ASTM E2059-20

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2059 − 20
Standard Practice for
Application and Analysis of Nuclear Research Emulsions for
Fast Neutron Dosimetry
This standard is issued under the fixed designation E2059; 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 ropy of the in-situ neutron field (4, 5, 7). It is not possible for
active detectors to provide such data because of in-situ
1.1 Nuclear Research Emulsions (NRE) have a long and
perturbations and finite-size effects (see Section 11).
illustrioushistoryofapplicationsinthephysicalsciences,earth
sciences and biological sciences (1, 2) . In the physical
1.4 The existence of hydrogen as a major constituent of
sciences, NRE experiments have led to many fundamental NRE affords neutron detection through neutron scattering on
discoveries in such diverse disciplines as nuclear physics,
hydrogen, that is, the well known (n,p) reaction. NRE mea-
cosmic ray physics and high energy physics. In the applied surements in low power reactor environments have been
physical sciences, NRE have been used in neutron physics
predominantly based on this (n,p) reaction. NRE have also
6 4 10 7
experiments in both fission and fusion reactor environments been used to measure the Li (n,t) He and the B(n,α) Li
6 10
(3-6). Numerous NRE neutron experiments can be found in
reactions by including Li and B in glass specks near the
otherapplieddisciplines,suchasnuclearengineering,environ- mid-plane of the NRE (8, 9). Use of these two reactions does
mental monitoring and health physics. Given the breadth of
not provide the general advantages of the (n,p) reaction for
NRE applications, there exist many textbooks and handbooks neutron dosimetry in low power reactor environments (see
that provide considerable detail on the techniques used in the
Section4).Asaconsequence,thisstandardwillberestrictedto
NRE method (1-4, 6). As a consequence, this practice will be theuseofthe(n,p)reactionforneutrondosimetryinlowpower
restricted to the application of the NRE method for neutron
reactor environments.
measurements in reactor physics and nuclear engineering with
1.5 Limitations—The NRE method possesses four major
particular emphasis on neutron dosimetry in benchmark fields
limitations for applicability in low power reactor environ-
(see Matrix E706).
ments.
1.2 NRE are passive detectors and provide time integrated
1.5.1 Gamma-Ray Sensitivity—Gamma-rays create a sig-
reaction rates. As a consequence, NRE provide fluence mea-
nificantlimitationforNREmeasurements.Aboveagamma-ray
surements without the need for time-dependent corrections,
exposure of approximately 0.025 Gy, NRE can become fogged
such as arise with radiometric (RM) dosimeters (see Test
by gamma-ray induced electron events. At this level of
Method E1005). NRE provide permanent records, so that
gamma-ray exposure, neutron induced proton-recoil tracks can
optical microscopy observations can be carried out any time
no longer be accurately measured. As a consequence, NRE
after exposure. If necessary, NRE measurements can be re-
experiments are limited to low power environments such as
peated at any time to examine questionable data or to obtain
found in critical assemblies and benchmark fields. Moreover,
refined results.
applications are only possible in environments where the
buildup of radioactivity, for example, fission products, is
1.3 Since NRE measurements are conducted with optical
limited.
microscopes, high spatial resolution is afforded for fine struc-
1.5.2 Low Energy Limit—In the measurement of track
ture experiments. The attribute of high spatial resolution can
length for proton recoil events, track length decreases as
also be used to determine information on the angular anisot-
proton-recoil energy decreases. Proton-recoil track length be-
low approximately 3µm in NRE cannot be adequately mea-
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear
sured with optical microscopy techniques. As proton-recoil
Technology and Applications, and is the direct responsibility of Subcommittee
track length decreases below approximately 3 µm, it becomes
E10.05 on Nuclear Radiation Metrology.
Current edition approved July 1, 2020. Published August 2020. Originally
very difficult to measure track length accurately. This 3-µm
ɛ1
approved in 2000. Last previous edition approved in 2015 as E2059-15 . DOI:
track length limit corresponds to a low energy limit of
10.1520/E2059-20.
2 applicability in the range of approximately 0.3 to 0.4 MeV for
The boldface numbers in parentheses refer to the list of references at the end of
the text. neutron induced proton-recoil measurements in NRE.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2059 − 20
1.5.3 High-Energy Limits—As a consequence of finite-size E854Test Method for Application and Analysis of Solid
limitations, fast-neutron spectrometry measurements are lim- State Track Recorder (SSTR) Monitors for Reactor Sur-
ited to ≤15 MeV. The limit for in-situ spectrometry in reactor veillance
environments is ≤8MeV. E910Test Method for Application and Analysis of Helium
1.5.4 Track Density Limit—The ability to measure proton Accumulation Fluence Monitors for Reactor Vessel Sur-
recoiltracklengthwithopticalmicroscopytechniquesdepends veillance
on track density. Above a certain track density, a maze or E944Guide for Application of Neutron Spectrum Adjust-
labyrinth of overlapping tracks is created, which precludes the ment Methods in Reactor Surveillance
use of optical microscopy techniques. For manual scanning, E1005Test Method for Application and Analysis of Radio-
4 2
this limitation arises above approximately 10 tracks/cm , metric Monitors for Reactor Vessel Surveillance
whereas interactive computer-based scanning systems can
5 2
extend this limit up to approximately 10 tracks/cm . These 3. Alternate Modes of NRE Neutron Measurements
6 7 −2
limits correspond to neutron fluences of 10 −10 cm ,
3.1 Neutron Spectrum Measurements—The neutron energy
respectively.
range of interest in reactors environments covers approxi-
1.6 Neutron Spectrometry (Differential Measurements)—For
mately nine orders of magnitude, extending from thermal
differential neutron spectrometry measurements in low-power
energies up to approximately 20 MeV. No single high-
reactor environments, NRE experiments can be conducted in
resolution method of neutron spectrometry exists that can
two different modes. In the more general mode, NRE are
completely cover this energy range of interest (12). Work with
irradiated in-situ in the low power reactor environment. This
proton-recoil proportional counters has not been extended
mode of NRE experiments is called the 4π mode, since the
beyondafewMeV,duetotheescapeofmoreenergeticprotons
in-situ irradiation creates tracks in all directions (see 3.1.1). In
from the finite sensitive volume of the counter. In fact,
special circumstances, where the direction of the neutron flux
correction of in-situ proportional counters for such finite-size
is known, NRE are oriented parallel to the direction of the
effects can be non-negligible above 0.5 MeV (13). Finite-size
neutron flux. In this orientation, one edge of the NRE faces the
effects are much more manageable in NRE because of the
incident neutron flux, so that this measurement mode is called
reduced range of recoil protons. As a consequence, NRE fast
the end-on mode. Scanning of proton-recoil tracks is different
neutron spectrometry has been applied at energies up to 15
for these two different modes. Subsequent data analysis is also
MeV (3). For in-situ spectrometry in reactor environments,
different for these two modes (see 3.1.1 and 3.1.2).
NREmeasurementsupto8.0MeVarepossiblewithverysmall
finite-size corrections (14-16).
1.7 Neutron Dosimetry (Integral Measurements)—NREalso
3.1.1 4π Mode—It has been shown (3-6) that a neutron
afford integral neutron dosimetry through use of the (n,p)
fluence-spectrumcanbededucedfromtheintegralrelationship
reaction in low power reactor environments. Two different
types of (n,p) integral mode dosimetry reactions are possible,
` σ E Φ E
~ ! ~ !
np
M~E! 5 n V dE (1)
*
p
namely the I-integral (see 3.2.1) and the J-integral (see 3.2.2)
E
E
(10, 11). Proton-recoil track scanning for these integral reac-
where:
tions is conducted in a different mode than scanning for
Φ(E) = neutron fluence in n/(cm –MeV),
differential neutron spectrometry (see 3.2). Integral mode data
σ (E) = neutron-proton scattering cross section (cm)at
analysis is also different than the analysis required for differ- np
neutron energy, E,
ential neutron spectrometry (see 3.2). This practice will em-
E = neutron or proton energy (MeV),
phasize NRE (n,p) integral neutron dosimetry, because of the
n = atomic hydrogen density in the NRE (atoms/cm ),
p
utility and advantages of integral mode measurements in low
V = volume of NRE scanned (cm ), and
power benchmark fields.
M (E) = proton spectrum (protons/MeV) observed in the
1.8 This international standard was developed in accor-
NRE volume V at energy E.
dance with internationally recognized principles on standard-
The neutron fluence can be derived from Eq 1 and takes the
ization established in the Decision on Principles for the
form:
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical 2E dM
Φ~E! 5 (2)
Barriers to Trade (TBT) Committee.
σ ~E!n V dE
np p
Eq 2 reveals that the neutron fluence spectrum at energy E
2. Referenced Documents
depends upon the slope of the proton spectrum at energy E.As
2.1 ASTM Standards:
a consequence, approximately 10 tracks must be measured to
E706MasterMatrixforLight-WaterReactorPressureVessel
give statistical accuracies of the order of 10% in the neutron
Surveillance Standards
fluence spectrum (with a corresponding energy resolution of
the order of 10%). It must be emphasized that spectral
measurements determined with NRE in the 4π mode are
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
absolute.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
3.1.2 End-On Mode—Differential neutron spectrometry
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. with NRE is considerably simplified when the direction of
E2059 − 20
neutron incidence is known, such as for irradiations in colli- 3.2.1 The I Integral Relation—The first integral relationship
mated or unidirectional neutron beams. In such exposures, the follows directly from Eq 1.The integral in Eq 1 can be defined
kinematicsof(n,p)scatteringcanbeusedtodetermineneutron as:
energy. Observation of proton-recoil direction and proton-
` σ ~E!
I E 5 Φ E dE (4)
recoil track length provide the angle of proton scattering ~ ! * ~ !
T
E E
T
relative to the incident neutron direction, θ, and the proton
energy, E , respectively. In terms of these observations, the Here, I(E ) possesses units of proton-recoil tracks/MeV per
p
T
neutron energy, E , is simply: hydrogen atom. Clearly, I(E ) is a function of the lower proton
n T
energy cut-off used for analyzing the emulsion data. Using Eq
E
p
E 5 (3)
2 4 in Eq 1, one finds the integral relation:
n
cos θ
M E
~ !
T
In collimated or unidirectional neutron irradiations, the
I~E ! 5 (5)
T
n V
p
emulsion is exposed end-on as depicted in Fig. 1. The end-on
mode can be used to advantage in media where neutron
I(E ) is evaluated by using a least squares fit of the scanning
T
scattering is negligible for two types of benchmark field
data in the neighborhood of E=E . Alternatively, since:
T
experiments, namely:
dR E
~ !
3.1.2.1 Benchmark field validation of the NRE method or
M E 5 M R (6)
~ ! ~ !
T T
dE
characterization of point neutron sources, for example, the
standard Cf neutron field at the National Institute of Stan-
where: R(E) is the proton-recoil range at energy E in the
dards and Technology (NIST) (17).
NRE and dR/dE is known from the proton range-energy
3.1.2.2 Measurement of leakage neutron spectra at suffi-
relation for the NRE. One need only determine M(R)inthe
ciently large distances from the neutron source, for example,
neighborhood of R= R . Here M(R) is the number of proton-
T
neutron spectrum measurements at the Little Boy Replica
recoil tracks/µm observed in the NRE. Consequently, scanning
(LBR) benchmark field (18).
efforts can be concentrated in the neighborhood of R=R in
T
order to determine I(E ). In this manner, the accuracy attained
3.2 Integral Mode—It is possible to use emulsion data to T
in I(E ) is comparable to the accuracy of the differential
obtain both differential and integral spectral information.
T
determination of Φ(E), as based on Eq 2, but with a signifi-
Emulsion work is customarily carried out in the differential
cantly reduced scanning effort.
mode (3-6). In contrast, NRE work in the integral mode is less
frequently used and, therefore, a fuller explanation of this 3.2.2 The J Integral Relation—The second integral relation
approach is included below. In this integral mode, NRE canbeobtainedbyintegrationoftheobservedprotonspectrum
provide absolute integral reaction rates, which can be used in
M(E ). From Eq 1:
T
spectral adjustment codes. The significance of NRE integral
` ` ` σ~E!
M E dE 5 n V dE Φ E dE (7)
reaction rates stems from the underlying response, which is * ~ ! * * ~ !
T T p T
E E E E
min min T
based on the elastic scattering cross section of hydrogen. This
σ (E)crosssectionisuniversallyacceptedasastandardcross where: E is the lower proton energy cut-off used in
np min
section and is known to an accuracy of approximately 1%. analyzing the NRE data. Introducing into Eq 7 the definitions:
FIG. 1 Geometrical Configuration for End-On Irradiation of NRE
E2059 − 20
`
proton-recoil tracks/MeVper hydrogen atom and proton-recoil
µ~E ! 5 * M~E !dE (8)
min T T
E
min
tracks per hydrogen atom, respectively.
and:
4.2 Applicability for Spectral Adjustment Codes—In the
` ` σ E integral mode, NRE provide absolute integral reaction rates
~ !
J~E ! 5 dE Φ~E! dE (9)
* *
min T
E E that can be used in neutron spectrum least squares adjustment
E
min T
codes (see Guide E944). In the past, such adjustment codes
has:
could not utilize NRE integral reaction rates because of the
µ E
~ ! non-existence of NRE data. NRE integral reaction rates pro-
min
J~E ! 5 (10)
min
n V vide unique benchmark data for use in least squares spectral
p
adjustment codes. The unique significance of NRE integral
Hence, the second integral relation, namely Eq 10, can be
data arises from a number of attributes, which are described
expressed in a form analogous to the first integral relation,
separatelybelow.Thus,inclusionofNREintegralreactionrate
namely Eq 5. Here µ(E ) is the integral number of proton-
min
data in the spectral adjustment calculations can result in a
recoiltracksperhydrogenatomobservedaboveanenergy E
min
significant improvement in the determination of neutron spec-
in the NRE. Consequently, the integral J(E ) possesses units
min
tra in low power benchmark fields.
ofproton-recoiltracksperhydrogenatom.Theintegral J(E )
min
4.3 The Neutron Scattering Cross Section of Hydrogen—
can be reduced to the form:
Integral NRE reaction rates are based on the standard neutron
` E
min
J E 5 1 2 σ E Φ E dE (11) scattering cross section of hydrogen. For fast neutron spec-
~ ! * S D ~ ! ~ !
min
E E
min
trometry and dosimetry applications, the accuracy of this (n,p)
In addition by using Eq 6, the observable µ(E ) can be cross section over extended energy regions is essentially
min
expressed in the form: unmatched. A semi-empirical representation of the energy-
dependence of the (n,p) cross section is given in Eq 13.
`
µ~E ! 5 * M~R!dR (12)
min
R 2 2 21
min
σ E 5 3π 1.206E1 21.86010.0941491E10.000130658E
~ ! @ ~ ! #
np
2 21
Hence, to determine the second integral relationship, one 1π 1.206E1 0.422310.1300E (13)
@ ~ ! #
need only count proton-recoil tracks above R=R . Tracks
min
where: E is in MeV and σ (E) is in barns. This energy-
np
considerably longer than R need not be measured, but
min
dependentrepresentationofthe(n,p)crosssectionpossessesan
simply counted. However, for tracks in the neighborhood of R
uncertainty of approximately 1% at the (1σ) level (19).
=R , track length must be measured so that an accurate
min
lower bound R can be effectively determined.
4.4 Threshold Energy Definition—In contrast with all other
min
fast neutron dosimetry cross sections, the threshold energy of
4. Significance and Use the I and J integral reaction rates can be varied. NRE integral
reaction threshold variability extends down to approximately
4.1 Integral Mode Dosimetry—As shown in 3.2, two differ-
0.3 to 0.4 MeV, which is the lower limit of applicability of the
entintegralrelationshipscanbeestablishedusingproton-recoil
NRE method. Threshold variation is readily accomplished by
emulsion data. These two integral reactions can be obtained
using different lower bounds of proton track length to analyze
with roughly an order of magnitude reduction in scanning
NRE proton-recoil track length distributions. Furthermore,
effort. Consequently, this integral mode is an important
these NRE thresholds are more accurately defined than the
complementary alternative to the customary differential mode
corresponding thresholds of all other fast neutron dosimetry
of NRE spectrometry. The integral mode can be applied over
cross sections. NRE therefore provide a response with an
extendedspatialregions,forexample,perhapsuptoasmanyas
extremely sharp energy cutoff that is not only unmatched by
ten in-situ locations can be covered for the same scanning
other cross sections, but an energy threshold that is indepen-
effort that is expended for a single differential measurement.
dent of the in-situ neutron spectrum. No other fast neutron
Hence the integral mode is especially advantageous for dosim-
dosimetry cross sections possess a threshold response with
etryapplicationswhichrequireextensivespatialmapping,such
these significant attributes. The behavior of the I-integral and
as exist in Light Water Reactor-Pressure Vessel (LWR-PV)
J-integral response for different threshold energies is shown in
benchmark fields (see Test Method E1005). In low power
Figs. 2 and 3, respectively, in comparison to the threshold
benchmark fields, NRE can be used as integral dosimeters in a
Np(n,f) reaction used in RM dosimetry.
manner similar to RM, solid state track recorders (SSTR) and
helium accumulation monitors (HAFM) neutron dosimeters 4.5 Complimentary Energy Response—It is of interest to
(see Test Methods E854 and E910). In addition to spatial compare the differential energy responses available from these
mapping advantages of these other dosimetry methods, NRE two integral relations. From Eq 4 and 11, one finds responses
offerfinespatialresolutionandcanthereforebeused in-situfor of the form σ(E)/E and (1 –E /E)σ(E) for the I and J integral
min
fine structure measurements. In integral mode scanning, both relations, respectively. These two responses are compared in
absolutereactionrates,thatisI(E )andJ(E ),aredetermined Fig.4usingacommoncut-offof0.5MeVforboth E and E .
T min T min
simultaneously. Separate software codes need to be used to Since these two responses are substantially different, simulta-
permit operation of a computer based interactive system in the neous application of these two integral relations would be
integral mode (see Section 9). It should be noted that the highly advantageous.As shown in Fig. 4, the energy response
integrals I(E ) and J(E ) possess different units, namely of the I and J integral reaction rates complement each other.
T min
E2059 − 20
data. This conclusion is supported by the calculation to
experimentratios(C/E)obtainedfromNREexperimentsinthe
VENUS-1 LWR-PV benchmark field. For these VENUS-1
NRE experiments, the C/E values for the I integral possessed
larger variation and deviated more widely from unity than the
corresponding C/E values for the J-integral (20).
5. Apparatus
5.1 Dark Room—A dark room equipped with a sink, pro-
cessing baths and a safe light.There should be adequate bench
space in the dark room for pre-irradiation preparation of NRE
as well as for the transfer of NRE between processing trays.
5.2 Constant Temperature Baths—The constant temperature
baths in the dark room should possess temperature control to
0.1°C. One cooling bath should be equipped with a circulating
pump so that tap water can be circulated through the coils of
the processing bath. One thermostatically controlled process-
FIG. 2 Comparison of the I-Integral Response with the Np (n,f)
ing bath.
Threshold Reaction
5.3 Refrigerator—Thedarkroomshouldbeequippedwitha
refrigerator for storing reagents and chemicals.
5.4 Stainless Steel Trays—Stainless steel (SS) trays and
cover lids are required, approximately 25 by 15 cm in area by
2.5 cm deep, for NRE processing.
5.5 Racks—Racks are required to position and hold the SS
traysintheconstanttemperaturebaths.TheseracksholdtheSS
trays in the constant temperature bath so that the top of the SS
trays project above the bath surface by approximately 0.5 cm.
5.6 Cooling Coil—A cooling coil is required that is im-
mersed in the constant temperature bath and connected by a
suitabletubetothecold-watertap.Anotheridenticaltubemust
serveasadrainlinefromthecoolingcoiltothesink.Anin-line
valve for control of tap water flow should be installed so that
a small steady stream of water can be regulated.
5.7 Optical Microscopes—Optical microscopes are required
FIG. 3 Comparison of the J-Integral Response for E = 0.404,
for NRE scanning with a magnification of 1000X or higher,
T
0.484, 0.554 and 0.620 MeV with the Np (n,f) Threshold Reac-
utilizing oil immersion techniques. Microscope stages should
tion
be graduated with position readout to better than 1 µm and
should also possess at least 1-µm repositioning accuracy. The
The J-integral response increases with increasing neutron
depth of focus (z-coordinate) should be controlled to the
energy above the threshold value and therefore possesses an
nearest 0.1 µm with similar repositioning accuracy. Calibrated
energy dependence qualitatively similar to most fast neutron
stage micrometers and graduated eyepiece grids (reticles) are
dosimetry cross sections. However, significant quantitative
also required for track scanning.
differencesexist.Asdiscussedabove,theJ-integralresponseis
5.8 Filar Micrometer—A filar micrometer is required for
more accurately defined in terms of both the energy-dependent
measuring thickness with electronic readout to at least the
cross section and threshold energy definition. The I-integral
nearest 0.1 µm.
possesses a maximum value at the threshold energy and
decreases rapidly from this maximum value as neutron energy
5.9 Dial Gages—Dial thickness gauges, preferably with
increases above the threshold value. As can be seen in Fig. 4,
digital readouts, are required with readout scales of at least 2
the I-integral possesses a much more narrowly defined energy
µm per division.
response than the J-integral. While the J-integral response is
5.10 Certified Gage Blocks—Certified gauge blocks in the
broadly distributed, most of the I-integral response is concen-
anticipated NRE thickness range are required to verify the
trated in the neutron energy just above threshold. As a
accuracy of thickness measurements.
consequence, the I-integral reaction rate data generally pro-
vides a more rigorous test of the ability of neutron transport 5.11 Scribes—Diamond point scribes are required for mark-
calculations to describe the complex spatial and energy varia- ing NRE glass backing with suitable pre-irradiation identifica-
tions that exist in benchmark fields than does the J-integral tion labels
E2059 − 20
FIG. 4 Energy Dependent Response for the Integral Reactions I(E ) and J(E )
T min
TABLE 2 Anti-Fog Stock Solution
5.12 Thermometers—Thermometers are required for mea-
Reagent Volume/Mass
suring temperature with readout to at least the nearest 0.1°C.
Ethylene Glycol (50°C) 175 cc
A
5.13 Interactive Scanning System—Acomputer based inter- Kodak Anti-Fog #1 41.68 g
B
Ethylene Glycol ' 75 cc
active scanning system is required for the measurement of
A
Dissolve in warm ((50°C)) Ethylene Glycol
proton-recoil track length in NRE. Hardware and software
B
Cool to 24°C and add cool Ethylene glycol to make 250 cc.
requirements are described in Section 9.
6. Reagents and Materials
A
TABLE 3 Fixing Solution
6.1 Purity of Reagents—Distilled or demineralized water
Reagent Volume/Mass
and analytical grade reagents should be used at all times.
Distilled Water 1 L
Na S O (Hypo) 400 g
2 2 3
6.2 Reagents—Tables1-4providedetailedspecificationsfor
B
NaHSO 10 g
the processing solutions.
A
Chemicals dissolved in order listed at room temperature.
6.2.1 Developing Solution—As specified in Table 1,
B
If Na S O is used, decrease mass by a factor of 0.87.
2 2 5
Amidol, 2,4–Diaminophenol Dihydrochloride is used to de-
velop the NRE (Eastman Organic Chemicals, No. P614, other
commerciallypreparedamidoldevelopersalsoworkwell.)The TABLE 4 Drying Solutions
anti-fog solution specified in Table 2 is used to suppress
Volume, %
Reagent Solution 1 Solution 2
chemical fog and prevent the development of gamma-ray
Distilled Water 35 0.00
induced electron tracks and thereby improve proton-recoil
Glycerine 30 30
A
track length measurements.
Ethyl Alcohol (95%) 35 70
6.2.2 Stop Bath Solution—The stop bath solution should be
A
Absolute alcohol should not be used, since it contains traces of benzene.
a 1% glacial acetic acid in distilled water.
A
TABLE 1 Developing Solution
Reagent Volume/Mass
6.2.3 Fixing Solution—Afixing solution containing sodium
Distilled Water 1.0 L
Boric Acid Crystals 3.0 g
thiosulfate (hypo) and sodium bisulfite is required (see Table
Potassium Bromide 1.0 g
3).
Desiccated Na SO 50 g
2 3
Amidol 2.0 g
6.2.4 Drying Solutions—Two drying solutions of glycerine,
Anti-Fog Solution 6.0 cc
ethyl alcohol, and distilled water are required (see Table 4).
A
Chemicals dissolved in order listed at room temperature.
6.3 Materials:
E2059 − 20
6.3.1 Emulsions—Ilford type L-4 NRE, 200- and 400-µm necessarily be optimum for any given batch, these procedures
thick pellicles, mounted on glass backing.The glass backing is can be used as a starting point to attain optimum procedures
approximately 2.5 by 7.5 cm in area by 1 mm thick. desired for the specific NRE neutron dosimetry application
under consideration. Table 5 summarizes the various steps
7. Pre-Irradiation NRE Preparation
utilized in the post-irradiation NRE processing procedures.
8.1.1 Pre-Soaking Step—Use a mixture of approximately
7.1 NRE Preparation—CareshouldbetakentohandleNRE
50% distilled water and 50% ethylene glycol in the cooling
by the edges to avoid potential damage to surfaces adjacent to
bath to maintain a temperature of 2°C. Fill a SS tray with
measurement locations both during preparation and after the
distilled water. Pre-cool the distilled water soaking solution to
measurements.The NRE should be cut to an acceptable size in
5°C before inserting the NRE into the distilled water.This will
the dark room. A safe light with a yellow filter may be used.
keep the NRE swelling to a minimum. Insert the SS trays into
The diamond point scribe should be used to rule the glass
the 2°C bath. The purpose of the pre-soaking step is to
backing undersurface of the NRE and the glass backing can
facilitateuniformpenetrationoftheAmidoldeveloperthrough-
thenbesnappedalongtherulemarkstoobtainthedesiredNRE
outthefullthicknessoftheNRE.Inthisway,developmentwill
dosimeter size. NRE dosimeters down to approximately 5mm
be uniform, that is, independent of depth (denoted by the z
by 5mm area can be readily obtained. The diamond point
coordinate).Pre-soak200µmL-4NREfor1hand400µmL-4
scribe should then be used to mark an ID number on the
NRE for 2 h.
undersurface of the glass backing. The NRE should then be
wrapped in lens paper and then in aluminum foil (;0.002 cm
8.2 Developing Step at 1.2°C—Prepareafreshdevelopment
thick)forfurtherhandlingandtopreventexposuretolight.The
solutionasprescribedinTables1and2.Placethedevelopment
NRE ID number can then be written on the Al-foil wrapping
solution in a SS tray and insert the tray into the cooling bath at
with an indelible pen. If it is necessary to know the orientation
1.2°C.TransfertheNREdirectlyfromthepre-soakingsolution
of the NRE in the irradiation field, the undersurface NRE glass
to the development solution. The rate of NRE development is
backing is marked with an indelible pen to provide a known
very sensitive to the temperature of the developer. Use of the
orientationfortheNRE.Thismarkingorientationmustthenbe
low 1.2°C temperature provides enhanced developer penetra-
transcribed to the Al-foil wrapping. The NRE can then be
tion with very little actual development.The length of time the
removed from the dark room. However, if the NRE are to be
NRE remain in the 1.2°C developer depends on the NRE
deployed inAl or Cd buckets for the irradiation, this assembly
thickness. Develop Ilford L-4 200 µm and 400 µm NRE for
procedure should also be conducted in the dark room if at all
approximately 1 h and 2.5 h, respectively.
possible. It will then be necessary to transcribe the NRE ID
8.3 Developing Step at 5°C—Transfer the tray containing
number and orientation information to the outer surface of the
the NRE in the development solution from the cooling bath at
irradiationbucket.Spacersorothermeansshouldbeemployed
1.2°C to the processing bath which is maintained at 5°C. Here
to maintain the NRE orientation within the bucket to the
adevelopmenttimeofapproximately35to40mincanbeused,
desired accuracy. A knowledge of NRE orientation together
independent of NRE thickness.
with a complete record of proton-recoil scanning data (see
8.4 Stop-Bath Step—The stop-bath solution (1% glacial
Section 9 can then be used to determine any anisotropy of the
aceticacidindistilledwater)shouldbepre-mixedandstoredin
in-situ neutron field.
a plastic bottle in the refrigerator. Fill another SS tray with
7.2 NRE Exposure Time—Neutron fluences of approxi-
stop-bath solution and place the tray in the processing tank so
5 −2
mately 10 cm will give optimum track densities for scan-
it cools to the 5°C temperature of the processing bath. Remove
6 −2
ning. Fluences greater than 10 cm for manual scanning and
both trays from the processing bath and place the trays on a
7 −2
10 cm for computer-based scanning will result in unaccept-
convenient flat surface in the dark room. Rapidly transfer the
ably high track densities.
NRE from the developer tray into the stop-bath tray and place
7.3 NRE Thickness Measurement—To measure the original
thestop-bathtraybackintotheprocessingbath.Careshouldbe
thickness of the emulsion, HO, place the glass undersurface of
exercised to avoid touching the NRE surface.The NRE should
the NRE on a flat surface in the dark room. Use the dial
behandledbyholdingtheglassbacking.Thetimedurationthat
thickness gauge to measure the thickness of the emulsion and
glass backing. Repeat this measurement five to ten times at
TABLE 5 Summary of NRE Processing Steps
different locations so that a precise average is obtained. The
glass backing thickness is determined after irradiation and
Time Duration
Temperature,
Step Solution
A A
°C
post-irradiation processing (see 8.8).
200 µm 400 µm
Pre-soaking Distilled H O 2 1h 2h
8. Post-Irradiation Processing Procedures Developing-1 See Tables 1 and 2 1.2 1 h 2.5 h
Developing-2 See Tables 1 and 2 5 35to40min 35 to 40 min
8.1 Processingprocedureswilldependtosomeextentonthe
Stop Bath 1 % Glacial Acetic 5 15to20min 1h
Acid
particular batches of Ilford NRE that are used. Consequently,
Fixing See Table 3 5 2 h to 1 day 2 to 3 days
while the processing procedures recommended below will not
Washing Tap Water 6 1 day 1 day
Drying-1 See Table 4 5 1 h 2.5 h
Drying-2 See Table 4 5 1 h 2.5 h
A
Details of NRE characteristics and specifications can be found at http://
Ilford L-4 NRE thickness in µm.
www.polysciences.com/default/ilford-emulsions-l4.
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the NRE remain in the stop-bath solution depends on NRE NREarethenairdriedatroomtemperatureforatleast24h.In
thickness. For 200-µm NRE, approximately 15 to 20 min will this drying process, the water in the NRE is replaced with
do, whereas approximately 60 min should be used for 400-µm alcohol which, in turn, evaporates and glycerine replaces the
NRE. The stop-bath solution changes the pH of the NRE to silver bromide that was in the unprocessed emulsions.
stop development. (Actually, the glycerine fills the holes from which the silver
bromide was removed in the fixing process.)
8.5 Fixing Solution Step at 5°C—The fixing solution (see
Table 3) should be pre-mixed and stored in a plastic bottle in
8.8 Post-Irradiation NRE Thickness Measurements—After
the refrigerator. Remove the fixing solution from the refrigera-
processing is complete, place the NRE on edge under a
tor and fill a SS tray at least half-way with the fixing solution.
microscope equipped with a filar micrometer eyepiece. Mea-
PlacetheSStrayintheprocessingbathuntilthefixingsolution
sure the glass backing and processed emulsion thickness
comes to equilibrium at 5°C. Remove both the stop-bath tray
separately. Make 5 to 10 observations of each thickness so that
and the fixing solution trays from the processing bath onto a
a precise average of both the emulsion thickness and the glass
convenient flat surface in the dark room. Rapidly transfer the
backing thickness can be determined. These data provide the
NREfromthestop-bathtraytothefixingsolutiontray.Replace
processed NRE thickness, HP, and the glass backing thickness
the fixing solution tray back into the processing bath. The
can then be used with the pre-irradiation thickness measure-
fixingsolutiondissolvestheundevelopedsilverbromidegrains
ments to determine the original NRE thickness, HO. To obtain
in the NRE, so that the NRE become transparent for track
the true z-coordinate position in the (irradiated) NRE, z , from
tr
scanningpurposes.TheresidencetimeoftheNREinthefixing
the observed z-coordinate, z , one must use the relation
obs
solution depends on NRE thickness. For 200-µm NRE, it takes
HO
several hours to a day. For 400-µm NRE, it can take several
z 5 z (14)
tr obs
HP
days. The NRE should remain in the fixing solution approxi-
mately 1.5 times the time duration that it takes for the NRE to 8.9 NRE Microscope Mounting—The processed NRE is
clear. When using the fixing solution for several days, as mounted on a watch glass (microscope cover glass), which is
needed for the 400-µm NRE, replenish the fixing solution at cemented in a rigid frame that can, in turn, be attached to the
least once a day by pouring off 50% of the old solution and microscope stage. The rigid frame must not obstruct the
adding 50% new fixing solution. portionsoftheNREthataretobescanned,andthemicroscope
coverglassispermanentlygluedorcementedtotheframe.The
8.6 NRE Washing—The fixing solution needs to be thor-
NRE is than placed on the microscope glass and glued or
oughly removed from the NRE. This washing process can be
cemented to the glass at several edge locations to ensure that
done in daylight.Actually, the darkroom (bright) lights can be
the NRE will maintain a constant position relative to the frame
turned on as soon as the fixing process is completed. Wash the
during measurements. When NRE are not being scanned, they
NREwithastreamoftapwater,whichrunsthroughcoilsatthe
should be stored in Petrie dishes under controlled temperature
bottomofthe1.2°Ccoolingbath.Letcoldtapwaterrunslowly
and humidity conditions. Standard room temperature is
throughatubetothecoilsinthecoolingbathandthenthrough
acceptable, but 50% relative humidity is preferable, since the
a tube to an empty SS tray in the sink.Agood control valve is
glycerineissomewhathydroscopic.Largechangesinhumidity
needed on the tube carrying the cold tap water so as to ensure
during storage should be avoided.
a good even flow of water. When the water in the tray has
reached a temperature of ≈6°C, transfer the fixed emulsions
9. Track Scanning
from the SS tray in the 5°C bath to the tray in the sink.The tap
water should run into the SS tray slowly so as not to produce
9.1 Instrumentation—The principal disadvantage of the
a significant stream that might distort the emulsions. The NRE
NRE method of fast neutron dosimetry is the need to measure
should be washed in this manner for approximately 24 h.
proton-recoil track length for many tracks. Accurate differen-
8.7 Drying Solution Steps—The NRE obtained from the tial spectrometry measurements require measurement of ap-
washing step are swelled with water to two to three times the proximately 10 tracks, so that many hours of scanning are
required. To facilitate proton-recoil track length measurements
originalthickness.Thepurposeofthedryingsolutionstepisto
removethewaterandtherebyreducedistortionandatthesame and provide a much more cost-effective measurement system,
time provide for more precise thickness (z-coordinate) mea- a computer-based interactive system is indispensable. Such a
surements. Two drying solutions are prepared as prescribed in systemcanstoreallthe(3D)scanninginformation,indetail,as
Table 4. The two drying solutions are placed into SS trays and well as provide on-line computations for individual track
allowed to come to equilibrium in the 5°C processing bath. analysis.To conduct all of these operations manually would be
Using some convenient flat surface in the dark room, the NRE impractical. Such a computer-based interactive system was
are transferred from the washing tray to SS tray containing the built and used successfully for NRE neutron dosimetry some
first drying solution. The SS tray containing the NRE in the time ago (17). The specifications and scanning procedures
first drying solution is placed in the 5°C processing tank for described here are based on this system, which was called the
approximately1hfor200-µmNREand2.5hfor400-µmNRE. Emulsion Scanning Processor (ESP). Since the ESP system
This step is repeated with the second drying solution. Upon was built some time ago, many of the components of the ESP
removal from the second drying solution, the NRE can be system are outdated because of the rapid development of
placed(emulsionsideup)onaflatsurfacesothattheNREcan computer technology that has ensued. Consequently, to fabri-
be gently blotted to remove the excess drying solution. The cate such a system today, one should only use this description
E2059 − 20
as an overall guide and replace all components with state-of- emulsion; whereas, another Cartesian coordinate system (X, Y,
the-art components, which will be invariably faster, more Z) is used to describe track-ending locations in the emulsion.
reliable and less expensive.
The perimeters of a reticle located in the eyepiece of the
9.1.1 Overall Design—Some of the major considerations in microscope serve as the G, R boundaries of the field of view.
thedevelopmentofaninteractivesystemforNREscanningare
The S-coordinate is the depth or focus coordinate. In using the
simplicity, ease of operation, stability, and reliability of perfor-
interactive (ESP) system, the selected emulsion is divided into
mance. In the design of the interactive system, the flexibility
a number of field volumes. The volume of a field corresponds
and power of computer control should be utilized to the
to the area of a field of view times the preselected depth of the
maximum possible extent. A photograph of the ESP system
emulsion as shown in Fig. 6. The distance ∆S is prescribed in
microscope, and joystick control boxes with push buttons is
order that scanning be primarily confined to the interior of the
shown in Fig. 5. An operator must interact with the system to
emulsion, where proton-recoil escape probabilities are either
obtain the desired results. The joystick and push button
negligible or small. Hence, a field volume FV is given by the
controls are used to set parameters and boundaries, focus,
relation:
locatetracks,measuretracklengths,categorize,andstoretrack
FV 5∆G·∆R·S (15)
data.The(X, Y, Z)stagemotion,includingdepth,thatis,focus,
ofthemicroscopeisperformedbythecomputerunderoperator
Toprovideorientationfortrackscanningfromday-to-dayas
control.Thecomputerreceivesalloperatorinstructions,moves
well as between different scanners, a zero reference point must
the stage as directed, and stores positional information on
be chosen on the emulsion. To this end, a needle having a red
command. Software programs, stored on computer disks,
dye on its tip is mounted on a microscope objective holder and
provide the flexibility needed to conveniently tailor operating,
is used to pierce the emulsion surface thereby leaving a red
storage, and data presentation formats to satisfy different
spot. A color microphotograph is taken of the spot. A proton
experiments and scanning modes.
track escaping from the top surface of the emulsion is selected
9.2 Scanning Coordinate Systems—A Cartesian coordinate near the spot. The zero reference point, G=O, R=O, S=O,
system (G, R, S) is used to describe field locations in the is then stored as the point of escape of this proton-recoil track.
FIG. 5 Close Up of the ESP Microscope Showing Push Buttons and Stage Controls
E2059 − 20
FIG. 6 Maximum Traverse Dimensions, G and R , Together with the Field Dimensions, ∆G and ∆R, Define the Number of NRE Scanning Fields Available for ESP Opera-
max max
tion
E2059 − 20
9.3 Track Scanning—The actual measurement of a typical fieldsareorderedaccordingtothematrix(G R)orbydirecting
k j
track in an emulsion using the interactive ESP system is the interactive system to a prescribed field (G R), which is
k j
described below. Fig. 5 shows the ESPcontrols in more detail. obtained by entering the integers (k,j) at the computer key-
Operations with the left (L) and right (R) push buttons are board.
summarized in Table 6.The left joystick controls the Z (focus)
9.3.4 NRE Thickness Measurement—Whenthefieldofview
position, whereas, the right joystick controls both X and Y
isreached,theemulsionthicknessismeasuredbyfirstfocusing
positions. The design of the interactive system permits perfor-
on the top surface, then on the bottom surface, and recording
mance of all track scanning and recording activities without
the respective S levels with push button 2R. The computer
interruptingtheobservationofproton-recoiltracksintheNRE.
calculates the NRE thickness and automatically returns the
9.3.1 Recording the Zero Reference Point—The emulsion is
focus to the preselected depth∆S, as measured from the top of
clamped to the microscope stage, and the operating program
the emulsion (see Fig. 7). In this way, the thickness of the
for the interactive (ESP) system is initiated in the computer
processed NRE is measured for each field that is scanned. The
system. The first step is to bring the zero reference point into
initials of the operator must be entered for each field scanned.
focusunderthereticlecrosshair,thatis,theexactcenterofthe
Thispermitscomparisonsbetweenscanningresultsofdifferent
reticle grid. Pressing push button 3R (see Table 6) stores the
individuals as well as comparisons between an individual
coordinates of the zero reference point G=0, R=0, S=0on
scanner and the mean results obtained by a group of observers.
a (scanning) data disk.
Consequently, the objectivity and accuracy of any given
9.3.2 Field of View Parameters—The scanner must then
scanner can be examined.
measure a number of parameters that are to be used in the
9.3.5 Track Selection—The field is scanned by continuously
analysis of the proton-recoil track scanning data. The field
increasing the S coordinate with the left joystick. The micro-
width ∆G and fie
...