Decommissioning plan submitted for Shimane 1

06 May 2016

Chugoku Electric Power Company has submitted an overview of its decommissioning plan for unit 1 of the Shimane nuclear power plant in Japan's Shimane prefecture to the country's nuclear regulator. The company expects dismantling of the plant to take 30 years to complete.

Shimane - 400 (Chugoku)
The Shimane plant (Image: Chugoku)

The utility submitted an outline of its plans for decommissioning the unit to the Nuclear Regulation Authority (NRA) on 28 April, having announced a year ago that it did not plan to restart the reactor.

Chugoku said decommissioning of Shimane 1 - a 460 MWe boiling water reactor that started commercial operation in March 1974 - is to be carried out in four stages. The first stage, lasting about six years, will involve preparing the reactor for dismantling (including the removal of all fuel and surveying radioactive contamination), while the second, lasting eight years, will be to dismantle peripheral equipment from the reactor and other major equipment. The third stage, also taking about eight years, will involve the demolition of the reactor itself, while the fourth stage, again taking about eight years, will see the demolition of all remaining buildings and the release of land for other uses.

During the first stage, all fuel is to be removed from the unit. This includes 722 used fuel assemblies that will be sent for reprocessing and 92 fresh fuel assemblies that will be stored in the unit's storage pool before being returned to the fuel fabricator.

Chugoku said it currently expects the decommissioning work to be completed by March 2046. However, it noted that while it has completed a detailed plan for the first phase of work, specific 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 it anticipates a total of some 60 tonnes of high-level waste to be generated during the decommissioning of Shimane 1, including components such as the control rods. A further 670 tonnes of intermediate-level waste, including the reactor vessel, will be produced, as well as 5350 tonnes of low-level waste. Some 20,680 tonnes of waste will not need to be treated as radioactive waste.

Shimane 1 was one of five older Japanese reactors to be officially declared for decommissioning in mid-March 2015 following the introduction of an accounting-related system earlier that month to determine which units should not be restarted. The other units included 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.

Researched and written
by World Nuclear News