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

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.