1、Designation: E526 08 (Reapproved 2013)E526 17Standard 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 o
2、f revision, 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 reaction rates by the activation reactions 46
3、Ti(n,p) 46Sc + 47Ti(n, np)46Sc+ 47Ti(n,d)46Sc.NOTE 1Since the The cross section for the 47(n,np)Ti(n,np+d) reaction is relatively small for energies less than 12 MeV and is not easily distinguishedfrom that of the 46(n,p) reaction, thisTi(n,p) reaction. This test method will referapply to the (n,p)c
4、omposite natTi(n,X) 46reaction only. Sc reaction thatis typically used for dosimetry purposes.1.2 The reaction is useful for measuring neutrons with energies above approximately 4.4 MeV and for irradiation times times,under uniform power, up to about 250 days (for longer irradiations, or for varying
5、 power levels, see Practice E261).1.3 With suitable techniques, fission-neutron fluence rates above 109 cm2s1 can be determined. However, in the presence ofa high thermal-neutron fluence rate, 46Sc depletion should be investigated.1.4 Detailed procedures for other fast-neutron detectors are referenc
6、ed in Practice E261.1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this sta
7、ndard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the De
8、cision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E170 Terminology Relating to Radiation Measurements and DosimetryE177 Practice
9、for Use of the Terms Precision and Bias in ASTM Test MethodsE181 Test Methods for Detector Calibration and Analysis of RadionuclidesE261 Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation TechniquesE262E456 Test Method for Determining Thermal Neutron Reaction Rate
10、s and Thermal Neutron Fluence Rates by Radioacti-vation TechniquesTerminology Relating to Quality and StatisticsE844 Guide for Sensor Set Design and Irradiation for Reactor SurveillanceE944 Guide for Application of Neutron Spectrum Adjustment Methods in Reactor SurveillanceE1005 Test Method for Appl
11、ication and Analysis of Radiometric Monitors for Reactor Vessel SurveillanceE1018 Guide for Application of ASTM Evaluated Cross Section Data File3. Terminology3.1 Definitions:3.1.1 Refer to TerminologyTerminologies E170 and E456.1 This test method is under the jurisdiction of ASTM Committee E10 on N
12、uclear Technology and Applicationsand is the direct responsibility of Subcommittee E10.05 onNuclear Radiation Metrology.Current edition approved Jan. 1, 2013Aug. 1, 2017. Published January 2013October 2017. Originally approved in 1976. Last previous edition approved in 20082013 asE526 08.E526 08(201
13、3). DOI: 10.1520/E0526-08R13.10.1520/E0526-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document i
14、s not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as approp
15、riate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test Method4.1 High-purity titanium is irradiated
16、 in a fast-neutron field, thereby producing radioactive 46Sc from the 46Ti(n,p)46Scactivation reaction.4.2 The gamma rays emitted by the radioactive decay of 46Sc are counted in accordance with Methods E181 and the reactionrate, as defined by Test Method E261, is calculated from the decay rate and t
17、he irradiation conditions.4.3 The neutron fluence rate above about 4.4 MeV can then be calculated from the spectral-weighted neutron activation crosssection as defined by Test Method E261.5. Significance and Use5.1 Refer to Guide E844 for the selection, irradiation, and quality control of neutron do
18、simeters.5.2 Refer to Test Method E261 for a general discussion of the determination of fast-neutron fluence rate with thresholddetectors.5.3 Titanium has good physical strength, is easily fabricated, has excellent corrosion resistance, has a melting temperature of1675C,1668C, and can be obtained wi
19、th satisfactory purity.5.4 46Sc has a half-life of 83.79 days.83.787 (16)3 The days(461Sc ).decay4 The 46Sc decay emits a 0.8893 0.889271 (2) MeVgamma 99.984 % 99.98374 (35) % of the time and a second gamma with an energy of 1.1205 MeV 99.987 % 1.120537 (3) MeV99.97 (2) % of the time.5.5 The isotopi
20、c content of natural titanium recommended for 46Ti is 8.25 %. (2)5.6 The radioactive products of the neutron reactions 47Ti(n,p)47Sc (1/2 = 3.3492 3.3485 (9) d) (1) and 48Ti(n,p)48Sc (1/2 =43.67 h), (2) might interfere with the analysis of 46Sc.5.7 Contaminant activities (for example, 65Zn and 182Ta
21、) might interfere with the analysis of 46Sc. See Sections 7.1.2 and 7.1.3for more details on the 182Ta and 65Zn interference.5.8 46Ti and 46Sc have cross sections for thermal neutrons of 0.59 and 8 6 0.18 and 8.0 6 1.0 barns, respectively (3); therefore,when an irradiation exceeds a thermal-neutron
22、fluence greater than about 2 1021 cm2, provisions should be made to either usea thermal-neutron shield to prevent burn-up of 46Sc or measure the thermal-neutron fluence rate and calculate the burn-up.5.9 Fig. 1 shows a plot of the Russian Reactor Dosimetry File (RRDF-2002) cross section (4) versus n
23、eutron energy for the3 Nuclear Wallet Cards, National Nuclear Data Center, prepared by Jagdish K. Tuli, April 2005.The value of uncertainty, in parentheses, refers to the corresponding lastdigits, thus 14.958(2) corresponds to 14.958 6 0.002.4 Evaluated Nuclear Structure Data File (ENSDF), maintaine
24、d by the National Nuclear Data Center (NNDC), Brookhaven National Laboratory, on behalf of theInternational Network for Nuclear Structure Data Evaluation.4 Nuclear Data retrieval program NUDAT, a computer file of evaluated nuclear structure and radioactive decay data, which is maintained by the Nati
25、onal Nuclear DataCenter (NNDC), Brookhaven National Laboratory (BNL), on behalf of the International Network for Nuclear Structure Data Evaluation, which functions under the auspicesof the Nuclear Data Section of the International Atomic Energy Agency (IAEA). The URL is http:/www.nndc.bnl.gov/nudat2
26、/indx_sigma.jsp. The boldface numbers inparentheses refer to a list of references at the end of this standard.7 Zolotarev, 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/n
27、dspub/libraries2/rrdf98/FIG. 1 NatTi(n,X)46Sc Cross Section (Normalized per Ti-46 Atom Using Natural Abundance Data)E526 172fast-neutron reactions of titanium which produce produce 46Sc that is, NatTi(n,X)46Sc. This cross section is identical, for energiesup to 20 MeV, to what is found in the latest
28、 International Atomic Energy Agency (IAEA) International Reactor Dosimetry andFusion File, IRDFF-1.05 (5). Included in the plot is the 46Ti(n,p) reaction and the 47Ti(n,np) contribution to the 46Sc production,normalized (at 14.7 MeV)per 46Ti atom. atom using the natural abundances (2). This figure i
29、s for illustrative purposes only toindicate the range of response of the natTi(n,p) 46Ti(n,p)Sc reaction. Refer to Guide E1018 for descriptions of recommendedtabulated dosimetry cross sections. Fig. 2 compares the cross section for the 46Ti(N,p)47Sc reaction to the current experimentaldatabase (6, 7
30、).Fig. 3 compares the cross section for the 47Ti(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 is usefulwhen contaminant activities are present. See Methods E181
31、and E1005.6.2 Precision Balance, able to achieve the required accuracy.6.3 Digital Computer, useful for data analysis (optional).7. Materials7.1 Titanium MetalHigh-purity titanium metal in the form of wire or foil is available.7.1.1 The metal should be tested for impurities by a neutron activation t
32、echnique. If the measurement is to be made in athermal-neutron environment, scandium impurity must be low because of the reaction, 45Sc(n,)46Sc. To reduce this interference,the use of a thermal-neutron shield during irradiation would be advisable if scandium impurity is suspected. As an example, whe
33、na titanium sample containing 6 ppm scandium has been irradiated in a neutron field with equal thermal and fast-neutron fluencerates about 1 % of the 46Sc in the sample is due to the reaction 45Sc(n,)46Sc.7.1.2 Tantalum impurities can also cause a problem. The low-energy response of the 181Ta(n,)182
34、Ta reaction produces gammaactivity that interferes with the measurement of 46Sc radioactivity produced from the 46Ti(n,p)46Sc high-energy threshold reaction.The radioactive 182Ta isotope has a half-life of 1/2 = 114.43 114.61 (13) d and emits a 1121.302 1121.290 (3) keV photon 34.7 %35.17 (33) % of
35、the time.time (1). This photon is very close in energy to one of the two photons emitted by 46Sc (889.3 (889.271(2) keV and 1120.5 1120.537 (3) keV). Moreover, during the 46Sc decay, the 1120.51120.537 keV and 889.3889.271 keV photonsare emitted in true coincidence and the random coincidence between
36、 the 1121.3021121.395 keV photons from 182Ta and the889.3889.271 keV photons from 46Sc can affect the application of summing corrections when the counting is done in a closegeometry and the 46Sc activity is being monitoring with 889.3889.271 keV photon.7.1.3 Zinc contamination can lead to the produc
37、tion of 65Zn via the 64Zn(n,)65Zn reaction. The radioactive 65Zn isotope hasa half-life of 1/2 = 243.66 244.01 (9) d and emits a 1115.5181115.539 keV photon 50.75 % 50.22 (11) % of the time. These1115.5181115.539 keV photons can interfere with the 1120.5 keV line from 46Sc and require a multi-peak r
38、esolution. For a smallcontaminant level the 65Zn line may be hidden in the background of the larger 46Sc peak. There is no other high probability 65Zndecay gamma with which to monitor or correct for the presence of zinc in the titanium sample.7.1.4 Impurity problems in titanium are a particular conc
39、ern for applications to reactor pressure vessel surveillance dosimetrybecause the 46Ti(n,p)46Sc, along with the 63Cu(n,)60Co reaction, are the two highest-energy dosimetry reactions used to detectspectrum differences in reactor neutron environments. Incorrect radioactivity measurements of these two
40、reactions can alter thehigh-energy end of the derived spectrum, and result in the incorrect prediction of neutron irradiation damage.9 Taylor, B. N. , Kuyatt, C. E. , Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results,NIST Technical Note 1297, National Institute ofS
41、tandards and Technology, Gaithersburg, MD, 1994.FIG. 2 46Ti(n,p)46Sc Cross Section, from RRDF-2002/IRDFF-1.05, with EXFOR Experimental DataE526 1737.2 Encapsulating MaterialsBrass, stainless steel, copper, aluminum, quartz, or vanadium have been used as primaryencapsulating materials. The container
42、should be constructed in such a manner that it will not create significant flux perturbationand that it may be opened easily, especially if the monitors must be removed remotely (see Guide E844).8. Procedure8.1 Decide on the size and shape of the titanium sample to be irradiated, taking into conside
43、ration the size and shape of theirradiation space. The mass and exposure time are parameters that can be varied to obtain a desired disintegration rate for a givenneutron-fluence rate level. (See Guide E844.)8.2 Weigh the sample.8.3 Irradiate the sample for the predetermined time period. Record the
44、power level and any changes in power during theirradiation, the time at the beginning and end of each power level and the relative position of the monitors in the irradiation facility.8.4 If the counting procedure available requires that the activity be pure 46Sc, a waiting period of about 20 days i
45、srecommended between termination of the exposure and analyzing the samples for 46Sc content. This allows the 43.67-h 43.67 (9)-h 48Sc (2)to decay so that there is no interference from the gamma rays emitted by 48Sc, that is, the 0.175, 0.983, 1.037, and1.312-MeV gamma rays.0.175361, 0.983526, 1.0375
46、22, and 1.312120-MeV gamma rays (2). If the 0.159-MeV0.159373-MeVgamma ray emitted by 3.3492-day3.3485-day 47Sc interferes with counting conditions, a longer decay time may be necessary. The5.76-min (2)51Ti will usually have decayed by count time. However, gamma-ray spectra may be taken with germani
47、um detectorssoon after irradiation, if count rates are not excessive.8.5 Check the sample for activity from cross-contamination by other irradiated materials. Clean, if necessary, and reweigh.8.6 Analyze the sample for 46Sc content in disintegrations per second using the gamma-ray spectrometer (see
48、Methods E181and E1005).8.7 Disintegrations of 46Sc nuclei produces 0.8893-MeV and 1.1205-MeV1.120537-MeV gamma rays with probabilities perdecay of 0.99984 and 0.99997, 0.9998374 (25)4 and 0.9997 (2), respectively. When analyzing either peak in the gamma-raysystem, a correction for coincidence summin
49、g may be required if the sample is placed close to the detector (10 cm or less) (seeMethods E181).9. Calculation9.1 Calculate the saturation activity, As, as follows:As5A/12exp2ti#! exp2tw#!# (1)where:A = 46Sc disintegrations per second measured by counting, = decay constant for 46Sc = 9.5746 108 s1, = decay constant for 46Sc = 9.574918 108 s1,ti = irradiation duration, s,tw = elapsed time between the end of irradiation and counting, s.NOTE 2The equation for As is valid if the reactor operated at essentially constant power and if corre
