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ASTM E704-19
Standard Test Method for Measuring Reaction Rates by Radioactivation of Uranium-238
NORMA vydaná dňa 1.10.2019
Informácie o norme:
Označenie normy: ASTM E704-19
Dátum vydania normy: 1.10.2019
Kód tovaru: NS-972596
Počet strán: 5
Približná hmotnosť: 15 g (0.03 libier)
Krajina: Americká technická norma
Kategória: Technické normy ASTM
Kategórie - podobné normy:
Anotácia textu normy ASTM E704-19 :
Keywords:
fission dosimeter, fission product, fission reaction rates, Uranium-238 ,, ICS Number Code 17.240 (Radiation measurements), 27.120.30 (Fissile materials and nuclear fuel technology)
Doplňujúce informácie
| Significance and Use | ||||||||||||||||||||||
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5.1 Refer to Practice E261 for a general discussion of the determination of fast-neutron fluence rate with fission detectors. 5.2 238U is available as metal foil, wire, or oxide powder (see Guide E844). It is usually encapsulated in a suitable container to prevent loss of, and contamination by, the 238U 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. 5.3.1 137Cs-137mBa
is chosen frequently for long irradiations. Radioactive
products 134Cs and 136Cs may be present,
which can interfere with the counting of the 0.662 MeV
137Cs-137mBa gamma rays (see Test Method
E320).
5.3.2 140Ba-140La is chosen frequently for short irradiations (see Test Method E393). 5.3.3 95Zr can be counted directly, following chemical separation, or with its daughter 95Nb using a high-resolution gamma detector system. 5.3.4 144Ce is a high-yield fission product applicable to 2- to 3-year irradiations. 5.4 It is necessary to surround the 238U monitor with a thermal neutron absorber to minimize fission product production from a quantity of 235U in the 238U target and from 239Pu from (n,γ) reactions in the 238U material. Assay of the 239Pu concentration when a significant contribution is expected. 5.4.1 Fission product production in a light-water reactor by neutron activation product 239Pu has been calculated to be insignificant (<2 %), compared to that from 238U(n,f), for an irradiation period of 12 years at a fast-neutron (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 5.5 Good agreement between neutron fluence measured by 238U fission and the 54Fe(n,p)54Mn reaction has been demonstrated 5.6 The 238U fission neutron spectrum-averaged cross section in several benchmark neutron fields is given in Table 3 of Practice E261. Sources for the latest recommended cross sections are given in Guide E1018. In the case of the 238U(n,f)F.P. reaction, the recommended cross section source is the ENDF/B-VI release 8 cross section (MAT = 9237) FIG. 1 ENDF/B-VI Cross Section Versus Energy for the 238U(n,f)F.P. Reaction Note 1: The data is taken from the Evaluated Nuclear Data
File, ENDF/B-VI, rather than the later ENDF/B-VII. This is in
accordance with Guide E1018,
Section 6.1, since the later ENDF/B-VII data files do not include
covariance information. Some covariance information exists
for 238U in the standard sublibrary, but this is only
for energies greater than 1 MeV. For more details, see Section H of
Ref 1.1 This test method covers procedures
for measuring reaction rates by assaying a fission product (F.P.)
from the fission reaction 238U(n,f)F.P.
1.2 The reaction is useful for measuring neutrons with energies from approximately 1.5 to 7 MeV and for irradiation times up to 30 to 40 years, provided that the analysis methods described in Practice E261 are followed. 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, health, and environmental 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. |
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| 2. Referenced Documents | ||||||||||||||||||||||
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