Photo/IllutrationAn aerial view of the Monju prototype fast-breeder reactor in Tsuruga, Fukui Prefecture (Asahi Shimbun file photo)

The government on Dec. 21 formally turned out the lights on the Monju prototype fast-breeder reactor in Tsuruga, Fukui Prefecture, which cost more than 1 trillion yen ($8.5 billion) but operated for only 250 days.

A meeting of relevant Cabinet ministers connected with nuclear energy policy decided on Dec. 21 to mothball the embattled project.

But befitting its long history of problems, the end did not come quietly as Fukui Governor Issei Nishikawa blasted the central government for opting for decommissioning without giving adequate consideration to whether the work will actually be safe.

On the morning of Dec. 21, Nishikawa met with Hirokazu Matsuno, the science minister, and Hiroshige Seko, the economy minister.

Responding to the concerns previously raised by Nishikawa about the overall evaluation of the Monju project and the establishment of a safety control structure to oversee the decommissioning process, the central government officials promised to continue discussions with Fukui prefectural government officials.

Pledging to set up a comprehensive structure to lead the decommissioning, the government asked for the understanding of the Fukui prefectural government and said a more detailed plan for decommissioning Monju would be presented in April 2017.

But Nishikawa was not satisfied. In particular, he criticized the government approach of having the Japan Atomic Energy Agency assume the lead role in decommissioning Monju.

Saying he could not consent to that position, Nishikawa told reporters that he, as governor, had not given his approval for the decommissioning.

Nishikawa has pointed to concerns of his constituents because the Nuclear Regulation Authority has stated the JAEA has not adequately dealt with maintenance and management of the Monju reactor.

Nishikawa said he would continue to ask the central government for a more detailed explanation.

While agreeing to decommission Monju, the central government also decided to continue developing a fast reactor.

Science ministry officials said it would take a minimum of eight years to prepare a new reactor at the Monju site so it could resume operations as a fast reactor. It would also cost 540 billion yen to operate that reactor for an eight-year period.

The cost of decommissioning the fast-breeder reactor would be a minimum of 375 billion yen.

However, the central government has decided that proceeding with the development of a new fast reactor would create greater returns for the investment.

Decommissioning will start in the next fiscal year with preparations to remove the spent nuclear fuel, the removal of which will take until fiscal 2022. The entire decommissioning process is expected to be completed in 30 years.

When the Monju reactor was planned in the 1950s, it was considered a "dream" project that would produce more fuel than it consumed.

Monju was begun with the hope of producing a quasi-domestic energy industry for Japan, which has few natural energy resources.

Monju reached criticality in 1994, but the leaking of sodium coolant occurred the following year, causing a fire. The manner in which that accident was dealt with, as well as other problems in subsequent years, led to Monju barely being in an operable state.

In November 2015, the NRA recommended to the science minister that a new body be established to run Monju.

The science ministry took more than six months to establish a new body, but could not obtain the cooperation of electric power companies or equipment manufacturers.

In September 2016, the relevant ministers handling nuclear energy policy decided on a comprehensive review of the Monju project, including the possibility of decommissioning.