ASTM E265-15(2020)
(Test Method)Standard Test Method for Measuring Reaction Rates and Fast-Neutron Fluences by Radioactivation of Sulfur-32
Standard Test Method for Measuring Reaction Rates and Fast-Neutron Fluences by Radioactivation of Sulfur-32
SIGNIFICANCE AND USE
5.1 Refer to Guides E720 and E844 for the selection, irradiation, and quality control of neutron dosimeters.
5.2 Refer to Practice E261 for a general discussion of the determination of fast-neutron fluence and fluence rate with threshold detectors.
5.3 The activation reaction produces 32P, which decays by the emission of a single beta particle in 100 % of the decays, and which emits no gamma rays. The half life of 32P is 14.284 (36)3 days (1) 4 and the maximum beta energy is 1710.66 (21) keV (1).
5.4 Elemental sulfur is readily available in pure form and any trace contaminants present do not produce significant amounts of radioactivity. Natural sulfur, however, is composed of 32S (94.99 % (26)), 34S (4.25 % (24)) (2), and trace amounts of other sulfur isotopes. The presence of these other isotopes leads to several competing reactions that can interfere with the counting of the 1710-keV beta particle. This interference can usually be eliminated by the use of appropriate techniques, as discussed in Section 8.
SCOPE
1.1 This test method describes procedures for measuring reaction rates and fast-neutron fluences by the activation reaction 32S(n,p)32P.
1.2 This activation reaction is useful for measuring neutrons with energies above approximately 3 MeV.
1.3 With suitable techniques, fission-neutron fluences from about 5 × 108 to 1016 n/cm 2 can be measured.
1.4 Detailed procedures for other fast-neutron detectors are described in Practice E261.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 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.
General Information
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Standards Content (Sample)
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: E265 − 15 (Reapproved 2020)
Standard Test Method for
Measuring Reaction Rates and Fast-Neutron Fluences by
Radioactivation of Sulfur-32
This standard is issued under the fixed designation E265; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope E261Practice for Determining Neutron Fluence, Fluence
Rate, and Spectra by Radioactivation Techniques
1.1 This test method describes procedures for measuring
E720Guide for Selection and Use of Neutron Sensors for
reaction rates and fast-neutron fluences by the activation
32 32 Determining Neutron Spectra Employed in Radiation-
reaction S(n,p) P.
Hardness Testing of Electronics
1.2 Thisactivationreactionisusefulformeasuringneutrons
E721Guide for Determining Neutron Energy Spectra from
with energies above approximately 3 MeV.
Neutron Sensors for Radiation-Hardness Testing of Elec-
tronics
1.3 With suitable techniques, fission-neutron fluences from
8 16 2
about 5×10 to 10 n/cm can be measured. E844Guide for Sensor Set Design and Irradiation for
Reactor Surveillance
1.4 Detailed procedures for other fast-neutron detectors are
E944Guide for Application of Neutron Spectrum Adjust-
described in Practice E261.
ment Methods in Reactor Surveillance
1.5 This standard does not purport to address all of the
E1018Guide for Application of ASTM Evaluated Cross
safety concerns, if any, associated with its use. It is the
Section Data File
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3. Terminology
mine the applicability of regulatory limitations prior to use.
3.1 Definitions:
1.6 This international standard was developed in accor-
3.1.1 Refer to Terminology E170.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
4. Summary of Test Method
Development of International Standards, Guides and Recom-
4.1 Elemental sulfur or a sulfur-bearing compound is irra-
mendations issued by the World Trade Organization Technical
diatedinaneutronfield,producingradioactive Pbymeansof
Barriers to Trade (TBT) Committee.
32 32
the S(n,p) P activation reaction.
2. Referenced Documents
4.2 The beta particles emitted by the radioactive decay of
2.1 ASTM Standards:
ParecountedbytechniquesdescribedinMethodsE181and
E170Terminology Relating to Radiation Measurements and
thereactionrate,asdefinedinPracticeE261,iscalculatedfrom
Dosimetry
the decay rate and irradiation conditions.
E181Test Methods for Detector Calibration andAnalysis of
4.3 The neutron fluence above 3 MeV can then be calcu-
Radionuclides
lated from the spectral-averaged neutron activation cross
section, σ¯, as defined in Practice E261.
ThistestmethodisunderthejurisdictionofASTMCommitteeE10onNuclear
Technology and Applicationsand is the direct responsibility of Subcommittee
5. Significance and Use
E10.07 on Radiation Dosimetry for Radiation Effects on Materials and Devices.
Current edition approved July 1, 2020. Published August 2015. Originally
5.1 Refer to Guides E720 and E844 for the selection,
approved in 1970. Last previous edition approved in 2015 as E265–15. DOI:
irradiation, and quality control of neutron dosimeters.
10.1520/E0265-15R20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.2 Refer to Practice E261 for a general discussion of the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
determination of fast-neutron fluence and fluence rate with
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. threshold detectors.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E265 − 15 (2020)
32 32
5.3 The activation reaction produces P, which decays by Due to the relatively long half-life of P, it may not be
the emission of a single beta particle in 100% of the decays, practicaltouseapelletmorethanonce.Aperiodofatleastone
and which emits no gamma rays. The half life of Pis 14.284 year is recommended between uses. However, see 8.2 regard-
3 4
(36) days (1) and the maximum beta energy is 1710.66 (21) ing long-lived interfering reaction products.
keV (1).
7.2 Where temperatures approaching the melting point of
5.4 Elemental sulfur is readily available in pure form and sulfur are encountered (113°C), sulfur-bearing compounds
any trace contaminants present do not produce significant
such as ammonium sulfate (NH ) SO , lithium sulfate Li SO ,
4 2 4 2 4
amounts of radioactivity. Natural sulfur, however, is composed or magnesium sulfate MgSO can be used. These are suitable
32 34
of S(94.99%(26)), S(4.25%(24)) (2),andtraceamounts
fortemperaturesupto250,850,and1000°C,respectively.The
of other sulfur isotopes. The presence of these other isotopes reduced sensitivity of these compounds offers no disadvantage
leads to several competing reactions that can interfere with the
since high temperatures are usually associated with a high-
counting of the 1710-keV beta particle. This interference can neutron fluence rate. The sulfur content by weight of
usually be eliminated by the use of appropriate techniques, as
(NH ) SO is 24%, of Li SO is 29.2%, and of MgSO is
4 2 4 2 4 4
discussed in Section 8. 26.6%.
7.3 The isotopic abundance of S in natural sulfur is 94.99
6. Apparatus
6 0.26 atom% (2,3).
6.1 Sinceonlybetaparticlesof Parecounted,proportional
counters or scintillation detectors can be used. Because of the
8. Sample Preparation and Irradiation
high resolving time associated with Geiger-Mueller counters,
8.1 Place sulfur in pellet or powdered form in a uniform
their use is not recommended. They can be used only with
fast-neutron flux for a predetermined period of time. Record
relatively low counting rates, and then only if reliable correc-
the beginning and end of the irradiation period.
tions for coincidence losses are applied.
8.2 Table 2 lists competing reaction products that must be
6.2 RefertoTestMethodsE181forpreparationofapparatus
eliminated from the counting. Those resulting from thermal-
and counting procedures.
33 35 37
neutroncapture,thatis, P, S,and S,canbereducedbythe
7. Materials and Manufacture
irradiation of the sulfur inside 1 mm-thick cadmium shields.
This should be done whenever possible in thermal-neutron
7.1 Commercially available sublimed flowers of sulfur are
environments. Those reaction products having relatively short
inexpensive and sufficiently pure for normal usage. Sulfur can
31 34 31 37
half-lives, that is, S, P, Si, and S, can be eliminated by
be used directly as a powder or pressed into pellets. Sulfur
a waiting period before the counting is started.Adelay of 24 h
pelletsarenormallymadeatleast3mmthickinordertoobtain
is sufficient for the longest lived of these, although shorter
maximum counting sensitivity independent of small variations
delays are possible depending on the degree of thermalization
in pellet mass. A 0.8 g/cm pellet can be considered infinitely
of the neutron field. Finally, those with relatively low beta
thickforthemostenergeticbetaparticlefrom P(seeTable1).
33 35
particle energies, that is, Pand S, can be eliminated by the
inclusion of a 70-mg/cm aluminum absorber in front of the
The non-boldface number in parentheses after the nuclear data indicates the
detector.Forparticularlylongdecaytimes,anabsorbermustbe
uncertainty in the last significant digit of the preceding number. For example, 8.1 s 35
used because the S becomes dominant. Note that the use of
(5) means 8.1 6 0.5 seconds.
an internal (windowless) detector maximizes the interference
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this test method. in counting from S.
8.3 Irradiated sulfur can be counted directly, or may be
TABLE 1 Sulfur Counting Rate Versus Mass for a Pellet of
burned to increase the efficiency of the counting system.
25.4-mm Diameter
Dilution may be used to reduce counting system efficiency for
Sample Mass, g Relative Counting Rate
measurements of high neutron fluences.
0.4 0.46
0.6 0.58
8.4 Burning the sulfur leaves a residue of P that can be
0.8 0.66
counted without absorption of the beta particles in the sulfur
1.0 0.73
pellet. Place the sulfur in an aluminum planchet on a hot plate
1.2 0.78
1.4 0.82
until the sulfur melts and turns to a dark amber color. At this
1.6 0.86
point the liquid gives off sulfur fumes. Ignite the fumes by
1.8 0.89
bringing a flame close to the dish, and allow the sulfur to burn
2.0 0.91
2.2 0.93
out completely. In order to reduce the sputtering that can lead
2.4 0.94 32
to variations in the amount of P remaining on the planchet,
2.6 0.95
thehotplatemustbeonlyashotasnecessarytomeltthesulfur.
2.8 0.96
3.0 0.97
In addition, air flow to the burning sulfur must be controlled,
3.2 0.98
suchasbytheplacementofachimneyaroundthesulfur.Count
3.4 0.99
the residue remaining on the dish for beta activity.
3.6 0.99
3.8 1.0
4.0 1.0 NOTE 1—The fumes given off by the burning sulfur are toxic. Burning
should be done under a ventilating hood.
E265 − 15 (2020)
TABLE 2 Neutron-induced Reactions in Sulfur Giving Radioactive Products
Maximum Average Isotopic
Cross Section Cross Section (mb)
Product Energy of Energy of Abundance
B
U
Reaction Fast Halflife Product Product of
A 252
Library(5) Material ID Thermal Thermal Cf
(1,2,3) Beta (MeV) Beta Target (%)
Fission
Fission
(1,4) (MeV) (1,4) (2)
32 32
1. S(n,p) P RRDF-2008 1625 . 68.2 74.10 14.284 1.71066 0.6955 (3) 94.99 (26)
d (36) (21)
32 31 −6 −5
2. S(n,2n) S JENDL-4.0 1625 . 7.760 × 10 2.5×10 2.572 s 5.3956 1.9975 94.99 (26)
(13) (β+) (β+)
33 33
3. S(n,p) P JENDL-4.0 1628 2 ± 1 57.46 58.72 25.383 0.2485 (11) 0.0764 (5) 0.75 (2)
d (40)
34 34
4. S(n,p) P JENDL-4.0 1631 . 0.8001 1.080 12.43 s 5.374 (5) 2.30 (9) 4.25 (24)
(8)
34 31
5. S(n,α) Si JENDL-4.0 1631 . 3.281 4.067 157.3 m 1.4905 (4) 0.595231 4.25 (24)
(3)
34 35
6. S(n,γ) S JENDL-4.0 1631 256 ± 9 0.2753 0.2710 87.37 d 0.16714 (8) 0.04863 4.25 (24)
(4)
36 37
7. S(n,γ) S JENDL-4.0 1637 236 ± 6 0.2511 0.2508 5.05 m 4.86530 0.800 (16) 0.01 (1)
(2) (25)
A
The thermal cross section corresponds to neutrons with a velocity of 2200 m/s or energy of 0.0253 eV.
B 235
The fast cross section corresponds to the spectrum-averaged cross section from the ENDF/B-VI (MAT=9228, MF=5, MT=18) U thermal fission spectrum (6,7) and
the ENDF/B-VI (MAT=9861, MF=5, MT=18) Cf spontaneous fission spectrum (6-8).
8.5 An alternative to burning is sublimation of the sulfur determining neutron energy spectra as described in Practice
under a heat lamp. Removal of the sulfur is very gradual, and E721 and Practice E944.
there is no loss of P from sputtering. 235 252
9.2 U fission and Cf spontaneous fission neutron
8.6 Counting of dilute samples is useful for measuring high sources of known source strength have been used for direct
neutron fluences, although it is applicable to virtually all free-field calibrations (9).
irradiation conditions. Use lithium sulfate, reagent grade or
9.3 Once a sulfur counting system is calibrated, it must be
better, as the target material because of its high melting point
monitored to ensure that the calibration remains valid. There
(860°C), good solubility in water, and minimum production of
are several isotopes that can be used as reference standards for
undesirable activation products. Prepare a dry powder by 234
this monitoring. One is Pa, having a maximum beta energy
spreading about 10 g of Li SO in a weighing bottle and place
2 4
of about 2000 keV, comparable to the 1710-keVbeta from P.
in a drying oven for 24 h at 150°C. Place the dried Li SO in 238
2 4
It is obtained as a daughter of U, that can be dispersed as a
a dessicator for cooling and storage. Prepare a phosphorus
powder in plastic granules and formed to the shape of a
carrier solution by dissolving 21.3 g of (NH ) HPO in water 238
4 2 4
standard pellet. The concentration of U can be varied to
to make 1 L of solution. Prepare a Li SO sample for
2 4
obtain the desired counting rate. Uranium alpha particles can
irradiation by placing about 150 mg of material in an air-tight
be prevented from reaching the detector by use of a 7-mg/cm
2 210
aluminum capsule or other suitable container. Following the
absorber. Another useful isotope is Bi that produces beta
irradiation, accurately weigh a sample of about 100 mg and
particles having a maximum energy of 1161 keV. It is obtained
dissolve in 5 mL of phosphorus carrier solution to minimize
asadaughterof Pb,andsourcesarecommerciallyavailable.
adsorptionof Pontheglasscontainer.Adropofconcentrated
10. Activity and Fluence by Detector Efficiency Method
HCl may be used to speed solution of the sample. Place the
solution in a volumetric flask and add additional phosphorus
10.1 Using a sulfur sample irradiated in a calibration neu-
carrier solution to bring the total volume to 100 mL. Prepare a
tron field, determine the efficiency, ε, for the detector system:
sample for counting by pipetting 0.050 mL of the P solution
Cf exp@λt # λ t
τ d i
onto a standard planchet and evaporating in air to dryness.
ε 5 (1)
N σ¯ Φ 1 2 exp 2λt 1 2 exp 2λt
~ @ #!~ @ #!
s c i
Counting procedures and calculations are the same as in other
methods with the exception that an aliquot factor of 2000 must
where:
be introduced for the 0.050-mL sample removed from the
C = counts recorded in detector, less background,
100-mL flask.
f = correction for coincidence losses, if needed,
τ
32 −7 −1
λ = P decay constant,=5.625×10 s ,
9. Calibration
t = decay time, s,
d
t = count time, s,
9.1 Calibration is achieved by irradiation of sulfur in a
c
t = duration of irradiation, s,
fast-neutron field of known spectrum and intensity, and mea-
i
N = number of S atoms in pellet,
suring the resulting P activity to determine a counting
σ¯ = spectrum-averaged cross section for S in the calibra-
s
system’s efficiency. This calibration is specific for a given
2 24
tion neutron field, cm =10 b, and
detector system, counting geometry, and sulfur pellet size and
Φ = neutron fluence, n/cm .
mass or sample preparation. It is, however, valid for subse-
quentuseinmeasuringactivitiesinanyarbitraryspectrum,and 10.1.1 Fig. 1 shows a plot of
...
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