ASTM E854-03(2009)
(Test Method)Standard Test Method for Application and Analysis of Solid State Track Recorder (SSTR) Monitors for Reactor Surveillance, E706(IIIB)
Standard Test Method for Application and Analysis of Solid State Track Recorder (SSTR) Monitors for Reactor Surveillance, E706(IIIB)
SIGNIFICANCE AND USE
The SSTR method provides for the measurement of absolute-fission density per unit mass. Absolute-neutron fluence can then be inferred from these SSTR-based absolute fission rate observations if an appropriate neutron spectrum average fission cross section is known. This method is highly discriminatory against other components of the in-core radiation field. Gamma rays, beta rays, and other lightly ionizing particles do not produce observable tracks in appropriate LWR SSTR candidate materials. However, photofission can contribute to the observed fission track density and should therefore be accounted for when nonnegligible. For a more detailed discussion of photofission effects, see 13.4.
In this test method, SSTR are placed in surface contact with fissionable deposits and record neutron-induced fission fragments. By variation of the surface mass density (μg/cm2) of the fissionable deposit as well as employing the allowable range of track densities (from roughly 1 event/cm2 up to 105 events/cm2 for manual scanning), a range of total fluence sensitivity covering at least 16 orders of magnitude is possible, from roughly 102 n/cm 2 up to 5 × 1018 n/cm2. The allowable range of fission track densities is broader than the track density range for high accuracy manual scanning work with optical microscopy cited in 1.2. In particular, automated and semi-automated methods exist that broaden the customary track density range available with manual optical microscopy. In this broader track density region, effects of reduced counting statistics at very low track densities and track pile-up corrections at very high track densities can present inherent limitations for work of high accuracy. Automated scanning techniques are described in Section 11.
For dosimetry applications, different energy regions of the neutron spectrum can be selectively emphasized by changing the nuclide used for the fission deposit.
It is possible to use SSTR directly for neutron dosimetry as described ...
SCOPE
1.1 This test method describes the use of solid-state track recorders (SSTRs) for neutron dosimetry in light-water reactor (LWR) applications. These applications extend from low neutron fluence to high neutron fluence, including high power pressure vessel surveillance and test reactor irradiations as well as low power benchmark field measurement. (1) This test method replaces Method E 418. This test method is more detailed and special attention is given to the use of state-of-the-art manual and automated track counting methods to attain high absolute accuracies. In-situ dosimetry in actual high fluence-high temperature LWR applications is emphasized.
1.2 This test method includes SSTR analysis by both manual and automated methods. To attain a desired accuracy, the track scanning method selected places limits on the allowable track density. Typically good results are obtained in the range of 5 to 800 000 tracks/cm2 and accurate results at higher track densities have been demonstrated for some cases. (2) Track density and other factors place limits on the applicability of the SSTR method at high fluences. Special care must be exerted when measuring neutron fluences (E>1MeV) above 1016 n/cm2. (3)
1.3 High fluence limitations exist. These limitations are discussed in detail in Section 13 and in references (3-5).
1.4 SSTR observations provide time-integrated reaction rates. Therefore, SSTR are truly passive-fluence detectors. They provide permanent records of dosimetry experiments without the need for time-dependent corrections, such as decay factors 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 used for “fine-structure” measurements. For example, spatial distributions of isotopic fission rates can be obtained at very high resolution with SSTR.
1.6 This standard does not purport to address the safety problems as...
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Designation:E854 −03(Reapproved 2009)
Standard Test Method for
Application and Analysis of Solid State Track Recorder
(SSTR) Monitors for Reactor Surveillance, E706(IIIB)
This standard is issued under the fixed designation E854; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope butions of isotopic fission rates can be obtained at very high
resolution with SSTR.
1.1 This test method describes the use of solid-state track
1.6 This standard does not purport to address the safety
recorders (SSTRs) for neutron dosimetry in light-water reactor
problems associated with its use. It is the responsibility of the
(LWR) applications. These applications extend from low
user of this standard to establish appropriate safety and health
neutron fluence to high neutron fluence, including high power
practices and determine the applicability of regulatory limita-
pressurevesselsurveillanceandtestreactorirradiationsaswell
tions prior to use.
as low power benchmark field measurement. (1) This test
method replaces Method E418. This test method is more
2. Referenced Documents
detailed and special attention is given to the use of state-of-
2.1 ASTM Standards:
the-art manual and automated track counting methods to attain
high absolute accuracies. In-situ dosimetry in actual high E418Test Method for Fast-Neutron Flux Measurements by
Track-Etch Techniques (Withdrawn 1984)
fluence-high temperature LWR applications is emphasized.
E844Guide for Sensor Set Design and Irradiation for
1.2 This test method includes SSTR analysis by both
Reactor Surveillance, E 706 (IIC)
manual and automated methods. To attain a desired accuracy,
the track scanning method selected places limits on the
3. Summary of Test Method
allowable track density. Typically good results are obtained in
2 3.1 SSTR are usually placed in firm surface contact with a
the range of 5 to 800 000 tracks/cm and accurate results at
fissionable nuclide that has been deposited on a pure nonfis-
higher track densities have been demonstrated for some cases.
sionable metal substrate (backing). This typical SSTR geom-
(2) Track density and other factors place limits on the appli-
etry is depicted in Fig. 1. Neutron-induced fission produces
cability of the SSTR method at high fluences. Special care
latent fission-fragment tracks in the SSTR. These tracks may
must be exerted when measuring neutron fluences (E>1MeV)
16 2 be developed by chemical etching to a size that is observable
above 10 n/cm . (3)
with an optical microscope. Microphotographs of etched fis-
1.3 High fluence limitations exist. These limitations are
siontracksinmica,quartzglass,andnaturalquartzcrystalscan
discussed in detail in Section 13 and in references (3-5).
be seen in Fig. 2.
3.1.1 While the conventional SSTR geometry depicted in
1.4 SSTR observations provide time-integrated reaction
Fig. 1 is not mandatory, it does possess distinct advantages for
rates. Therefore, SSTR are truly passive-fluence detectors.
dosimetry applications. In particular, it provides the highest
They provide permanent records of dosimetry experiments
efficiency and sensitivity while maintaining a fixed and easily
withouttheneedfortime-dependentcorrections,suchasdecay
reproducible geometry.
factors that arise with radiometric monitors.
3.1.2 Thetrackdensity(thatis,thenumberoftracksperunit
1.5 Since SSTR provide a spatial record of the time-
area) is proportional to the fission density (that is, the number
integratedreactionrateatamicroscopiclevel,theycanbeused
of fissions per unit area). The fission density is, in turn,
for “fine-structure” measurements. For example, spatial distri-
proportionaltotheexposurefluenceexperiencedbytheSSTR.
The existence of nonuniformity in the fission deposit or the
presence of neutron flux gradients can produce non-uniform
ThistestmethodisunderthejurisdictionofASTMCommitteeE10onNuclear
Technology and Applicationsand is the direct responsibility of Subcommittee
E10.05 on Nuclear Radiation Metrology. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved June 1, 2009. Published June 2009. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1981. Last previous edition approved in 2003 as E854–03. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E0854-03R09. the ASTM website.
2 4
The boldface numbers in parentheses refer to the list of references appended to The last approved version of this historical standard is referenced on
this test method. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E854−03 (2009)
tions for work of high accuracy. Automated scanning tech-
niques are described in Section 11.
4.3 For dosimetry applications, different energy regions of
the neutron spectrum can be selectively emphasized by chang-
ing the nuclide used for the fission deposit.
4.4 ItispossibletouseSSTRdirectlyforneutrondosimetry
as described in 4.1 or to obtain a composite neutron detection
efficiency by exposure in a benchmark neutron field. The
fluenceandspectrum-averagedcrosssectioninthisbenchmark
fieldmustbeknown.Furthermore,applicationinotherneutron
fields may require adjustments due to spectral deviation from
the benchmark field spectrum used for calibration. In any
event, it must be stressed that the SSTR-fission density
FIG. 1 Typical Geometrical Configuration Used for SSTR Neutron
measurements can be carried out completely independent of
Dosimetry
any cross-section standards (6). Therefore, for certain
applications, the independent nature of this test method should
not be compromised. On the other hand, many practical
track density. Conversely, with fission deposits of proven
applications exist wherein this factor is of no consequence so
uniformity, gradients of the neutron field can be investigated
that benchmark field calibration would be entirely appropriate.
with very high spatial resolution.
3.2 The total uncertainty of SSTR fission rates is comprised
5. Apparatus
of two independent sources.These two error components arise
5.1 Optical Microscopes, with a magnification of 200×or
from track counting uncertainties and fission-deposit mass
higher, employing a graduated mechanical stage with position
uncertainties. For work at the highest accuracy levels, fission-
readout to the nearest 1 µm and similar repositioning accuracy.
deposit mass assay should be performed both before and after
Acalibrated stage micrometer and eyepiece scanning grids are
the SSTR irradiation. In this way, it can be ascertained that no
also required.
significant removal of fission deposit material arose in the
course of the experiment. 5.2 Constant-Temperature Bath, for etching, with tempera-
ture control to 0.1°C.
4. Significance and Use
5.3 Analytical Weighing Balance, for preparation of etching
4.1 The SSTR method provides for the measurement of
bath solutions, with a capacity of at least 1000 g and an
absolute-fission density per unit mass. Absolute-neutron flu-
accuracy of at least 1 mg.
ence can then be inferred from these SSTR-based absolute
fission rate observations if an appropriate neutron spectrum 6. Reagents and Materials
average fission cross section is known. This method is highly
6.1 Purity of Reagents—Distilled or demineralized water
discriminatory against other components of the in-core radia-
and analytical grade reagents should be used at all times. For
tion field. Gamma rays, beta rays, and other lightly ionizing
high fluence measurements, quartz-distilled water and ultra-
particles do not produce observable tracks in appropriate LWR
pure reagents are necessary in order to reduce background
SSTR candidate materials. However, photofission can contrib-
fission tracks from natural uranium and thorium impurities.
utetotheobservedfissiontrackdensityandshouldthereforebe
This is particularly important if any pre-irradiation etching is
accounted for when nonnegligible. For a more detailed discus-
performed (see 8.2).
sion of photofission effects, see 13.4.
6.2 Reagents:
4.2 In this test method, SSTR are placed in surface contact
6.2.1 Hydrofluoric Acid (HF), weight 49%.
with fissionable deposits and record neutron-induced fission
6.2.2 Sodium Hydroxide Solution (NaOH), 6.2 N.
fragments.Byvariationofthesurfacemassdensity(µg/cm )of
6.2.3 Distilled or Demineralized Water.
the fissionable deposit as well as employing the allowable
6.2.4 Potassium Hydroxide Solution (KOH), 6.2 N.
2 5
range of track densities (from roughly 1 event/cm up to 10
6.2.5 Sodium Hydroxide Solution (NaOH), weight 65%.
events/cm for manual scanning), a range of total fluence
6.3 Materials:
sensitivitycoveringatleast16ordersofmagnitudeispossible,
2 2 18 2
6.3.1 Glass Microscope Slides.
from roughly 10 n/cm up to 5×10 n/cm . The allowable
6.3.2 Slide Cover Glasses.
rangeoffissiontrackdensitiesisbroaderthanthetrackdensity
range for high accuracy manual scanning work with optical
7. SSTR Materials for Reactor Applications
microscopy cited in 1.2. In particular, automated and semi-
automated methods exist that broaden the customary track 7.1 Required Properties—SSTR materials for reactor appli-
densityrangeavailablewithmanualopticalmicroscopy.Inthis cations should be transparent dielectrics with a relatively high
broader track density region, effects of reduced counting ionization threshold, so as to discriminate against lightly
statistics at very low track densities and track pile-up correc- ionizing particles. The materials that meet these prerequisites
tions at very high track densities can present inherent limita- most closely are the minerals mica, quartz glass, and quartz
E854−03 (2009)
NOTE 1—The track designated by the arrow 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 Mica
crystals. Selected characteristics for these SSTR are summa- presence of neutron-induced recoil tracks from elements such
rized in Table 1. Other minerals such as apatite, sphene, and ascarbonandoxygenpresentintheSSTR.Thesedetectorsare
zirconarealsosuitable,butarenotusedduetoinferioretching
also more sensitive (in the form of increased bulk etch rate) to
properties compared to mica and quartz. These alternative the β and γ components of the reactor radiation field (13).
SSTR candidates often possess either higher imperfection
Also, they are more sensitive to high temperatures, since the
density or poorer contrast and clarity for scanning by optical onset of track annealing occurs at a much lower temperature
microscopy.Micaandparticularlyquartzcanbefoundwiththe
for plastic SSTR materials.
additional advantageous property of low natural uranium and
7.2 Limitations of SSTR in LWR Environments:
thorium content. These heavy elements are undesirable in
7.2.1 Thermal Annealing—High temperatures result in the
neutron-dosimetry work, since such impurities lead to back-
erasure of tracks due to thermal annealing. Natural quartz
groundtrackdensitieswhenSSTRareexposedtohighneutron
crystal is least affected by high temperatures, followed by
fluence. In the case of older mineral samples, a background of
mica. Lexan and Makrofol are subject to annealing at much
fossil fission track arises due mainly to the spontaneous fission
lower temperatures. An example of the use of natural quartz
decay of U. Glasses (and particularly phosphate glasses)
crystal SSTRs for high-temperature neutron dosimetry mea-
are less suitable than mica and quartz due to higher uranium
surements is the work described in reference (14).
and thorium content. Also, the track-etching characteristics of
many glasses are inferior, in that these glasses possess higher 7.2.2 Radiation Damage—Lexan and Makrofol are highly
bulk etch rate and lower registration efficiency. Other SSTR
sensitive to other components of the radiation field. As men-
5 6
materials, such as Lexan and Makrofol are also used, but are tioned in 7.1, the bulk-etch rates of plastic SSTR are increased
less convenient in many reactor applications due to the
by exposure to β and γ radiation. Quartz has been observed to
have a higher bulk etch rate after irradiation with a fluence of
21 2
4×10 neutrons/cm , but both quartz and mica are very
Lexan is a registered trademark of the General Electric Co., Pittsfield, MA.
6 insensitive to radiation damage at lower fluences (<10
Makrofol is a registered trademark of Farbenfabriken Bayer AG, U. S.
representative Naftone, Inc., New York, NY. neutrons/cm ).
E854−03 (2009)
FIG. 2 Quartz Glass (continued)
FIG. 2 Quartz Crystal (001 Plane) (continued)
7.2.3 Background Tracks—Plastic track detectors will reg-
from the much smaller induced tracks revealed by a 90-min
ister recoil carbon and oxygen ions resulting from neutron post-etch (see Fig. 2)).
scattering on carbon and oxygen atoms in the plastic. These
8.2.2 Quartz Crystals—Pre-etching is needed to chemically
fastneutron-inducedrecoilscanproduceabackgroundofshort polish the surface. Polish a crystal mechanically on the 001 or
tracks.Quartzandmicawillnotregistersuchlightionsandare
100 plane so that it appears smooth under microscopical
not subject to such background tracks.
examination, etch for 10 min in 49% HF at room temperature,
then boil in 65% NaOH solution for 25 min. Examine the
8. SSTR Pre- and Post-Irradiation Processing
crystal surface microscopically. If it is sufficiently free of pits,
8.1 Pre-Irradiation Annealing:
select it for use as an SSTR.
8.1.1 In the case of mica SSTR, a pre-annealing procedure 8.2.3 Quartz Glass—If the glass has been polished
designed to remove fossil track damage is advisable for work mechanically, or has a smooth surface, then pre-etch in 49%
at low neutron fluences. The standard procedure is annealing HF for 5 min at room temperature. Upon microscopical
for6hat 600°C (longer time periods may result in dehydra- examination a few etch pits may be present even in good-
tion). Fossil track densities are so low in good Brazilian quartz qualityquartzglass.Ifso,theywillbelargerthantracksdueto
crystals that pre-annealing is not generally necessary. Anneal- fission fragments revealed in the post-etch, and readily distin-
ingisnotadvisedforplasticSSTRbecauseofthepossibilityof guished from them.
thermal degradation of the polymer or altered composition, 8.2.4 Plastic-Track Recorders—If handled properl
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:E854–98 Designation: E 854 – 03 (Reapproved 2009)
Standard Test Method for
Application and Analysis of Solid State Track Recorder
(SSTR) Monitors for Reactor Surveillance, E706(IIIB)
This standard is issued under the fixed designation E854; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 Thistestmethoddescribestheuseofsolid-statetrackrecorders(SSTRs)forneutrondosimetryinlight-waterreactor(LWR)
applications. These applications extend from low neutron fluence to high neutron fluence, including high power pressure vessel
surveillance and test reactor irradiations as well as low power benchmark field measurement. (1) This test method replaces
MethodE418.Thistestmethodismoredetailedandspecialattentionisgiventotheuseofstate-of-the-artmanualandautomated
track counting methods to attain high absolute accuracies. In-situ dosimetry in actual high fluence-high temperature LWR
applications is emphasized.
1.2 This test method includes SSTR analysis by both manual and automated methods. To attain a desired accuracy, the track
scanning method selected places limits on the allowable track density. Typically good results are obtained in the range of 5 to
800 000 tracks/cm and accurate results at higher track densities have been demonstrated for some cases. (2) Track density and
other factors place limits on the applicability of the SSTR method at high fluences. Special care must be exerted when measuring
16 2
neutron fluences (E>1MeV) above 10 n/cm . (3)
1.3 High fluence limitations exist. These limitations are discussed in detail in Section 13 and in references (3-5).
1.4 SSTR observations provide time-integrated reaction rates. Therefore, SSTR are truly passive-fluence detectors. They
provide permanent records of dosimetry experiments without the need for time-dependent corrections, such as decay factors 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 used for
“fine-structure” measurements. For example, spatial distributions of isotopic fission rates can be obtained at very high resolution
with SSTR.
1.6 This standard does not purport to address the safety problems associated with its use. It is the responsibility of the user of
this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior
to use.
2. Referenced Documents
2.1 ASTM Standards:
E418 Method for Fast-Neutron Flux Measurements by Track-Etch Techniques
E844 Guide for Sensor Set Design and Irradiation for Reactor Surveillance, E 706(IIC)
3. Summary of Test Method
3.1 SSTR are usually placed in firm surface contact with a fissionable nuclide that has been deposited on a pure nonfissionable
metal substrate (backing). This typical SSTR geometry is depicted in Fig. 1. Neutron-induced fission produces latent
fission-fragmenttracksintheSSTR.Thesetracksmaybedevelopedbychemicaletchingtoasizethatisobservablewithanoptical
microscope. Microphotographs of etched fission tracks in mica, quartz glass, and natural quartz crystals can be seen in Fig. 2.
3.1.1 While the conventional SSTR geometry depicted in Fig. 1 is not mandatory, it does possess distinct advantages for
ThistestmethodisunderthejurisdictionofASTMCommitteeE-10E10onNuclearTechnologyandApplicationsandisthedirectresponsibilityofSubcommitteeE10.05
on Nuclear Radiation Metrology.
Current edition approved Jan. 10, 1998. Published May 1998. Originally published as E854–81. Last previous edition E854–90.
Current edition approved June 1, 2009. Published June 2009. Originally approved in 1981. Last previous edition approved in 2003 as E854–03.
Discontinued; see 1983 Annual Book of ASTM Standards, Vol 12.02.
The boldface numbers in parentheses refer to the list of references appended to this test method.
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.For Annual Book of ASTM Standards
, Vol 12.02.volume information, refer to the standard’s Document Summary page on the ASTM website.
Lexan is a registered trademark of the General Electric Co., Pittsfield, MA.
Withdrawn. The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 854 – 03 (2009)
FIG. 1 Typical Geometrical Configuration Used for SSTR Neutron
Dosimetry
NOTE 1—The track designated by the arrow 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 Mica
dosimetry applications. In particular, it provides the highest efficiency and sensitivity while maintaining a fixed and easily
reproducible geometry.
3.1.2 The track density (that is, the number of tracks per unit area) is proportional to the fission density (that is, the number of
fissionsperunitarea).Thefissiondensityis,inturn,proportionaltotheexposurefluenceexperiencedbytheSSTR.Theexistence
ofnonuniformityinthefissiondepositorthepresenceofneutronfluxgradientscanproducenon-uniformtrackdensity.Conversely,
with fission deposits of proven uniformity, gradients of the neutron field can be investigated with very high spatial resolution.
3.2 ThetotaluncertaintyofSSTRfissionratesiscomprisedoftwoindependentsources.Thesetwoerrorcomponentsarisefrom
track counting uncertainties and fission-deposit mass uncertainties. For work at the highest accuracy levels, fission-deposit mass
E 854 – 03 (2009)
FIG. 2 Quartz Glass (continued)
assayshouldbeperformedbothbeforeandaftertheSSTRirradiation.Inthisway,itcanbeascertainedthatnosignificantremoval
of fission deposit material arose in the course of the experiment.
4. Significance and Use
4.1 The SSTR method provides for the measurement of absolute-fission density per unit mass. Absolute-neutron fluence can
thenbeinferredfromtheseSSTR-basedabsolutefissionrateobservationsifanappropriateneutronspectrumaveragefissioncross
section is known.This method is highly discriminatory against other components of the in-core radiation field. Gamma rays, beta
rays,andotherlightlyionizingparticlesdonotproduceobservabletracksinappropriateLWRSSTRcandidatematerials.However,
photofission can contribute to the observed fission track density and should therefore be accounted for when nonnegligible. For
a more detailed discussion of photofission effects, see 13.4.
4.2 In this test method, SSTR are placed in surface contact with fissionable deposits and record neutron-induced fission
fragments. By variation of the surface mass density (µg/cm ) of the fissionable deposit as well as employing the allowable range
2 5 2
of track densities (from roughly 1 event/cm up to 10 events/cm for manual scanning), a range of total fluence sensitivity
2 2 18 2
coveringatleast16ordersofmagnitudeispossible,fromroughly10 n/cm upto5 310 n/cm .Theallowablerangeoffission
track densities is broader than the track density range for high accuracy manual scanning work with optical microscopy cited in
1.2. In particular, automated and semi-automated methods exist that broaden the customary track density range available with
manual optical microscopy. In this broader track density region, effects of reduced counting statistics at very low track densities
and track pile-up corrections at very high track densities can present inherent limitations for work of high accuracy. Automated
scanning techniques are described in Section 11.
4.3 Fordosimetryapplications,differentenergyregionsoftheneutronspectrumcanbeselectivelyemphasizedbychangingthe
nuclide used for the fission deposit.
4.4 It is possible to use SSTR directly for neutron dosimetry as described in 4.1 or to obtain a composite neutron detection
efficiencybyexposureinabenchmarkneutronfield.Thefluenceandspectrum-averagedcrosssectioninthisbenchmarkfieldmust
be known. Furthermore, application in other neutron fields may require adjustments due to spectral deviation from the benchmark
field spectrum used for calibration. In any event, it must be stressed that the SSTR-fission density measurements can be carried
E 854 – 03 (2009)
FIG. 2 Quartz Crystal (001 Plane) (continued)
out completely independent of any cross-section standards (6). Therefore, for certain applications, the independent nature of this
test method should not be compromised. On the other hand, many practical applications exist wherein this factor is of no
consequence so that benchmark field calibration would be entirely appropriate.
5. Apparatus
5.1 Optical Microscopes, with a magnification of 200 3or higher, employing a graduated mechanical stage with position
readouttothenearest1µmandsimilarrepositioningaccuracy.Acalibratedstagemicrometerandeyepiecescanninggridsarealso
required.
5.2 Constant-Temperature BathsConstant-Temperature Bath, for etching, with temperature control to 0.1°C.
5.3 Analytical Weighing Balance , for preparation of etching bath solutions, with a capacity of at least 1000 g and an accuracy
of at least 1 mg.
6. Reagents and Materials
6.1 Purity of Reagents—Distilled or demineralized water and analytical grade reagents should be used at all times. For high
fluence measurements, quartz-distilled water and ultra-pure reagents are necessary in order to reduce background fission tracks
from natural uranium and thorium impurities. This is particularly important if any pre-irradiation etching is performed (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 Hydroxide 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.
E 854 – 03 (2009)
7. SSTR Materials for Reactor Applications
7.1 Required Properties—SSTR materials for reactor applications should be transparent dielectrics with a relatively high
ionizationthreshold,soastodiscriminateagainstlightlyionizingparticles.Thematerialsthatmeettheseprerequisitesmostclosely
are the minerals mica, quartz glass, and quartz crystals. Selected characteristics for these SSTR are summarized in Table 1. Other
minerals such as apatite, sphene, and zircon are also suitable, but are not used due to inferior etching properties compared to mica
and quartz. These alternative SSTR candidates often possess either higher imperfection density or poorer contrast and clarity for
scanning by optical microscopy. Mica and particularly quartz can be found with the additional advantageous property of low
naturaluraniumandthoriumcontent.Theseheavyelementsareundesirableinneutron-dosimetrywork,sincesuchimpuritieslead
tobackgroundtrackdensitieswhenSSTRareexposedtohighneutronfluence.Inthecaseofoldermineralsamples,abackground
offossilfissiontrackarisesduemainlytothespontaneousfissiondecayof U.Glasses(andparticularlyphosphateglasses)are
less suitable than mica and quartz due to higher uranium and thorium content. Also, the track-etching characteristics of many
glassesareinferior,inthattheseglassespossesshigherbulketchrateandlowerregistrationefficiency.OtherSSTRmaterials,such
5 6
as Lexanand Makrofol and Makrofol are also used, but are less convenient in many reactor applications due to the presence of
neutron-induced recoil tracks from elements such as carbon and oxygen present in the SSTR. These detectors are also more
sensitive(intheformofincreasedbulketchrate)tothe band gcomponentsofthereactorradiationfield (13).Also,theyaremore
sensitive to high temperatures, since the onset of track annealing occurs at a much lower temperature for plastic SSTR materials.
7.2 Limitations of SSTR in LWR Environments:
7.2.1 Thermal Annealing—High temperatures result in the erasure of tracks due to thermal annealing. Natural quartz crystal is
least affected by high temperatures, followed by mica. Lexan and Makrofol are subject to annealing at much lower temperatures.
AnexampleoftheuseofnaturalquartzcrystalSSTRsforhigh-temperatureneutrondosimetrymeasurementsistheworkdescribed
in reference (14) .
7.2.2 Radiation Damage—Lexan and Makrofol are highly sensitive to other components of the radiation field. As mentioned
in 7.1, the bulk-etch rates of plastic SSTR are increased by exposure to b and g radiation. Quartz has been observed to have a
21 2
higher bulk etch rate after irradiation with a fluence of 4 310 neutrons/cm , but both quartz and mica are very insensitive to
21 2
radiation damage at lower fluences (<10 neutrons/cm ).
7.2.3 Background Tracks—Plastic track detectors will register recoil carbon and oxygen ions resulting from neutron scattering
on carbon and oxygen atoms in the plastic. These fast neutron-induced recoils can produce a background of short tracks. Quartz
and mica will not register such light ions and are not subject to such background tracks.
8. SSTR Pre- and Post-Irradiation Processing
8.1 Pre-Irradiation Annealing:
8.1.1 InthecaseofmicaSSTR,apre-annealingproceduredesignedtoremovefossiltrackdamageisadvisableforworkatlow
neutronfluences.Thestandardprocedureisannealingfor6hat600°C(longertimeperiodsmayresultindehydration).Fossiltrack
densities are so low in good Brazilian quartz crystals that pre-annealing is not generally necessary. Annealing is not advised for
plastic SSTR because of the possibility of thermal degradation of the polymer or altered composition, both of which could effect
track registration properties of the plastic.
Makrofol is a registered trademark of Farbenfabriken Bayer AG, U. S. representative Naftone, Inc., New York, NY.
Lexan is a registered trademark of the General Electric Co., Pittsfield, MA.
Measurement uncertainty is described in terms of precision and bias in this standard.Another acceptable approach is to use TypeAand B uncertainty components (40,
41).ThisTypeA/B uncertainty specification is now used in International Organization for Standardization (ISO) standards, and this approach can be expected to play a more
prominent role in future uncertainty analyses.
Makrofol is a registered tradema
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