ASTM E264-2002 Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Nickel《通过镍的辐射活化测定快中子反应速率的标准试验方法》.pdf

1、Designation: E 264 02Standard Test Method forMeasuring Fast-Neutron Reaction Rates by Radioactivationof Nickel1This standard is issued under the fixed designation E 264; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l

2、ast revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method covers procedures fo

3、r measuring reac-tion rates by the activation reaction58Ni(n,p)58Co.1.2 This activation reaction is useful for measuring neutronswith energies above approximately 2.1 MeV and for irradiationtimes up to about 200 days in the absence of high thermalneutron fluence rates (for longer irradiations, see P

4、racticeE 261).1.3 With suitable techniques fission-neutron fluence ratesdensities above 107cm2s1can be determined.1.4 Detailed procedures for other fast-neutron detectors arereferenced in Practice E 261.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with

5、its use. It is 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:E 170 Terminology Relating to Radiation Measurementsand Dosimetry2E 18

6、1 Test Methods for Detector Calibration and Analysisof Radionuclides2E 261 Practice for Determining Neutron Fluence Rate, Flu-ence, and Spectra by Radioactivation Techniques2E 844 Guide for Sensor Set Design and Irradiation forReactor Surveillance, E 706 (IIC)2E 944 Guide for Application of Neutron

7、Spectrum Adjust-ment Methods in Reactor Surveillance, E 706 (IIA)2E 1005 Test Method for Application and Analysis of Radio-metric Monitors for Reactor Vessel Surveillance, E 706(IIIA)2E 1018 Guide for Application of ASTM Evaluated CrossSection Data File, Matrix E 706 (IIB)23. Terminology3.1 Definiti

8、ons:3.1.1 Refer to Terminology E 170.4. Summary of Test Method4.1 High-purity nickel is irradiated in a neutron field,thereby producing radioactive58Co from the58Ni(n,p)58Coactivation reaction.4.2 The gamma rays emitted by the radioactive decay of58Co are counted in accordance with Test Methods E 18

9、1 andthe reaction rate, as defined by Practice E 261, is calculatedfrom the decay rate and irradiation conditions.4.3 The neutron fluence rate above about 2.1 MeV can thenbe calculated from the spectral-weighted neutron activationcross section as defined by Practice E 261.5. Significance and Use5.1

10、Refer to Guide E 844 for the selection, irradiation, andquality control of neutron dosimeters.5.2 Refer to Practice E 261 for a general discussion of thedetermination of fast-neutron fluence rate with threshold de-tectors.5.3 Pure nickel in the form of foil or wire is readilyavailable, and easily ha

11、ndled.5.458Co has a half-life of 70.86 days and emits a gammaray with an energy of 0.8107593-MeV.35.5 Competing activities65Ni(2.5172 h) and57Ni(35.60 h)are formed by the reactions64Ni(n,g)65Ni, and58Ni(n,2n)57Ni,respectively.5.6 A second 9.04h isomer,58mCo, is formed that decays to70.82-day58Co. Lo

12、ss of58Co and58mCo by thermal-neutronburnout will occur in environments having thermal fluencerates of 3 3 1012cm2s1and above. The58Co(n,g)59Co and58mCo(n,g)59Co cross sections have been measured at 16501This test method is under the jurisdiction of ASTM Committee E10 on NuclearTechnology and Applic

13、ations and is the direct responsibility of SubcommitteeE10.05 on Nuclear Radiation Metrology.Current edition approved June 10, 2002. Published September 2002. Originallypublished as E 264 65 T. Last edition E 264 92(1996).2Annual Book of ASTM Standards, Vol 12.02.3Evaluated Nuclear Structure Data Fi

14、le (ENSDF), a computer file of evaluatednuclear structure and radioactive decay data, which is maintained by the NationalNuclear Data Center (NNDC), Brookhaven National Laboratory (BNL), on behalfof the International Network for Nuclear Structure Data Evaluation, which functionsunder the auspices of

15、 the Nuclear Data Section of the International Atomic EnergyAgency (IAEA). The URL is http;/www.nndc.bnl.gov/nndc/ensdf. The data quotedhere comes from the database as of January 1, 2002.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United State

16、s.and 1.4 3 105barns, respectively.4Burnout correction factors,R, are plotted as a function of time for several thermal fluxes inFig. 1.5.7 Fig. 2 shows a plot of cross section versus energy for thefast-neutron reaction58Ni(n,p)58Co.5This figure is for illus-trative purposes only to indicate the ran

17、ge of response of the58Ni(n,p) reaction. Refer to Guide E 1018 for descriptions ofrecommended tabulated dosimetry cross sections.6. Apparatus6.1 NaI (T1) or High Resolution Gamma-Ray Spectrometer.Because of its high resolution, the germanium detector isuseful when contaminant activities are present

18、(see Test Meth-ods E 181 and E 1005).6.2 Precision Balance, able to achieve the required accu-racy.6.3 Digital Computer, useful for data analysis (optional).7. Materials7.1 The nickel metal must be low in contained cobalt toprevent the production of60Co by thermal-neutron capture.Nickel produced by

19、the carbonyl (Mond) process is sufficientlyfree of cobalt for even the most adverse conditions. Wheneverpossible, all nickel should be tested for interfering impuritiesby neutron activation.7.2 Encapsulating MaterialsBrass, stainless steel, copper,aluminum, quartz, or vanadium have been used as prim

20、aryencapsulating materials. The container should be constructedin such a manner that it will not create significant fluxperturbation and that it may be opened easily, especially if thecapsule is to be opened remotely (see Guide E 844).8. Procedure8.1 Decide on the size and shape of nickel sample to

21、beirradiated. This is influenced by the irradiation space and theexpected production of58Co. Calculate the expected produc-tion rate of58Co from the activation equation described inSection 9, and adjust the sample size and irradiation time sothat the58Co may be counted accurately.8.2 Determine the l

22、evel of thermal-neutron fluence rate byincluding a thermal-fluence rate monitor. Place the sample in aboron or cadmium shield if required.8.3 Weigh the sample.8.4 Irradiate the sample for the predetermined time period.Record the power level and any changes in power during theirradiation, the time at

23、 the beginning and end of the irradiationperiod, and the relative position of the monitors in theirradiation facility.8.5 A waiting period of at least 4 days is recommendedbetween termination of the exposure and start of counting. Thisallows the 9.04-h58mCo to decay entirely to the 70.86-day58Cogrou

24、nd state. Activated impurities such as 2.52-h65Ni, 35.6-h57Ni, and 23.72-h187W, sometimes observed in nickel pre-pared by high-temperature sintering in tungsten, will also beeliminated by allowing the sample to decay over an extendedperiod.8.6 Check the sample for activity from cross-contaminationby

25、 other irradiated materials. Clean, if necessary, and reweigh.8.7 Analyze the sample for58Co content in disintegrationsper second using the gamma-ray spectrometer (see Test Meth-ods E 181 and E 1005).8.8 Disintegration of58Co nuclei produces 0.8107593-MeVgamma rays with a probability per decay of 0.

26、9945.6Whenanalyzing the peak in the gamma-ray spectrum, a correction forcoincidence summing may be required if the sample is placedclose to the detector (10 cm or less) (see Test Methods E 181).9. Calculations9.1 Calculate the saturation activity, As, as follows:As5 A/1 2 exp 2 lti#! exp 2 ltw#!# (1

27、)where:A =58Co disintegrations per second measured by count-ing,l = decay constant for58Co = 1.132 3 107s1,ti= irradiation duration, s, andtw= elapsed time between the end of irradiation andcounting, s.NOTE 1The equation for Asis valid if the reactor operated atessentially constant power and if corr

28、ections for other reactions (forexample, impurities, burnout, etc.) are negligible. Refer to Practice E 261for more generalized treatments.9.2 Calculate the reaction rate, Rs, as follows:Rs5 As/No(2)where:As= saturation activity, andNo= number of58Ni atoms.9.3 Refer to Practice E 261 and Guide E 944

29、 for a discus-sion of fast-neutron fluence rate and fluence.10. Report10.1 Practice E 261 describes how data should be reported.4Hogg, C. H., Weber, L. D., and Yates, E. C., “Isomers and the Effects on FastFlux Measurements Using Nickel,” Atomic Energy Commission R and D ReportIDO-16744, 1962.5ENDF-

30、201, ENDF/B-VI Summary Documentation, edited by P. F. Rose,Brookhaven National Laboratory Report BNL-NCS-1741, 4thEdition, October1991.6J. K. Tulti, “Nuclear Wallet Cards,” National Nuclear Data Center, BrookhavenNational Laboratory, Upton, New York, January 2000.FIG. 1 R Correction Values as a Func

31、tion of Irradiation Time andNeutron FluxE26402211. Precision and BiasNOTE 2Measurement uncertainty is described by a precision and biasstatement in this standard. Another acceptable approach is to use Type Aand B uncertainty components.7,7This Type A/B uncertainty specificationis now used in Interna

32、tional Organization for Standardization (ISO)Standards and this approach can be expected to play a more prominentrole in future uncertainty analyses.11.1 General practice indicates that disintegration rates canbe determined with a bias of 6 3 % (1S %) and with aprecision of 6 1 % (1S %).12. Keywords

33、12.1 activation; activation reaction; cross section; dosim-etry; fast-neutron monitor; neutron metrology; nickel; pressurevessel surveillance; reaction rateASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard

34、. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed

35、every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible te

36、chnical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoh

37、ocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).7B. N. Taylor, C.E. Kuyatt, Guidelines for Evaluating and Expressing theUncertainty of NIST Measurement Results, NIST Technical Note 1297, NationalInstitute of Standards and Technology, Gaithersburg, MD, 1994.E264023