1、Designation: E 263 09Standard Test Method forMeasuring Fast-Neutron Reaction Rates by Radioactivationof Iron1This standard is issued under the fixed designation E 263; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las
2、t 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 fo
3、r 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 PracticeE 261).1.3 With suitable techniques, fission-neu
4、tron fluence ratesabove 108cm2s1can be determined. However, in the pres-ence of a high thermal-neutron fluence rate (for example, 2 31014cm2s1)54Mn depletion should be investigated.1.4 Detailed procedures describing the use of other fast-neutron detectors are referenced in Practice E 261.1.5 This st
5、andard 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 and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1
6、 ASTM Standards:2D 1193 Specification for Reagent WaterE 170 Terminology Relating to Radiation Measurementsand DosimetryE 181 Test Methods for Detector Calibration and Analysisof RadionuclidesE 261 Practice for Determining Neutron Fluence, FluenceRate, and Spectra by Radioactivation TechniquesE 844
7、Guide 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 forApplication andAnalysis of Radio-metric Monitors for Reactor Vessel Surveillance, E706(IIIA)E 1
8、018 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 for definitions of termsrelating to radiation measurements and neutron dosimetry.4. Summary of Test Method4.1 High-purity iron is irradiated in a neutr
9、on 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 E 181. Thereaction rate, as defined by Practice E 261, is calculated fromthe decay rate and irradiation condition
10、s.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 neutron fluence rate above about 2.2 MeV can thenbe calculated from the spectral-weighted neutron activationcross se
11、ction as defined by Practice E 261.5. Significance and Use5.1 Refer to Guide E 844 for guidance on the selection,irradiation, and quality control of neutron dosimeters.5.2 Refer to Practice E 261 for a general discussion of thedetermination of fast-neutron fluence rate with threshold de-tectors.5.3
12、Pure iron in the form of foil or wire is readily availableand easily handled.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 the1This test method is under the jurisdiction
13、 ofASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE10.05 on Nuclear Radiation Metrology.Current edition approved June 1, 2009. Published June 2009. Originallyapproved in 1965 as E 263 65 T. Last previous edition approved in 2005 asE 263 05.2F
14、or 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 Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to the list of refer
15、ences located at theend of this test method.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.range of response of the54Fe(n,p)54Mn reaction. Refer toGuide E 1018 for descriptions of recommended tabulateddosimetry cross sections.5.554M
16、n has a half-life of 312.13 days (3)4(2) and emits agamma ray with an energy of 834.845 keV (5). (2)55.6 Interfering activities generated by neutron activationarising from thermal or fast neutron interactions are 2.57878(46)-h56Mn, 44.95-d (8)59Fe, and 5.2710-y (8)60Co (2,3).(Consult Ref (2) for mor
17、e precise values currently accepted forthe half-lives.) Interference from56Mn can be eliminated bywaiting 48 h before counting. Although chemical separationof54Mn from the irradiated iron is the most effective methodfor eliminating59Fe and60Co, direct counting of iron for54Mnis possible using high-r
18、esolution detector systems or unfoldingor stripping techniques, especially if the dosimeter was coveredwith cadmium or boron during irradiation.Altering the isotopiccomposition of the iron dosimeter is another useful techniquefor eliminating interference from extraneous activities whendirect sample
19、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 from irondosimeters at high temperature. Encapsula
20、ting 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 activity.When one elects to count the irondosimeters
21、directly, those portions of Sections 6, 7 and 8 thatpertain 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, and9-12.6. Apparatus (Note 1)6.1 HighResolution Ga
22、mma-Ray Spectrometer, because ofits high resolution, the germanium detector is useful whencontaminant activities are present. See Test Methods E 181 andE 1005.6.2 Precision Balance, able to achieve the required accu-racy.6.3 Digital Computer, useful for data analysis (optional).6.4 Chemical Separati
23、on 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 (Note 1)7.1 Purity of ReagentsReagent-grade ch
24、emicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.6Other grades may beused, provided it is first ascertai
25、ned that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the activity determination.4The un-bolded number in parenthesis after the unit indicates the uncertainty inthe least significant digits. For example, 1.89 keV (2) would indicate a value of 1.89keV 6
26、 0.02 keV.5Ref (2) gives a value of 834.8348 keV (5) as the most precise value currentlyaccepted for the54Mn decay gamma-ray energy.6“Reagent Chemicals,American Chemical Society Specifications,”Am. Chemi-cal Soc., Washington, DC. For suggestions on the testing of reagents not listed bythe American C
27、hemical Society, see “Analar Standards for Laboratory Chemicals,”BDH Ltd., Poole, Dorset, U.K., and the “United States Pharmacopeia.”FIG. 154Fe(n,p)54Mn Cross SectionFIG. 2 Ion-Exchange Separation ApparatusE2630927.2 Purity of Water Unless otherwise indicated, refer-ences to water shall be understoo
28、d to mean reagent-grade waterconforming to Specification D 1193.7.3 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 (1 + 3)Mix 1 volume of concen
29、-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 as primaryencapsulating mate
30、rials. 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 E 844.)7.10 The purity of the iron is important in that no impuritiesshould be present whi
31、ch 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 byemission spectroscopy or by activ
32、ation 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 beproduced to permit accurate radio
33、assay. 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 manipulationsdescribed below function best with a
34、n 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 iron let onto the resin should
35、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 A waiting period of 2 days i
36、s 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 impurity man-ganese, to decay below levels at which it may cause error in the54Mn assay. Check the samples for acti
37、vity from cross con-tamination 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 irradiation, dissolve the sa
38、mple 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 hydrochloric acid and u
39、se 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 and keep the column under
40、liquid 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 the column. This aliquo
41、tshould 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 column.8.13 Place a 50-mL
42、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 allow elution of a 50-mL vo
43、lume 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 cobalt from the resin. Regen
44、erate the column as before bypassing concentrated hydrochloric acid through until the acid completelydisplaces the water.NOTE 4The54Mn recovery should be checked by passing a known54Mn spike solution and iron carrier through the column.8.16 Stopper the flask and invert several times to mix theconten
45、ts 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 into a cup planchet and dried unde
46、r a heatlamp.8.18 Analyze the samples for54Mn content in disintegra-tions per second using the gamma ray spectrometer (see TestMethods E 181 and E 1005).E2630938.19 Disintegration of an54Mn nucleus produces onegamma ray with a probability per decay of 0.9998 (2)7.9. Calculation9.1 Calculate the satu
47、ration activity As, as follows:As5A exp ltw#1 2 exp 2lti#!(1)where:A =54Mn disintegrations per second measured by count-ing, s1,l = decay constant for54Mn = 2.570 3 108,s1,ti= irradiation duration, s, andtw= elapsed time between the end of irradiation andcounting, s.NOTE 5The equation for Asis valid
48、 if the reactor is operated atconstant power and if corrections for other reactions (for example,impurities, burnout, etc.) are negligible. Refer to Practice E 261 for moregeneralized treatments.9.2 Calculate the reaction rate, Rs, as follows:Rs5 As/No(2)where:As= saturation activity, andNo= number
49、of54Fe atoms.9.3 Refer to Method E 261 and Practice E 944 for a discus-sion of fast-neutron fluence rate and fluence.10. Report10.1 Practice E 261 describes how data should be reported.11. Precision and Bias11.1 General practice indicates that54Mn decay rate can bedetermined with a bias of 63%(1s) and with a precision of61%(1s). 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 attributed toknowledge of the
