, or enriched uranium as defined in
neutrons from spontaneous fission as does plutonium.
Terminology C 859.
3.1.3.1 Discussion—Alternative test sources may have short
3.1.9.1 Discussion—This term is used here to describe both
decay half-lives in comparison to SNM isotopes; for example,
SNM and strategic SNM, which includes plutonium, U, and
133 252
the half-life of Ba is 10.7 years and Cf 2.64 years. Larger
uranium enriched to 20 % or more in the U isotope.
source activities than initially needed are often purchased to
3.1.10 SNM monitor—radiation detection system that mea-
obtain a longer working lifetime for the source.
sures ambient radiation intensity, determines an alarm thresh-
3.1.4 confidence coeffıcient—the theoretical proportion of
old from the result, and then, when it monitors, sounds an
confidence intervals from an infinite number of repetitions of
alarm if its measured radiation intensity exceeds the threshold.
an evaluation that would contain the true result.
3.1.11 standard SNM test source—a metallic sphere or cube
3.1.4.1 Discussion—In a demonstration, if the true result
of SNM having maximum self attenuation of its emitted
were known the theoretical confidence coefficient would be the
radiation and an isotopic composition listed below that mini-
approximate proportion of confidence intervals, from a large
mizes the intensity of its radiation emission. Encapsulation and
number of repetitions of an evaluation, that contain the true
filtering also affect radiation intensity, and particular details are
result. Typical confidence coefficients are 0.90, 0.95 and 0.99.
listed for each source. This type of test source is used in
3.1.5 Confidence Interval for a Detection Probability—An
laboratory evaluation but, if suitable and readily available, may
interval, based on an actual evaluation situation, so constructed
be used for in-plant evaluation.
that it contains the (true) detection probability with a stated
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—Although probabilities are properly ex-
three or more years have elapsed since separation of plutonium
pressed as proportions, performance requirements for detection
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
pressed in percentage. In that case, the detection probability as
encapsulation should be in as many layers as local rules
a proportion can be obtained by dividing the percentage by
require. A nonradioactive encapsulation material, such as,
100.
aluminum (#0.32 cm-thick) or thin (#0.16 cm-thick) stainless
3.1.7 nuisance alarm—a monitoring alarm not caused by
steel or nickel, should be used to reduce unnecessary radiation
SNM but by other causes, such as statistical variation in the
absorption.
measurement process, a background intensity variation, or an
3.1.13 standard uranium test source—a metallic sphere or
equipment malfunction.
cube of highly enriched uranium (HEU) containing at least
93 % U and less than 0.25 % impurities. Protective encap-
A
TABLE 1 Alternative Test Source Equivalent Amounts
sulation should be thin plastic or thin aluminum (#0.32 cm
Ba (μCi)
thick) to reduce unnecessary radiation absorption in the encap-
Required in
sulation. No additional filter is needed.
Monitor Monitor Plutonium, Uranium,
NaI(T1) Plastic
Category Description g g
3.2 Definitions of Terms Specific to This Standard:
Scintillator Scintillator
Monitors Monitors
3.2.1 post-calibration evaluation—verifies performance af-
I Standard plutonium 1 64 2.5 3.2
ter repair, relocation, or recalibration. Monitor is prepared for
II Standard uranium 0.29 10 0.9 1.4
best operation. Monitor is not yet in routine operation. Only
III Improved sensitivity 0.08 3 0.4 0.6
sensitivity is evaluated.
IV High sensitivity 0.03 1 0.2 0.3
A
3.2.2 routine-operational evaluation—verifies performance
This table combines information from Tables II and V of the report referenced
in Footnote 8. Note that the term “category” refers to an SNM monitor performance
in routine operation. Simulates normal use of a monitor. Uses
category used in that report and not to an SNM accountability category. Also note
no monitor preparation procedures. Both sensitivity and nui-
that the Ba source strengths depend on individual differences in how the
scintillators respond to radiation from the barium isotope and plutonium. sance alarm probability or rate are evaluated.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C 993
4. Summary of Guide plans use SNM monitors as one means to prevent theft or
unauthorized removal of designated quantities of SNM from
4.1 Preliminary Steps Common to Both Forms of In-Plant
access areas. Daily testing of the monitors with radioactive
Evaluation:
sources guarantees only the continuity of alarm circuits. The
4.1.1 The monitor being evaluated is an automatic
in-plant evaluation is a way to estimate whether an acceptable
walkthrough-portal or monitoring booth.
level of performance for detecting chosen quantities of SNM is
4.1.2 The monitor’s indicated background measurement
obtained from a monitor in routine service or after repair or
value is recorded for possible future use in troubleshooting.
calibration.
4.1.3 Nonmandatory Information—If a gamma-ray survey
5.2 The evaluation verifies acceptable performance or dis-
meter (see 6.1) capable of quickly and precisely measuring
closes faults in hardware or calibration.
environmental gamma-ray intensity is available, its use and
5.3 The evaluation uses test sources shielded only by
recording its measurement value may provide additional ben-
normal source filters and encapsulation and, perhaps, by
eficial information for future troubleshooting. Independent
intervening portions of the transporting individual’s body. The
knowledge of the ambient background intensity also can help
transporting individual also provides another form of shielding
to interpret performance differences at different monitor loca-
when the body intercepts environmental radiation that would
tions or at one location at different times.
otherwise reach the monitor’s detectors. Hence, transporting
4.2 Steps for Routine Operational Evaluation:
individuals play an important role in the evaluation by repro-
4.2.1 Determine nuisance alarm probability during the pe-
ducing an important condition of routine operation.
riod since the monitor was last maintained, calibrated, or
5.4 The evaluation, when applied as a routine-operational
evaluated (see 8.1). Use recorded numbers of alarms and
evaluation, provides evidence for continued compliance with
pedestrian passages from records kept during routine monitor
the performance goals of security plans or regulatory guidance.
use.
It is the responsibility of the users of this evaluation to
4.2.1.1 Handwritten alarm logs or records from the moni-
coordinate its application with the appropriate regulatory
tor’s control unit can provide total alarms (see Section 6) from
authority so that mutually agreeable evaluation frequency, test
which alarms from daily or other performance testing and
sources, way of transporting the test source, number of
alarms explained by radioactive material presence in follow-up
test-source passages, and nuisance-alarm-rate goals are used.
searches must be subtracted.
Agreed written procedures should be used to document the
4.2.1.2 Total pedestrian passages can be estimated from
coordination.
operating logs or recorded information from the monitor’s
control unit.
6. Apparatus
4.2.2 Estimate detection probability by transporting a stan-
6.1 Gamma Ray Survey Meter (Nonmandatory
dard SNM, process-SNM, or alternative test source (see
Information)—Historical records of gamma-ray background
Section 7) th
...