1、Designation: E854 141Standard Test Method forApplication and Analysis of Solid State Track Recorder(SSTR) Monitors for Reactor Surveillance1This standard is issued under the fixed designation E854; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of 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.1NOTEThe title of this test method and the Referenced Documents were updated editorially in May 2017.1.
3、 Scope1.1 This test method describes the use of solid-state trackrecorders (SSTRs) for neutron dosimetry in light-water reactor(LWR) applications. These applications extend from lowneutron fluence to high neutron fluence, including high powerpressure vessel surveillance and test reactor irradiations
4、 as wellas low power benchmark field measurement. (1)2This testmethod replaces Method E418. This test method is moredetailed and special attention is given to the use of state-of-the-art manual and automated track counting methods to attainhigh absolute accuracies. In-situ dosimetry in actual highfl
5、uence-high temperature LWR applications is emphasized.1.2 This test method includes SSTR analysis by bothmanual and automated methods. To attain a desired accuracy,the track scanning method selected places limits on theallowable track density. Typically good results are obtained inthe range of 5 to
6、800 000 tracks/cm2and accurate results athigher track densities have been demonstrated for some cases.(2) Track density and other factors place limits on the appli-cability of the SSTR method at high fluences. Special caremust be exerted when measuring neutron fluences (E1MeV)above 1016n/cm2(3).1.3
7、Low fluence and high fluence limitations exist. Theselimitations are discussed in detail in Sections 13 and 14 and inRefs (3-5).1.4 SSTR observations provide time-integrated reactionrates. Therefore, SSTR are truly passive-fluence detectors.They provide permanent records of dosimetry experimentswith
8、out the need for time-dependent corrections, such as decayfactors that arise with radiometric monitors.1.5 Since SSTR provide a spatial record of the time-integrated reaction rate at a microscopic level, they can be usedfor “fine-structure” measurements. For example, spatial distri-butions of isotop
9、ic fission rates can be obtained at very highresolution with SSTR.1.6 This standard does not purport to address the safetyproblems associated with its use. It is the responsibility of theuser of this standard to establish appropriate safety and healthpractices and determine the applicability of regu
10、latory limita-tions prior to use.1.7 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade
11、Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3E418 Test Method for Fast-Neutron Flux Measurements byTrack-Etch Techniques (Withdrawn 1984)4E844 Guide for Sensor Set Design and Irradiation forReactor Surveillance3. Summary of Test Method3.1 SSTR ar
12、e usually placed in firm surface contact with afissionable nuclide that has been deposited on a pure nonfis-sionable metal substrate (backing). This typical SSTR geom-etry is depicted in Fig. 1. Neutron-induced fission produceslatent fission-fragment tracks in the SSTR. These tracks maybe developed
13、by chemical etching to a size that is observablewith an optical microscope. Microphotographs of etched fis-sion tracks in mica, quartz glass, and natural quartz crystals canbe seen in Fig. 2.3.1.1 While the conventional SSTR geometry depicted inFig. 1 is not mandatory, it does possess distinct advan
14、tages for1This test method is under the jurisdiction ofASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE10.05 on Nuclear Radiation Metrology.Current edition approved July 1, 2014. Published October 2014. Originallyapproved in 1981. Last previo
15、us edition approved in 2009 as E854 03(2009). DOI:10.1520/E0854-14E01.2The boldface numbers in parentheses refer to the list of references appended tothis test method.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual
16、Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United Sta
17、tesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Tr
18、ade (TBT) Committee.1dosimetry applications. In particular, it provides the highestefficiency and sensitivity while maintaining a fixed and easilyreproducible geometry.3.1.2 The track density (that is, the number of tracks per unitarea) is proportional to the fission density (that is, the numberof f
19、issions per unit area). The fission density is, in turn,proportional to the exposure fluence experienced by the SSTR.The existence of nonuniformity in the fission deposit or thepresence of neutron fluence rate gradients can produce non-uniform track density. Conversely, with fission deposits ofprove
20、n uniformity, gradients of the neutron field can beinvestigated with very high spatial resolution.3.2 The total uncertainty of SSTR fission rates is comprisedof two independent sources. These two error components arisefrom track counting uncertainties and fission-deposit massuncertainties. For work
21、at the highest accuracy levels, fission-deposit mass assay should be performed both before and afterthe SSTR irradiation. In this way, it can be ascertained that nosignificant removal of fission deposit material arose in thecourse of the experiment.4. Significance and Use4.1 The SSTR method provides
22、 for the measurement ofabsolute-fission density per unit mass. Absolute-neutron flu-ence can then be inferred from these SSTR-based absolutefission rate observations if an appropriate neutron spectrumaverage fission cross section is known. This method is highlydiscriminatory against other components
23、 of the in-core radia-tion field. Gamma rays, beta rays, and other lightly ionizingparticles do not produce observable tracks in appropriate LWRSSTR candidate materials. However, photofission can contrib-ute to the observed fission track density and should therefore beaccounted for when nonnegligibl
24、e. For a more detailed discus-sion of photofission effects, see 14.4.4.2 In this test method, SSTR are placed in surface contactwith fissionable deposits and record neutron-induced fissionfragments. By variation of the surface mass density (g/cm2)ofthe fissionable deposit as well as employing the al
25、lowablerange of track densities (from roughly 1 event/cm2up to 105events/cm2for manual scanning), a range of total fluencesensitivity covering at least 16 orders of magnitude is possible,from roughly 102n/cm2up to 5 1018n/cm2. The allowablerange of fission track densities is broader than the track d
26、ensityrange for high accuracy manual scanning work with opticalmicroscopy cited in 1.2. In particular, automated and semi-automated methods exist that broaden the customary trackdensity range available with manual optical microscopy. In thisbroader track density region, effects of reduced countingst
27、atistics at very low track densities and track pile-up correc-tions at very high track densities can present inherent limita-tions for work of high accuracy. Automated scanning tech-niques are described in Section 11.4.3 For dosimetry applications, different energy regions ofthe neutron spectrum can
28、 be selectively emphasized by chang-ing the nuclide used for the fission deposit.4.4 It is possible to use SSTR directly for neutron dosimetryas described in 4.1 or to obtain a composite neutron detectionefficiency by exposure in a benchmark neutron field. Thefluence and spectrum-averaged cross sect
29、ion in this benchmarkfield must be known. Furthermore, application in other neutronfields may require adjustments due to spectral deviation fromthe benchmark field spectrum used for calibration. In anyevent, it must be stressed that the SSTR-fission densitymeasurements can be carried out completely
30、independent ofany cross-section standards (6). Therefore, for certainapplications, the independent nature of this test method shouldnot be compromised. On the other hand, many practicalapplications exist wherein this factor is of no consequence sothat benchmark field calibration would be entirely ap
31、propriate.5. Apparatus5.1 Optical Microscopes, with a magnification of 200 orhigher, employing a graduated mechanical stage with positionreadout to the nearest 1 m and similar repositioning accuracy.A calibrated stage micrometer and eyepiece scanning grids arealso required.5.2 Constant-Temperature B
32、ath, for etching, with tempera-ture control to 0.1C.5.3 Analytical Weighing Balance, for preparation of etchingbath solutions, with a capacity of at least 1000 g and anaccuracy of at least 1 mg.6. Reagents and Materials6.1 Purity of ReagentsDistilled or demineralized waterand analytical grade reagen
33、ts should be used at all times. Forhigh fluence measurements, quartz-distilled water and ultra-pure reagents are necessary in order to reduce backgroundfission tracks from natural uranium and thorium impurities.This is particularly important if any pre-irradiation etching isperformed (see 8.2).6.2 R
34、eagents:6.2.1 Hydrofluoric Acid (HF), weight 49 %.6.2.2 Sodium Hydroxide Solution (NaOH), 6.2 N.6.2.3 Distilled or Demineralized Water.6.2.4 Potassium Hydroxide Solution (KOH), 6.2 N.6.2.5 Sodium Hydroxide Solution (NaOH), weight 65 %.6.3 Materials:FIG. 1 Typical Geometrical Configuration Used for S
35、STR NeutronDosimetryE854 14126.3.1 Glass Microscope Slides.6.3.2 Slide Cover Glasses.7. SSTR Materials for Reactor Applications7.1 Required PropertiesSSTR materials for reactor appli-cations should be transparent dielectrics with a relatively highionization threshold, so as to discriminate against l
36、ightlyionizing particles. The materials that meet these prerequisitesmost closely are the minerals mica, quartz glass, and quartzcrystals. Selected characteristics for these SSTR are summa-rized in Table 1. Other minerals such as apatite, sphene, andzircon are also suitable, but are not used due to
37、inferior etchingproperties compared to mica and quartz. These alternativeSSTR candidates often possess either higher imperfectiondensity or poorer contrast and clarity for scanning by opticalmicroscopy. Mica and particularly quartz can be found with theadditional advantageous property of low natural
38、 uranium andthorium content. These heavy elements are undesirable inneutron-dosimetry work, since such impurities lead to back-ground track densities when SSTR are exposed to high neutronfluence. In the case of older mineral samples, a background offossil fission track arises due mainly to the spont
39、aneous fissiondecay of238U. Glasses (and particularly phosphate glasses) areless suitable than mica and quartz due to higher uranium andthorium content. Also, the track-etching characteristics ofmany glasses are inferior, in that these glasses possess higherbulk etch rate and lower registration effi
40、ciency. Other SSTRmaterials, such as Lexan5and Makrofol6are also used, but areless convenient in many reactor applications due to thepresence of neutron-induced recoil tracks from elements suchas carbon and oxygen present in the SSTR. These detectors arealso more sensitive (in the form of increased
41、bulk etch rate) tothe and components of the reactor radiation field (13). Also,they are more sensitive to high temperatures, since the onset oftrack annealing occurs at a much lower temperature for plasticSSTR materials.7.2 Limitations of SSTR in LWR Environments:7.2.1 Thermal AnnealingHigh temperat
42、ures result in theerasure of tracks due to thermal annealing. Natural quartzcrystal is least affected by high temperatures, followed bymica. Lexan and Makrofol are subject to annealing at muchlower temperatures. An example of the use of natural quartzcrystal SSTRs for high-temperature neutron dosime
43、try mea-surements is the work described in Ref (14).5Lexan is a registered trademark of the General Electric Co., Pittsfield, MA.6Makrofol is a registered trademark of Farbenfabriken Bayer AG, U. S.representative Naftone, Inc., New York, NY.NOTE 1The track designated by the arrow in the mica SSTR is
44、 a fossil fission track that has been enlarged by suitable pre-irradiation etching.FIG. 2 Microphotograph of Fission Fragment Tracks in MicaE854 14137.2.2 Radiation DamageLexan and Makrofol are highlysensitive to other components of the radiation field. As men-tioned in 7.1, the bulk-etch rates of p
45、lastic SSTR are increasedby exposure to and radiation. Quartz has been observed tohave a higher bulk etch rate after irradiation with a fluence of41021neutrons/cm2, but both quartz and mica are veryinsensitive to radiation damage at lower fluences (1021neutrons/cm2).7.2.3 Background TracksPlastic tr
46、ack detectors will reg-ister recoil carbon and oxygen ions resulting from neutronscattering on carbon and oxygen atoms in the plastic. Thesefast neutron-induced recoils can produce a background of shorttracks. Quartz and mica will not register such light ions and arenot subject to such background tr
47、acks.7.2.4 Thermal Stability of Fissionable Material FoilsUranium foils habe been observed to completely convert tooxide during high temperature irradiation.8. SSTR Pre- and Post-Irradiation Processing8.1 Pre-Irradiation Annealing:8.1.1 In the case of mica SSTR, a pre-annealing proceduredesigned to
48、remove fossil track damage is advisable for workat low neutron fluences. The standard procedure is annealingfor6hat600C (longer time periods may result in dehydra-tion). Fossil track densities are so low in good Brazilian quartzcrystals that pre-annealing is not generally necessary. Anneal-ing is no
49、t advised for plastic SSTR because of the possibility ofthermal degradation of the polymer or altered composition,both of which could affect track registration properties of theplastic.8.2 Pre-Irradiation Etching:8.2.1 MicaUnannealed fossil tracks in mica are easilydistinguished from induced tracks by pre-etching for a timethat is long compared to the post-etching conditions. In thecase of mica, a 6-h etch in 48 % HF at room temperature resultsin large diamond-shaped tracks that are easily distinguishedfrom the much smaller induced tracks revealed by
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