Measurement of ²³³U-HU Substitution Reactivity Worth in KUCA for Integral Validation of ²³³U Nuclear Data

¹ Atomic Energy Research Institute, Kindai University, 3-4-1 Kowakae, Higashiosaka-shi, Osaka, Japan
² Institute for Integrated Radiation and Nuclear Science, Kyoto University, 1010 Asashiro, Kumatori-cho, Osaka, Japan

^* Corresponding author: t-sano@kindai.ac.jp

Published online: 26 May 2023

Abstract

In order to perform an integral evaluation of ²³³U nuclear data, measurements of substitution reactivity worth between ²³³U sample and high enriched uranium (HU) sample in the Kyoto University Critical Assembly (KUCA) were carried out. In this study, the experimental core was consisted of 24 fuel elements and 1 special fuel element with the ²³³U or HU sample. The fuel element was consisted of 31 unit cells and sandwiched by a upper and a lower polyethylene reflector. The unit has one enriched uranium plate of 1/16” thickness, three polyethylene plates of 1/8” thickness. The special fuel element was loaded at the center of the core. The substitution reactivity worth was defined as difference between the excess reactivity of the core in which the ²³³U sample or the HU sample inserted the core. The excess reactivities ware measured by the positive period method. As the result, the substation reactivity was obtained 0.0146±0.0006 %∆k/k. A numerical result by MVP3 with JENDL-4.0 was 0.0141±0.0002 %∆k/k and a C/E was 0.964 ± 0.041. On the other hand, the calculated substitution reactivity worth with JENDL-5 was 0.0168±0.0002 %∆k/k and a C/E was 1.151±0.047.