1、Designation: C 1169 97 (Reapproved 2003)Standard Guide forLaboratory Evaluation of Automatic Pedestrian SNM MonitorPerformance1This standard is issued under the fixed designation C 1169; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 The requirement to search pedestrians for specialnuclear material (SNM) to prevent its theft has long
3、 been a partof both United States Department of Energy and United StatesNuclear Regulatory Commission rules for the physical protec-tion of SNM. Information on the application of SNM monitorsto perform such searches is provided in Guide C 1112. Thisguide establishes a means to compare the performanc
4、e ofdifferent SNM pedestrian monitors operating in a specificlaboratory environment.2The goal is to provide relativeinformation on the capability of monitors to search pedestriansfor small quantities of concealed SNM under characterizedconditions. The outcome of testing assigns a sensitivity cat-ego
5、ry to a monitor related to its SNM mass-detection probabil-ity; the monitors corresponding nuisance-alarm probability forthat sensitivity category is also determined and reported.1.2 The evaluation uses a practical set of worst-case envi-ronmental, radiation emission, and radiation response factorss
6、o that a monitors lowest level of performance in a practicaloperating environment for detecting small quantities of SNM isevaluated. As a result, when that monitor is moved fromlaboratory to routine operation, its performance will likelyimprove. This worst-case procedure leads to unclassifiedevaluat
7、ion results that understate rather than overstate theperformance of a properly used SNM monitor in operationaluse.1.3 The evaluation applies to two types of SNM monitorsthat are used to detect small quantities of SNM. Both areautomatic monitors; one monitors pedestrians as they walkthrough a portal
8、formed by the monitors radiation detectors(walkthrough or portal monitor), and the other monitorspedestrians who are stationary for a short period of time whilethey are monitored (wait-in monitor). The latter can be a portalmonitor with a delay mechanism to halt a pedestrian for a fewseconds or it c
9、an be an access-control booth or room thatcontains radiation detectors to monitor a pedestrian waiting forclearance to pass.1.4 The values stated in SI units are to be regarded asstandard.1.5 This standard does not purport to address the safetyconcerns, if any, associated with its use. It is the res
10、ponsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:C 859 Terminology Relating to Nuclear Materials3C 993 Guide for In-Plant Performance Evaluation
11、of Auto-matic Pedestrian SNM Monitors3C 1112 Guide for Application of Radiation Monitors to theControl and Physical Security of Special Nuclear Material3C 1189 Guide to Procedures for Calibrating AutomaticPedestrian SNM Monitors33. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1
12、confidence coeffcientthe theoretical proportion ofconfidence intervals from an infinite number of repetitions ofan evaluation that would contain the true result.3.1.1.1 DiscussionIn a demonstration, if the true resultwere known the theoretical confidence coefficient would be theapproximate proportio
13、n of confidence intervals, from a largenumber of repetitions of an evaluation, that contain the trueresult. Typical confidence coefficients are 0.90, 0.95 and 0.99.3.1.2 Confidence Interval for a Detection ProbabilityAninterval, based on an actual evaluation situation, so constructedthat it contains
14、 the (true) detection probability with a statedconfidence.3.1.2.1 DiscussionConfidence is often expressed as100*the confidence coefficient. Thus, typical confidence levelsare 90, 95 and 99 %.1This guide is under the jurisdiction of ASTM Committee C26 on Nuclear FuelCycle and is the direct responsibi
15、lity of Subcommittee C26.12 on SafeguardApplications.Current edition approved June 10, 1997. Published May 1998. Originallyapproved in 1991. Last previous edition approved in 1997 as C 1169 97.2Note that this is a laboratory evaluation and is not designed for routine in-plantuse. A separate guide, C
16、 993, is available for verifying routine in-plant performance.3Annual Book of ASTM Standards, Vol 12.01.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.3 detection probabilitythe proportion of passages forwhich the monitor is exp
17、ected to alarm during passages of aparticular test source.3.1.3.1 DiscussionAlthough probabilities are properly ex-pressed as proportions, performance requirements for detectionprobability in regulatory guidance have sometimes been ex-pressed in percentage. In that case, the detection probability as
18、a proportion can be obtained by dividing the percentage by100.3.1.4 detection sensitivity categoryspecified in terms of atest source mass for which the monitor has a 0.50 or greaterdetection probability, as measured by a test procedure having a95 % confidence coefficient for its result. The specifie
19、d 0.50 orgreater detection probability is a very convenient one fortesting. The limited number of test source masses used todefine sensitivity categories (see Table 1 and Table 2) ad-equately describe the performance of SNM monitors that candetect small quantities of SNM.3.1.5 nuisance alarma monito
20、ring alarm not caused bySNM but by one of two other causes, which are statisticalvariation in the measurement process or natural backgroundintensity variation. Other contributors to nuisance alarms, suchas interfering radiation sources and equipment malfunction,should not be present during testing.3
21、.1.6 radiation intensityexpressed as the number of pho-tons or neutrons emitted by a material per second or as theenvironmental background radiation dose rate.3.1.7 SNM (special nuclear material)plutonium of anyisotopic composition,233U, or enriched uranium as defined inTerminology C 859. This term
22、is used here to describe bothSNM and strategic SNM, which is plutonium, uranium-233,and uranium enriched to 20 % or more in the235U isotope.3.1.8 SNM monitora radiation detection system that mea-sures ambient radiation intensity, determines an alarm thresh-old from the result, and then, when it moni
23、tors, sounds analarm if its measured radiation intensity exceeds the threshold.3.1.9 standard SNM test sourcea metallic sphere or cubeof SNM having maximum self attenuation of its emittedradiation and an isotopic composition to minimize that emis-sion as described below. Encapsulation and filtering
24、also affectradiation intensity, and particular details are listed for eachsource.3.1.9.1 standard plutonium sourcea metallic sphere orcube of low-burnup plutonium containing at least 93 %239Pu,less than 6.5 %240Pu, and less than 0.5 % impurities.3.1.9.2 DiscussionA cadmium filter can reduce the impa
25、ctof241Am, a plutonium decay product that will slowly build upin time and emit increasing amounts of 60-keV radiation.Begin use of 0.04-cm-thick cadmium filter when three or moreyears have elapsed since separation of plutonium decay prod-ucts. If ten or more years have elapsed since separation, use
26、acadmium filter 0.08-cm thick. The protective encapsulationshould be in as many layers as local rules require of anon-radioactive material such as aluminum (#0.32-cm thick)or thin (#0.16-cm thick) stainless steel or nickel to reduceunnecessary radiation absorption.3.1.9.3 standard uranium sourcea me
27、tallic sphere or cubeof highly-enriched uranium (HEU) containing at least 93 %235U and less than 0.25 % impurities. Protective encapsulationshould be thin plastic or thin aluminum (#0.32-cm thick) toreduce unnecessary radiation absorption in the encapsulation.No additional filter is needed.4. Summar
28、y of Guide4.1 Evaluation follows a sequence of steps, each of whichshould reach an acceptable outcome before the next is begun.The steps are: placing the monitor into operation; determiningnuisance alarm probability; determining detection probability;and categorizing the results.4.2 The monitor is p
29、ut into operation in a nominal 20 R/h(5.2 nC/kg h or 1.43 pA/kg) background environment. Themanufacturers instructions are followed to assemble, calibrate(see Section 10), and begin using the monitor.4.3 Nuisance alarm probability is determined (see Section11) by automatic data collection with a sys
30、tem that cycles themonitor alternately through a group of simulated pedestrianpassages and a background update while recording the back-ground intensity and each of its alarms.4.4 Detection probability is determined (see Section 12) bytransporting SNM test sources through the monitors leastsensitive
31、 region, which is determined as part of the evaluation.Different individuals transport the SNM at their accustomedpace but in a specified manner. Results (number of detectionsand passages) are analyzed as a binomial experiment to give aconfidence interval for the probability of detection that maypla
32、ce the monitor in a sensitivity category. If the monitor canbe operated in different modes or at more than one spacingbetween its detectors, it should be evaluated in each mode andat each spacing that is expected to be used operationally.4.5 The sensitivity category of a monitor is determined (seeSe
33、ction 13) by the smallest test source for which the monitorhas a 0.50 or greater detection probability with 95 % confi-dence at an acceptable nuisance alarm probability.TABLE 1 Mass Detection Sensitivities of SNM MonitorsACategory Description UraniumB(g) PlutoniumC(g)I Standard Plutonium 64 1II Stan
34、dard Uranium 10 0.29III Improved Sensitivity 3 0.08IV High Sensitivity 1 0.03AIn a nominal 20 R/h background intensity using standard metallic test sourcesand procedures described in 11.2.BHEU as described in 8.4.CLow-burnup plutonium as described in 8.5.TABLE 2 Mass Detection Sensitivities in Pedes
35、trian NeutronMonitorsACategory Description PlutoniumB(g)NI Standard Neutron 250NII Improved Neutron 100NIII High SensitivityNeutron30AIn a nominal 20 R/h background intensity using standard metallic test sourcesand procedures described in 11.2.BLow-burnup plutonium as described in 8.5. For monitors
36、having gamma-raysensitivity in addition to neutron sensitivity the plutonium must be shielded in 5-cmthick lead.C 1169 97 (2003)25. Significance and Use5.1 SNM monitors are an effective and unobtrusive meansto search pedestrians for concealed SNM. Nuclear facilitysecurity plans often include SNM mon
37、itors as one means tohelp prevent theft or unauthorized removal of designatedquantities of SNM from access areas. This guide describes away to evaluate and categorize the relative performance ofavailable SNM monitors that might be considered for use in asecurity plan.5.2 The significance of the eval
38、uation for monitor users isthat evaluated monitoring equipment has a verified capability.Unexpected deficiencies such as low sensitivity for highlyself-absorbing forms of SNM, lower than expected sensitivityin areas having high natural background intensity, or a highnuisance-alarm probability from e
39、lectronic noise or faultyalarm logic often can be detected during evaluation andcorrected before a monitor is placed in operation or furthermarketed.5.3 The significance of the evaluation for monitor manufac-turers is that it may disclose deficiencies in design or construc-tion that, when corrected,
40、 will improve the product. A monitorverified to be in a particular sensitivity category will be aproduct that customers who need that level of performance canpurchase in good faith.5.4 The established sensitivity categories for evaluatedmonitors will provide information to regulatory agencies on the
41、performance range of monitoring equipment for detectingsmall quantities of SNM.5.5 Independent monitor evaluation will encourage monitormanufacturers to provide appropriate documentation for cali-brating and operating their monitors to obtain the best possibleperformance for detecting SNM.5.6 The un
42、derlying assumptions in this guide are that SNMmonitors are applied in a wide range of background environ-ments at facilities that process a variety of chemical andphysical forms of SNM. The operational experience with amonitor at one facility provides little comparative informationfor a user of SNM
43、 monitors at another facility where theenvironment and materials are different. A laboratory evalua-tion in a characterized environment using characterized testsources and providing information on both SNM detectionprobability and nuisance alarm probability does provide usefulcomparative information
44、 on different monitors.5.7 The user of evaluation results is warned that the resultsare comparative ones for selection of monitoring equipmentused to detect small quantities of SNM. Obtaining equivalentor better results for monitoring small quantities of SNM at anyfacility rests on properly installi
45、ng the monitor at an appropri-ate location, maintaining monitor calibration, keeping themonitor in good repair with a testing and maintenance pro-gram, and providing proper training for operating personnel.5.8 The evaluation uses essentially unshielded test sources;hence, results are based on detect
46、ing the entire gamma-ray orneutron spectrum of the sources. The effect of deliberate use ofshielding materials on the performance of SNM monitors isbeyond the scope of this guide.6. Interferences6.1 The evaluation requires a nominal natural backgroundenvironment that has an intensity in the range of
47、 the highestfound in the continental United States nominal 20 R/h (5.2nC/kg h or 1.43 pA/kg) and has only natural variation.Locations having low backgrounds are not suitable for testing;other locations are unsuitable as well when variable back-grounds from other than natural causes are present. A si
48、mulatedhigh intensity background produced by point sources is unsuit-able.6.2 Parts of the evaluation use specific values or measure-ments that can alter the testing outcome if not done properly.For example, an improperly measured background intensity(see 7.1) that is actually much higher or lower t
49、han stated in 6.1will bias the results toward a lower or higher sensitivitycategory. Similarly, inattention to test source specification,method of carrying test sources through the monitor, andimproper interpretation and reporting of results will bias theoutcome. Other possible errors and biases in the evaluationresults are discussed in Section 13.7. Apparatus7.1 Measuring the gamma-ray background intensity re-quires a precision ion chamber or similar environmentalradiation measurement device that is calibrated to providegamma-ray dose rate. For neutron monit
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