1、Designation: E 705 96 (Reapproved 2002)Standard Test Method forMeasuring Reaction Rates by Radioactivation of Neptunium-2371This standard is issued under the fixed designation E 705; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、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 covers procedures for measuring reac-tion rates by assaying a fission product (F.P.) fro
3、m the fissionreaction237Np(n,f)F.P.1.2 The reaction is useful for measuring neutrons withenergies from approximately 0.7 to 6 MeV and for irradiationtimes up to 30 to 40 years.1.3 Equivalent fission neutron fluence rates as defined inPractice E 261 can be determined.1.4 Detailed procedures for other
4、 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 its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bilit
5、y of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:E 170 Terminology Relating to Radiation Measurementsand Dosimetry2E 181 Test Methods for Detector Calibration and Analysisof Radionuclides2E 261 Practice for Determining Neutron Fluence Rate, Flu-ence, and Spectra by
6、Radioactivation Techniques2E 262 Test Method for Determining Thermal Neutron Re-action and Fluence Rates by Radioactivation Techniques2E 320 Test Methods for Cesium-137 in Nuclear Fuel Solu-tions by Radiochemical Analysis2E 393 Test Method for Measuring Reaction Rates by Analy-sis of Barium-140 from
7、 Fission Dosimeters2E 482 Guide for Application of Neutron Transport Methodsfor Reactor Vessel Surveillance, E706 (IID)2E 704 Test Method for Measuring Reaction Rates by Ra-dioactivation of Uranium-2382E 844 Guide for Sensor Set Design and Irradiation forReactor Surveillance, E706 (IIC)2E 944 Guide
8、for Application of Neutron Spectrum Adjust-ment Methods in Reactor Surveillance, (IIA)2E 1005 Test Method for Application and Analysis of Radio-metric Monitors for Reactor Vessel Surveillance, E706(IIIA)2E 1018 Guide for Application of ASTM Evaluated CrossSection Data File, Matrix E 706 (IIB)23. Ter
9、minology3.1 Definitions:3.1.1 Refer to Terminology E 170.4. Summary of Test Method4.1 High-purity237Np ( 1 MeV) fluence rate of 1 3 1011cm2s1,provided the237Np is shielded from thermal neutrons (see Fig.2 of Guide E 844).5.4.2 Fission product production from photonuclear reac-tions, that is, (g,f) r
10、eactions, while negligible near-power andresearchreactor cores, can be large for deep-water penetrations(1).45.5 Good agreement between neutron fluence measured by237Np fission and the54Fe(n,p)54Mn reaction has been dem-onstrated (2). The reaction237Np(n,f) F.P. is useful since it isresponsive to a
11、broader range of neutron energies than mostthreshold detectors.5.6 The237Np fission neutron spectrum-averaged crosssection in several benchmark neutron fields are given in Table3 of Practice E 261. Sources for the latest recommended crosssections are given in Guide E 1018. In the case of the237Np(n,
12、f)F.P. reaction, the recommended cross section sourceis the ENDF/B-VI cross section (MAT = 9346) revision 1 (3).Fig. 1 shows a plot of the recommended cross section versusneutron energy for the fast-neutron reaction237Np(n,f)F.P.6. Apparatus6.1 Gamma-Ray Detection Equipment that can be used toaccura
13、tely measure the decay rate of fission product activity arethe following two types (4):6.1.1 NaI(T1) Gamma-Ray Scintillation Spectrometer (seeTest Methods E 181 and E 1005).6.1.2 Germanium Gamma-Ray Spectrometer (see TestMethods E 181 and E 1005)Because of its high resolution,the germanium detector
14、is useful when contaminant activitiesare present.6.2 Balance, providing the accuracy and precision requiredby the experiment.6.3 Digital Computer, useful for data analysis, but is notnecessary (optional).7. Materials7.1 Neptunium-237 Alloy or OxideHigh-purity237Np inthe form of alloy wire, foil, or
15、oxide powder is available.7.1.1 The237Np target material should be furnished with acertificate of analysis indicating any impurity concentrations.7.2 Encapsulating MaterialsBrass, stainless steel, copper,aluminum, vanadium, and quartz have been used as primaryencapsulating materials. The container s
16、hould be constructedin such a manner that it will not create significant perturbationof the neutron spectrum or fluence rate and that it may beopened easily, especially if the capsule is to be openedremotely. Certain encapsulation materials, for example, quartzand vanadium, allow gamma-ray counting
17、without opening thecapsule since there are no interfering activities.8. Procedure8.1 Select the size and shape of the sample to be irradiated,taking into consideration the size and shape of the irradiationspace. The mass and exposure time are parameters that can bevaried to obtain a desired count ra
18、te for a given neutron fluencerate.8.2 Weigh the sample to the accuracy and precision requiredof the experiment; encapsulate; and, if irradiated in a thermalneutron environment, surround with a suitable high-meltingthermal neutron absorber.4The boldface numbers in parentheses refer to the list of re
19、ferences appended tothis test method.TABLE 1 Recommended Nuclear Parameters for Certain FissionProductsFissionProductParentHalf-LifeA(6)PrimaryRadiationA(7) (keV)g Probability ofDecayA(7)MaximumUsefulIrradiationDuration95Zr 64.04 (4) d 724.199 (5) 0.4417 (19) 6 months756.729 (12) 0.544699Mo 65.94 (1
20、) h 0.1213 739.5 300 hours0.0435 777.921103Ru 39.254 (8) d 497.084 (10) 0.910 (23) 4 months137Cs 30.0 (2) yr 661.660 (3)B0.8510B3040 years140Ba140La 12.746 (10) d 537.31 (4) 0.2439 11.5 months1596.54 (14) 0.9540C1.1515D144Ce 284.9 (2) d 133.515 (8) 0.1109 (4) 23 yearsAThe lightface numbers in parent
21、heses are the magnitude of plus or minusuncertainties in the last digit(s) listed.BWith137mBa (2.552 min) in equilibrium.CProbability of daughter140La decay.DWith140La (1.6780 d) in transient equilibrium.TABLE 2 Recommended Fission Yields for Certain FissionProductsAFissileIsotopeNeutronEnergyReacti
22、onProductTypeYieldENDF/B-VIB,AFission Yield (%)237Np(n,f) 0.5 MeV95Zr RC 5.68896 6 2.8 %99Mo RC 6.11547 6 4%103Ru RC 5.56212 6 2.8 %137Cs RC 6.16977 6 2.8 %137mBa RI 1.438e-5 6 64 %140Ba RC 6.17171 6 2%140La RI 4.421e-5 6 64 %144Ce RC 4.12987 6 2%AEngland, T. R., and Rider, B. F., ENDF-349 Evaluatio
23、n and Compilation ofFission Product Yields, Los Alamos National Laboratory, Los Alamos, NM, reportLA-UR-94-3106, ENDF-349, October 1994.BAll yield data given as a %; RC represents a cumulative yield; RI represents anindependent yield.E 7052NOTE 1The melting point of elemental cadmium is 321C. Foradd
24、itional precautions, see Test Method E 262.8.3 Irradiate the sample for the predetermined time period.Record the power level and any changes in power during theirradiation, the time at the beginning and end of each powerlevel, and the relative position of the monitors in the irradiationfacility.8.4
25、Check the sample for activity from cross contaminationby other monitors or material irradiated in the vicinity or fromany foreign substance adhering to the sample. Clean andreweigh, if necessary. If the sample is encapsulated oxidepowder and if it is necessary to open the capsule, suitablecontainmen
26、t will be required.8.4.1 If chemical separation is necessary, dissolution can beachieved in 6 N HCl-1 N HF with periodic additions of H2O2,followed by fuming with H2SO4.NOTE 2Fuming with H2SO4may expel volatile fission productruthenium and, unless performed with care, losses of other fissionproducts
27、 by spattering can occur.NOTE 3A specific dissolution procedure has been developed forvanadium-encapsulated neptunium oxide specimens (5).8.5 Analyze the sample for fission-product content in dis-integrations per second (see Test Methods E 181, E 320, andE 1005).8.5.1 It is assumed that the availabl
28、e apparatus has beencalibrated to measure F.P. activity, and that the experimenter iswell versed in the operation of the apparatus.8.5.2 Disintegration of137Cs nuclei produces 0.662-MeVgamma rays with a probability per decay of 0.852. It isrecommended that a137Cs activity standard is used.8.5.3 If t
29、he analyst is well versed in germanium countingand carefully calibrates the system, it is feasible to count137Cs-137mBa,140Ba-140La,95Zr, and144Ce directly withoutchemical separation.9. Calculation9.1 Calculate the saturation activity, As, as follows:As5 A/y1 2 exp 2lti!exp 2ltw!# (1)where:l = disin
30、tegration constant for F.P., s1,A = number of disintegrations, measured during the count-ing period, s1,ti= irradiation duration, s,tw= elapsed time between the end of irradiation andcounting, s, andy = fission yield.NOTE 4Where transient equilibrium has been established, l is that ofthe parent spec
31、ies.NOTE 5The equation for Asis valid if the reactor operated atessentially constant power and if corrections for other reactions (forexample, impurities, burnout, etc.) are negligible. Refer to Practice E 261for more generalized treatments.9.2 Calculate the reaction rate,5Rs, as follows:Rs5 As/No(2
32、)where:No= number of target atoms.9.3 Refer to Practice E 261 and Guide E 944 for a discus-sion of the determination of fast neutron fluence rate.10. Report10.1 Practice E 261 describes how data should be reported.11. Precision and Bias11.1 General practice indicates that disintegration rates can5Th
33、e terms “fission rate” and “reaction rate” can be used synonymously.FIG. 1 ENDF/B-VI Cross Section Versus Energy for the237Np(n,f)F.P. ReactionE 7053be determined with a bias of 65 % (1S %) and with a precisionof 61 % (1S %).11.2 The237Np cumulative fission product yields have anuncertainty between
34、2 % and 4 % (1S %) for the various fissionproducts as indicated in Table 1.12. Keywords12.1 fission dosimeter; fission product; fission reactionrates; Neptunium-237REFERENCES(1) Verbinski, V. V., et al, “Measurements and Calculations of PhotofissionEffects in a Swimming Pool Type Reactor,” Transacti
35、ons of theAmerican Nuclear Society, Washington, DC, Vol 30, November 1978.(2) Barry, K. M., and Corbett, J. A., “Measurement of Neutron Fluence byNeptunium-237 and Uranium-238 Fission Dosimeters,” Nuclear Tech-nology, Vol 11, May 1971.(3) ENDF/B-V Dosimetry Tape 531-G, Mat. No. 6399 (93-Np-237),Octo
36、ber 1979.(4) Crouthamel, C. E. (Revised by Adams, F., and Dams, R.), AppliedGamma-Ray Spectrometry, Pergamon Press, 1970.(5) “ENDF-201, ENDF/B-VI Summary Documentation,” P. F. Rose, Ed.Brookhaven National Laboratory Report BNL-NCS-174, 4th Edition,October, 1991.(6) Nuclear Wallet Cards, compiled by
37、J. K. Tuli, National Nuclear DataCenter, July 1990.(7) Nuclear Data retrieval program NUDAT, a computer file of evaluatednuclear structure and radioactive decay data, which is maintained bythe National Nuclear Data Center (NNDC), Brookhaven NationalLaboratory (BNL), on behalf of the International Ne
38、twork for NuclearStructure Data Evaluation, which functions under the auspices of theNuclear Data Section of the International Atomic Energy Agency(IAEA).ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard.
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41、nical 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 Conshohocken, 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).E 7054
