ASTM C1237-99
(Guide)Standard Guide to In-Plant Performance Evaluation of Hand-Held SNM Monitors
Standard Guide to In-Plant Performance Evaluation of Hand-Held SNM Monitors
SCOPE
1.1 This guide is one of a series on the application and evaluation of special nuclear material (SNM) monitors. Other guides in the series are listed in Section 2, and the relationship of in-plant performance evaluation to other procedures described in the series is illustrated in Fig. 1. Hand-held SNM monitors are described in 5.1 of Guide C1112, and performance criteria illustrating their capabilities can be found in Appendix X1.
1.2 The purpose of this guide to in-plant performance evaluation is to provide a comparatively rapid procedure to verify that a hand-held SNM monitor performs as expected for detecting SNM or alternative test sources or to disclose the need for repair. The procedure can be used as a routine operational evaluation or it can be used to verify performance after a monitor is calibrated.
1.3 In-plant performance evaluations are more comprehensive than daily functional tests. They take place less often, at intervals ranging from weekly to once every three months, and derive their result from multiple trials.
1.4 Note that the performance of both the hand-held monitor and its operator are important for effective monitoring. Operator training is discussed in Appendix X2.
1.5 The values stated in SI units are to be regarded as standard.
1.6 This standard does not purport to address all of 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.
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Designation:C1237–99
Standard Guide to
In-Plant Performance Evaluation of Hand-Held SNM
Monitors
This standard is issued under the fixed designation C 1237; 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
1.1 This guide is one of a series on the application and
evaluation of special nuclear material (SNM) monitors. Other
guides in the series are listed in Section 2, and the relationship
of in-plant performance evaluation to other procedures de-
scribed in the series is illustrated in Fig. 1. Hand-held SNM
monitors are described in of Guide C 1112, and performance
criteria illustrating their capabilities can be found inAppendix
X1.
1.2 The purpose of this guide to in-plant performance
evaluation is to provide a comparatively rapid procedure to
verify that a hand-held SNM monitor performs as expected for
detecting SNM or alternative test sources or to disclose the
need for repair. The procedure can be used as a routine
operational evaluation or it can be used to verify performance
after a monitor is calibrated.
1.3 In-plant performance evaluations are more comprehen-
sive than daily functional tests. They take place less often, at
intervals ranging from weekly to once every three months, and
derive their result from multiple trials.
1.4 Notethattheperformanceofboththehand-heldmonitor
and its operator are important for effective monitoring. Opera-
tor training is discussed in Appendix X2.
1.5 The values stated in SI units are to be regarded as
standard.
NOTE 1—The procedures shown “above” the user provide the user with
1.6 This standard does not purport to address all of the
information before acquiring a monitor, and those “below” assist the user
safety problems, if any, associated with its use. It is the
to obtain continuing acceptable performance from the monitor.
responsibility of the user of this standard to establish appro-
FIG. 1 The Relationship of In-plant Evaluation to Other
priate safety and health practices and determine the applica-
Procedures Described in Guides for SNM Monitors
bility of regulatory limitations prior to use.
2. Referenced Documents
C 859 Terminology Relating to Nuclear Materials
C 993 Guide for In-Plant Performance Evaluation of Auto-
2.1 The guide is based on ASTM standards that describe
matic Pedestrian SNM Monitors
application and evaluation of SNM monitors, as well as
C 1112 Guide for Application of Radiation Monitors to the
technical publications that describe aspects of SNM monitor-
ControlandPhysicalSecurityofSpecialNuclearMaterial
ing.
C 1169 Guide for Laboratory Evaluation of Automatic Pe-
2.2 ASTM Standards:
destrian SNM Monitor Performance
This guide is under the jurisdiction ofASTM Committee C-26 on Nuclear Fuel
Cycleand is the direct responsibility of Subcommittee C26.12 on Safeguard
Applications.
Current edition approved June 10, 1999. Published July 1999. 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.
C1237
C 1189 Guide to Procedures for Calibrating Automatic 3.1.6 detection probability— for hand-held monitors, ex-
Pedestrian SNM Monitors pressed as the proportion of trials with a particular test source
for which the monitor is expected to detect the source.
C 1236 Guide to In-Plant Performance Evaluation of Auto-
matic Vehicle SNM Monitors
3.1.6.1 Discussion—Althoughprobabilitiesareproperlyex-
pressedasproportions,performancerequirementsfordetection
3. Terminology probability in regulatory guidance have sometimes been ex-
pressed in percentage. In that case, the detection probability as
3.1 Definitions:
a proportion can be obtained by dividing the percentage by
3.1.1 alarm—the audible sound made by a hand-held SNM
100.
monitor to indicate that it has detected radiation intensity at or
3.1.7 hand-held SNM monitor—a hand-held radiation de-
above the alarm threshold.
tection system that measures ambient radiation intensity, de-
3.1.1.1 Discussion—One or more closely spaced alarms
termines an alarm threshold from the result, and then when it
may be chosen to signify detection of SNM.
is used for monitoring, sounds an alarm whenever its measured
3.1.2 alternative test source—Althoughnootherradioactive
radiation intensity exceeds the threshold.
materials individually or collectively duplicate the radioactive
3.1.8 nuisance alarm—a monitoring alarm not caused by
emissions of uranium or plutonium, some materials have
SNM but by other causes, that may be a statistical variation in
similar attributes and are sometimes used as alternative test
the measurement process, a background intensity variation, or
sources.
an equipment malfunction.
3.1.2.1 alternative gamma-ray test sources—Examples of
3.1.9 operator—an individual who uses a hand-held SNM
alternative gamma-ray sources are highly enriched uranium
monitor to search pedestrians, packages, or vehicles to detect
(HEU) or Ba used in place of plutonium when a plutonium
the presence of SNM.
source is not readily available or is prohibited.
3.1.10 process-SNM test source—an SNM test source fab-
3.1.2.2 Discussion—Table 1 tabulates amounts of HEU
ricated by a facility from process material that differs in
mass, plutonium mass, and Ba source activity that produce
physical or isotopic form from the material recommended in
equal response in two different types of monitor.
3.1.12 for standard test sources.
3.1.2.3 alternative neutron test source—Acommon alterna-
3.1.10.1 Discussion—This type of source is used when it
tive neutron source used in place of plutonium is Cf, which
meetsplantoperatororregulatoryagencyperformancerequire-
emits neutrons from spontaneous fission as does plutonium.
ments and a standard source is not appropriate or readily
3.1.2.4 Discussion—Alternativetestsourcesmayhaveshort
available. Encapsulation and filtering should follow that rec-
decay half-lives in comparison to SNM isotopes, for example
133 252
ommended in 3.1.12.
the half-life of Ba is 10.7 years and Cf 2.64 years. Larger
3.1.11 SNM (special nuclear material)—plutonium of any
source activities than initially needed are often purchased to
isotopic composition, U, or enriched uranium as defined in
obtain a longer working lifetime for the source.
Terminology C 859.
3.1.3 confidence coeffıcient—the approximate percentage of
3.1.11.1 Discussion—This term is used here to describe
confidence intervals from a large number of repetitions of an
both SNM and strategic SNM, which is plutonium, U, and
evaluation that would contain the true result.
uranium enriched to 20 % or more in the U isotope.
3.1.3.1 Discussion—For example, a confidence coefficient
3.1.12 standard SNM test source—a metallic sphere or cube
is being referred to by the words “with 95 % confidence”.
of SNM having maximum self attenuation of its emitted
3.1.4 confidence interval—a range that contains the (true)
radiation and an isotopic composition listed below that mini-
detection probability for an evaluation situation with a stated
mizes the intensity of its radiation emission. Encapsulation and
confidence.
filtering also affect radiation intensity, and particular details are
3.1.5 detection—one or more alarm sounds from a hand-
listed for each source. This type of test source is used in
held SNM monitor may constitute detection of SNM.
laboratory evaluation but, if suitable and readily available, also
3.1.5.1 Discussion—Nuisance alarms are more likely to
may be used for in-plant evaluation.
occur in hand-held monitors than in other types of SNM
3.1.12.1 standard uranium SNM test source—a metallic
monitors for several reasons. Repeated alarms are most often
sphere or cube of HEU containing at least 93 % U and less
used to indicate detection of SNM.
than0.25 %impurities.Protectiveencapsulationshouldbethin
plastic or thin aluminum (#0.32 cm thick) to reduce unneces-
A sary radiation absorption in the encapsulation. No additional
TABLE 1 Alternative Test Source Equivalent Amounts
filter is needed.
Monitor Ba (µCi) Required in:
NaI(Tl) Plastic 3.1.12.2 standard plutonium SNM test source—a metallic
Plutonium, g Uranium, g
Category Description Scintillator Scintillator
sphere or cube of low-burnup plutonium containing at least
Monitors Monitors
239 240
93 % Pu, less than 6.5 % Pu, and less than 0.5 %
I Plutonium 1 64 2.5 3.2
II Uranium 0.29 10 0.9 1.4 impurities.
A
This table combines information from Tables II and V of the report referenced 3.1.12.3 Discussion—A cadmium filter can reduce the im-
in Footnote 5. Note that the term “category” refers to an SNM monitor performance
pact of Am, a plutonium decay product that will slowly
category used in that report and not to an SNM accountability category. Also note
133 build up in time and emit increasing amounts of 60-keV
that the Ba source strengths depend on individual differences in how the
scintillators respond to radiation from the barium isotope and plutonium. radiation. Begin use of a 0.04-cm thick cadmium filter when
C1237
three or more years have elapsed since separation of plutonium 4.1.2.7 Report the results (see Section 10).
decay products. If ten or more years have elapsed since
5. Significance and Use
separation, use a 0.08 cm thick cadmium filter. The protective
5.1 Hand-held SNM monitors are an effective and unobtru-
encapsulation should be in as many layers as local rules
sive means to search pedestrians or vehicles for concealed
require. A nonradioactive encapsulating material, such as
SNM when automatic SNM monitors are not available or have
aluminum (#0.32-cm thick) or thin (#0.16-cm thick) stainless
sounded an alarm. Facility security plans apply SNM monitors
steel or nickel, should be used to reduce unnecessary radiation
as one means to prevent theft or unauthorized removal of SNM
absorption.
from designated areas. Functional testing of monitors on a
3.2 Descriptions of Terms Specific to This Standard:
dailybasiswithradioactivesourcescanassuretheyareingood
3.2.1 post-calibration evaluation—verifies the performance
working order. The significance of a less frequent, in-plant
of a hand-held monitor immediately after calibration, recali-
evaluation of an SNM monitor is to verify that the monitor
bration, or repair and calibration. The hand-held monitor is
achieves an expected probability of detection for an SNM or
prepared for best performance.
alternative test source.
3.2.2 routine-operational evaluation—verifies the routine
5.2 The evaluation verifies acceptable performance or dis-
performanceofahand-heldmonitor.Themonitorisbeingused
closes faults in hardware or calibration.
in routine operation.
5.3 The evaluation uses test sources shielded only by
3.2.3 saturation—anundesirableconditioninwhichahand-
normal source encapsulation. However, shielded SNM test
held SNM monitor exposed to intense radiation ceases to
sources could be used as well.
function, falls silent, and does not indicate that SNM or intense
5.4 The evaluation, when applied as a routine operational
radiation is present.
evaluation, provides evidence for continued compliance with
4. Summary of Guide
the performance goals of security plans or regulatory guidance.
4.1 Each evaluation, routine-operational or post-calibration,
NOTE 1—It is the responsibility of the users of this guide to coordinate
is carried out using a predetermined test source, number of
its application with the appropriate regulatory authority so that mutually
trials, and alarm criteria. The evaluation is summarized as
agreeable choices for evaluation frequency, test sources, detection criteria
follows:
(whether a single or multiple alarms constitute detection), minimum
4.1.1 Steps for Routine-Operational Evaluation: distance for first detection, number of trials, and reporting procedures are
used. Regulatory concurrence should be formally documented.
4.1.1.1 Put the monitor into operation and check for satu-
ration.
6. Apparatus
4.1.1.2 Use the evaluation procedure (see Section 8) in a
6.1 Besides a hand-held monitor to evaluate, the following
series of trials to check for nuisance alarms. Record the results,
list of apparatus and supplies are needed.
alarm or no alarm for each trial.
6.1.1 Metre Stick, Tape Measure, or Other Means for
4.1.1.3 Use the evaluation procedure again in a series of
Measuring Distance.
trials, this time to estimate the detection probability of a
6.1.2 Means of Support, for the test source and hand-held
hand-held monitor in routine operation. Record the results,
monitor during the evaluation. For example, the test source
detect or miss for each trial.
could be supported on a table or shelf and the monitor moved
4.1.1.4 End the testing when the preselected total number of
towards it by a person holding the monitor and moving slowly
trials is reached.
towards the source. A better example would be to use a long
4.1.1.5 Analyze the results (see Section 9) to determine
wooden,orsimilar,plank(testplank)withamarkedtestsource
whether the hand-held monitor achieves a minimum require-
position and marked minimum distance for first detection. The
ment.
plank could be supported with sawhorses. The person could
4.1.1.6 Report the results (see Section 10).
then slowly move the monitor along the plank towards the test
4.1.2 Steps for Post-Calibration Evaluation:
source in a more reproducible manner.
4.1.2.1 Calibrate the monitor according to procedures sug-
6.1.3 Evaluation Report Forms and Some Means to Record
gested by the manufacturer or other standard practice.
Evaluation Results.
4.1.2.2 Put the monitor into operation and check for satu-
ration.
7. Test Materials
4.1.2.3 Use the evaluation procedure (see Section 8) in a
7.1 The materials needed for performance evaluation are
series of trials to check for nuisance alarms. Record the results,
preselected (and agreed upon, see 5.4.1) test sources that may
alarm or no alarm for each trial.
be standard SNM (see 3.1.12), process SNM (see 3.1.10), or
4.1.2.4 Use the evaluation procedure again in a series of
alternative test sources (see 3.1.2). Standard 3-g and 10-g
trials, this time to estimate whether the detection probability of
235U spherical test sources (see 3.1.12.1) are used in laboratory
the hand-held monitor meets a minimum requirement. Record
evaluations of automatic pedestrian monitors. Standard low-
the results, detect or miss for each trial.
burnup plutonium test sources, triply encapsulated and filtered
4.1.2.5 End the testing when the preselected tota
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