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Atomic energy agency submits Monju reactor decommissioning plan

In this Oct. 20, 2017 file photo, the Monju prototype fast-breeder nuclear reactor is seen in Tsuruga, Fukui Prefecture. (Mainichi)

The Japan Atomic Energy Agency (JAEA) submitted a plan to the Nuclear Regulation Authority (NRA) on Dec. 6 stating that it aims to complete decommissioning of the Monju prototype fast-breeder nuclear reactor in Tsuruga, Fukui Prefecture, by fiscal 2047.

If the NRA approves the plan, the JAEA will be able to go ahead with decommissioning work at the reactor. However, a range of issues such as where to place the spent nuclear fuel scheduled to be extracted from the site as well as how to remove liquid sodium still remain.

According to the plan, the decommissioning process will be split into four stages. The first stage is set to take place between fiscal 2018 and fiscal 2022 and will consist of removal of all 370 nuclear fuel assemblies from the reactor.

In the second and subsequent stages, which are scheduled to occur between fiscal 2023 and 2047, approximately 1,670 metric tons of liquid sodium coolant are planned to be extracted. Moreover, the building housing the reactor is set to be dismantled during this period.

The JAEA has not yet drawn up a specific schedule. However, it is planning to submit a more detailed plan to the NRA, with the view of undergoing some form of screening process.

The Monju reactor is unique because there are no previous examples of fast-breeder reactors being decommissioned in Japan. It differs to conventional nuclear power plants, as the method for extracting nuclear fuel from the site is complicated. Therefore, the NRA has decided to opt for the rare move of conducting screening from the relatively early stage of nuclear fuel removal.

With regard to the total amount of radioactive waste, it is estimated that approximately 26,700 tons will need to be removed from the reactor before the end of decommissioning.

In the morning on Dec. 6, JAEA executive director Hajime Ito visited the NRA to submit the decommissioning plan. "Taking various regrets into account, I want to win back the trust of the people by carrying out safe and reliable decommissioning," Ito said.

The decision to decommission the Monju reactor was made by the government in December 2016. However, the submission of the decommissioning plan was delayed as local representatives demanding regeneration of the area and enhanced safety measures failed to reach an agreement with the government.

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