ASTM E854-98
(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)
SCOPE
1.1 This test method describes the use of solid-state track recorders (SSTR) 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. This test method replaces Method E418. 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 environs 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 500 000 tracks/cm and accurate results at higher track densities have been demonstrated for some cases. 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 10 16 n/cm .
1.3 High fluence limitations exist. Successful results have been reported for total fluences up to approximately 10 16 n/cm . Beyond 10 16 n/cm some workers report problems (1), but others report no problems with total fluences up to approximately 5 X 10 18 n/cm (2).
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.
General Information
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Standards Content (Sample)
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Designation: E 854 – 98
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 E 854; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope practices and determine the applicability of regulatory limita-
tions prior to use.
1.1 This test method describes the use of solid-state track
recorders (SSTRs) for neutron dosimetry in light-water reactor
2. Referenced Documents
(LWR) applications. These applications extend from low
2.1 ASTM Standards:
neutron fluence to high neutron fluence, including high power
E 418 Method for Fast-Neutron Measurements by Track-
pressure vessel surveillance and test reactor irradiations as well
Etch Techniques
as low power benchmark field measurement. (1) This test
E 844 Guide for Sensor Set Design and Irradiation for
method replaces Method E 418. This test method is more
Reactor Surveillance, E706 (IIC)
detailed and special attention is given to the use of state-of-
the-art manual and automated track counting methods to attain
3. Summary of Test Method
high absolute accuracies. In-situ dosimetry in actual high
3.1 SSTR are usually placed in firm surface contact with a
fluence-high temperature LWR applications is emphasized.
fissionable nuclide that has been deposited on a pure nonfis-
1.2 This test method includes SSTR analysis by both
sionable metal substrate (backing). This typical SSTR geom-
manual and automated methods. To attain a desired accuracy,
etry is depicted in Fig. 1. Neutron-induced fission produces
the track scanning method selected places limits on the
latent fission-fragment tracks in the SSTR. These tracks may
allowable track density. Typically good results are obtained in
be developed by chemical etching to a size that is observable
the range of 5 to 800 000 tracks/cm and accurate results at
with an optical microscope. Microphotographs of etched fis-
higher track densities have been demonstrated for some cases.
sion tracks in mica, quartz glass, and natural quartz crystals can
(2) Track density and other factors place limits on the appli-
be seen in Fig. 2.
cability of the SSTR method at high fluences. Special care
3.1.1 While the conventional SSTR geometry depicted in
must be exerted when measuring neutron fluences (E>1MeV)
16 2 Fig. 1 is not mandatory, it does possess distinct advantages for
above 10 n/cm . (3)
dosimetry applications. In particular, it provides the highest
1.3 High fluence limitations exist. These limitations are
efficiency and sensitivity while maintaining a fixed and easily
discussed in detail in Section 13 and in references (3-5).
reproducible geometry.
1.4 SSTR observations provide time-integrated reaction
3.1.2 The track density (that is, the number of tracks per unit
rates. Therefore, SSTR are truly passive-fluence detectors.
area) is proportional to the fission density (that is, the number
They provide permanent records of dosimetry experiments
of fissions per unit area). The fission density is, in turn,
without the need for time-dependent corrections, such as decay
proportional to the exposure fluence experienced by the SSTR.
factors that arise with radiometric monitors.
The existence of nonuniformity in the fission deposit or the
1.5 Since SSTR provide a spatial record of the time-
presence of neutron flux gradients can produce non-uniform
integrated reaction rate at a microscopic level, they can be used
track density. Conversely, with fission deposits of proven
for “fine-structure” measurements. For example, spatial distri-
uniformity, gradients of the neutron field can be investigated
butions of isotopic fission rates can be obtained at very high
with very high spatial resolution.
resolution with SSTR.
3.2 The total uncertainty of SSTR fission rates is comprised
1.6 This standard does not purport to address the safety
of two independent sources. These two error components arise
problems associated with its use. It is the responsibility of the
from track counting uncertainties and fission-deposit mass
user of this standard to establish appropriate safety and health
uncertainties. For work at the highest accuracy levels, fission-
deposit mass assay should be performed both before and after
the SSTR irradiation. In this way, it can be ascertained that no
This test method is under the jurisdiction of ASTM Committee E-10 on Nuclear
significant removal of fission deposit material arose in the
Technology and Applicationsand is the direct responsibility of Subcommittee
E10.05on Nuclear Radiation Metrology.
Current edition approved Jan. 10, 1998. Published May 1998. Originally
Discontinued; see 1983 Annual Book of ASTM Standards, Vol 12.02.
published as E 854 – 81. Last previous edition E 854 – 90. Annual Book of ASTM Standards, Vol 12.02.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 854
the benchmark field spectrum used for calibration. In any
event, it must be stressed that the SSTR-fission density
measurements can be carried out completely independent of
any cross-section standards (6). Therefore, for certain applica-
tions, 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 bench-
mark field calibration would be entirely appropriate.
5. Apparatus
5.1 Optical Microscopes, with a magnification of 200 3 or
higher, employing a graduated mechanical stage with position
readout to the nearest 1 μm and similar repositioning accuracy.
A calibrated stage micrometer and eyepiece scanning grids are
FIG. 1 Typical Geometrical Configuration Used for SSTR Neutron
also required.
Dosimetry
5.2 Constant-Temperature Baths, for etching, with tempera-
ture control to 0.1°C.
course of the experiment.
5.3 Analytical Weighing Balance, for preparation of etching
bath solutions, with a capacity of at least 1000 g and an
4. Significance and Use
accuracy of at least 1 mg.
4.1 The SSTR method provides for the measurement of
6. Reagents and Materials
absolute-fission density per unit mass. Absolute-neutron flu-
ence can then be inferred from these SSTR-based absolute
6.1 Purity of Reagents—Distilled or demineralized water
fission rate observations if an appropriate neutron spectrum and analytical grade reagents should be used at all times. For
average fission cross section is known. This method is highly
high fluence measurements, quartz-distilled water and ultra-
discriminatory against other components of the in-core radia- pure reagents are necessary in order to reduce background
tion field. Gamma rays, beta rays, and other lightly ionizing
fission tracks from natural uranium and thorium impurities.
particles do not produce observable tracks in appropriate LWR This is particularly important if any pre-irradiation etching is
SSTR candidate materials. However, photofission can contrib-
performed (see 8.2).
ute to the observed fission track density and should therefore be
6.2 Reagents:
accounted for when nonnegligible. For a more detailed discus-
6.2.1 Hydrofluoric Acid (HF), weight 49 %.
sion of photofission effects, see 13.4.
6.2.2 Sodium Hydroxide Solution (NaOH), 6.2 N.
4.2 In this test method, SSTR are placed in surface contact
6.2.3 Distilled or Demineralized Water.
with fissionable deposits and record neutron-induced fission
6.2.4 Potassium Hydroxide Solution (KOH), 6.2 N.
fragments. By variation of the surface mass density (μg/cm )of
6.2.5 Sodium Hydroxide Solution (NaOH), weight 65 %.
the fissionable deposit as well as employing the allowable
6.3 Materials:
2 5
range of track densities (from roughly 1 event/cm up to 10 6.3.1 Glass Microscope Slides.
events/cm for manual scanning), a range of total fluence
6.3.2 Slide Cover Glasses.
sensitivity covering at least 16 orders of magnitude is possible,
2 2 18 2
7. SSTR Materials for Reactor Applications
from roughly 10 n/cm up to 5 3 10 n/cm . The allowable
range of fission track densities is broader than the track density 7.1 Required Properties—SSTR materials for reactor appli-
range for high accuracy manual scanning work with optical cations should be transparent dielectrics with a relatively high
microscopy cited in 1.2. In particular, automated and semi- ionization threshold, so as to discriminate against lightly
automated methods exist that broaden the customary track ionizing particles. The materials that meet these prerequisites
density range available with manual optical microscopy. In this most closely are the minerals mica, quartz glass, and quartz
broader track density region, effects of reduced counting crystals. Selected characteristics for these SSTR are summa-
statistics at very low track densities and track pile-up correc- rized in Table 1. Other minerals such as apatite, sphene, and
tions at very high track densities can present inherent limita- zircon are also suitable, but are not used due to inferior etching
tions for work of high accuracy. Automated scanning tech- properties compared to mica and quartz. These alternative
niques are described in Section 11. SSTR candidates often possess either higher imperfection
4.3 For dosimetry applications, different energy regions of
density or poorer contrast and clarity for scanning by optical
the neutron spectrum can be selectively emphasized by chang- microscopy. Mica and particularly quartz can be found with the
ing the nuclide used for the fission deposit. additional advantageous property of low natural uranium and
4.4 It is possible to use SSTR directly for neutron dosimetry thorium content. These heavy elements are undesirable in
as described in 4.1 or to obtain a composite neutron detection neutron-dosimetry work, since such impurities lead to back-
efficiency by exposure in a benchmark neutron field. The ground track densities when SSTR are exposed to high neutron
fluence and spectrum-averaged cross section in this benchmark fluence. In the case of older mineral samples, a background of
field must be known. Furthermore, application in other neutron fossil fission track arises due mainly to the spontaneous fission
fields may require adjustments due to spectral deviation from decay of U. Glasses (and particularly phosphate glasses) are
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 854
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
less suitable than mica and quartz due to higher uranium and crystal SSTRs for high-temperature neutron dosimetry mea-
thorium content. Also, the track-etching characteristics of surements is the work described in reference (14).
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-
4 5
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 b and g radiation. Quartz has been observed to
presence of neutron-induced recoil tracks from elements such
have a higher bulk etch rate after irradiation with a fluence of
as carbon and oxygen present in the SSTR. These detectors are 21 2
4 3 10 neutrons/cm , but both quartz and mica are very
also more sensitive (in the form of increased bulk etch rate) to
insensitive to radiation damage at lower fluences (<10
the b and g components of the reactor radiation field (13).
neutrons/cm ).
Also, they are more sensitive to high temperatures, since the
7.2.3 Background Tracks—Plastic track detectors will reg-
onset of track annealing occurs at a much lower temperature
ister recoil carbon and oxygen ions resulting from neutron
for plastic SSTR materials.
scattering on carbon and oxygen atoms in the plastic. These
7.2 Limitations of SSTR in LWR Environments:
fast neutron-induced recoils can produce a background of short
7.2.1 Thermal Annealing—High temperatures result in the
tracks. Quartz and mica will not register such light ions and are
erasure of tracks due to thermal annealing. Natural quartz
not subject to such background tracks.
crystal is least affected by high temperatures, followed by
mica. Lexan and Makrofol are subject to annealing at much
8. SSTR Pre- and Post-Irradiation Processing
lower temperatures. An example of the use of natural quartz
8.1 Pre-Irradiation Annealing:
8.1.1 In the case of mica SSTR, a pre-annealing procedure
Lexan is a registered trademark of the General Electric Co., Pittsfield, MA.
5 designed to remove fossil track damage is advisable for work
Makrofol is a registered trademark of Farbenfabriken Bayer AG, U. S.
representative Naftone, Inc., New York, NY. at low neutron fluences. The standard procedure is annealing
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 854
FIG. 2 Quartz Glass (continued)
FIG. 2 Quartz Crystal (001 Plane) (continued)
tion a few etch pits may be present even in good-quality quartz
for6hat 600°C (longer time periods may result in dehydra- glass. If so, they will be larger than tracks due to fission
tion). Fossil track densities are so low in good Brazilian quartz fragments revealed in the post-etch, and readily distinguished
crystals that pre-annealing is not generally necessary. Anneal- from them.
ing is not advised for plastic SSTR because of the possibility of 8.2.4 Plastic-Track Recorders—If handled properly, back-
thermal degradation of the polymer or altered composition, ground from natural sources, such as radon, will be negligible.
both of which could effect track registration properties of the Consequently, both preannealing and pre-etching should be
plastic. unnecessary.
8.2 Pre-Irradiation Etching: 8.3 Post-Irradiation Etching:
8.2.1 Mica—Unannealed fossil tracks in mica are easily 8.3.1 Mica—Customary
...
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