Measurements of neutron capture cross section of Np for fast neutrons

Harada, Hideo   ; Nakamura, Shoji  ; Hatsukawa, Yuichi; Toh, Yosuke   ; Kimura, Atsushi   ; Ishiwatari, Yuki*; Yasumi, Atsushi*; Mabuchi, Yukio*; Nakagawa, Tsutomu*; Okamura, Kazuo*; Saito, Isao*; Oka, Yoshiaki*

The neutron capture cross section of Np has been measured for fast neutrons supplied at the center of the core in the Yayoi reactor. The activation method was used for the measurement, in which the amount of the product Np was determined by -ray spectroscopy using a Ge detector. The representative neutron energy and the corresponding capture cross section of Np in the experiment were analytically deduced as 0.80 0.04 b at 0.214 0.009 MeV from the measured reaction rate by combining the energy dependence of the cross section in the nuclear data library ENDF/VII.0. The deduced cross section of Np at the representative neutron energy agrees with the evaluated data of ENDF/B-VII.0, but shows 15% larger value than that of JENDL-3.3 and 13% larger value than that of JENDL/AC-2008.