1、Designation: E 854 03 (Reapproved 2009)Standard Test Method forApplication and Analysis of Solid State Track Recorder(SSTR) Monitors for Reactor Surveillance, E706(IIIB)1This standard is issued under the fixed designation E 854; the number immediately following the designation indicates the year ofo
2、riginal adoption or, in the case 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.1. Scope1.1 This test method describes the use of solid-state trackrecor
3、ders (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 as wellas low power benchmark field measurement. (1)2This testmethod
4、replaces Method E 418. 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 highfluence-high temperature LWR applications is emphasized.1.2 This test m
5、ethod 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 800 000 tracks/cm2and accurate results athigher track densities have
6、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 High fluence limitations exist. These limitations arediscussed in de
7、tail in Section 13 and in references (3-5).1.4 SSTR observations provide time-integrated reactionrates. Therefore, SSTR are truly passive-fluence detectors.They provide permanent records of dosimetry experimentswithout the need for time-dependent corrections, such as decayfactors that arise with rad
8、iometric 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 isotopic fission rates can be obtained at very highresolution with SSTR.1.6 This standard d
9、oes 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 regulatory limita-tions prior to use.2. Referenced Documents2.1 ASTM Standards:3E 418 Met
10、hod for Fast-Neutron Flux Measurements byTrack-Etch Techniques4E 844 Guide for Sensor Set Design and Irradiation forReactor Surveillance, E 706(IIC)3. Summary of Test Method3.1 SSTR are usually placed in firm surface contact with afissionable nuclide that has been deposited on a pure nonfis-sionable
11、 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 by chemical etching to a size that is observablewith an optical microscope. Microphotographs of etched fis-sion trac
12、ks 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 advantages fordosimetry applications. In particular, it provides the highestefficiency and sensitivity while maintaining
13、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 fissions per unit area). The fission density is, in turn,proportional to the exposure fluence experienced by the SSTR.The existen
14、ce of nonuniformity in the fission deposit or thepresence of neutron flux gradients can produce non-uniformtrack density. Conversely, with fission deposits of provenuniformity, gradients of the neutron field can be investigatedwith very high spatial resolution.3.2 The total uncertainty of SSTR fissi
15、on rates is comprisedof two independent sources. These two error components arise1This 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 June
16、1, 2009. Published June 2009. Originallyapproved in 1981. Last previous edition approved in 2003 as E 854 03.2The 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
17、Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Withdrawn. The last approved version of this historical standard is referencedon www.astm.org1Copyright ASTM International, 100 Barr Harbor Drive, PO Box
18、C700, West Conshohocken, PA 19428-2959, United States.from track counting uncertainties and fission-deposit massuncertainties. For work 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 no
19、significant removal of fission deposit material arose in thecourse of the experiment.4. Significance and Use4.1 The SSTR method provides for the measurement ofabsolute-fission density per unit mass. Absolute-neutron flu-ence can then be inferred from these SSTR-based absolutefission rate observation
20、s if an appropriate neutron spectrumaverage fission cross section is known. This method is highlydiscriminatory against other components of the in-core radia-tion field. Gamma rays, beta rays, and other lightly ionizingparticles do not produce observable tracks in appropriate LWRSSTR candidate mater
21、ials. However, photofission can contrib-ute to the observed fission track density and should therefore beaccounted for when nonnegligible. For a more detailed discus-sion of photofission effects, see 13.4.4.2 In this test method, SSTR are placed in surface contactwith fissionable deposits and record
22、 neutron-induced fissionfragments. By variation of the surface mass density (g/cm2)ofthe fissionable deposit as well as employing the allowablerange of track densities (from roughly 1 event/cm2up to 105events/cm2for manual scanning), a range of total fluencesensitivity covering at least 16 orders of
23、 magnitude is possible,from roughly 102n/cm2up to 5 3 1018n/cm2. The allowablerange of fission track densities is broader than the track densityrange for high accuracy manual scanning work with opticalmicroscopy cited in 1.2. In particular, automated and semi-automated methods exist that broaden the
24、 customary trackdensity range available with manual optical microscopy. In thisbroader track density region, effects of reduced countingstatistics 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. Auto
25、mated scanning tech-niques are described in Section 11.4.3 For dosimetry applications, different energy regions ofthe neutron spectrum can 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
26、or to obtain a composite neutron detectionefficiency by exposure in a benchmark neutron field. Thefluence and spectrum-averaged cross section in this benchmarkfield must be known. Furthermore, application in other neutronfields may require adjustments due to spectral deviation fromthe benchmark fiel
27、d spectrum used for calibration. In anyevent, it must be stressed that the SSTR-fission densitymeasurements can be carried out completely independent ofany cross-section standards (6). Therefore, for certain applica-tions, the independent nature of this test method should not becompromised. On the o
28、ther hand, many practical applicationsexist wherein this factor is of no consequence so that bench-mark field calibration would be entirely appropriate.5. Apparatus5.1 Optical Microscopes, with a magnification of 200 3 orhigher, employing a graduated mechanical stage with positionreadout to the near
29、est 1 m and similar repositioning accuracy.A calibrated stage micrometer and eyepiece scanning grids arealso required.5.2 Constant-Temperature Bath, 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 1
30、000 g and anaccuracy of at least 1 mg.6. Reagents and Materials6.1 Purity of ReagentsDistilled or demineralized waterand analytical grade reagents should be used at all times. Forhigh fluence measurements, quartz-distilled water and ultra-pure reagents are necessary in order to reduce backgroundfiss
31、ion tracks from natural uranium and thorium impurities.This is particularly important if any pre-irradiation etching isperformed (see 8.2).6.2 Reagents: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 Hydro
32、xide Solution (KOH), 6.2 N.6.2.5 Sodium Hydroxide Solution (NaOH), weight 65 %.6.3 Materials:6.3.1 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 rela
33、tively highionization threshold, so as to discriminate against lightlyionizing 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 apatit
34、e, sphene, andzircon are also suitable, but are not used due to 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
35、be found with theadditional advantageous property of low natural uranium andthorium content. These heavy elements are undesirable inFIG. 1 Typical Geometrical Configuration Used for SSTR NeutronDosimetryE 854 03 (2009)2neutron-dosimetry work, since such impurities lead to back-ground track densities
36、 when SSTR are exposed to high neutronfluence. In the case of older mineral samples, a background offossil fission track arises due mainly to the spontaneous fissiondecay of238U. Glasses (and particularly phosphate glasses)are less suitable than mica and quartz due to higher uraniumand thorium conte
37、nt. Also, the track-etching characteristics ofmany glasses are inferior, in that these glasses possess higherbulk etch rate and lower registration efficiency. Other SSTRmaterials, such as Lexan5and Makrofol6are also used, but areless convenient in many reactor applications due to thepresence of neut
38、ron-induced recoil tracks from elements suchas carbon and oxygen present in the SSTR. These detectors arealso more sensitive (in the form of increased bulk etch rate) tothe b and g components of the reactor radiation field (13).Also, they are more sensitive to high temperatures, since theonset of tr
39、ack annealing occurs at a much lower temperaturefor plastic SSTR materials.7.2 Limitations of SSTR in LWR Environments:7.2.1 Thermal AnnealingHigh temperatures result in theerasure of tracks due to thermal annealing. Natural quartzcrystal is least affected by high temperatures, followed bymica. Lexa
40、n and Makrofol are subject to annealing at muchlower temperatures. An example of the use of natural quartzcrystal SSTRs for high-temperature neutron dosimetry mea-surements is the work described in reference (14).7.2.2 Radiation DamageLexan and Makrofol are highlysensitive to other components of the
41、 radiation field. As men-tioned in 7.1, the bulk-etch rates of plastic SSTR are increasedby exposure to b and g radiation. Quartz has been observed tohave a higher bulk etch rate after irradiation with a fluence of4 3 1021neutrons/cm2, but both quartz and mica are veryinsensitive to radiation damage
42、 at lower fluences (1021neutrons/cm2).7.2.3 Background TracksPlastic track 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 wil
43、l not register such light ions and arenot subject to such background tracks.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 a
44、rrow in the mica SSTR is a fossil fission track that has been enlarged by suitable preirradiation etching.FIG. 2 Microphotograph of Fission Fragment Tracks in MicaE 854 03 (2009)38. SSTR Pre- and Post-Irradiation Processing8.1 Pre-Irradiation Annealing:8.1.1 In the case of mica SSTR, a pre-annealing
45、 proceduredesigned to 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 neces
46、sary. Anneal-ing is not advised for plastic SSTR because of the possibility ofthermal degradation of the polymer or altered composition,both of which could effect track registration properties of theplastic.8.2 Pre-Irradiation Etching:8.2.1 MicaUnannealed fossil tracks in mica are easilydistinguishe
47、d 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 a 90-minpost-etch (se
48、e Fig. 2).8.2.2 Quartz CrystalsPre-etching is needed to chemicallypolish the surface. Polish a crystal mechanically on the 001 or100 plane so that it appears smooth under microscopicalexamination, etch for 10 min in 49 % HF at room temperature,then boil in 65 % NaOH solution for 25 min. Examine thec
49、rystal surface microscopically. If it is sufficiently free of pits,select it for use as an SSTR.8.2.3 Quartz GlassIf the glass has been polished me-chanically, or has a smooth surface, then pre-etch in 49 % HFfor 5 min at room temperature. Upon microscopical examina-tion a few etch pits may be present even in good-quality quartzglass. If so, they will be larger than tracks due to fissionfragments revealed in the post-etch, and readily distinguishedfrom them.8.2.4 Plastic-Track RecordersIf handled properly, back-ground from natural sources, such as radon, will be neg
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