1、Designation: E 910 07Standard Test Method forApplication and Analysis of Helium Accumulation FluenceMonitors for Reactor Vessel Surveillance, E706 (IIIC)1This standard is issued under the fixed designation E 910; the number immediately following the designation indicates the year oforiginal adoption
2、 or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes the concept and use ofhelium accumulation for ne
3、utron fluence dosimetry for reactorvessel surveillance. Although this test method is directedtoward applications in vessel surveillance, the concepts andtechniques are equally applicable to the general field of neutrondosimetry. The various applications of this test method forreactor vessel surveill
4、ance are as follows:1.1.1 Helium accumulation fluence monitor (HAFM) cap-sules,1.1.2 Unencapsulated, or cadmium or gadolinium covered,radiometric monitors (RM) and HAFM wires for heliumanalysis,1.1.3 Charpy test block samples for helium accumulation,and1.1.4 Reactor vessel (RV) wall samples for heli
5、um accumu-lation.1.2 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 and health practices and determine the applica-bility of regulatory limitations prior to us
6、e.2. Referenced Documents2.1 ASTM Standards:2C 859 Terminology Relating to Nuclear Materials3E 170 Terminology Relating to Radiation Measurementsand DosimetryE 244 Test Method for Atom Percent Fission in Uraniumand Plutonium Fuel (Mass Spectrometric Method) (Dis-continued 2001)3E 261 Practice for De
7、termining Neutron Fluence, FluenceRate, and Spectra by Radioactivation TechniquesE 482 Guide for Application of Neutron Transport Methodsfor Reactor Vessel Surveillance, E706 (IID)E 706 Master Matrix for Light-Water Reactor PressureVessel Surveillance Standards, E 706(0)E 844 Guide for Sensor Set De
8、sign and Irradiation forReactor Surveillance, E 706(IIC)E 853 Practice for Analysis and Interpretation of Light-Water Reactor Surveillance Results, E706(IA)E 854 Test Method for Application and Analysis of SolidState Track Recorder (SSTR) Monitors for Reactor Sur-veillance, E706(IIIB)E 900 Guide for
9、 Predicting Radiation-Induced TransitionTemperature Shift in Reactor Vessel Materials, E706 (IIF)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 Surveilla
10、nce, E706(IIIA)E 1018 Guide for Application of ASTM Evaluated CrossSection Data File, Matrix E 706 (IIB)3. Terminology3.1 DefinitionsFor definition of terms used in this testmethod, refer to Terminology C 859 and E 170. For terms notdefined therein, reference may be made to other publishedglossaries
11、.44. Summary of the HAFM Test Method4.1 Helium accumulation fluence monitors (HAFMs) arepassive neutron dosimeters that have a measured reactionproduct that is helium. The monitors are placed in the reactorlocations of interest, and the helium generated through (n,a)reactions accumulates and is reta
12、ined in the HAFM (or HAFMcapsule) until the time of removal, perhaps many years later.The helium is then measured very precisely by high-sensitivity1This test method is under the jurisdiction ofASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE
13、10.05 on Nuclear Radiation Metrology.Current edition approved June 1, 2007. Published July 2007. Originally approvedin 1982. Last previous edition approved in 2001 as E 910 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. Fo
14、r Annual Book of ASTMStandards volume information, refer to the standards Document Summary page ontheASTM website. The roman numeral-alphabetical designation at the end of someof the titles indicates that a brief description of this standard may be found in MatrixE 706.3Withdrawn.4See Dictionary of
15、Scientific Terms, 3rd Edition, Sybil P. Parker, Ed., McGrawHill, Inc.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.gas mass spectrometry (1, 2).5The neutron fluence is thendirectly obtained by dividing the measured helium concentra
16、-tion by the spectrum-averaged cross section. Competing he-lium producing reactions, such as (g,a) do not, exceptfor9Be(g,a), affect the HAFM results. The range of heliumconcentrations that can be accurately measured in irradiatedHAFMs extends from 1014to 101atom fraction. This rangepermits the HAFM
17、s to be tested in low fluence environmentsyet to work equally well for high fluence situations.4.2 Typically, HAFMs are either individual small solidsamples, such as wire segments (3) or miniature encapsulatedsamples of small crystals of powder (4), as shown in Fig. 1.Aswith radiometric dosimetry, d
18、ifferent materials are used toprovide different energy sensitivity ranges. Encapsulation isnecessary for those HAFM materials and reactor environmentcombinations where sample melting, sample contamination, orloss of generated helium could possibly occur. Additionally,encapsulation generally facilita
19、tes the handling and identifica-tion of the HAFM both prior to and following irradiation. Thecontents of HAFM capsules typically range from 0.1 to 10 mg.4.3 Following irradiation, encapsulated HAFMs are cleanedand identified in preparation for helium analysis. Heliumanalysis is then accomplished by
20、vaporizing both the capsuleand its contents and analyzing the helium in the resulting gasesin a high sensitivity mass spectrometer system (5). The amountof4He is determined by measuring the4He-to-3He isotopicratio in the sample gases subsequent to the addition of anaccurately calibrated amount of3He
21、 “spike.” UnencapsulatedHAFMs, for example, pure element wires, are usually etched toremove a predetermined layer of outer material before heliumanalysis (3). This eliminates corrections for both cross con-tamination between samples and a-recoil into or out of thesample during the irradiation.4.4 Th
22、e4He concentration in the HAFM, in general terms, isproportional to the incident neutron fluence. Considerationmust, however, be made for such factors as HAFM materialburnup, neutron self-shielding and flux depression, a-recoil,and neutron gradients. Corrections for these effects are dis-cussed more
23、 fully in Section 13. Generally, they total less than5 % of the measured helium concentration. Since the individualcorrections are usually known to within 50 %, the total errorfrom these corrections amounts to #2 %. Sources of uncer-tainty also lie in the HAFM material mass, isotopic composi-tion, a
24、nd mass spectrometric helium analysis. As indicated inSection 13, however, these uncertainties generally contributeless than 1 % of the total uncertainty for routine analyses.4.5 Applying the above corrections to the measured HAFMhelium concentration, the total incident neutron fluence (overthe ener
25、gy range of sensitivity of the HAFM) can be obtaineddirectly from a knowledge of the spectrum-integrated totalhelium production cross section for the particular irradiationenvironment.At the present time, the uncertainty in the derivedneutron fluence is mainly due to uncertainty in the spectrum-inte
26、grated cross section of the HAFM sensor material ratherthan the combined uncertainties in the helium determinationprocess. This situation is expected to improve as the crosssections are more accurately measured, integrally tested inbenchmark facilities (6), and reevaluated.5. Significance and Use5.1
27、 The HAFM test method is one of several availablepassive neutron dosimetry techniques (see, for example, Meth-ods E 854 and E 1005). This test method can be used incombination with other dosimetry methods, or, if sufficient dataare available from different HAFM sensor materials, as analternative dos
28、imetry test method. The HAFM method yields adirect measurement of total helium production in an irradiatedsample. Absolute neutron fluence can then be inferred fromthis, assuming the appropriate spectrum integrated total heliumproduction cross section. Alternatively, a calibration of thecomposite ne
29、utron detection efficiency for the HAFM methodmay be obtained by exposure in a benchmark neutron fieldwhere the fluence and spectrum averaged cross section are bothknown (see Matrix E 706 IIE).5.2 HAFMs have the advantage of producing an end prod-uct, helium, which is stable, making the HAFM method
30、veryattractive for both short-term and long-term fluence measure-ments without requiring time-dependent corrections for decay.HAFMs are therefore ideal passive, time-integrating fluencemonitors. Additionally, the burnout of the daughter product,helium, is negligible.5.2.1 Many of the HAFM materials
31、can be irradiated in theform of unencapsulated wire segments (see 1.1.2). Thesesegments can easily be fabricated by cutting from a standard5The boldface numbers in parentheses refer to the list of references appended tothis test method.FIG. 1 Helium Accumulation Fluence Monitor CapsuleE910072invento
32、ried material lot. The advantage is that encapsulation,with its associated costs, is not necessary. In several cases,unencapsulated wires such as Fe, Ni,Al/Co, and Cu, which arealready included in the standard radiometric (RM) dosimetrysets (Table 1) can be used for both radiometric and heliumaccumu
33、lation dosimetry. After radiometric counting, thesamples are later vaporized for helium measurement.5.3 The HAFM method is complementary to RM and solidstate track recorder (SSTR) foils, and has been used as anintegral part of the multiple foil method. The HAFM methodfollows essentially the same pri
34、nciple as the RM foil technique,which has been used successfully for accurate neutron dosim-etry for the past 20 to 25 years. Various HAFM sensormaterials exist which have significantly different neutronenergy sensitivities from each other. HAFMs containing10Band6Li have been used routinely in LMFBR
35、 applications inconjunction with RM foils. The resulting data are entirelycompatible with existing adjustment methods for radiometricfoil neutron dosimetry (refer to Method E 944).5.4 An application for the HAFM method lies in the directanalysis of pressure vessel wall scrapings or Charpy blocksurve
36、illance samples. Measurements of the helium productionin these materials can provide in situ integral information onthe neutron fluence spectrum. This application can providedosimetry information at critical positions where conventionaldosimeter placement is difficult if not impossible. Analysesmust
37、 first be conducted to determine the boron, lithium, andother component concentrations, and their homogeneities, sothat their possible contributions to the total helium productioncan be determined. Boron (and lithium) can be determined byconverting a fraction of the boron to helium with a knowntherm
38、al neutron exposure. Measurements of the helium in thematerial before and after the exposure will enable a determi-nation of the boron content (7). Boron level down to less than1 wt. ppm can be obtained in this manner.5.5 By careful selection of the appropriate HAFM sensormaterial and its mass, heli
39、um concentrations ranging from;1014to 101atom fraction can be generated and measured. Interms of fluence, this represents a range of roughly 1012to 1027n/cm2. Fluence (1 MeV) values that may be encounteredduring routine surveillance testing are expected to range from;3 3 1014to 2 3 1020n/cm2, which
40、is well within the rangeof the HAFM technique.5.6 The analysis of HAFMs requires an absolute determi-nation of the helium content. The analysis system specified inthis test method incorporates a specialized mass spectrometerin conjunction with an accurately calibrated helium spikingsystem. Helium de
41、termination is by isotope dilution withsubsequent isotope ratio measurement. The fact that the heliumis stable makes the monitors permanent with the heliumanalysis able to be conducted at a later time, often without theinconvenience in handling caused by induced radioactivity.Such systems for analys
42、is exist, and additional analysis facili-ties could be reproduced, should that be required. In thisrespect, therefore, the analytical requirements are similar toother ASTM test methods (compare with Test Method E 244).6. Apparatus6.1 High-Sensitivity Gas Mass Spectrometer System, ca-pable of vaporiz
43、ing both unencapsulated and encapsulatedHAFM materials and analyzing the resulting total heliumcontent is required. A description of a suitable system iscontained in Ref (5).6.2 Analytical Microbalance for Accurate Weighing ofHAFM Samples, minimum specifications: 200-mg capacitywith an absolute accu
44、racy of 60.5 g. Working standardmasses must be traceable to appropriate national or interna-tional mass standards. Additionally, a general purpose balancewith a capacity of at least 200 g and an accuracy of 0.1 mg isrequired for weighing larger specimens.6.3 Laminar flow (optional) clean benches, fo
45、r use in thepreparation of HAFM samples and capsules.6.4 Stereo microscope, with 7 to 30 magnification, a;0.1-mm graticule, and an optical illuminator.6.5 Electron beam welder, with moveable platform stage,for sealing HAFM capsules, minimum specifications: variableTABLE 1 Neutron Characteristics of
46、Candidate HAFM Materials for Reactor Vessel SurveillanceHAFM SensorMaterialPrincipal HeliumProducing ReactionThermal Neutron CrossSection, (b)Fission Neutron SpectrumCross Section,(mb)A90 %ResponseRange,(MeV)ALi6Li(n,a)T 942 457 0.1675.66Be9Be(n,a)6He;ra6Li . 284 2.57.3B10B(n,a)7Li 3838 494 0.0665.2
47、5N14N(n,a)11B . 86.2 1.75.7F19F(n,a)16N . 27.6 3.79.7AlB 27Al(n,a)24Na . 0.903 6.4711.9S32S(n,a)29Si . . .Cl35Cl(n,a)32P . ;13 (Cl) 2.68.3TiB 47Ti(n,a)44Ca . 0.634 (Ti) 6.512.8FeB 56Fe(n,a)53Cr . 0.395 (Fe) 5.211.9NiB 58Ni(n,a)55Fe . 5.58 (Ni) 3.910.1CuB 63Cu(n,a)60Co . 0.330 4.7411.13162SSPV SteelC
48、harpy BlockJHelium Production Largelyfrom56Fe and58NiAEvaluated235U fission neutron spectrum averaged helium production cross section and energy range in which 90 % of the reactions occur. All values are obtainedfrom ENDF/B-V Gas Production Dosimetry File data. Bracketed terms indicate cross section
49、 is for naturally occurring element.BOften included in dosimetry sets as a radiometric monitor, either as a pure element foil or wire or, in the case of aluminum, as an allaying material for other elements.E910073beam power to 0 to 1 kW, variable beam size capable offocusing down to a diameter of 0.5 mm. Controls must also beavailable to permit automatic control of beam duration andonset and offset beam power slopes.6.6 High temperature vacuum furnace for out-gassingHAFM materials, capsules, and mass spectrometer systemfurnace components. Minimum specifications: 1000
