1、Designation: C 1455 07Standard Test Method forNondestructive Assay of Special Nuclear Material HoldupUsing Gamma-Ray Spectroscopic Methods1This standard is issued under the fixed designation C 1455; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se of revision, 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 This test method describes gamma-ray methods used tonondestructively measure the quantity
3、 of235U, or239Pu re-maining as holdup in nuclear facilities. Holdup occurs in allfacilities where nuclear material is processed, in processequipment, in exhaust ventilation systems and in building wallsand floors.1.2 This test method includes information useful for man-agement, planning, selection o
4、f equipment, consideration ofinterferences, measurement program definition, and the utili-zation of resources (1, 2, 3, 4).21.3 The measurement of nuclear material hold up in processequipment requires a scientific knowledge of radiation sourcesand detectors, transmission of radiation, calibration, f
5、acilityoperations and error analysis. It is subject to the constraints ofthe facility, management, budget, and schedule; plus health andsafety requirements; as well as the laws of physics. Themeasurement process includes defining measurement uncer-tainties and is sensitive to the form and distributi
6、on of thematerial, various backgrounds, and interferences. The workincludes investigation of material distributions within a facility,which could include potentially large holdup surface areas.Nuclear material held up in pipes, ductwork, gloveboxes, andheavy equipment, is usually distributed in a di
7、ffuse andirregular manner. It is difficult to define the measurementgeometry, to identify the form of the material, and to measureit without interference from adjacent sources of radiation.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is
8、 theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3C 1009 Guide for Establishing a Quality Assurance Pro-gram for Analytical Chemistry
9、 Laboratories Within theNuclear IndustryC 1490 Guide for the Selection, Training and Qualificationof Nondestructive Assay (NDA) PersonnelC 1673 Terminology of C26.10 Nondestructive AssayMethods2.2 ANSI Standards:4ANSI N15.20 Guide to Calibrating Nondestructive AssaySystems2.3 U.S. Nuclear Regulatory
10、 Commission RegulatoryGuides:5Regulatory Guide 5.23, In Situ Assay of Plutonium Re-sidual Holdup3. Terminology3.1 Refer to Terminology C 1673 for definitions used in thistest method.4. Summary of Test Method4.1 IntroductionHoldup measurements range from thesolitary assay of a single item to routine
11、measurement of apiece of equipment, to an extensive campaign of determiningthe total SNM in-process inventory for a processing plant.Holdup measurements differ from other nondestructive mea-surement methods in that the assays are performed in situ onequipment or items instead of on multiple items wi
12、th similarcharacteristics measured in a specialized, isolated room. Oftenthe chemical form and geometric distribution of the SNM arenot well known. These challenges require unique preparation1This test method is under the jurisdiction ofASTM Committee C26 on NuclearFuel Cycle and is the direct respo
13、nsibility of Subcommittee C26.10 on NonDestructive Assay.Current edition approved June 1, 2007. Published July 2007. Originally approvedin 2000. Last previous edition approved in 2000 as C 1455 00.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For re
14、ferenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from American National Standards Institute (ANSI), 25 W.
15、43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.5Available from the U.S. Nuclear Regulatory Commission, Washington, DC,20555.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.for every measurement to obtain a quality result
16、but unknownscan lead to large measurement uncertainties.4.2 Definition of RequirementsDefinition of the holdupmeasurement requirements should include, as a minimum, themeasurement objectives (that is, criticality control, SNMaccountability, safety, or combinations thereof); time andresource constrai
17、nts; the desired measurement sensitivity, ac-curacy, and uncertainty, and available resources (schedule,funds, and subject matter experts).4.3 Information Gathering and Initial EvaluationInformation must be gathered concerning the item or items tobe assayed and an initial evaluation should be made o
18、f the levelof effort needed to meet the holdup measurement requirements.Preliminary measurements may be needed to assess the prob-lem; to define the location and extent of the holdup, todetermine the SNM isotopic composition or enrichment, and toidentify potential interfering radionuclides. Factors
19、to be con-sidered include the geometric configuration of the item orprocess equipment to be assayed, location of the equipment inthe facility, attenuating materials, sources of background orinterferences, facility processing status, radiological and indus-trial safety considerations, plus the person
20、nel and equipmentneeded to complete the assay. Sources of information mayinclude a visual survey, engineering drawings, process knowl-edge, process operators, and prior assay documentation.4.3.1 Subsequent measurement campaigns may well pro-ceed faster, especially when the objective is to quantifych
21、anges from the previous measurement campaigns and nochanges have been made to the process.4.3.2 Shutdown facilities are frequently measured oncethrough carefully and completely. Any subsequent measure-ment campaigns may only verify a subset of the data set.4.4 Task Design and PreparationThe initial
22、evaluationprovides a basis for choosing the quantitative method, assaymodel, and subsequently leads to determination of the detec-tion system and calibration method to be used. Appropriatestandards and support equipment are developed or assembledfor the specific measurement technique. A measurement
23、planshould be developed. The plan will include measurementlocations and geometries or guidance for their selection, ittypically outlines required documentation, operating proce-dures, background measurement methods and frequencies, plustraining, quality and measurement control requirements (GuideC 1
24、009). Necessary procedures, including those for measure-ment control, should be developed, documented, and approved.4.4.1 During the initial measurement campaign the taskdesign and preparation may require 50% of the time allotted tothe measurement campaign, subsequent campaigns typicallyrequire a mu
25、ch smaller fraction of the total measurementcampaign time for task design and preparation.4.5 CalibrationCalibration and initialization of measure-ment control is completed before measurements of unknowns.Calibration requires traceable standards.4.6 MeasurementsPerform measurements and measure-ment
26、control as detailed in the measurement plan or procedure.4.7 Evaluation of Measurement DataAs appropriate, cor-rections are made for gamma-ray attenuation effects, forexample, the container, item matrix, absorbers, and measuredbackground. As appropriate, corrections are made for finitegeometry effec
27、ts. These corrections are applied in the calcula-tion of the assay value. Measurement uncertainties are estab-lished based on factors affecting the assay.4.7.1 Converting measurement data to estimates of thequantity of nuclear material holdup requires careful evaluationof the measurement parameters
28、against calibration assump-tions. Depending on the calibration and measurement methodsused, corrections may be necessary for geometric effects(differences between holdup measurement and calibrationgeometries), gamma-ray attenuation effects, background, andinterferences. Measurement uncertainties (ra
29、ndom and system-atic) are estimated based on uncertainties in assay parameters,for example, holdup distribution, attenuation effects, measuredcount rates and finite source corrections.4.7.2 Results should be evaluated against previous results orclean out data, if either is available. If a discrepanc
30、y is evident,an evaluation should be made. Additional measurements withsubsequent evaluation may be required.4.8 DocumentationMeasurement documentation shouldinclude the plans and procedures, a description of measurementparameters considered important to the calibration and for eachmeasurement locat
31、ion, the measurement techniques used, theraw data, assumptions and correction factors used in theanalysis, the results with estimated precision and bias, andcomparison to other measurement techniques.5. Significance and Use5.1 This test method assists in demonstrating regulatorycompliance in such ar
32、eas as safeguards SNM inventory con-trol, criticality control, waste disposal, and decontaminationand decommissioning (D properindustrial safety practices must be followed.8.2 Technical Hazards:8.2.1 High gamma-ray flux generally will cause pulsepileup, which affects the observed energy and resoluti
33、on of thepeaks, as well as, the total counts observed in the peaks due tosumming effects. Extremely high activity holdup may saturatethe electronics of certain types of preamplifiers resulting in nocounts being registered by the equipment.8.2.2 Electronic instability can significantly alter assay re
34、-sults. For example, noise or microphonics can degrade theenergy resolution of the spectra.8.2.3 Secular EquilibriumIf the gamma ray from a daugh-ter radionuclide is used to quantify holdup, such as with238Uand234mPa, secular equilibrium within the holdup should beverified. If secular equilibrium is
35、 assumed but not establishedmeasurement results could be biased.8.2.4 Infinitely Thick SNM HoldupIf the holdup deposit isinfinitely thick to the measurement of gamma rays, transmis-sion corrections are not simple to perform and the measure-ment results will likely be biased low.8.2.5 Backgroundlack
36、of understanding of backgroundeffects on the measurement or incorrect background measure-ments may impact the results significantly. Measurement itemsor items affecting background should not be moved duringmeasurements.8.2.5.1 It can be challenging to position the detector toproperly account for bac
37、kground.8.2.6 Temperature changes at the measurement locationmay result in a detector gain drift. Stabilization methods maybe necessary to mitigate this effect.8.2.7 Unexpected presence of brehmstralung in the spectramay cause a bias in low resolution measurements. For ex-ample, brehmstralung caused
38、 by99Tc or238U.9. Procedure9.1 A Holdup Measurement Campaign procedure generallyincludes the following:9.1.1 Development (or Review) of Measurement Strategyand Development (or Review) of Detailed Measurement Plan,9.1.2 Preparation for Measurements,9.1.3 Perform the Measurements,9.1.4 Calculations (o
39、ften in parallel while the data is ac-quired),9.1.5 Estimation of Measurement Uncertainty (typicallyPrecision and Bias), and,9.1.6 Recording of data and results (3, 4, 9, 10, 11) NRCRegulatory Guide 5.23).9.2 ProcedureMeasurement Strategy/Plan Development:9.2.1 Measurement Program RequirementsPrior
40、to theevaluation of an assay situation, specific information must begathered regarding what is expected of the measurement ormeasurement program. The information should provide theboundaries for the task or project. This information typicallyincludes the following:9.2.1.1 Identification of item or p
41、iece of equipment to bemeasured.9.2.1.2 Radionuclide or radionuclides of interest.9.2.1.3 Acceptable level of measurement uncertainty.9.2.1.4 Acceptable lower detection limit for the assay.9.2.1.5 Intended and potential applications for results, forexample, criticality risk assessment, SNM accountab
42、ility,health physics, or decontamination and demolition.9.2.1.6 Administrative requirements, for example, qualityassurance requirements, documentation and reporting require-ments.9.2.2 Constraints that are useful to know about:9.2.2.1 The time available to perform the measurement(s),that is how long
43、 before a report or compilation of data isrequired.9.2.2.2 Resources available to perform the individual mea-surement or the measurement program.9.2.3 Personnel and ProceduresNote there are typicallytwo levels of procedures: generic or all encompassing such asthe measurement strategy or selection of
44、 models and thedetailed work instructions for each data acquisition:9.2.3.1 Since holdup measurements are made with little orno sample preparation and under a wide range of conditions,formal procedures might be developed for the item measure-ments. Procedures can evolve to incorporate lessons learne
45、dfrom previous experience.9.2.3.2 Personnel performing holdup measurements musthave adequate training, education, and experience. Definitionof adequate training, educations, and experience can be foundin Guide C 1490. Development of measurement plans, strategyand work instructions and the initial me
46、asurements generallyrequire much more expertise than routine or subsequentre-measurements, which can be performed by trained person-nel using established procedures.9.2.4 Safety ConditionsEvaluation and mitigation, if pos-sible, of radiological and industrial safety issues must beperformed prior to
47、initiating measurements.9.2.5 Facility EvaluationThe objective of the evaluationis to develop a measurement plan. This consists of severalactivities, which are difficult to perform sequentially. Some areperformed in parallel and iteration often is helpful. Each assaysituation is unique. Information
48、must be gathered and evalu-ated concerning the item or items to be assayed, as well as,concerning the level of effort necessary to obtain the requiredlevel of quality and precision for the assays.C14550749.2.5.1 Inspect the area(s), equipment, or both, to be assayedto gain an overview of the task at
49、 hand. Consider measurementgeometry, other sources of radiation, attenuating materials, andthe physical location of the item or equipment.9.2.5.2 If possible, interview any personnel who may befamiliar with the area(s) or equipment to be assayed during themeasurement campaign. They may be able to provide first-hand information on current and historical process information,and other important insights for consideration. Also, processoperators and management that have participated in previousclean out campaigns and maintenance projects may be avaluable resource in deter
