Measurement of Effective Capture Cross Section of ^<238>Np for Thermal Neutrurons

概要

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The effective capture cross section (\\hatσ) of 238Np for thermal neutrons has been measured as data for the burn-up analysis of irradiated fuels and for the study of nuclear transmutation of minor actinides. A sample of 237Np was irradiated for 10 hours at the Kyoto University Reactor. Neptunium-238 and -239 were produced simultaneously via the double neutron capture reactions 237Np(n, γ)238Np(n, γ)239Np. The neutron flux at the irradiation position was monitored using Au and Co wires. The epithermal index r\\sqrtT⁄T0 in Westcott’s convention was deduced as 0.03. To measure the activities of 238Np and 239Np, a high-purity Ge detector with a BGO (Bi4Ge3O12) anti-coincidence shield has been developed. The \\hatσ of 238Np was deduced from the ratio of these activities. The result obtained is 479± 24 b for the \\hatσ of 238Np. The result is compared with data in the evaluated nuclear data libraries, ENDL-86, ENDF/B-VI, and JENDL-3.3.
社団法人日本原子力学会の論文
2004-01-25