ASTM C1189-11(2018)
(Guide)Standard Guide to Procedures for Calibrating Automatic Pedestrian SNM Monitors
Standard Guide to Procedures for Calibrating Automatic Pedestrian SNM Monitors
SIGNIFICANCE AND USE
5.1 SNM monitors are an effective means to search pedestrians for concealed SNM. Maintaining monitor effectiveness rests on appropriate calibration and adjustment being part of a continuing maintenance program.
5.2 The significance of this guide for monitor users who must detect SNM is to describe calibration and adjustment procedures for the purpose.
5.3 The significance of this guide for monitor manufacturers is to describe calibration procedures, particularly for detecting forms of SNM that may not be readily available to them.
SCOPE
1.1 This guide covers calibrating the energy response of the radiation detectors and setting the discriminator and alarm thresholds used in automatic pedestrian special nuclear material (SNM) monitors.
1.2 Automatic pedestrian SNM Monitors and their application are described in Guide C1112, which suggests that the monitors be calibrated and tested when installed and that, thereafter, the calibration should be checked and the monitor tested with SNM at three-month intervals.
1.3 Dependable operation of SNM monitors rests, in part, on an effective program to test, calibrate, and maintain them. The procedures and methods described in this guide may help both to achieve dependable operation and obtain timely warning of misoperation.
1.4 This guide can be used in conjunction with other ASTM standards. Fig. 1 illustrates the relationship between calibration and other procedures described in standard guides, and it also shows how the guides relate to an SNM monitor user. The guides below the user in the figure deal with routine procedures for operational monitors. Note that Guide C993 is an in-plant performance evaluation that is used to verify acceptable detection of SNM after a monitor is calibrated. The guides shown above the user in Fig. 1 give information on applying SNM monitors (C1112) and on evaluating SNM monitors (C1169) to provide comparative information on monitor performance.
FIG. 1 The Relationship of Calibration to Other Procedures Described in Standard Guides for SNM Monitors
1.5 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
Relations
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: C1189 − 11 (Reapproved 2018)
Standard Guide to
Procedures for Calibrating Automatic Pedestrian SNM
Monitors
This standard is issued under the fixed designation C1189; 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 2. Referenced Documents
1.1 This guide covers calibrating the energy response of the 2.1 ASTM Standards:
radiation detectors and setting the discriminator and alarm C859 Terminology Relating to Nuclear Materials
thresholds used in automatic pedestrian special nuclear mate- C993 Specification for Welded Wire Lath (Withdrawn
rial (SNM) monitors.
2021)
C1112 Guide for Application of Radiation Monitors to the
1.2 Automatic pedestrian SNM Monitors and their applica-
Control and Physical Security of Special Nuclear Material
tion are described in Guide C1112, which suggests that the
(Withdrawn 2014)
monitors be calibrated and tested when installed and that,
C1169 Guide for Laboratory Evaluation of Automatic Pe-
thereafter, the calibration should be checked and the monitor
destrian SNM Monitor Performance (Withdrawn 2021)
tested with SNM at three-month intervals.
E876 Practice for Use of Statistics in the Evaluation of
1.3 Dependable operation of SNM monitors rests, in part, Spectrometric Data (Withdrawn 2003)
on an effective program to test, calibrate, and maintain them.
The procedures and methods described in this guide may help
3. Terminology
both to achieve dependable operation and obtain timely warn-
3.1 Definitions of Terms Specific to This Standard:
ing of misoperation.
3.1.1 calibration—a multistep procedure that uniformly ad-
1.4 This guide can be used in conjunction with other ASTM
justs the energy response of a monitor’s detector array and sets
standards. Fig. 1 illustrates the relationship between calibration
the operating parameters of its detection circuits for optimum
and other procedures described in standard guides, and it also
performance. In a few monitors, an additional analog adjust-
shows how the guides relate to an SNM monitor user. The
ment of a signal detection circuit is required.
guides below the user in the figure deal with routine procedures
3.1.2 SNM—special nuclear material: plutonium of any
for operational monitors. Note that Guide C993 is an in-plant
isotopic composition, U, or enriched uranium as defined in
performance evaluation that is used to verify acceptable
Terminology C859.
detection of SNM after a monitor is calibrated. The guides
3.1.2.1 Discussion—This term is used here to describe both
shown above the user in Fig. 1 give information on applying
SNM and strategic SNM, which is plutonium, uranium-233,
SNM monitors (C1112) and on evaluating SNM monitors
and uranium enriched to 20 % or more in the U isotope.
(C1169) to provide comparative information on monitor per-
formance.
3.1.3 SNM Monitor—a radiation detection system that mea-
sures ambient radiation intensity, determines an alarm thresh-
1.5 This international standard was developed in accor-
old from the result, and then when it monitors, sounds an alarm
dance with internationally recognized principles on standard-
if its measured radiation intensity exceeds the threshold.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- 3.1.3.1 Discussion—The automatic pedestrian SNM moni-
mendations issued by the World Trade Organization Technical tor discussed here is a walk-through or wait-in portal or
Barriers to Trade (TBT) Committee. monitoring booth.
1 2
This guide is under the jurisdiction of ASTM Committee C26 on Nuclear Fuel For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Cycle and is the direct responsibility of Subcommittee C26.10 on Non Destructive contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Assay. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Nov. 1, 2018. Published December 2018. Originally the ASTM website.
approved in 1991. Last previous edition approved in 2011 as C1189 – 11. DOI: The last approved version of this historical standard is referenced on
10.1520/C1189-11R18. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1189 − 11 (2018)
5.3 The significance of this guide for monitor manufacturers
is to describe calibration procedures, particularly for detecting
forms of SNM that may not be readily available to them.
6. Interferences
6.1 The monitor should be in proper operating condition
when calibrated. Any indication that the monitor does not stay
in calibration or that it drifts substantially during the interval
between calibration checks is cause for repair or renovation
and then recalibration.
7. Apparatus
7.1 SNM Automatic Pedestrian Monitors, having arrays of
radiation detectors that form a portal through which pedestrians
pass or that surround a pedestrian as he waits in a booth for
clearance to pass.
7.2 Radiation Detectors, used in SNM monitors may detect
gamma rays, neutrons, or both. One of three types of detector
FIG. 1 The Relationship of Calibration to Other Procedures De-
scribed in Standard Guides for SNM Monitors listed is usually used. All of types of detector operate in a
pulse-counting mode to obtain good sensitivity for detecting
small changes in radiation intensity.
7.2.1 Inorganic Scintillation Detectors, such as sodium
4. Summary of Guide
iodide [NaI(T1)], detect gamma rays but have little response to
neutrons from SNM. This detector is useful for detecting
4.1 This guide covers various instructions for calibrating
unshielded SNM.
SNM pedestrian monitors for optimum performance in normal
7.2.2 Neutron Proportional Counters, containing BF
operation. The order of procedures is as follows.
or He as a converter gas, detect thermal neutrons and are used
4.1.1 The energy response of inorganic or organic scintilla-
with a moderator to thermalize fast neutrons from SNM. This
tion detectors or of neutron proportional counters, is calibrated
detector is useful for detecting unshielded or shielded pluto-
to produce appropriate signal pulse heights for SNM radiation
nium.
(see Section 10).
7.2.3 Organic Scintillators, detect both gamma rays and fast
4.1.2 The monitor’s pulse height discriminators are cali-
neutrons from SNM. This detector is useful for detecting
brated to form a region of interest containing SNM radiation
unshielded SNM and shielded plutonium.
from highly enriched uranium or low-burnup plutonium (see
Sections 9 and 11), or for detecting neutrons in proportional
7.3 Oscilloscope or Multi-Channel Analyzer, for viewing
counters (see Section 9).
reference detector pulses produced by a specific radiation
4.1.3 The monitor’s transient signal detection logic is ad-
source during energy calibration.
justed for appropriate response to walk-through or wait-in
7.3.1 Gamma-Ray Detectors, reference pulses from 662-
monitoring (see Section 12).
keV gamma rays emitted by a Cs source with a nominal
8-microCurie (0.3-kBq) activity are used for calibration.
4.2 This guide covers adjusting various thresholds used in
7.3.2 Neutron Proportional Counters, reference pulses from
SNM monitors.
neutrons emitted by a Cf neutron source with less than
4.2.1 This guide describes setting background alarm thresh-
2 × 10 neutron/s (0.009-μg) source strength can be used for
olds that may be used to announce loss of detection sensitivity
calibration.
or detector failure (see Section 13).
4.2.2 This guide discusses setting the lowest practical dis-
NOTE 1—Acquisition, storage, and use of sources should be under the
criminator levels for the radiation detectors (see Section 11). guidance of a responsible radiation safety officer (see Section 8 on
hazards).
4.3 When calibration is complete, the monitor should be
7.4 Manufacturer’s or Designer’s Operation and Mainte-
tested using in-plant evaluation procedures described in Guide
nance Manual, essential for quick and efficient monitor cali-
C993.
bration. The manufacturer’s suggested calibration scheme is a
good starting place, if not the best approach to calibration.
5. Significance and Use
Calibration requires knowledge of test point and adjustment
5.1 SNM monitors are an effective means to search pedes-
locations that should be described in the manuals.
trians for concealed SNM. Maintaining monitor effectiveness
rests on appropriate calibration and adjustment being part of a 8. Hazards
continuing maintenance program.
8.1 Make sure that the use of radioactive materials is under
5.2 The significance of this guide for monitor users who the guidance of a responsible radiation safety officer who can
must detect SNM is to describe calibration and adjustment provide any needed radiation safety training, personnel
procedures for the purpose. dosimetry, and handling procedures for radiation sources.
C1189 − 11 (2018)
8.2 The radiation detectors in SNM monitors all operate at an organic scintillator is 11.4 to 102 keV. The resulting
high voltages that may be hazardous. Although a person is not discriminator levels for calibrations using 2 and 3.3 V for Cs
usually exposed to high voltage during calibration, make sure pulse height are as follows:
that the work is performed with the approval of a responsible (a) Calibration using 2 V in a NaI(Tl) detector: 0.18 to 0.66
safety officer with proper attention given to electrical safety V,
training and reading any warnings of high voltage exposure in (b) Calibration using 3.3 V in a NaI(Tl) detector: 0.3 to
manuals or posted on equipment. 1.10 V,
(c) Calibration using 2 V in a plastic detector: 0.05 to 0.43
9. Pulse-Height Analysis Calibration
V, and
(d) Calibration using 3.3 V in a plastic detector: 0.08 to
9.1 Once a monitor’s detector array is adjusted to uniform
0.70 V.
pulse height, the pulse-height analysis circuitry can be ad-
9.3.2 Low-Burnup Plutonium—The optimum region of in-
justed. The point is to set a lower-level discriminator to exclude
terest for low-burnup plutonium extends from 0 to 450 keV (1).
electronic noise and pulses from radiation below the SNM
The value 0 means the lowest practical value achieved by one
energy range. Most often a second-level discriminator or
of the means discussed in Section 11. The corresponding
window is also set to discriminate energy above the SNM
deposited energy range in an organic scintillator is 0 to 287
radiation, thus forming an SNM energy region of interest.
keV. The resulting discriminator levels for calibrations using 2
9.2 Discriminator Settings for SNM—The lower-level dis-
and 3.3 V for Cs pulse height are as follows:
criminator setting and the window or upper-level discriminator
(a) Calibration using 2 V in a NaI(Tl) detector: 0 to 1.36 V,
setting, if used, may depend on the type of SNM to be detected
(b) Calibration using 3.3 V in a NaI(Tl) detector: 0 to 2.24
and the type of detector used for the following reasons.
V,
9.2.1 The two types of SNM, highly enriched uranium
(c) Calibration using 2 V in a plastic detector: 0 to 1.20 V,
(HEU) and low-burnup plutonium, differ in their intrinsic
and
gamma-ray spectra.
(d) Calibration using 3.3 V in a plastic detector: 0 to 1.97
9.2.2 Inorganic and organic scintillators respond differently
V.
to gamma rays. Inorganic scintillators produce pulse heights
9.3.3 In case of other gamma-ray pulse-height calibrations
that are proportional to the detected gamma-ray energy.
for Cs gamma rays than are given here, use values directly
However, organic scintillators do not, as Fig. 2 illustrates. At
scaled from the listed values for the same type of detector.
low gamma-ray energies, a smaller fraction of the incident
9.4 Optimum Neutron Analysis Windows, for proportional
gamma-ray energy is deposited in an organic scintillator, and it
counters are given here.
produces a proportionately smaller pulse height. Hence, inor-
ganic and organic scintillators calibrated to the same reference
NOTE 2—For organic scintillators, adequate fast neutron response for
pulse height will have different upper and lower discriminator
present-day SNM monitoring applications is usually achieved using the
plastic detector discriminator levels for gamma rays given in 9.3.2.
voltage levels for an SNM region of interest. The examples
following illustrate the differences.
9.4.1 Neutron proportional counters detect moderated neu-
trons from plutonium and each type of proportional counter has
9.3 Gamma-Ray Regions of Interest for SNM:
its own pulse-height spectrum for detected neutrons.
9.3.1 HEU—The HEU gamma-ray region extends from 60
9.4.2 The upper level is unimportant in this case because
to 220 keV (1). The corresponding deposited energy range in
there is no high level background. Only a lower-level discrimi-
nator may be available in some monitors. Suggested operating
ranges are as follows:
The boldface numbers in parentheses refer to the list of references at the end of
this guide.
(a) For BF calibrated to 2 V, from 0.3 to 10 V;
(b) For He calibrated to 2 V, from 0.4 to 10 V;
(c) For BF calibrated to 8 V, from 1.2 to 10 V; and
(d) For He calibrated to 8 V, from 1.6 to 10 V.
9.4.3 In case another neutron pulse height than given here is
used, the values can be directly scaled from the listed values
for the same type of detector.
9.5 Setting the Discriminators:
9.5.1 Set the appropriate values in the monitor’s discrimi-
nators or single-channel analyzers (SCA) noting the following
special cases:
9.5.1.1 Interpreting Window Discriminator Voltage
Levels—Monitors having both a level discriminator and a
window discriminator float the window voltage level on top of
the level-discriminator voltage level. Hence, the upper dis-
criminator value, which is the upper limit of the operating
ranges just tabulated, is the sum of the monitor’s level
FIG. 2 The Relationship Between Incident Gamma-Ray Energy
and Energy Deposited in NaI(Tl) and Plastic Scintillators discriminator and window values.
C1189 − 11 (2018)
9.5.1.2 Zero Discriminator Values—The value 0 means the
lowest practical value. It will be determined later using a
procedure described in Section 11.
9.5.1.3 Backlash in Potentiometer Adjustments—When set-
ti
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