1、Designation: C993 97 (Reapproved 2012)Standard Guide forIn-Plant Performance Evaluation of Automatic PedestrianSNM Monitors1This standard is issued under the fixed designation C993; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide is affiliated with Guide C1112 on applyingspecial nuclear material (SNM) monitors, Guide C1169 o
3、nlaboratory performance evaluation, Guide C1189 on calibrat-ing pedestrian SNM monitors, and Guides C1236 and C1237on in-plant evaluation. This guide to in-plant performanceevaluation is a comparatively rapid way to verify whether apedestrian SNM monitor performs as expected for detectingSNM or SNM-
4、like test sources.1.1.1 In-plant performance evaluation should not be con-fused with the simple daily functional test recommended inGuide C1112. In-plant performance evaluation takes place lessoften than daily tests, usually at intervals ranging from weeklyto once every three months. In-plant evalua
5、tions are also moreextensive than daily tests and may examine both a monitorsnuisance alarm record and its detection sensitivity for aparticular SNM or alternative test source.1.1.2 In-plant performance evaluation also should not beconfused with laboratory performance evaluation. In-plantevaluation
6、is comparatively rapid, takes place in the monitorsroutine operating environment, and its results are limited toverifying that a monitor is operating as expected, or todisclosing that it is not and needs repair or recalibration.1.2 In-plant evaluation is one part of a program to keepSNM monitors in
7、proper operating condition. Every monitor ina facility is evaluated. There are two applications of thein-plant evaluation: one used during routine operation andanother used after calibration.1.2.1 Routine Operational EvaluationIn this form of theevaluation, nuisance alarm records for each monitor ar
8、e exam-ined, and each monitors detection sensitivity is estimatedduring routine operation. The routine operational evaluation isintended to reassure the plant operator, and his regulatoryagency, that the monitor is performing as expected duringroutine operation. This evaluation takes place without p
9、re-testing, recalibration, or other activity that might change themonitors operation, and the evaluation simulates the normaluse of the monitor.1.2.2 Post-Calibration EvaluationThis form of the evalu-ation is part of a maintenance procedure; it should alwaysfollow scheduled monitor recalibration, or
10、 recalibration con-nected with repair or relocation of the monitor, to verify that anexpected detection sensitivity is achieved. Nuisance alarm datado not apply in this case because the monitor has just beenrecalibrated. Also, having just been calibrated, the monitor islikely to be operating at its
11、best, which may be somewhat betterthan its routine operation.1.3 The values stated in SI units are to be regarded asstandard.1.4 This standard does not purport to address the safetyproblems, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriat
12、e safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 The guide is based on ASTM standards that describeapplication and evaluation of SNM monitors, as well astechnical publications that describe aspects of SNM monitordesign and
13、use.2.2 ASTM Standards:2C859 Terminology Relating to Nuclear MaterialsC1112 Guide for Application of Radiation Monitors to theControl and Physical Security of Special Nuclear MaterialC1169 Guide for Laboratory Evaluation of Automatic Pe-destrian SNM Monitor PerformanceC1189 Guide to Procedures for C
14、alibrating Automatic Pe-destrian SNM MonitorsC1236 Guide for In-Plant Performance Evaluation of Auto-matic Vehicle SNM MonitorsC1237 Guide to In-Plant Performance Evaluation of Hand-Held SNM Monitors1This guide is under the jurisdiction of ASTM Committee C26 on Nuclear FuelCycle and is the direct re
15、sponsibility of Subcommittee C26.12 on SafeguardApplications.Current edition approved Jan. 1, 2012. Published January 2012. Originallyapproved in 1991. Last previous edition approved in 1997 as C993 97(2003). DOI:10.1520/C0993-97R12.2For referenced ASTM standards, visit the ASTM website, www.astm.or
16、g, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3. Terminolog
17、y3.1 Definitions:3.1.1 alternative test sourcealthough no other radioactivematerials individually or collectively duplicate the radioactiveemissions of uranium or plutonium, some materials havesomewhat similar attributes and are sometimes used as alter-native test sources.3.1.2 alternative gamma-ray
18、 test sourcesexamples of al-ternative gamma-ray sources are HEU or133Ba used in place ofplutonium when a plutonium source is not readily available oris prohibited.3.1.2.1 DiscussionTable 1 tabulates amounts of HEUmass, plutonium mass, and133Ba source activity that produceequal response in two differ
19、ent types of monitor.3.1.3 alternative neutron test sourcea common alternativeneutron source used in place of plutonium is252Cf that emitsneutrons from spontaneous fission as does plutonium.3.1.3.1 DiscussionAlternative test sources may have shortdecay half-lives in comparison to SNM isotopes; for e
20、xample,the half-life of133Ba is 10.7 years and252Cf 2.64 years. Largersource activities than initially needed are often purchased toobtain a longer working lifetime for the source.3.1.4 confidence coeffcientthe theoretical proportion ofconfidence intervals from an infinite number of repetitions ofan
21、 evaluation that would contain the true result.3.1.4.1 DiscussionIn a demonstration, if the true resultwere known the theoretical confidence coefficient would be theapproximate proportion of confidence intervals, from a largenumber of repetitions of an evaluation, that contain the trueresult. Typica
22、l confidence coefficients are 0.90, 0.95 and 0.99.3.1.5 Confidence Interval for a Detection ProbabilityAninterval, based on an actual evaluation situation, so constructedthat it contains the (true) detection probability with a statedconfidence.3.1.5.1 DiscussionConfidence is often expressed as 100*t
23、he confidence coefficient. Thus, typical confidence levels are90, 95 and 99 %.3.1.6 detection probabilitythe proportion of passages forwhich the monitor is expected to alarm during passages of aparticular test source.3.1.6.1 DiscussionAlthough probabilities are properly ex-pressed as proportions, pe
24、rformance requirements for detectionprobability in regulatory guidance have sometimes been ex-pressed in percentage. In that case, the detection probability asa proportion can be obtained by dividing the percentage by100.3.1.7 nuisance alarma monitoring alarm not caused bySNM but by other causes, su
25、ch as statistical variation in themeasurement process, a background intensity variation, or anequipment malfunction.3.1.8 process-SNM test sourcean SNM test source fabri-cated by a facility from process material that differs in physicalor isotopic form from the material recommended in 3.1.11 forstan
26、dard test sources.3.1.8.1 DiscussionThis type of source is used when itmeets plant operator or regulatory agency performance require-ments and a suitable standard source is not readily available.Encapsulation and filtering should follow that recommended in3.1.11.3.1.9 SNMspecial nuclear material: pl
27、utonium of anyisotopic composition,233U, or enriched uranium as defined inTerminology C859.3.1.9.1 DiscussionThis term is used here to describe bothSNM and strategic SNM, which includes plutonium,233U, anduranium enriched to 20 % or more in the235U isotope.3.1.10 SNM monitorradiation detection syste
28、m that mea-sures ambient radiation intensity, determines an alarm thresh-old from the result, and then, when it monitors, sounds analarm if its measured radiation intensity exceeds the threshold.3.1.11 standard SNM test sourcea metallic sphere or cubeof SNM having maximum self attenuation of its emi
29、ttedradiation and an isotopic composition listed below that mini-mizes the intensity of its radiation emission. Encapsulation andfiltering also affect radiation intensity, and particular details arelisted for each source. This type of test source is used inlaboratory evaluation but, if suitable and
30、readily available, maybe used for in-plant evaluation.3.1.12 standard plutonium test sourcea metallic sphere orcube of low-burnup plutonium containing at least 93 %239Pu,less than 6.5 %240Pu, and less than 0.5 % impurities.3.1.12.1 DiscussionA cadmium filter can reduce the im-pact of241Am, a plutoni
31、um decay product that will slowlybuild up in time and emit increasing amounts of 60-keVradiation. Begin use of a 0.04-cm thick cadmium filter whenthree or more years have elapsed since separation of plutoniumdecay products. If ten or more years have elapsed sinceseparation, use a cadmium filter 0.08
32、 cm thick. The protectiveencapsulation should be in as many layers as local rulesrequire. A nonradioactive encapsulation material, such as,aluminum (#0.32 cm-thick) or thin (#0.16 cm-thick) stainlesssteel or nickel, should be used to reduce unnecessary radiationabsorption.3.1.13 standard uranium tes
33、t sourcea metallic sphere orcube of highly enriched uranium (HEU) containing at least93 %235U and less than 0.25 % impurities. Protective encap-sulation should be thin plastic or thin aluminum (#0.32 cmthick) to reduce unnecessary radiation absorption in the encap-sulation. No additional filter is n
34、eeded.3.2 Definitions of Terms Specific to This Standard:3.2.1 post-calibration evaluationverifies performance af-ter repair, relocation, or recalibration. Monitor is prepared forTABLE 1 Alternative Test Source Equivalent AmountsAMonitorCategoryMonitorDescriptionPlutonium,gUranium,g133Ba (Ci)Require
35、d inNaI(T1)ScintillatorMonitorsPlasticScintillatorMonitorsI Standard plutonium 1 64 2.5 3.2II Standard uranium 0.29 10 0.9 1.4III Improved sensitivity 0.08 3 0.4 0.6IV High sensitivity 0.03 1 0.2 0.3AThis table combines information from Tables II and V of the report referencedin Footnote 8. Note tha
36、t the term “category” refers to an SNM monitor performancecategory used in that report and not to an SNM accountability category. Also notethat the133Ba source strengths depend on individual differences in how thescintillators respond to radiation from the barium isotope and plutonium.C993 97 (2012)
37、2best operation. Monitor is not yet in routine operation. Onlysensitivity is evaluated.3.2.2 routine-operational evaluationverifies performancein routine operation. Simulates normal use of a monitor. Usesno monitor preparation procedures. Both sensitivity and nui-sance alarm probability or rate are
38、evaluated.4. Summary of Guide4.1 Preliminary Steps Common to Both Forms of In-PlantEvaluation:4.1.1 The monitor being evaluated is an automaticwalkthrough-portal or monitoring booth.4.1.2 The monitors indicated background measurementvalue is recorded for possible future use in troubleshooting.4.1.3
39、Nonmandatory InformationIf a gamma-ray surveymeter (see 6.1) capable of quickly and precisely measuringenvironmental gamma-ray intensity is available, its use andrecording its measurement value may provide additional ben-eficial information for future troubleshooting.3Independentknowledge of the amb
40、ient background intensity also can helpto interpret performance differences at different monitor loca-tions or at one location at different times.4.2 Steps for Routine Operational Evaluation:4.2.1 Determine nuisance alarm probability during the pe-riod since the monitor was last maintained, calibrat
41、ed, orevaluated (see 8.1). Use recorded numbers of alarms andpedestrian passages from records kept during routine monitoruse.4.2.1.1 Handwritten alarm logs or records from the moni-tors control unit can provide total alarms (see Section 6) fromwhich alarms from daily or other performance testing and
42、alarms explained by radioactive material presence in follow-upsearches must be subtracted.4.2.1.2 Total pedestrian passages can be estimated fromoperating logs or recorded information from the monitorscontrol unit.4.2.2 Estimate detection probability by transporting a stan-dard SNM, process-SNM, or
43、alternative test source (seeSection 7) through the monitor in a specific way adopted forevaluation beforehand (see 8.2).4.2.2.1 Record the results, detect or miss for each passage.4.2.2.2 End testing when a total number of passages, se-lected beforehand, is reached.4.2.2.3 Analyze the results as a b
44、inomial experiment (see8.2).4.3 Steps for Post-Calibration Evaluation:4.3.1 Calibrate the monitor according to procedures sug-gested by the manufacturer, Guide C1189, or local practice.4.3.2 Estimate detection probability by transporting a stan-dard SNM, process-SNM, or alternative test source (seeS
45、ection 7) through the monitor in a specific way adoptedbeforehand (see 8.2).4.3.2.1 Record the results, detect or miss for each passage.4.3.2.2 End testing when a total number of passages, se-lected beforehand, is reached.4.3.2.3 Analyze the results as a binomial experiment (see8.2).5. Significance
46、and Use5.1 SNM monitors are an effective and unobtrusive meansto search pedestrians for concealed SNM. Facility securityplans use SNM monitors as one means to prevent theft orunauthorized removal of designated quantities of SNM fromaccess areas. Daily testing of the monitors with radioactivesources
47、guarantees only the continuity of alarm circuits. Thein-plant evaluation is a way to estimate whether an acceptablelevel of performance for detecting chosen quantities of SNM isobtained from a monitor in routine service or after repair orcalibration.5.2 The evaluation verifies acceptable performance
48、 or dis-closes faults in hardware or calibration.5.3 The evaluation uses test sources shielded only bynormal source filters and encapsulation and, perhaps, byintervening portions of the transporting individuals body. Thetransporting individual also provides another form of shieldingwhen the body int
49、ercepts environmental radiation that wouldotherwise reach the monitors detectors. Hence, transportingindividuals play an important role in the evaluation by repro-ducing an important condition of routine operation.5.4 The evaluation, when applied as a routine-operationalevaluation, provides evidence for continued compliance withthe performance goals of security plans or regulatory guidance.It is the responsibility of the users of this evaluation tocoordinate its application with the appropriate regulatoryauthority so that mutually agreeable evalu
