1、Designation: E526 08 (Reapproved 2013)Standard 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 revis
2、ion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers procedures for measuring reac-tion rates by the activation reactions46Ti(n,p)
3、46Sc +47Ti(n,np)46Sc.NOTE 1Since the cross section for the (n,np) reaction is relativelysmall for energies less than 12 MeV and is not easily distinguished fromthat of the (n,p) reaction, this test method will refer to the (n,p) reactiononly.1.2 The reaction is useful for measuring neutrons withener
4、gies above approximately 4.4 MeV and for irradiationtimes up to about 250 days (for longer irradiations, see PracticeE261).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
5、 be investigated.1.4 Detailed procedures for other fast-neutron detectors 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
6、, 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 of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E170 Terminology Relating to Radiation Meas
7、urements andDosimetryE181 Test Methods for Detector Calibration and Analysis ofRadionuclidesE261 Practice for Determining Neutron Fluence, FluenceRate, and Spectra by Radioactivation TechniquesE262 Test Method for Determining Thermal Neutron Reac-tion Rates and Thermal Neutron Fluence Rates by Radio
8、-activation TechniquesE844 Guide for Sensor Set Design and Irradiation forReactor Surveillance, E 706 (IIC)E944 Guide for Application of Neutron Spectrum Adjust-ment Methods in Reactor Surveillance, E 706 (IIA)E1005 Test Method for Application and Analysis of Radio-metric Monitors for Reactor Vessel
9、 Surveillance, E 706(IIIA)E1018 Guide for Application of ASTM Evaluated CrossSection Data File, Matrix E706 (IIB)3. Terminology3.1 Definitions:3.1.1 Refer to Terminology E170.4. Summary of Test Method4.1 High-purity titanium is irradiated in a fast-neutron field,thereby producing radioactive46Sc fro
10、m the46Ti(n,p)46Scactivation reaction.4.2 The gamma rays emitted by the radioactive 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
11、4.4 MeV can thenbe calculated from the spectral-weighted neutron activationcross section as defined by Test Method E261.5. Significance and Use5.1 Refer to Guide E844 for the selection, irradiation, andquality control of neutron dosimeters.5.2 Refer to Test Method E261 for a general discussion ofthe
12、 determination of fast-neutron fluence rate with thresholddetectors.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 Jan. 1, 2013. Publi
13、shed January 2013. Originallyapproved in 1976. Last previous edition approved in 2008 as E526 08. DOI:10.1520/E0526-08R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, ref
14、er to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.3 Titanium has good physical strength, is easilyfabricated, has excellent corrosion resistance, has a meltingtemperature of
15、 1675C, and can be obtained with satisfactorypurity.5.446Sc has a half-life of 83.79 days.3The46Sc decay4emits a 0.8893 MeV gamma 99.984 % of the time and a secondgamma with an energy of 1.1205 MeV 99.987 % of the time.5.5 The isotopic content of natural titanium recommendedfor46Ti is 8.25 %.35.6 Th
16、e radioactive products of the neutron reactions47Ti(n,p)47Sc (1/2= 3.3492 d) and48Ti(n,p)48Sc (1/2= 43.67h), might interfere with the analysis of46Sc.5.7 Contaminant activities (for example,65Zn and182Ta)might interfere with the analysis of46Sc. See Sections 7.1.2and 7.1.3 for more details on the182
17、Ta and65Zn interference.5.846Ti and46Sc have cross sections for thermal neutronsof 0.59 and 8 barns, respectively5; therefore, when an irradia-tion exceeds a thermal-neutron fluence greater than about 2 1021cm2, provisions should be made to either use a thermal-neutron shield to prevent burn-up of46
18、Sc or measure thethermal-neutron fluence rate and calculate the burn-up.5.9 Fig. 1 shows a plot of cross section versus neutronenergy for the fast-neutron reactions of titanium which produce46Sc that is,NatTi(n,X)46Sc. Included in the plot is the46Ti(n,p) reaction6and the47Ti(n,np) contribution to t
19、he46Scproduction,7normalized (at 14.7 MeV)8per46Ti atom. Thisfigure is for illustrative purposes only to indicate the range ofresponse of the46Ti(n,p) reaction. Refer to Guide E1018 fordescriptions of recommended tabulated dosimetry cross sec-tions.6. Apparatus6.1 NaI(Tl) or High Resolution Gamma-Ra
20、y Spectrometer.Because of its high resolution, the germanium detector isuseful when contaminant activities are present. See MethodsE181 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
21、-purity titanium metal in the formof wire or foil is available.7.1.1 The metal should be tested for impurities by a neutronactivation 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 thisinterfer
22、ence, the use of a thermal-neutron shield during irra-diation would be advisable if scandium impurity is suspected.As an example, 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
23、is due to the reaction45Sc(n,)46Sc.7.1.2 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 radioactive182
24、Ta isotope has ahalf-life of 1/2= 114.43 d and emits a 1121.302 keV photon34.7 % of the time. This photon is very close in energy to oneof the two photons emitted by46Sc (889.3 keV and 1120.5keV). Moreover, during the46Sc decay, the 1120.5 keV and889.3 keV photons are emitted in true coincidence and
25、 therandom coincidence between the 1121.302 keV photons from182Ta and the 889.3 keV photons from46Sc can affect theapplication of summing corrections when the counting is donein a close geometry and the46Sc activity is being monitoringwith 889.3 keV photon.7.1.3 Zinc contamination can lead to the pr
26、oduction of65Znvia the64Zn(n,)65Zn reaction. The radioactive65Zn isotopehas a half-life of 1/2= 243.66 d and emits a 1115.518 keVphoton 50.75 % of the time. These 1115.518 keV photons can3Nuclear Wallet Cards, National Nuclear Data Center, prepared by Jagdish K.Tuli, April 2005.4Evaluated Nuclear St
27、ructure Data File (ENSDF), maintained by the NationalNuclear Data Center (NNDC), Brookhaven National Laboratory, on behalf of theInternational Network for Nuclear Structure Data Evaluation.5Nuclear Data retrieval program NUDAT, a computer file of evaluated nuclearstructure and radioactive decay data
28、, which is maintained by the National NuclearData Center (NNDC), Brookhaven National Laboratory (BNL), on behalf of theInternational Network for Nuclear Structure Data Evaluation, which functions underthe auspices of the Nuclear Data Section of the InternationalAtomic EnergyAgency(IAEA). The URL is
29、http:/www.nndc.bnl.gov/nudat2/indx_sigma.jsp.6“International Reactor Dosimetry File (IRDF-2002),” International AtomicEnergy Agency, Nuclear Data Section, Technical Reports Series No. 452, 2006,Document available from URL http:/www-nds.iaea.org/irdf2002/docs/irdf-2002.pdf.7Zolotarev, K. I., Ignatyuk
30、, A. V., Mahokhin, V. N., Pashchenko, A. B.,RRDF-98, Russian Reactor Dosimetry File, Rep. IAEA-NDS-193, Rev. 1, IAEA,Vienna, 2005. URL is http:/www-nds.ipen.br/ndspub/libraries2/rrdf98/8Meadows, J. W., Smith, D. L., Bretscher, M. M., and Cox, S.A., “Measurementof 14.7 MeV Neutron-Activation Cross Se
31、ctions for Fusion,” Annals of NuclearEnergy, Vol 1, No. 9, 1987 .FIG. 1NatTi(n,X)46Sc Cross Section (Normalized per Ti-46 Atom)E526 08 (2013)2interfere with the 1120.5 keV line from46Sc and require amulti-peak resolution. For a small contaminant level the65Znline may be hidden in the background of t
32、he 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 to reactor pressure vessel surveillance dosim-etry because the46Ti(n,p)46S
33、c, 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 high-energy end of the derived spectrum, andresult in the incorrect predic
34、tion 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 that it will not create significant fluxperturbation and that it may be ope
35、ned 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 irradiation space. The mass and exposure time are param-eters that can be varied to
36、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 during theirradiation, the time at the beginning and end of each powerlevel and
37、 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 exposure and ana-lyzing the samples for46Sc content. This allows the 43.67-h48Sc
38、 to decay so that there is no interference from the gammarays emitted by48Sc, that is, the 0.175, 0.983, 1.037, and1.312-MeV gamma rays. If the 0.159-MeV gamma ray emittedby 3.3492-day47Sc interferes with counting conditions, alonger decay time may be necessary. The 5.76-min51Ti willusually have dec
39、ayed by count time. However, gamma-rayspectra may be taken with germanium detectors soon afterirradiation, if count rates are not excessive.8.5 Check the sample for activity from cross-contaminationby other irradiated materials. Clean, if necessary, and reweigh.8.6 Analyze the sample for46Sc content
40、 in disintegrationsper second using the gamma-ray spectrometer (see MethodsE181 and E1005).8.7 Disintegrations of46Sc nuclei produces 0.8893-MeVand 1.1205-MeV gamma rays with probabilities per decay of0.99984 and 0.99997, respectively.4When analyzing eitherpeak in the gamma-ray system, a correction
41、for coincidencesumming may be required if the sample is placed close to thedetector (10 cm or less) (see Methods E181).9. Calculation9.1 Calculate the saturation activity, As, as follows:As5 A/1 2 exp2ti#!exp2tw#!# (1)where:A =46Sc disintegrations per second measured by counting, = decay constant fo
42、r46Sc = 9.5746 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 atessentially constant power and if corrections for other reactions (forexample, impurities, burnout, etc.) are negligible. Refer
43、to Test MethodE261 for more generalized treatments.9.2 Calculate the reaction rate, Rs, as follows:Rs5 As/No(2)where:As= saturation activity, andNo= 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
44、 E261 describes how data should bereported.11. Precision and BiasNOTE 3Measurement uncertainty is described by a precision and biasstatement in this standard. Another acceptable approach is to use Type Aand B uncertainty components.9,10This Type A/B uncertainty specifica-tion is now used in Internat
45、ional Organization for Standardization (ISO)standards and this approach can be expected to play a more prominent rolein future uncertainty analyses.11.1 General practice indicates that disintegration rates canbe determined with a bias of 63 % (1S %) and with a precisionof 61 % (1S %). For a fission
46、spectrum, the typical uncertaintyin the spectrum-averaged cross section11is 2.4 %.12. Keywords12.1 activation reaction; cross section; dosimetry; nuclearmetrology; pressure vessel surveillance; reaction rate; titanium9Taylor, B. N. , Kuyatt, C. E. , Guidelines for Evaluating and Expressing theUncert
47、ainty of NIST Measurement Results, NIST Technical Note 1297, NationalInstitute of Standards and Technology, Gaithersburg, MD, 1994.10Guide in the Expression of Uncertainty in Measurement , InternationalOrganization for Standardization, 1995, ISBN 92-67-10188-9.11Griffin, P. J. , “Comparison of Uncer
48、tainty Metrics for Calculated DosimetryActivities,” American Nuclear Society Proceedings of the 1996 Topical MeetingRadiation Protection and Shielding, held in No. Falmouth, Massachusetts, April2125, 1996, Vol. 1, pp. 27 35.E526 08 (2013)3ASTM International takes no position respecting the validity
49、of any patent rights asserted in connection with any item mentionedin this standard. 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 every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand sho
