Plans submitted for decommissioning unit 1 of Japan’s Shimane NPP

10 May 2016

Japan's Chugoku Electric Power Company has submitted an outline of its decommissioning plan for unit 1 of the Shimane NPP in Shimane prefecture to the Nuclear Regulation Authority (NRA) having previously submitted the plans to the Shimane prefectural government and the Matsue city government.

Shimane 1, a 460MWe boiling water reactor, started commercial operation in March 1974. The company expects dismantling to be completed by March 2046 and to cost a total of JPY38bn ($340m).

Decommissioning will be carried out in four stages. The first stage, lasting about six years, will prepare the reactor for dismantling, including the removal of all fuel and surveying radioactive contamination. Some 722 used fuel assemblies will be sent for reprocessing and 92 fresh fuel assemblies will be stored in the unit's storage pool before being returned to the fuel fabricator. Detailed plans for the subsequent stages will be "based on the results of the status of radioactive contaminant that will be performed in Phase 1", the company said. During the second stage (eight years), peripheral equipment from the reactor and other major equipment will be dismantled. The third stage (eight years) will involve the demolition of the reactor. All remaining buildings will be demolished during the fourth stage (eight years) and land will be released for other uses.

Chugoku estimates that some 60t of high-level waste will be generated during the decommissioning, including components such as the control rods. A further 670t of intermediate-level waste, including the reactor vessel, will be produced, as well as 5,350t of low-level waste. A further 20,680t will not be treated as radioactive waste.

Four other ageing Japanese reactors were officially listed for decommissioning in mid-March 2015 - Kansai Electric Power Company's Mihama units 1 and 2, unit 1 of Japan Atomic Power Company's (JAPC's) Tsuruga plant, and Kyushu Electric Power Company's Genkai 1. Kyushu submitted its decommissioning plan for Genkai 1 to the NRA last December, while JAPC and Kansai submitted their respective plans for Tsuruga 1 and Mihama units 1 and 2 in February.

In March this year, Shikoku Electric Power Company announced that unit 1 of its Ikata plant would officially enter the decommissioning phase on 10 May.

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