1、Designation: E526 171Standard Test Method forMeasuring Fast-Neutron Reaction Rates by Radioactivationof Titanium1This standard is issued under the fixed designation E526; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEEditorial changes, such as removing extra spacing, correcting notation and a variable, were made in November2017.1. Scope1.1
3、This test method covers procedures for measuring reac-tion rates by the activation reactions46Ti(n,p)46Sc +47Ti(n,np)46Sc +47Ti(n,d)46Sc.NOTE 1The cross section for the47Ti(n,np+d) reaction is relativelysmall for energies less than 12 MeV and is not easily distinguished fromthat of the46Ti(n,p) reac
4、tion. This test method will apply to the compositenatTi(n,X)46Sc reaction that is typically used for dosimetry purposes.1.2 The reaction is useful for measuring neutrons withenergies above approximately 4.4 MeV and for irradiationtimes, under uniform power, up to about 250 days (for longerirradiatio
5、ns, or for varying power levels, see Practice E261).1.3 With suitable techniques, fission-neutron fluence ratesabove 109cm2s1can be determined. However, in the pres-ence of a high thermal-neutron fluence rate,46Sc depletionshould be investigated.1.4 Detailed procedures for other fast-neutron detecto
6、rs arereferenced in Practice E261.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user
7、of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in th
8、e Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E170 Terminology Relating to Radiation Measurements andDosimetryE177 Practi
9、ce for Use of the Terms Precision and Bias inASTM Test MethodsE181 Test Methods for Detector Calibration and Analysis ofRadionuclidesE261 Practice for Determining Neutron Fluence, FluenceRate, and Spectra by Radioactivation TechniquesE456 Terminology Relating to Quality and StatisticsE844 Guide for
10、Sensor Set Design and Irradiation forReactor SurveillanceE944 Guide for Application of Neutron Spectrum Adjust-ment Methods in Reactor SurveillanceE1005 Test Method for Application and Analysis of Radio-metric Monitors for Reactor Vessel SurveillanceE1018 Guide for Application of ASTM Evaluated Cros
11、sSection Data File3. Terminology3.1 Definitions:3.1.1 Refer to Terminologies E170 and E456.4. Summary of Test Method4.1 High-purity titanium is irradiated in a fast-neutron field,thereby producing radioactive46Sc from the46Ti(n,p)46Scactivation reaction.4.2 The gamma rays emitted by the radioactive
12、decay of46Sc are counted in accordance with Methods E181 and thereaction rate, as defined by Test Method E261, is calculatedfrom the decay rate and the irradiation conditions.4.3 The neutron fluence rate above about 4.4 MeV can thenbe calculated from the spectral-weighted neutron activationcross sec
13、tion as defined by Test Method E261.1This test method is under the jurisdiction ofASTM Committee E10 on NuclearTechnology and Applicationsand is the direct responsibility of SubcommitteeE10.05 on Nuclear Radiation Metrology.Current edition approved Aug. 1, 2017. Published October 2017. Originallyapp
14、roved in 1976. Last previous edition approved in 2013 as E526 08(2013). DOI:10.1520/E0526-17E01.2For referenced 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 Docume
15、nt Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Pri
16、nciples for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15. Significance and Use5.1 Refer to Guide E844 for the selection, irradiation, andquality control of neutron dosimeters.5.2 Refer to T
17、est Method E261 for a general discussion ofthe determination of fast-neutron fluence rate with thresholddetectors.5.3 Titanium has good physical strength, is easilyfabricated, has excellent corrosion resistance, has a meltingtemperature of 1668C, and can be obtained with satisfactorypurity.5.446Sc h
18、as a half-life of 83.787 (16)3days(1).4The46Scdecay emits a 0.889271 (2) MeV gamma 99.98374 (35) % ofthe time and a second gamma with an energy of 1.120537 (3)MeV 99.97 (2) % of the time.5.5 The isotopic content of natural titanium recommendedfor46Ti is 8.25 %. (2)5.6 The radioactive products of the
19、 neutron reactions47Ti(n,p)47Sc (1/2= 3.3485 (9) d) (1) and48Ti(n,p)48Sc (1/2= 43.67 h), (2) might interfere with the analysis of46Sc.5.7 Contaminant activities (for example,65Zn and182Ta)might interfere with the analysis of46Sc. See 7.1.2 and 7.1.3for more details on the182Ta and65Zn interference.5
20、.846Ti and46Sc have cross sections for thermal neutronsof 0.59 6 0.18 and 8.0 6 1.0 barns, respectively (3); therefore,when an irradiation exceeds a thermal-neutron fluence greaterthan about21021cm2, provisions should be made to eitheruse a thermal-neutron shield to prevent burn-up of46Sc ormeasure
21、the thermal-neutron fluence rate and calculate theburn-up.5.9 Fig. 1 shows a plot of the Russian Reactor DosimetryFile (RRDF-2002) cross section (4) versus neutron energy forthe fast-neutron reactions of titanium which produce46Sc thatis,natTi(n,X)46Sc. This cross section is identical, for energiesu
22、p to 20 MeV, to what is found in the latest InternationalAtomic Energy Agency (IAEA) International Reactor Dosim-etry and Fusion File, IRDFF-1.05 (5). Included in the plot isthe46Ti(n,p) reaction and the47Ti(n,np) contribution to the46Sc production, normalized per46Ti atom using the naturalabundance
23、s (2). This figure is for illustrative purposes only toindicate the range of response of thenatTi(n,p)46Sc reaction.Refer to Guide E1018 for descriptions of recommendedtabulated dosimetry cross sections. Fig. 2 compares the crosssection for the46Ti(N,p)47Sc reaction to the current experimen-tal data
24、base (6, 7). Fig. 3 compares the cross section for the47Ti(N, np+d) reaction to the current experimental database (6,7).6. Apparatus6.1 NaI(Tl) or High Resolution Gamma-Ray Spectrometer.Because of its high resolution, the germanium detector isuseful when contaminant activities are present. See Metho
25、dsE181 and E1005.6.2 Precision Balance, able to achieve the required accu-racy.6.3 Digital Computer, useful for data analysis (optional).7. Materials7.1 Titanium MetalHigh-purity titanium metal in the formof wire or foil is available.7.1.1 The metal should be tested for impurities by a neutronactiva
26、tion technique. If the measurement is to be made in athermal-neutron environment, scandium impurity must be lowbecause of the reaction,45Sc(n,)46Sc. To reduce thisinterference, the use of a thermal-neutron shield during irra-diation would be advisable if scandium impurity is suspected.As an example,
27、 when a titanium sample containing 6 ppmscandium has been irradiated in a neutron field with equalthermal and fast-neutron fluence rates about 1 % of the46Sc inthe sample is due to the reaction45Sc(n,)46Sc.3The value of uncertainty, in parentheses, refers to the corresponding last digits,thus 14.958
28、(2) corresponds to 14.958 6 0.002.4The boldface numbers in parentheses refer to a list of references at the end ofthis standard.FIG. 1NatTi(n,X)46Sc Cross Section (Normalized per Ti-46 AtomUsing Natural Abundance Data)FIG. 246Ti(n,p)46Sc Cross Section, from RRDF-2002/IRDFF-1.05,with EXFOR Experiment
29、al DataE526 17127.1.2 Tantalum impurities can also cause a problem. Thelow-energy response of the181Ta(n,)182Ta reaction producesgamma activity that interferes with the measurement of46Scradioactivity produced from the46Ti(n,p)46Sc high-energythreshold reaction. The radioactive182Ta isotope has a ha
30、lf-lifeof 1/2= 114.61 (13) d and emits a 1121.290 (3) keV photon35.17 (33) % of the time (1). This photon is very close inenergy to one of the two photons emitted by46Sc (889.271 (2)keV and 1120.537 (3) keV). Moreover, during the46Sc decay,the 1120.537 keV and 889.271 keV photons are emitted in true
31、coincidence and the random coincidence between the 1121.395keV photons from182Ta and the 889.271 keV photons from46Sc can affect the application of summing corrections whenthe counting is done in a close geometry and the46Sc activityis being monitoring with 889.271 keV photon.7.1.3 Zinc contaminatio
32、n can lead to the production of65Znvia the64Zn(n,)65Zn reaction. The radioactive65Zn isotopehas a half-life of 1/2= 244.01 (9) d and emits a 1115.539 keVphoton 50.22 (11) % of the time. These 1115.539 keV photonscan interfere with the 1120.5 keV line from46Sc and require amulti-peak resolution. For
33、a small contaminant level the65Znline may be hidden in the background of the larger46Sc peak.There is no other high probability65Zn decay gamma withwhich to monitor or correct for the presence of zinc in thetitanium sample.7.1.4 Impurity problems in titanium are a particular concernfor applications
34、to reactor pressure vessel surveillance dosim-etry because the46Ti(n,p)46Sc, along with the63Cu(n,)60Coreaction, are the two highest-energy dosimetry reactions usedto detect spectrum differences in reactor neutron environments.Incorrect radioactivity measurements of these two reactionscan alter the
35、high-energy end of the derived spectrum, andresult in the incorrect prediction of neutron irradiation damage.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 t
36、hat it will not create significant fluxperturbation and that it may be opened easily, especially if themonitors must be removed remotely (see Guide E844).8. Procedure8.1 Decide on the size and shape of the titanium sample tobe irradiated, taking into consideration the size and shape ofthe irradiatio
37、n space. The mass and exposure time are param-eters that can be varied to obtain a desired disintegration ratefor a given neutron-fluence rate level. (See Guide E844.)8.2 Weigh the sample.8.3 Irradiate the sample for the predetermined time period.Record the power level and any changes in power durin
38、g theirradiation, the time at the beginning and end of each powerlevel and the relative position of the monitors in the irradiationfacility.8.4 If the counting procedure available requires that theactivity be pure46Sc, a waiting period of about 20 days isrecommended between termination of the exposu
39、re and ana-lyzing the samples for46Sc content. This allows the 43.67 (9)-h48Sc (2) to decay so that there is no interference from thegamma rays emitted by48Sc, that is, the 0.175361, 0.983526,1.037522, and 1.312120-MeV gamma rays (2).Ifthe0.159373-MeV gamma ray emitted by 3.3485-day47Sc inter-feres
40、with counting conditions, a longer decay time may benecessary. The 5.76-min (2)51Ti will usually have decayed bycount time. However, gamma-ray spectra may be taken withgermanium detectors soon after irradiation, if count rates arenot excessive.8.5 Check the sample for activity from cross-contaminati
41、onby other irradiated materials. Clean, if necessary, and reweigh.8.6 Analyze the sample for46Sc content in disintegrationsper second using the gamma-ray spectrometer (see MethodsE181 and E1005).8.7 Disintegrations of46Sc nuclei produces 0.8893-MeVand 1.120537-MeVgamma rays with probabilities per de
42、cay of0.9998374 (25) and 0.9997 (2), respectively. When analyzingeither peak in the gamma-ray system, a correction for coinci-dence summing may be required if the sample is placed closeto the detector (10 cm or less) (see Methods E181).9. Calculation9.1 Calculate the saturation activity, As, as foll
43、ows:As5 A/1 2 exp2ti#!exp2tw#!# (1)where:A =46Sc disintegrations per second measured by counting, = decay constant for46Sc = 9.574918 108s1,ti= irradiation duration, s,tw= elapsed time between the end of irradiation andcounting, s.NOTE 2The equation for Asis valid if the reactor operated atessential
44、ly constant power and if corrections for other reactions (forexample, impurities, burnout, etc.) are negligible. Refer to Test MethodE261 for more generalized treatments.9.2 Calculate the reaction rate, R, as follows:R 5 As/No(2)where:As= saturation activity, andFIG. 347Ti(n,np+d)46Sc Cross Section,
45、 from RRDF-2002/IRDFF-1.05, with EXFOR Experimental DataE526 1713No= number of46Ti atoms.9.3 Refer to Test Method E261 and Practice E944 for adiscussion of fast-neutron fluence rate and fluence.10. Report10.1 Test Method E261 describes how data should bereported.11. Precision and BiasNOTE 3Measureme
46、nt uncertainty is described by a precision and biasstatement in this standard. Another acceptable approach is to use Type Aand B uncertainty components (8, 9). This Type A/B uncertainty specifi-cation is now used in International Organization for Standardization (ISO)standards and this approach can
47、be expected to play a more prominent rolein future uncertainty analyses.11.1 Precision and bias in this standard are treated inaccordance with Practice E177. General practice indicates thatdisintegration rates can be determined with a bias of 63%(1S %) and with a precision of 61 % (1S %).11.2 Fig. 4
48、 shows the energy-dependent uncertainty, at1-sigma standard deviation, for the46Ti(n,p)46Sc RRDF-2002/IRDFF-1.05 cross section evaluation. Experimental validationtesting yields a calculated-to-experimental ratio of 0.973 62.59 % in the252Cf spontaneous fission standard neutronbenchmark field and 0.9
49、00 6 5.95 % in the235U thermalfission reference benchmark neutron field (10).11.3 Fig. 5 shows the energy-dependent uncertainty, at1-sigma standard deviation, for the47Ti(n,np+d)46Sc RRDF-2002/IRDFF-1.05 cross section evaluation.12. Keywords12.1 activation reaction; cross section; dosimetry; nuclearmetrology; pressure vessel surveillance; reaction rate; titaniumFIG. 4 Energy-dependent Uncertainty in the Cross Section for theRRDF-2002/IRDFF-1.05 Evaluation of the46Ti(n,p)46Sc Cross Sec-tionE526 1714REFERENCES(1) Be, M. M., Chiste, V., Dulie
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