Outline and implementation status of decommissioning plan of JRR-4

Japan Research Reactor No.4 (JRR-4) had been shifted to decommissioning phase in December 2017 after we received the approval of the decommissioning plan of JRR-4 on June 2017 and the approval of the change of the safety regulations related to it. Decommissioning works are divided two phases and proceeded according to its plan. In the first phase (from fiscal 2017 to 2024), we perform reactor shutdown, fuel removal and maintenance management, and in the second phase (from fiscal 2025 to 2036), the dismantling works. JRR-4 was initially installed for the purpose of shielding experiments of the nuclear ship 'Mutsu', reached its first criticality in 1965, and had been operated for about 45 years until December 2010. However, in consideration of the expenses required for the new regulatory standards implemented after the Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Plant accident and aging degradation, the decommissioning of JRR-4 was determined according to the JAEA reform plan in September 2013. This report describes the outline of the decommissioning plan of JRR-4 and the status of its implementation. (author)