1、Designation: E 704 96 (Reapproved 2002)Standard Test Method forMeasuring Reaction Rates by Radioactivation of Uranium-2381This standard is issued under the fixed designation E 704; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e 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.) from
3、the fissionreaction238U(n,f)F.P.1.2 The reaction is useful for measuring neutrons withenergies from approximately 1.5 to 7 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 fa
4、st-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-bility o
5、f 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 Rad
6、ioactivation 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 Fi
7、ssion Dosimeters2E 482 Guide for Application of Neutron Transport Methodsfor Reactor Vessel Surveillance, E706 (IID)2E 705 Test Method for Measuring Reaction Rates by Ra-dioactivation of Neptunium-2372E 844 Guide for Sensor Set Design and Irradiation forReactor Surveillance, E706 (IIC)2E 944 Guide f
8、or 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. Term
9、inology3.1 Definitions:3.1.1 Refer to Terminology E 170.4. Summary of Test Method4.1 High-purity238U ( 1 MeV)fluence rate of 1 3 1011cm2s1provided the238Uisshielded from thermal neutrons (see Fig. 2 of Guide E 844).5.4.2 Fission product production from photonuclear reac-tions, that is, (g,f) reactio
10、ns, while negligible near-power andresearch-reactor cores, can be large for deep-water penetrations(1).45.5 Good agreement between neutron fluence measured by238U fission and the54Fe(n,p)54Mn reaction has been demon-strated (2). The reaction238U(n,f) F.P. is useful since it isresponsive to a broader
11、 range of neutron energies than mostthreshold detectors.5.6 The238U fission neutron spectrum-averaged cross sec-tion in several benchmark neutron fields is given in Table 3 ofPractice E 261. Sources for the latest recommended crosssections are given in Guide E 1018. In the case of the238U(n,f)F.P. r
12、eaction, the recommended cross section sourceis the ENDF/B-VI cross section (MAT = 9237), revision 1 (3).Fig. 1 shows a plot of the recommended cross section versusneutron energy for the fast-neutron reaction238U(n,f)F.P.6. Apparatus6.1 Gamma-Ray Detection Equipment that can be used toaccurately mea
13、sure 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 is usefu
14、l when contaminant activitiesare present.6.2 Balance, providing the accuracy and precision requiredby the experiment.6.3 Digital Computer, useful for data analysis (optional).7. Materials7.1 Uranium-238 Alloy or OxideHigh-purity238Uintheform of alloy wire, foil, or oxide powder is available.7.1.1 Th
15、e238U target material should be furnished with acertificate of analysis indicating any impurity concentrations.7.2 Encapsulating MaterialsBrass, stainless steel, copper,aluminum, quartz, or vanadium have been used as primaryencapsulating materials. The container should be constructedin such a manner
16、 that it will not create significant perturbationof the neutron spectrum and 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 without opening thecapsule since th
17、ere 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 rate for a given neutron fluencerate.
18、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 references appended tothis test metho
19、d.TABLE 1 Recommended Nuclear Parameters for Certain FissionProductsFissionProductParentHalf-LifeA(6)PrimaryRadiationA(7) (keV)g ProbabilityofDecayA(7)MaximumUsefulIrradiationDuration95Zr 64.04 (4) d 724.199 (5) 0.4417 (19) 6 months756.729 (12) 0.544699Mo 65.94 (1) h 0.1213 739.5 300 hours0.0435 777
20、.921103Ru 39.254 (8) d 497.084 (10) 0.910 (23) 4 months137Cs 30.0 (2) yr 661.660 (3)B0.8510B3040 years140Ba 140La 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 parentheses are the magnitude of plus or
21、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 FissionProductsAFissileIsotopeNeutronEnergyReactionProductTypeYieldENDF/B-VIB,AFissi
22、on Yield238U(n,f) 0.5 MeV95Zr RC 5.15126 6 1%99Mo RC 6.18839 6 1.4 %103Ru RC 6.26113 6 1%137Cs RC 6.02075 6 1%137mBa RI 4.10011e-8 6 64 %140Ba RC 5.84596 6 1%140La RI 1.38004e-5 6 64 %144Ce RC 4.55034 6 1.4 %AEngland, T. R., and Rider, B. F., ENDF-349 Evaluation and Compilation ofFission Product Yie
23、lds, 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 7042NOTE 1The melting point of elemental cadmium is 321C. Foradditional precautions, see Test Method E
24、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 Check the sample for activity from cros
25、s 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, a suitablecontainment will be required.8.4.1 If chemical
26、separation is necessary, dissolution can beachieved in 8 N HNO3-0.05 N HF.NOTE 2If an ion-exchange separation is to be subsequently per-formed, follow the dissolution by fuming with sulfuric acid (H2SO4)toexpel fluorides. Fuming with H2SO4, however, may expel volatile fissionproduct ruthenium, and,
27、unless performed with care, losses of other fissionproducts by spattering can occur.NOTE 3A specific dissolution procedure has been developed forvanadium-encapsulated uranium oxide specimens (5).8.5 Analyze the sample for fission-product content in dis-integrations per second (see Test Methods E 181
28、, E 320, andE 1005).8.5.1 It is assumed that the available 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 isreco
29、mmended that a137Cs activity standard is used.8.5.3 If the 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 f
30、ollows:As5 A/y1 2 exp 2lti!exp 2ltw!# (1)where:l = disintegration 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 equili
31、brium has been established, l is that ofthe parent species.NOTE 5The equation for Asis valid if the reactor operated at essen-tially constant power and if corrections for other reactions (for example,impurities, burnout, etc.) are negligible. Refer to Practice E 261 for moregeneralized treatments.9.
32、2 Calculate the reaction rate,5Rs, as follows:Rs5 As/No(2)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 andfluence.5The terms “fission rate” and “reaction rate” can be used synonymously.FIG. 1 ENDF/B-V
33、I Cross Section Versus Energy for the238U(n,f)F.P. ReactionE 704310. Report10.1 Practice E 261 describes how data should be reported.11. Precision and Bias11.1 General practice indicates that disintegration rates canbe determined with a bias of 6 5 % (1S %) and with aprecision of 6 1 % (1S %).11.2 T
34、he238U cumulative fission product yields have anuncertainty between 1.4 % and 6 % (1S %) for the variousfission products as indicated in Table 1.12. Keywords12.1 fission dosimeter; fission product; fission reactionrates; Uranium-238REFERENCES(1) Verbinski, V. V., et al, “Measurements and Calculation
35、s of PhotofissionEffects in a Swimming Pool Type Reactor,” Transactions 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 19
36、71.(3) ENDF/B-V Dosimetry Tape 531-G, Material No. 6398 (92-U-238),October 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-NC
37、S-174, 4th Edition,October, 1991.(6) Nuclear Wallet Cards, compiled by 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),
38、 Brookhaven NationalLaboratory (BNL), on behalf of the International Network 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
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