ASTM E526-2008 459 Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Titanium《用钛的放射性测定快中子反应率的标准试验方法》.pdf

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1、Designation: E 526 08Standard Test Method forMeasuring Fast-Neutron Reaction Rates by Radioactivationof Titanium1This standard is issued under the fixed designation E 526; 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.1. Scope1.1 This test method covers procedures for measuring reac-tion rates by the activation reactions46Ti(n,p)46Sc +47Ti(n,np)

3、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 withenergies above appro

4、ximately 4.4 MeV and for irradiationtimes up to about 250 days (for longer irradiations, see PracticeE 261).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 investigate

5、d.1.4 Detailed procedures for other fast-neutron detectors arereferenced in Practice E 261.1.5 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, asso

6、ciated 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:2E 170 Terminology Relating to Radiation Measurementsand D

7、osimetryE 181 Test Methods for Detector Calibration and Analysisof RadionuclidesE 261 Practice for Determining Neutron Fluence, FluenceRate, and Spectra by Radioactivation TechniquesE 262 Test Method for Determining Thermal Neutron Re-action and Fluence Rates by Radioactivation TechniquesE 844 Guide

8、 for Sensor Set Design and Irradiation forReactor Surveillance, E 706(IIC)E 944 Guide for Application of Neutron Spectrum Adjust-ment Methods in Reactor Surveillance, E 706 (IIA)E 1005 Test Method for Application and Analysis of Radio-metric Monitors for Reactor Vessel Surveillance, E706(IIIA)E 1018

9、 Guide for Application of ASTM Evaluated CrossSection Data File, Matrix E 706 (IIB)3. Terminology3.1 Definitions:3.1.1 Refer to Terminology E 170.4. Summary of Test Method4.1 High-purity titanium is irradiated in a fast-neutron field,thereby producing radioactive46Sc from the46Ti(n,p)46Scactivation

10、reaction.4.2 The gamma rays emitted by the radioactive decay of46Sc are counted in accordance with Methods E 181 and thereaction rate, as defined by Test Method E 261, is calculatedfrom the decay rate and the irradiation conditions.4.3 The neutron fluence rate above about 4.4 MeV can thenbe calculat

11、ed from the spectral-weighted neutron activationcross section as defined by Test Method E 261.5. Significance and Use5.1 Refer to Guide E 844 for the selection, irradiation, andquality control of neutron dosimeters.1This test method is under the jurisdiction of ASTM Committee E10 on NuclearTechnolog

12、y and Applications and is the direct responsibility of SubcommitteeE10.05 on Nuclear Radiation Metrology.Current edition approved July 1, 2008. Published September 2008. Originallyapproved in 1976. Last previous edition approved in 2002 as E 526 97 (2002).2For referenced ASTM standards, visit the AS

13、TM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Unit

14、ed States.5.2 Refer to Test Method E 261 for a general discussion ofthe determination of fast-neutron fluence rate with thresholddetectors.5.3 Titanium has good physical strength, is easily fabri-cated, has excellent corrosion resistance, has a melting tem-perature of 1675C, and can be obtained with

15、 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 The radioactive products of the ne

16、utron reactions47Ti(n,p)47Sc (t1/2= 3.3492 d) and48Ti(n,p)48Sc (t1/2= 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 the182Ta and65Zn interference.5.846T

17、i 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 31021cm2, provisions should be made to either use a thermal-neutron shield to prevent burn-up of46Sc or measure thethermal-neut

18、ron 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 the46Scproduction,7normalized

19、(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 E 1018 fordescriptions of recommended tabulated dosimetry cross sec-tions.6. Apparatus6.1 NaI(Tl) or High Resolution Gamma-Ray Spectrometer.Because of it

20、s high resolution, the germanium detector isuseful when contaminant activities are present. See MethodsE 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 Titanium MetalHigh-purity titanium metal in

21、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,g)46Sc. To reduce this interfer-ence, the use of a ther

22、mal-neutron shield during irradiationwould be advisable if scandium impurity is suspected. As anexample, when a titanium sample containing 6 ppm scandiumhas been irradiated in a neutron field with equal thermal andfast-neutron fluence rates about 1 % of the46Sc in the sampleis due to the reaction45S

23、c(n,g)46Sc.7.1.2 Tantalum impurities can also cause a problem. Thelow-energy response of the181Ta(n,g)182Ta reaction producesgamma activity that interferes with the measurement of46Scradioactivity produced from the46Ti(n,p)46Sc high-energythreshold reaction. The radioactive182Ta isotope has a half-l

24、ifeof t1/2= 114.43 d and emits a 1121.302 keV photon 34.7 % ofthe time. This photon is very close in energy to one of the twophotons emitted by46Sc (889.3 keV and 1120.5 keV). More-over, during the46Sc decay, the 1120.5 keV and 889.3 keVphotons are emitted in true coincidence and the randomcoinciden

25、ce between the 1121.302 keV photons from182Taand the 889.3 keV photons from46Sc can affect the applicationof summing corrections when the counting is done in a closegeometry and the46Sc activity is being monitoring with 889.3keV photon.7.1.3 Zinc contamination can lead to the production of65Znvia th

26、e64Zn(n,g)65Zn reaction. The radioactive65Zn isotopehas a half-life of t1/2= 243.66 d and emits a 1115.518 keVphoton 50.75 % of the time. These 1115.518 keV photons caninterfere with the 1120.5 keV line from46Sc and require a3Nuclear Wallet Cards, National Nuclear Data Center, prepared by Jagdish K.

27、Tuli, April 2005.4Evaluated Nuclear Structure 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 nucle

28、arstructure and radioactive decay data, 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 International

29、Atomic EnergyAgency(IAEA). The URL is 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/ird

30、f-2002.pdf.7Zolotarev, K. I., Ignatyuk, 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., “Measuremento

31、f 14.7 MeV Neutron-Activation Cross Sections for Fusion,” Annals of NuclearEnergy, Vol 1, No. 9, 1987 .FIG. 1NatTi(n,X)46Sc Cross Section (Normalized per Ti-46 Atom)E526082multi-peak resolution. For a small contaminant level the65Znline may be hidden in the background of the larger46Sc peak.There is

32、 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)46Sc, along with the63Cu(n,a)6

33、0Coreaction, 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 prediction of neutron irradiatio

34、n 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 opened easily, especially if

35、themonitors must be removed remotely (see Guide E 844).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 obtain a desired disinteg

36、ration ratefor a given neutron-fluence rate level. (See Guide E 844.)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 the relative position o

37、f 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 to decay so that there

38、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 decayed by count time. Howe

39、ver, 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 in disintegrationsper s

40、econd using the gamma-ray spectrometer (see MethodsE 181 and E 1005).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 for coincidencesumming

41、 may be required if the sample is placed close to thedetector (10 cm or less) (see Methods E 181).9. Calculation9.1 Calculate the saturation activity, As, as follows:As5 A/1 2 exp2lti#! exp2ltw#!# (1)where:A =46Sc disintegrations per second measured by counting,l = decay constant for46Sc = 9.5746 3

42、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 to Test MethodE

43、 261 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 E 261 and Practice E 944 for adiscussion of fast-neutron fluence rate and fluence.10. Report10.1 Test Method E 261 descr

44、ibes 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 International Organ

45、ization 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 spectrum, t

46、he 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 theUncertainty of NI

47、ST 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 Uncertainty Metr

48、ics 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.E526083ASTM International takes no position respecting the validity of any patent right

49、s 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 should be addressed to ASTM Internation