1、Designation: E263 13Standard Test Method forMeasuring Fast-Neutron Reaction Rates by Radioactivationof Iron1This standard is issued under the fixed designation E263; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method describes procedures for
3、measuringreaction rates by the activation reaction54Fe(n,p)54Mn.1.2 This activation reaction is useful for measuring neutronswith energies above approximately 2.2 MeV and for irradiationtimes up to about 3 years (for longer irradiations, see PracticeE261).1.3 With suitable techniques, fission-neutro
4、n fluence ratesabove 108cm2s1can be determined. However, in the pres-ence of a high thermal-neutron fluence rate (for example, 2 1014cm2s1)54Mn depletion should be investigated.1.4 Detailed procedures describing the use of other fast-neutron detectors are referenced in Practice E261.1.5 The values s
5、tated 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 of this standard to establish appro-priate safety
6、and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE170 Terminology Relating to Radiation Measurements andDosimetryE181 Test Methods for Detector Calibration and Analysis ofRadio
7、nuclidesE261 Practice for Determining Neutron Fluence, FluenceRate, and Spectra by Radioactivation 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)E10
8、05 Test Method for Application and Analysis of Radio-metric Monitors for Reactor Vessel 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 for definitions of termsrelating to ra
9、diation measurements and neutron dosimetry.4. Summary of Test Method4.1 High-purity iron is irradiated in a neutron field, therebyproducing radioactive54Mn from the54Fe(n,p)54Mn activationreaction.4.2 The gamma rays emitted by the radioactive decay of54Mn are counted in accordance with Test Methods
10、E181. Thereaction rate, as defined by Practice E261, is calculated fromthe decay rate and irradiation conditions.4.3 Radioassay of the54Mn activity may be accomplishedby directly counting the irradiated iron dosimeter, or by firstchemically separating the54Mn activity prior to counting.4.4 The neutr
11、on fluence rate above about 2.2 MeV can thenbe calculated from the spectral-weighted neutron activationcross section as defined by Practice E261.5. Significance and Use5.1 Refer to Guide E844 for guidance on the selection,irradiation, and quality control of neutron dosimeters.5.2 Refer to Practice E
12、261 for a general discussion of thedetermination of fast-neutron fluence rate with threshold de-tectors.5.3 Pure iron in the form of foil or wire is readily availableand easily handled.1This test method is under the jurisdiction ofASTM Committee E10 on NuclearTechnology and Applications and is the d
13、irect responsibility of SubcommitteeE10.05 on Nuclear Radiation Metrology.Current edition approved June 1, 2013. Published July 2013. Originally approvedin 1965 as E263 65 T. Last previous edition approved in 2009 as E263 09. DOI:10.1520/E0263-13.2For referenced ASTM standards, visit the ASTM websit
14、e, 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1
15、5.4 Fig. 1 shows a plot of cross section as a function ofneutron energy for the fast-neutron reaction54Fe(n,p)54Mn(1).3This figure is for illustrative purposes only to indicate therange of response of the54Fe(n,p)54Mn reaction. Refer toGuide E1018 for descriptions of recommended tabulateddosimetry c
16、ross sections.5.554Mn has a half-life of 312.13 (3) days4(2) and emits agamma ray with an energy of 834.838 (5) keV (2).5.6 Interfering activities generated by neutron activationarising from thermal or fast neutron interactions are 2.5789(1)-h56Mn, 44.495 (9) day59Fe, and 1925.28 (1) day60Co(2,3). (
17、Consult the latest version of Ref (2) for more precisevalues currently accepted for the half-lives.) Interference from56Mn can be eliminated by waiting 48 h before counting.Although chemical separation of54Mn from the irradiated ironis the most effective method for eliminating59Fe and60Co,direct cou
18、nting of iron for54Mn is possible using high-resolution detector systems or unfolding or strippingtechniques, especially if the dosimeter was covered withcadmium or boron during irradiation. Altering the isotopiccomposition of the iron dosimeter is another useful techniquefor eliminating interferenc
19、e from extraneous activities whendirect sample counting is to be employed.5.7 The vapor pressures of manganese and iron are such thatmanganese diffusion losses from iron can become significant attemperatures above about 700C. Therefore, precautions mustbe taken to avoid the diffusion loss of54Mn fro
20、m irondosimeters at high temperature. Encapsulating the iron dosim-eter in quartz or vanadium will contain the manganese attemperatures up to about 900C.5.8 Sections 6, 7 and 8 that follow were specifically writtento describe the method of chemical separation and subsequentcounting of the54Mn activi
21、ty. When one elects to count theiron dosimeters directly, those portions of Sections 6, 7 and 8that pertain to radiochemical separation should be disregarded.NOTE 1The following portions of this test method apply also to directsample-counting methods: 6.1-6.3, 7.4, 7.9, 7.10, 8.1-8.5, 8.18, 8.19, an
22、d9-12.6. Apparatus (Note 1)6.1 HighResolution Gamma-Ray Spectrometer, because ofits high resolution, the germanium detector is useful whencontaminant activities are present. See Test Methods E181 andE1005.6.2 Precision Balance, able to achieve the required accu-racy.6.3 Digital Computer, useful for
23、data analysis (optional).6.4 Chemical Separation Cylinder, borosilicate glass, about25-mL capacity, equipped with stopcock and funnel. Thisapparatus is illustrated in Fig. 2.6.5 Beakers, borosilicate glass, 50 mL; volumetric flasks, 25and 50 mL, and volumetric pipets, 1 mL.7. Reagents and Materials
24、(Note 1)7.1 Purity of ReagentsReagent-grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended that3The boldface numbers in parentheses refer to the list of references located at theend of this test method.4The un-bolded number in parenthesis after the unit indicates the
25、 uncertainty inthe least significant digits. For example, 1.89 (2) keV would indicate a value of 1.89keV 6 0.02 keV.FIG. 154Fe(n,p)54Mn Cross Section FIG. 2 Ion-Exchange Separation ApparatusE263 132all reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the Ameri
26、can Chemical Society,where such specifications are available.5Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the activity determination.7.2 Purity of Water Unless otherwise indicated, referen
27、cesto water shall be understood to mean reagent-grade waterconforming to Specification D1193.7.3 Anion Exchange Resin, strongly basic type, 100 to 200mesh size.7.4 Iron Foil or Wire, high purity.7.5 Hydrochloric Acid (sp gr 1.19, 1190 kg/m3)Concentrated hydrochloric acid (HCl).7.6 Hydrochloric Acid
28、(1 + 3)Mix 1 volume of concen-trated HCl (sp gr 1.19) with 3 volumes of water.7.7 Manganese Carrier Solution (10 mg MnCl2/cm3).7.8 Nitric Acid (sp gr 1.42, 1420 kg/m3)Concentratednitric acid (HNO3).7.9 Encapsulating MaterialsBrass, stainless steel, copper,aluminum, quartz, or vanadium have been used
29、 as primaryencapsulating materials. The container should be constructedin such a manner that it will not create a significant fluxperturbation and that it may be opened easily, especially if thecapsule is to be opened remotely. (See Guide E844.)7.10 The purity of the iron is important in that no imp
30、uritiesshould be present which produce long-lived radionuclides thatinterfere with the54Mn radioassay. This condition includesspecies that will accompany54Mn through the separationscheme and that have gamma rays, of energy 0.6 MeV orhigher. The presence of impurities may be determined either byemiss
31、ion spectroscopy or by activation analysis.8. Procedure (Note 1)8.1 Decide on the size and shape of the iron sample to beirradiated. Consider convenience in handling and availableirradiation space when making this selection, but it is moreimportant to ensure that sufficient54Mn activity will beprodu
32、ced to permit accurate radioassay. A preliminary calcu-lation of the expected production of54Mn, using the activationequation described in Section 9, will aid in selecting the massof iron required.8.2 Determine a suitable irradiation time.8.3 Weigh the iron sample. The chemical manipulationsdescribe
33、d below function best with an iron dosimeter weighing10 to 20 mg.NOTE 2It is necessary to avoid a high iron concentration in thesolutions that are to be used for separation so that the efficiency of theion-exchange resin will not be seriously lowered. For the columndescribed herein the amount of iro
34、n let onto the resin should not exceed1 mg.8.4 Irradiate the samples for the predetermined time period.Record the power level and any changes in power during theirradiation, the time at the beginning and end of the irradiation,and the relative position of the monitors in the irradiationfacility.8.5
35、A waiting period of 2 days is recommended betweentermination of the exposure and the start of counting. Thisallows 2.58-h56Mn, produced by fast-neutron reactions with56Fe and also by thermal-neutron activation of impuritymanganese, to decay below levels at which it may cause errorin the54Mn assay. C
36、heck the samples for activity from crosscontamination by other monitors or material irradiated in thevicinity, and for any foreign substance adhering to the sample.Clean, if necessary, and reweigh. If direct-counting techniquesare used, disregard the remaining procedures to step 8.18.8.6 After irrad
37、iation, dissolve the sample in 10 mL ofconcentrated hydrochloric acid to which 2 drops of nitric acidhave been added. The solution may be heated gently to hastendissolution.8.7 After dissolution is complete, transfer the solution withwashing to a 25-mL volumetric flask. Wash only with concen-trated
38、hydrochloric acid and use this also in diluting to thecalibration mark on the volumetric flask.8.8 Prepare a slurry of anion exchange resin with distilled ordeionized water and pour it into the ion exchange columnapparatus (see Fig. 2) to a height of 100 mm. Place aglass-wool plug above the resin an
39、d keep the column underliquid at all times.8.9 Prepare the ion exchange column for use by passingconcentrated hydrochloric acid through until it completelydisplaces the water used to form the resin slurry.8.10 Transfer an aliquot of the sample solution by volumet-ric pipet to the empty funnel above
40、the column. This aliquotshould be of sufficient volume so that accurate counting datacan be obtained.8.11 Run the sample onto the column.8.12 Immediately pour a few millilitres from a premeasured50-mL volume of hydrochloric acid (1+3) into the funnel towash any remaining sample solution onto the col
41、umn.8.13 Place a 50-mL volumetric flask, to which 1 mL ofMnCl2carrier solution has been added, under the tip of thecolumn and open the column stopcock.8.14 Add the remaining hydrochloric acid (1+3) to thefunnel and adjust the stopcock to obtain a flow rate of about 1drop in 5 to 10 s. This will allo
42、w elution of a 50-mL volume inabout 2 h.8.15 Elute from the column until the solution reaches thecalibration mark on the volumetric flask.NOTE 3To prepare the ion exchange resin for further separations, runabout 50 mL of distilled or deionized water through the column. This willremove iron and cobal
43、t from the resin. Regenerate the column as before bypassing concentrated hydrochloric acid through until the acid completelydisplaces the water.5“Reagent Chemicals,American Chemical Society Specifications,”Am. Chemi-cal Soc., Washington, DC. For suggestions on the testing of reagents not listed byth
44、e American Chemical Society, see “Analar Standards for Laboratory Chemicals,”BDH Ltd., Poole, Dorset, U.K., and the “United States Pharmacopeia.”E263 133NOTE 4The54Mn recovery should be checked by passing a known54Mn spike solution and iron carrier through the column.8.16 Stopper the flask and inver
45、t several times to mix thecontents thoroughly.8.17 Remove an accurately measured aliquot from thevolumetric flask for radioassay.A1-mLsample is convenient ifthe counting is to be done with a well-type scintillationdetector. If assay is to be made using a solid crystal, the aliquotcan be deposited in
46、to a cup planchet and dried under a heatlamp.8.18 Analyze the samples for54Mn content in disintegra-tions per second using the gamma ray spectrometer (see TestMethods E181 and E1005).8.19 Disintegration of an54Mn nucleus produces onegamma ray with a probability per decay of 0.999746 (2).9. Calculati
47、on9.1 Calculate the saturation activity As, as follows:As5Aexptw#1 2 exp2ti#!(1)where:A =54Mn disintegrations per second measured by counting,s1, = decay constant for54Mn = 2.57025 108,s1,ti= irradiation duration, s, andtw= elapsed time between the end of irradiation andcounting, s.NOTE 5The equatio
48、n for Asis valid if the reactor is operated atconstant power and if corrections for other reactions (for example,impurities, burnout, etc.) are negligible. Refer to Practice E261 for moregeneralized treatments.9.2 Calculate the reaction rate, Rs, as follows:Rs5 As/No(2)where:As= saturation activity,
49、 andNo= number of54Fe atoms.9.3 Refer to Method E261 and Practice E944 for a discus-sion of fast-neutron fluence rate and fluence.10. Report10.1 Practice E261 describes how data should be reported.11. Precision and Bias11.1 General practice indicates that54Mn decay rate can bedetermined with a bias of 63%(1) and with a precision of61%(1). Measurement of54Mn activity produced from the54Fe(n,p)54Mn reaction in a235U thermal fission standardneutron field can be accomplished with an uncertainty of2.86 % (4), where the uncertainty component attribute
