ASTM E705-18

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Designation: E705 − 13a E705 − 18
Standard Test Method for
Measuring Reaction Rates by Radioactivation of Neptunium-
This standard is issued under the fixed designation E705; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers procedures for measuring reaction rates by assaying a fission product (F.P.) from the fission reaction
Np(n,f)F.P.
1.2 The reaction is useful for measuring neutrons with energies from approximately 0.7 to 6 MeV and for irradiation times up
to 30 to 40 years.90 years, provided that the analysis methods described in Practice E261 are followed. If dosimeters are analyzed
after irradiation periods longer than 90 years, the information inferred about the fluence during irradiation periods more than 90
years before the end of the irradiation should not be relied upon without supporting data from dosimeters withdrawn earlier.
1.3 Equivalent fission neutron fluence rates as defined in Practice E261 can be determined.
1.4 Detailed procedures for other fast-neutron detectors are referenced in Practice E261.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.7 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.
2. Referenced Documents
2.1 ASTM Standards:
E170 Terminology Relating to Radiation Measurements and Dosimetry
E181 Test Methods for Detector Calibration and Analysis of Radionuclides
E261 Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation Techniques
E262 Test Method for Determining Thermal Neutron Reaction Rates and Thermal Neutron Fluence Rates by Radioactivation
Techniques
E320 Test Method for Cesium-137 in Nuclear Fuel Solutions by Radiochemical Analysis (Withdrawn 1993)
E393 Test Method for Measuring Reaction Rates by Analysis of Barium-140 From Fission Dosimeters
E704 Test Method for Measuring Reaction Rates by Radioactivation of Uranium-238
E844 Guide for Sensor Set Design and Irradiation for Reactor Surveillance
E944 Guide for Application of Neutron Spectrum Adjustment Methods in Reactor Surveillance
E1005 Test Method for Application and Analysis of Radiometric Monitors for Reactor Vessel Surveillance
E1018 Guide for Application of ASTM Evaluated Cross Section Data File
3. Terminology
3.1 Definitions:
3.1.1 Refer to Terminology E170.
This test method is under the jurisdiction of ASTM Committee E10 on Nuclear Technology and Applicationsand is the direct responsibility of Subcommittee E10.05 on
Nuclear Radiation Metrology.
Current edition approved Aug. 1, 2013Dec. 1, 2018. Published August 2013December 2018. Originally approved in 1979. Last previous edition approved 2013 as
E705 – 13.E705 – 13a. DOI: 10.1520/E0705-13A.10.1520/E0705-18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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
E705 − 18
4. Summary of Test Method
4.1 High-purity Np (<40 ppm fissionable impurity) is irradiated in a fast-neutron field, thereby producing radioactive fission
products from the reaction Np(n,f)F.P.
137 137m 1140140 140 95 144
4.2 Various fission products such as Cs- Ba, Ba- La, Zr, and Ce can be assayed depending on the length
of irradiation, purpose of the experiment, etc.
4.3 The gamma rays emitted through radioactive decay are counted and the reaction rate, as defined in Practice E261, is
calculated from the decay rate and the irradiation conditions.
4.4 The neutron fluence rate for neutrons with energies from approximately 0.7 to 6 MeV can then be calculated from the
spectral-weighted neutron activation cross section as defined in Practice E261.
238 237
4.5 A parallel procedure that uses U instead of Np is given in Test Method E704.
5. Significance and Use
5.1 Refer to Practice E261 for a general discussion of the determination of fast-neutron fluence rate with fission detectors.
5.2 Np is available as metal foil, wire, or oxide powder. For further information, see Guide E844. It is usually encapsulated
237 4
in a suitable container to prevent loss of, and contamination by, the Np and its fission products.
5.3 One or more fission products can be assayed. Pertinent data for relevant fission products are given in Table 1 and Table
2.
137 137m 134 136
5.3.1 Cs- Ba is chosen frequently for long irradiations. Radioactive products Cs and Cs may be present, which can
137 137m
interfere with the counting of the 0.6620.661657 MeV Cs- Ba gamma ray (see Test Methods E320).
140 140
5.3.2 Ba- La is chosen frequently for short irradiations (see Test Method E393).
95 95
5.3.3 Zr can be counted directly, following chemical separation, or with its daughter Nb, using a high-resolution gamma
detector system.
5.3.4 Ce is a high-yield fission product applicable to 2- to 3-year irradiations.
5.4 It is necessary to surround the Np monitor with a thermal neutron absorber to minimize fission product production from
237 238 238 237
trace quantities of fissionable nuclides in the Np target and from Np and Pu from (n,γ) reactions in the Np material.
238 239
Assay of Pu and Pu concentration is recommended when a significant contribution is expected.
238 238
5.4.1 Fission product production in a light-water reactor by neutron activation products Np and Pu has been calculated
to be insignificant (1.2 %), compared to that from Np(n,f), for an irradiation period of 12 years at a fast neutron (E > 1 MeV)
11 −2 −1 237
fluence rate of 1 × 10 cm ·s , provided the Np is shielded from thermal neutrons (see Fig. 2 of Guide E844).
5.4.2 Fission product production from photonuclear reactions, that is, (γ,f) reactions, while negligible near-power and research
reactor cores, can be large for deep-water penetrations (13).
5.5 This dosimetry reaction is important in the area of reactor retrospective dosimetry (4, 5). Good agreement between neutron
237 54 54 237
fluence measured by Np fission and the Fe(n,p) Mn reaction has been demonstrated (26, 7). The reaction Np(n,f) F.P.
is useful since it is responsive to a broader range of neutron energies than most threshold detectors.
5.5.1 Fig. 1 shows the energy-dependent cross section for this dosimetry reaction. The figure shows that, while it is not strictly
a threshold detector, because of its sensitivity in the greater than 0.1 MeV neutron energy range it can function as a detector with
252 237
good sensitivity in the fast neutron region. In the fast fission Cf spontaneous fission benchmark field, ~1 % of the Np fission
dosimeter response comes from neutrons with an energy less than 0.1 MeV. In the cavity of a fast burst U reactor, ~5 % of the
Np ifssion dosimeter response comes from neutrons with an energy less than 0.1 MeV. In the cavity of a well-moderated
pool-type research reactor ~50 % of the fission response from the Np(n,f) reaction comes from energies less than 0.1 MeV. The
importance of this low neutron energy sensitivity should be determined based on the aplication.
5.6 The Np fission neutron spectrum-averaged cross section in several benchmark neutron fields are given in Table 3 of
Practice E261. Sources for the latest recommended cross sections are given in Guide E1018. In the case of the Np(n,f)F.P.
reaction, the recommended cross section source is the ENDF/B-VI Russian Reactor Dosimetry File, RRDF (8).cross section
(MAT = 9346) revision 1 This recommended cross section is identical, for energies up to 20 MeV, to what is found in the latest
International Atomic Energy (IAEA) International Reactor Dosimetry and Fusion File, IRDFF-1.05 (39).) . Fig. 1 shows a plot of
the recommended cross section versus neutron energy for the fast-neutron reaction Np(n,f)F.P.
NOTE 1—The data are taken from the Evaluated Nuclear Data file, ENDF/B-VI, rather than the later ENDF/B-VII. This is in accordance with Guide
The sole source of supply of Vanadium-encapsulated monitors of high purity known to the committee at this time in the United States is Isotope Sales Div., Oak the
National Isotope Development Center, Isotope Business Office, Oak Ridge National Laboratory, Oak Ridge, TN 37830. In Europe, the sole source of supply is European
Commission, JRC, Institute for Reference Materials and Measurements (IRMM) Reference Materials Unit Retieseweg 111, B-2440 Geel, Belgium. If you are aware of
alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible
technical committee, which you may attend.
The boldface numbers in parentheses refer to the list of references appended to this test method.
E705 − 18
TABLE 1 Recommended Nuclear Parameters for Certain Fission
Products
Maximum
Primary
Fission Parent γ Probability of Useful
A
Radiation
A A
Product Half-Life (6) Decay (7) Irradiation
(7) (keV)
Duration
Zr 64.032 (6) d 724.192 (4) 0.4427 (22) 6 months
756.725 (12) 0.5438
Mo 65.94 (1) hr 739.500 (17) 0.1213 (22) 300 hours
777.921 (20) 0.0426 (8)
Ru 39.26 (2) d 497.085 (10) 0.910 (12) 4 months
137 B B
Cs 30.05 (8) yr 661.657 (3) 0.8499 (20) 30–40 years
140 140
Ba– La 12.7527 (23) d 537.261 (3) 0.2439 (22) 1–1.5
months
C
1596.21 (4) 0.9540 (8)
D
1.1515
Ce 28.91 (5) d 133.515 (2) 0.1109 (19) 2–3 years
TABLE 1 Recommended Nuclear Parameters for Certain Fission
Products
Maximum
Primary
Fission Parent γ Probability of Useful
A
Radiation
A,E A,E
Product Half-Life (1) ,E Decay (1) Irradiation
(1) (keV)
Duration
Zr 64.032 (6) days 724.193 (3) 0.4427 (22) 6 months
756.729 (12) 0.5438 (22)
Mo 2.747 (6) days 739.500 (17) 0.122 (15) 300 h
777.921 (20) 0.0428 (8)
Ru 39.247 (13) days 497.085 (10) 0.910 (12) 4 months
137 B B
Cs 30.05 (8) years 661.657 (3) 0.8499 (20) 90 years
140 140
Ba– La 12.753 (4) days 537.303 (6) 0.2439 (22) 1–1.5
months
C
1596.203 (13) 0.9540 (5)
D
1.1516 (5)
Ce 284.89 (6) days 133.5152 (20) 0.1083 (12) 2–3 years
A
The The lightface numbers in parentheses are the magnitude of plus or minus
uncertainties in the last digit(s) listed.
B 137m
With With Ba (2.552 min) in equilibrium.
C 140
Probability Probability of daughter La decay.
D 140
With With La (1.67855(1.67850 d) in transient equilibrium.
E
Primary reference for half-life, gamma energy, and gamma emission probability
is Ref (1) when data is available. Note this reference is to the BIPM data that was
recommended at the time of the recommended fission yields were set, that is, as
of 2009, and not to the latest Vol 8 data that was published in 2016.
E1018 Guide for Application of ASTM Evaluated Cross Section Data File, 6.1. since the later ENDF/B-VII data files do not include covariance
information. For more details see Section H of (4)
6. Apparatus
6.1 Gamma-Ray Detection Equipment that can be used to accurately measure the decay rate of fission product activity are the
following two types (510):
6.1.1 NaI(T1) Gamma-Ray Scintillation Spectrometer (see Test Methods E181 and E1005).
6.1.2 Germanium Gamma-Ray Spectrometer (see Test Methods E181 and E1005)—Because of its high resolution, the
germanium detector is useful when contaminant activities are present.
6.2 Balance, providing the accuracy and precision required by the experiment.
6.3 Digital Computer, useful for data analysis, but is not necessary (optional).
7. Materials
7.1 Neptunium-237 Alloy or Oxide—High-purity Np in the form of alloy wire, foil, or oxide powder is available.
7.1.1 The Np target material should be furnished with a certificate of analysis indicating any impurity concentrations.
7.2 Encapsulating Materials—Brass, stainless steel, copper, aluminum, vanadium, and quartz have been used as primary
encapsulating materials. The container should be constructed in such a manner that it will not create significant perturbation of the
neutron spectrum or fluence rate and that it may be opened easily, especially if the capsule is to be opened remotely. Certain
encapsulation materials, for example, quartz and vanadium, allow gamma-ray counting without opening the capsule since there are
no interfering activities.
E705 − 18
TABLE 2 Recommended Fission Yields for Certain Fission
A
Products
B,A
Fissile Neutron Reaction Type JEFF 3.1
Fission Yield (%)
Isotope Energy Product Yield
237 95
Np(n,f) 0.5 MeV Zr RC 5.6147 ± 2.7 %
Mo RC 7.6118 ± 16.34 %
Ru RC 5.4305 ± 12.7 %
Cs RC 6.2654 ± 3.71 %
137m
Ba RI 1.4802e-3 ±
35.58 %
Ba RC 5.9160 ± 3.82 %
La RI 6.3568e-3 ±
36.68 %
Ce RC 4.1230 ± 4.7 %
TABLE 2 Recommended Fission Yields for Certain Fission
A
Products
B,A
Fissile Neutron Reaction Type JEFF 3.1.1
C
Fission Yield (%)
Isotope Energy Product Yield
237 95
Np(n,f) 0.4 MeV Zr RC 5.6147 ± 2.7 %
Mo RC 7.6218 ± 16.304 %
...