Determination methods of condition of soil etc. on confirmation of completion of decommissioning

Otsuka, Kaede*; Shimada, Taro ; Takahashi, Hiroaki*

Based on the Act on Regulation of Nuclear Source Materials, Nuclear Fuel Materials and Reactors (Act No. 166 of 1957), licensee shall develop decommissioning plan and submit it to the Nuclear Regulation Authority (hereinafter referred to as "NRA") when a nuclear power reactor or nuclear power business is to be decommissioned. When the decommissioning is completed, the result shall be confirmed by the NRA as being in compliance with the "criteria specified by the NRA", but no specific method has been established. As a result of Integrated Regulatory Review Service which was conducted in 2016, the International Atomic Energy Agency advised that criteria be established for site release after the completion of decommissioning. In response of the advice, the NRA issued "The guide for determining the condition of site soil etc." in 2022. To properly implement the Guide, it was considered that a specific method for collecting samples should be identified. Moreover, the Guide does not cover facilities affected by the fallout from the TEPCO's Fukushima Daiichi Nuclear Power Plant accident (hereinafter referred to as "1F fallout"). The Secretariat of the NRA had commissioned the research to the Japan Atomic Energy Agency (hereinafter referred to as "JAEA") between 2019 and 2022, in order to develop determination methods of condition of soil etc., of the decommissioning facility affected by 1F fallout. This report proposes the determination methods of condition of soil etc. on confirmation of completion of decommissioning, based on the result of commissioning research conducted by the JAEA.