Experiments of JRR-4 low-enriched-uranium-silicied fuel core

Hirane, Nobuhiko; Ishikuro, Yasuhiro ; Nagadomi, Hideki; Yokoo, Kenji ; Horiguchi, Hironori; Nemoto, Takumi; Yamamoto, Kazuyoshi ; Yagi, Masahiro ; Arai, Nobuyoshi; Watanabe, Shukichi; Kashima, Yoichi

JRR-4, a light-water-moderated and cooled, swimming pool type research reactor using high-enriched uranium plate-type fuels had been operated from 1965 to 1996. In order to convert to low-enriched-uranium-silicied fuels, modification work had been carried out for 2 years, from 1996 to 1998. After the modification, start-up experiments were carried out to obtain characteristics of the low-enriched-uranium-silicied fuel core. The measured excess reactivity, reactor shutdown margin and the maximum reactivity addition rate satisfied the nuclear limitation of the safety report for licensing. It was confirmed that conversion to low-enriched-uranium-silicied fuels was carried out properly. Besides, the necessary data for reactor operation were obtained, such as nuclear, thermal hydraulic and reactor control characteristics. This report describes the results of start-up experiments and burnup experiments. The first criticality of low-enriched-uranium-silicied core was achieved on 14th July 1998, and the operation for joint-use has been carried out since 6th October 1998.