1、Designation: C 1671 07Standard Practice forQualification and Acceptance of Boron Based MetallicNeutron Absorbers for Nuclear Criticality Control for DryCask Storage Systems and Transportation Packaging1This standard is issued under the fixed designation C 1671; the number immediately following the d
2、esignation indicates the year oforiginal adoption or, in the case 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 practice provides pro
3、cedures for qualification andacceptance of neutron absorber materials used to providecriticality control by absorbing thermal neutrons in systemsdesigned for nuclear fuel storage, transportation, or both.1.2 This practice is limited to neutron absorber materialsconsisting of metal alloys, metal matr
4、ix composites (MMCs),and cermets, clad or unclad, containing the neutron absorberboron-10 (10B).1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health p
5、ractices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B 557 Test Methods for Tension Testing Wrought and CastAluminum- and Magnesium-Alloy ProductsB 557M Test Methods for Tension Testing Wrought andCast Aluminum- and Magnesium-All
6、oy Products MetricC 791 Test Methods for Chemical, Mass Spectrometric, andSpectrochemical Analysis of Nuclear-Grade Boron Car-bideE8 Test Methods for Tension Testing of Metallic MaterialsE21 Test Methods for Elevated Temperature Tension Testsof Metallic MaterialsE 456 Terminology Relating to Quality
7、 and StatisticsE 1225 Test Method for Thermal Conductivity of Solids byMeans of the Guarded-Comparative-Longitudinal HeatFlow TechniqueE 1461 Test Method for Thermal Diffusivity by the FlashMethod3. Terminology3.1 Definitions:3.1.1 acceptance test, nfor a neutron absorber material,quality control, t
8、ests, and inspections conducted to determinewhether a specific production lot meets selected specifiedmaterial properties, characteristics, or both, so that the lot canbe accepted.3.1.2 areal density, nfor neutron absorber materials withflat parallel surfaces, the density of the neutron absorber tim
9、esthe thickness of the material (g/cm2).3.1.3 durability, nthe ability of neutron absorber materi-als to withstand service conditions without physical changesthat would render them unable to perform their design func-tions.3.1.4 lot, na quantity of a product or material accumu-lated under conditions
10、 that are considered uniform for sam-pling purposes. E 4563.1.5 moderator, na material used to reduce neutronenergy by scattering without appreciable capture.3.1.6 neutron absorber, na nuclide that has a large ther-mal neutron absorption cross section (also known as a neutronpoison).3.1.7 neutron-ab
11、sorber material, na compound, alloy,composite or other material that contains a neutron absorber.3.1.8 neutron attenuation test, nfor neutron absorbermaterials, a process in which a material is placed in a thermalneutron beam, and the number of neutrons transmitted throughthe material in a specified
12、 period of time is counted. Theneutron count can be converted to areal density by performingthe same test on a series of appropriate calibration standardsand comparing the results.3.1.9 neutron cross section, barn, na measure of theprobability that a neutron will interact with a nucleus in theabsorb
13、ing medium and is a function of the neutron energy.3.1.10 open porosity, nthe volume fraction of all pores,voids, and channels within a solid mass that are interconnectedwith each other and communicate with the external surface,1This practice is under the jurisdiction of ASTM Committee C26 on Nuclea
14、rFuel Cycle and is the direct responsibility of Subcommittee C26.03 on NeutronAbsorber Materials Specifications.Current edition approved July 15, 2007. Published August 2007.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For
15、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.and thus are measurable by gas or liquid penetration. C 242,C213.1.11 pa
16、ckaging, nin transport of radioactive material,the assembly of components necessary to enclose the radioac-tive contents completely.33.1.12 probability sampling, na sample selection proce-dure in which the sampling units are selected by a chanceprocess such that, at each step of the selection, a spe
17、cifiedprobability of selection can be attached to each sampling unitavailable for selection. E 4563.1.13 qualification, nfor neutron absorber materials, theprocess of evaluating, testing, or both, a material produced bya specific manufacturing process to demonstrate uniformityand durability for a sp
18、ecific application.3.1.14 systematic sampling, na sample selection proce-dure in which every kth element is selected from the universeor population, for example, u, u + k, u +2k, u +3k, etc., whereu is in the interval 1 to k. E 4563.2 Definition of Term Specific to This Standard:3.2.1 designer, nthe
19、 organization responsible for the de-sign or the license holder for the dry cask storage system ortransport packaging. The designer is usually the purchaser ofthe neutron absorber material, either directly or indirectly(through a fabrication subcontractor).4. Significance and Use4.1 For criticality
20、control of nuclear fuel in dry storage andtransportation, the most commonly used neutron absorbermaterials are borated stainless steel alloys, borated aluminumalloys, and boron carbide aluminum alloy composites. Theboron used in these neutron absorber materials may be naturalor enriched in the nucli
21、de10B. The boron is usually incorpo-rated either as an intermetallic phase (for example, AlB2,TiB2,CrB2, etc.) in an aluminum alloy or stainless steel, or as a stablechemical compound particulate such as boron carbide (B4C),typically in an aluminum MMC or cermet.4.2 While other neutron absorbers con
22、tinue to beinvestigated,10B has been most widely used in these applica-tions, and it is the only thermal neutron absorber addressed inthis standard.4.3 In service, many neutron absorber materials are inac-cessible and not amenable to a surveillance program. Theseneutron absorber materials are often
23、expected to perform overan extended period.4.4 Qualification and acceptance procedures demonstratethat the neutron absorber material has the necessary character-istics to perform its design functions during the servicelifetime.4.5 The criticality control function of neutron absorbermaterials in dry
24、cask storage systems and transportationpackagings is only significant in the presence of a moderator,such as during loading of fuel under water, or water ingressresulting from hypothetical accident conditions.4.6 The expected users of this standard include designers,neutron absorber material supplie
25、rs and purchasers, govern-ment agencies, consultants and utility owners. Adherence tothis standard does not guarantee regulatory approval; a gov-ernment regulatory authority may require different tests oradditional tests, and may impose limits or restrictions on theuse of a neutron absorber material
26、.5. Procedure5.1 Determination of Service Conditions and Design Re-quirements for the Neutron Absorber MaterialThe designershall specify the service conditions and design requirements,including environmental conditions, mechanical properties andareal density or equivalent measure of neutron absorber
27、 con-tent. Selection of environmental and service conditions that areimportant for neutron absorber material performance andqualification should take into consideration known failuremodes and industry experience.5.1.1 Environmental conditions to be considered include butare not limited to water chem
28、istry, water temperature, paireddissimilar materials, hydrostatic pressure, duration of immer-sion, gamma and fast neutron flux, heat-up rate after draining,and maximum temperature.5.1.2 For structural applications, specify the mechanicalproperties required by the structural analysis. For non-struct
29、ural uses of the neutron absorber material, specify me-chanical properties sufficient to assure material durabilityunder the service conditions for which it is designed.5.1.3 Specify other design properties, for example, thermalconductivity, surface finish, etc., as required for the applica-tion.5.1
30、.4 Product or feed material chemistry shall be specified.5.2 Neutron Absorber Material QualificationQualification shall consist of three components: (1) verifydurability for the intended service as defined in 5.2.5, (2) verifythat the physical characteristics of components meet theirdesign requireme
31、nts defined in 5.2.6, and (3) verify that theuniformity of the10B distribution in the neutron absorbermaterial is within acceptable bounds as specified by thedesigner as described in 5.2.6.5.2.1 Qualification is needed:5.2.1.1 When the neutron absorber material has not beenpreviously qualified,5.2.1
32、.2 When a new supplier is producing a qualifiedneutron absorber material, or5.2.1.3 When any key process or process control, as definedin 5.2.7, is altered for production of a qualified neutronabsorber material.5.2.2 The key processes and process controls for producingneutron absorber material for q
33、ualification should be the sameas those to be used for commercial production. Differencesshall be justified per 5.2.7.5.2.3 Re-qualification for a qualified neutron absorber ma-terial produced by a new supplier may consist of review of keyprocesses and process controls to verify that they have beena
34、dequately replicated by the new supplier.5.2.4 If a neutron absorber material can not be qualifiedcompletely by reference to prior testing with similar neutronabsorber materials for similar design functions and serviceconditions, complete the qualification by performing testing orportions thereof as
35、 described in 5.2.5 and 5.2.6.3“Regulations for the Safe Transport of Radioactive Material,” Safety SeriesStandards No. TS-R-1, International Atomic Energy Agency, Vienna, Austria.C16710725.2.5 Environmental Qualification TestsFor these tests,verify by visual and dimensional inspection, mechanical t
36、est-ing, neutron attenuation testing, etc., as appropriate, that theneutron absorber material does not undergo physical changesthat would render it unable to perform its design functions.5.2.5.1 For radiation and thermal testing, expose the neutronabsorber material to the service conditions or equiv
37、alentaccelerated conditions.5.2.5.2 Corrosion testing shall consist of exposing testspecimens of the neutron absorber material to simulate in-service immersion conditions.5.2.5.3 If the neutron absorber material has open porosity,test it under simulated loading and service conditions usingbounding p
38、ressure, temperature, time, and vacuum.5.2.6 Mechanical, Absorber Uniformity, and Other Qualifi-cation Testing:5.2.6.1 Perform tensile tests according to Test MethodB 557, B 557M, E8,orE21. Perform any other mechanicaltesting, for example, fracture toughness testing, bend testing,etc., in accordance
39、 with the appropriate ASTM test method.For neutron absorber materials where standardized testing isnot appropriate, such as for laminates, develop the mechanicaltest appropriate for the materials.NOTE 1Most neutron absorbers are non-structural and are held inplace during service by structural compon
40、ents. If the absorber material isintended as a structural member, other tests may be necessary to conformto a structural code (for example, ASME Boiler and Pressure VesselCodes). It may also be necessary to consider the long term servicetemperature and the effect of aging on the tensile strength of
41、aluminumalloy-based absorber materials.5.2.6.2 Assess the uniformity of the neutron absorber dis-tribution in the neutron absorber material by measuring either:(1) the neutron absorber density (g/cm3) and thickness, or (2)the areal density (g/cm2) by either: (1) probability sampling or(2) systematic
42、 sampling throughout the test material, providedthat the systematic sampling method is conservative. Deter-mine the lower tolerance limit of the measurements as de-scribed in item #3 below. If uniformity testing for areal densitywill be by means other than neutron attenuation, the user of thepropose
43、d method shall confirm that the proposed method isacceptable to the designer.(1) Neutron attenuation is a convenient method of deter-mining the10B content of the neutron absorber material andmay be used to analyze the10B distribution. For neutronattenuation testing, compare thermal neutron attenuati
44、onthrough the product with attenuation through calibration stan-dards. If materials with discrete absorber particles or phases areused for the calibration standards, then the size of the particlescontaining the neutron absorber shall be small enough so thatneutron streaming and self-shielding is ins
45、ignificant.4Theattenuation tests on the calibration standards and on the productshall use the same test equipment and configuration.(2) Neutron attenuation measurements shall be performedin accordance with written procedures that address, as aminimum, the following:(a) The calibration standards used
46、 and their validation,(b) The frequency of calibration as required to account for neutronbeam intensity variation, or source decay,(c) Neutron source and beam collimation, if any,(d) Method of interpolation between calibration points, and(e) Neutron detection instrumentation.(f) If the material used
47、 for calibration standards contains neutron ab-sorbing or scattering nuclides not present in the neutron absorbermaterial to be examined, the procedure shall address the effect ofthese nuclides on the accuracy of the measurements.(3) Using a goodness of fit test, determine if the set ofmeasurement d
48、ata is normally distributed. For a normal distri-bution, calculate the lower tolerance limit, T, for the arealdensity or neutron absorber density for each lot, that is, anumber T such that at least a proportion, P, of the lot is greaterthan T with confidence g. Usually, P $ 95 % and g $ 95 %.Calcula
49、te T as follows:T 5 xbar! K*s (1)where:T = the lower tolerance limit, g/cm2for areal densityor g/cm3for neutron absorber density,K = the one-sided tolerance limit factor for a normaldistribution with probability P and confidence g,5,dimensionless,x(bar) = the sample average, g/cm2or g/cm3, ands = the sample standard deviation, g/cm2or g/cm3.NOTE 2If the data set is not normally distributed, then a nonparamet-ric lower tolerance limit may be used. In this case, the method must bedocumented.NOTE 3The user is advised to consider the effect of the statisticalunce
