ASTM C1169-97(2003)

Standard Guide for Laboratory Evaluation of Automatic Pedestrian SNM Monitor Performance

SCOPE
1.1 The requirement to search pedestrians for special nuclear material (SNM) to prevent its theft has long been a part of both United States Department of Energy and United States Nuclear Regulatory Commission rules for the physical protection of SNM. Information on the application of SNM monitors to perform such searches is provided in Guide C1112. This guide establishes a means to compare the performance of different SNM pedestrian monitors operating in a specific laboratory environment.  The goal is to provide relative information on the capability of monitors to search pedestrians for small quantities of concealed SNM under characterized conditions. The outcome of testing assigns a sensitivity category to a monitor related to its SNM mass-detection probability; the monitor's corresponding nuisance-alarm probability for that sensitivity category is also determined and reported.
1.2 The evaluation uses a practical set of worst-case environmental, radiation emission, and radiation response factors so that a monitor's lowest level of performance in a practical operating environment for detecting small quantities of SNM is evaluated. As a result, when that monitor is moved from laboratory to routine operation, its performance will likely improve. This worst-case procedure leads to unclassified evaluation results that understate rather than overstate the performance of a properly used SNM monitor in operational use.
1.3 The evaluation applies to two types of SNM monitors that are used to detect small quantities of SNM. Both are automatic monitors; one monitors pedestrians as they walk through a portal formed by the monitor's radiation detectors (walkthrough or portal monitor), and the other monitors pedestrians who are stationary for a short period of time while they are monitored (wait-in monitor). The latter can be a portal monitor with a delay mechanism to halt a pedestrian for a few seconds or it can be an access-control booth or room that contains radiation detectors to monitor a pedestrian waiting for clearance to pass.
1.4 The values stated in SI units are to be regarded as standard.
1.5 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-Jun-1997
• ICS: 93.080.30 - Road equipment and installations
• Technical Committee: C26 - Nuclear Fuel Cycle

Relations

• Replaces: ASTM C1169-97 - Standard Guide for Laboratory Evaluation of Automatic Pedestrian SNM Monitor Performance
• Effective Date: 10-Jun-1997
• Referred By: ASTM C1189-11(2018) - Standard Guide to Procedures for Calibrating Automatic Pedestrian SNM Monitors
• Effective Date: 10-Jun-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: C1169 – 97 (Reapproved 2003)
Standard Guide for
Laboratory Evaluation of Automatic Pedestrian SNM Monitor
Performance
This standard is issued under the fixed designation C1169; 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 seconds or it can be an access-control booth or room that
contains radiation detectors to monitor a pedestrian waiting for
1.1 The requirement to search pedestrians for special
clearance to pass.
nuclearmaterial(SNM)topreventitsthefthaslongbeenapart
1.4 The values stated in SI units are to be regarded as
of both United States Department of Energy and United States
standard.
Nuclear Regulatory Commission rules for the physical protec-
1.5 This standard does not purport to address the safety
tion of SNM. Information on the application of SNM monitors
concerns, if any, associated with its use. It is the responsibility
to perform such searches is provided in Guide C1112. This
of the user of this standard to establish appropriate safety and
guide establishes a means to compare the performance of
health practices and determine the applicability of regulatory
different SNM pedestrian monitors operating in a specific
2 limitations prior to use.
laboratory environment. The goal is to provide relative
information on the capability of monitors to search pedestrians
2. Referenced Documents
for small quantities of concealed SNM under characterized
2.1 ASTM Standards:
conditions. The outcome of testing assigns a sensitivity cat-
C859 Terminology Relating to Nuclear Materials
egory to a monitor related to its SNM mass-detection probabil-
C993 Guide for In-Plant Performance Evaluation of Auto-
ity;themonitor’scorrespondingnuisance-alarmprobabilityfor
matic Pedestrian SNM Monitors
that sensitivity category is also determined and reported.
C1112 Guide for Application of Radiation Monitors to the
1.2 The evaluation uses a practical set of worst-case envi-
Control and Physical Security of Special Nuclear Material
ronmental, radiation emission, and radiation response factors
C1189 Guide to Procedures for Calibrating Automatic Pe-
so that a monitor’s lowest level of performance in a practical
destrian SNM Monitors
operatingenvironmentfordetectingsmallquantitiesofSNMis
evaluated. As a result, when that monitor is moved from
3. Terminology
laboratory to routine operation, its performance will likely
3.1 Definitions of Terms Specific to This Standard:
improve. This worst-case procedure leads to unclassified
3.1.1 confidence coeffıcient—the theoretical proportion of
evaluation results that understate rather than overstate the
confidence intervals from an infinite number of repetitions of
performance of a properly used SNM monitor in operational
an evaluation that would contain the true result.
use.
3.1.1.1 Discussion—In a demonstration, if the true result
1.3 The evaluation applies to two types of SNM monitors
were known the theoretical confidence coefficient would be the
that are used to detect small quantities of SNM. Both are
approximate proportion of confidence intervals, from a large
automatic monitors; one monitors pedestrians as they walk
number of repetitions of an evaluation, that contain the true
through a portal formed by the monitor’s radiation detectors
result. Typical confidence coefficients are 0.90, 0.95 and 0.99.
(walkthrough or portal monitor), and the other monitors
3.1.2 Confidence Interval for a Detection Probability—An
pedestrians who are stationary for a short period of time while
interval, based on an actual evaluation situation, so constructed
they are monitored (wait-in monitor).The latter can be a portal
that it contains the (true) detection probability with a stated
monitor with a delay mechanism to halt a pedestrian for a few
confidence.
3.1.2.1 Discussion—Confidence is often expressed as
100*the confidence coefficient. Thus, typical confidence levels
This guide is under the jurisdiction ofASTM Committee C26 on Nuclear Fuel
Cycle and is the direct responsibility of Subcommittee C26.12 on Safeguard
are 90, 95 and 99 %.
Applications.
Current edition approved Feb. 10, 2003. Published February 2003. Originally
approved in 1991. Last previous edition approved in 1997 as C1169 – 97. DOI:
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/C1169-97R03. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Note that this is a laboratory evaluation and is not designed for routine in-plant Standards volume information, refer to the standard’s Document Summary page on
use.Aseparate guide, C993, is available for verifying routine in-plant performance. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C1169 – 97 (2003)
TABLE 2 Mass Detection Sensitivities in Pedestrian Neutron
3.1.3 detection probability—the proportion of passages for
A
Monitors
which the monitor is expected to alarm during passages of a
B
Category Description Plutonium (g)
particular test source.
NI Standard Neutron 250
3.1.3.1 Discussion—Althoughprobabilitiesareproperlyex-
NII Improved Neutron 100
pressedasproportions,performancerequirementsfordetection
NIII High Sensitivity 30
probability in regulatory guidance have sometimes been ex-
Neutron
pressed in percentage. In that case, the detection probability as
A
In a nominal 20 µR/h background intensity using standard metallic test sources
a proportion can be obtained by dividing the percentage by and procedures described in 11.2.
B
Low-burnup plutonium as described in 8.5. For monitors having gamma-ray
100.
sensitivity in addition to neutron sensitivity the plutonium must be shielded in 5-cm
3.1.4 detection sensitivity category—specified in terms of a
thick lead.
test source mass for which the monitor has a 0.50 or greater
detection probability, as measured by a test procedure having a
95 % confidence coefficient for its result. The specified 0.50 or
Begin use of 0.04-cm-thick cadmium filter when three or more
greater detection probability is a very convenient one for
years have elapsed since separation of plutonium decay prod-
testing. The limited number of test source masses used to
ucts. If ten or more years have elapsed since separation, use a
define sensitivity categories (see Table 1 and Table 2) ad-
cadmium filter 0.08-cm thick. The protective encapsulation
equately describe the performance of SNM monitors that can
should be in as many layers as local rules require of a
detect small quantities of SNM.
non-radioactive material such as aluminum (#0.32-cm thick)
3.1.5 nuisance alarm—a monitoring alarm not caused by
or thin (#0.16-cm thick) stainless steel or nickel to reduce
SNM but by one of two other causes, which are statistical
unnecessary radiation absorption.
variation in the measurement process or natural background
3.1.9.3 standard uranium source—a metallic sphere or cube
intensity variation. Other contributors to nuisance alarms, such
of highly-enriched uranium (HEU) containing at least 93 %
as interfering radiation sources and equipment malfunction,
U and less than 0.25 % impurities. Protective encapsulation
should not be present during testing.
should be thin plastic or thin aluminum (#0.32-cm thick) to
3.1.6 radiation intensity—expressed as the number of pho-
reduce unnecessary radiation absorption in the encapsulation.
tons or neutrons emitted by a material per second or as the
No additional filter is needed.
environmental background radiation dose rate.
3.1.7 SNM (special nuclear material)—plutonium of any
4. Summary of Guide
isotopic composition, U, or enriched uranium as defined in
Terminology C859. This term is used here to describe both
4.1 Evaluation follows a sequence of steps, each of which
SNM and strategic SNM, which is plutonium, uranium-233,
should reach an acceptable outcome before the next is begun.
and uranium enriched to 20 % or more in the U isotope.
The steps are: placing the monitor into operation; determining
3.1.8 SNM monitor—a radiation detection system that mea-
nuisance alarm probability; determining detection probability;
sures ambient radiation intensity, determines an alarm thresh-
and categorizing the results.
old from the result, and then, when it monitors, sounds an
4.2 The monitor is put into operation in a nominal 20 µR/h
alarm if its measured radiation intensity exceeds the threshold.
(5.2 nC/kg h or 1.43 pA/kg) background environment. The
3.1.9 standard SNM test source—a metallic sphere or cube
manufacturer’s instructions are followed to assemble, calibrate
of SNM having maximum self attenuation of its emitted
(see Section 10), and begin using the monitor.
radiation and an isotopic composition to minimize that emis-
4.3 Nuisance alarm probability is determined (see Section
sion as described below. Encapsulation and filtering also affect
11) by automatic data collection with a system that cycles the
radiation intensity, and particular details are listed for each
monitor alternately through a group of simulated pedestrian
source.
passages and a background update while recording the back-
3.1.9.1 standard plutonium source—a metallic sphere or
ground intensity and each of its alarms.
cube of low-burnup plutonium containing at least 93 % Pu,
240 4.4 Detection probability is determined (see Section 12)by
less than 6.5 % Pu, and less than 0.5 % impurities.
transporting SNM test sources through the monitor’s least
3.1.9.2 Discussion—Acadmiumfiltercanreducetheimpact
241 sensitive region, which is determined as part of the evaluation.
of Am, a plutonium decay product that will slowly build up
Different individuals transport the SNM at their accustomed
in time and emit increasing amounts of 60-keV radiation.
pace but in a specified manner. Results (number of detections
and passages) are analyzed as a binomial experiment to give a
confidence interval for the probability of detection that may
A
TABLE 1 Mass Detection Sensitivities of SNM Monitors
place the monitor in a sensitivity category. If the monitor can
B C
Category Description Uranium (g) Plutonium (g)
be operated in different modes or at more than one spacing
I Standard Plutonium 64 1
between its detectors, it should be evaluated in each mode and
II Standard Uranium 10 0.29
at each spacing that is expected to be used operationally.
III Improved Sensitivity 3 0.08
IV High Sensitivity 1 0.03
4.5 The sensitivity category of a monitor is determined (see
A
In a nominal 20 µR/h background intensity using standard metallic test sources
Section 13) by the smallest test source for which the monitor
and procedures described in 11.2.
B has a 0.50 or greater detection probability with 95 % confi-
HEU as described in 8.4.
C
Low-burnup plutonium as described in 8.5. dence at an acceptable nuisance alarm probability.
C1169 – 97 (2003)
5. Significance and Use 6. Interferences
6.1 The evaluation requires a nominal natural background
5.1 SNM monitors are an effective and unobtrusive means
environment that has an intensity in the range of the highest
to search pedestrians for concealed SNM. Nuclear facility
found in the continental United States [nominal 20 µR/h (5.2
security plans often include SNM monitors as one means to
nC/kg h or 1.43 pA/kg)] and has only natural variation.
help prevent theft or unauthorized removal of designated
Locations having low backgrounds are not suitable for testing;
quantities of SNM from access areas. This guide describes a
other locations are unsuitable as well when variable back-
way to evaluate and categorize the relative performance of
groundsfromotherthannaturalcausesarepresent.Asimulated
available SNM monitors that might be considered for use in a
high intensity background produced by point sources is unsuit-
security plan.
able.
5.2 The significance of the evaluation for monitor users is
6.2 Parts of the evaluation use specific values or measure-
that evaluated monitoring equipment has a verified capability.
ments that can alter the testing outcome if not done properly.
Unexpected deficiencies such as low sensitivity for highly
For example, an improperly measured background intensity
self-absorbing forms of SNM, lower than expected sensitivity
(see
7.1)thatisactuallymuchhigherorlowerthanstatedin6.1
in areas having high natural background intensity, or a high
will bias the results toward a lower or higher sensitivity
nuisance-alarm probability from electronic noise or faulty
category. Similarly, inattention to test source specification,
alarm logic often can be detected during evaluation and
method of carrying test sources through the monitor, and
corrected before a monitor is placed in operation or further
improper interpretation and reporting of results will bias the
marketed.
outcome. Other possible errors and biases in the evaluation
5.3 The significance of the evaluation for monitor manufac- results are discussed in Section 13.
turers is that it may disclose deficiencies in design or construc-
tion that, when corrected, will improve the product.Amonitor 7. Apparatus
verified to be in a particular sensitivity category will be a
7.1 Measuring the gamma-ray background intensity re-
product that customers who need that level of performance can
quires a precision ion chamber or similar environmental
purchase in good faith.
radiation measurement device that is calibrated to provide
gamma-ray dose rate. For neutron monitors, the background
5.4 The established sensitivity categories for evaluated
intensity is inferred from the more readily measured gamma-
monitorswillprovideinformationtoregulatoryagenciesonthe
ray intensity because the cosmic-ray and terrestrial factors that
performance range of monitoring equipment for detecting
leadtohighnaturalgamma-rayintensityarethesameonesthat
small quantities of SNM.
produce high natural neutron background intensity.
5.5 Independent monitor evaluation will encourage monitor
7.2 The presence of unnatural sources of background during
manufacturers to provide appropriate documentation for cali-
nuisance alarm testing can be discovered by recording the
brating and operating their monitors to obtain the best possible
output of a background monitor or the output of the monitor’s
performance for detecting SNM.
radiation detection circuits. A strip-chart recorder, data logger,
5.6 The underlying assumptions in this guide are that SNM
and computer-generated display are convenient ways to record
monitors are applied in a wide range of background environ-
background data.
m
...