CRITICAL EXPERIMENT OF THORIUM LOADED THERMAL CORES AT KUCA (1) A NEW CRITICAL EXPERIMENT OF THORIUM LOADED CORE WITH HARDER NEUTRON SPECTRUM IN KUCA

摘要

In order to perform integral evaluation of~(232)Th capture cross section, a series of critical experiments for thorium-loaded and solid-moderated cores in KUCA had been carried out. In these experimental cores, H/~(235)U nuclide ratio ranged about from 150 to 315, and~(232)Th/~(235)U nuclide ratio ranged about from 13 to 19. In this study, a new critical experiment with Th loaded core in KUCA, which had about 70 of the H/~(235)U ratio and 12.7 of~(232)Th/~(235)U ratio, was carried out. As results, the excess reactivity was 0.086 ± 0.003 (% dk/k) and the k_(eff)was 1.0009 ± 0.0003, where the effective delayed neutron fraction was 7.656E-3. The k_(eff)was also calculated by MVP3.0 with different nuclear libraries. The respective calculations with JENDL-4.0, JENDL-3.3 and ENDF/B-VII.0 lead to 1.0056 ± 0.0086 (%), 1.0048 ± 0.0085 (%) and 1.0056 ± 0.0086 (%).On the other hand, the further MVP3.0 calculations, where only the~(232)Th cross sections were taken from JENDL-4.0, JENDL-3.3 or ENDF/B-VII.0 but all other nuclides were done from JENDL-4.0, were carried out to examine an impact of the difference of~(232)Th cross section among these nuclear libraries to the k_(eff). The k_(eff)calculated with respective~(232)Th cross sections from JENDL-3.3 and ENDF/B-VII.0 was 1.0038 ± 0.0086 (%) and 1.0040 ± 0.0086 (%).