Present status and future prospect of JRR-3 and JRR-4

Abstract The large-scale modification of the JRR-3 was carried out for the years 1985–1990 to meet the demands for higher performance and greater utilization. After the modification, the fuel was converted to the high-density silicide fuel for upgrading the fuel cycle performance in 1999. The exchange of the thermal neutron guide tube to the super-mirror tube has been advancing since 1998 for upgrading thermal neutron beams. In the JRR-4, the conversion to the LEU silicide fuel, the renewal of some reactor systems, and the installation of a medical irradiation facility, etc. were carried out for the years 1996–1998. The JRR-3 will be utilized over the future as a complementary neutron source with the high-intense spallation neutron source, which is being constructed in the Japan Atomic Energy Research Institute. The JRR-4 will contribute continuously to the advancement of the medical technology.