Japan on 21 December confirmed that it will decommission its Monju prototype fast breeder reactor in Fukui Prefecture at a cost of around JPY375bn ($3.2bn). This includes JPY225bn for maintenance, JPY135bn for dismantling the plant and JPY15bn for defuelling and preparations for decommissioning. The task will take more than 30 years. Used fuel will be removed from the reactor by 2022 and the dismantling process will be completed by 2047. The government said that Monju was not problematic technologically, but had management problems, including those of its “maintenance framework, human resource development, and the relationships of responsibility among its various stakeholders”. The government also noted that it would cost more than $4.6bn to ensure that Monju met the new post-Fukushima regulatory standards. However, Fukui governor Issei Nishikawa said he would not accept the decision and would ask the government reconsider it.
Monju achieved criticality for the first time in 1994, but has mostly been offline since December 1995, four months it began power transmission, after 640kg of liquid sodium leaked from the secondary cooling loop, causing a fire. While there were no injuries and no radioactivity escaped plant buildings, the problem was compounded by the Japan Atomic Energy Agency’s (JAEA’s) attempts to cover up the scale of the damage. Monju was allowed to restart in May 2010 after a review of the plant’s design, and its safety procedures by revealed inadequacies. However, operation was suspended again in August 2010 after a fuel handling machine was dropped into the reactor during a refuelling outage. The equipment was subsequently retrieved and replaced but the Nuclear Regulation Authority (NRA) did not permit the reactor to restart. In November 2015, following concerns over equipment inspections, the NRA determined JAEA was not competent to operate the reactor.
The government said it would oversee the decommissioning of Monju after Fukui prefecture governor Issei Nishikawa said he regarded JAEA as incapable of safely carrying out the dismantling of the reactor. Monju, a 246MWe sodium-cooled fast reactor, was regarded as the core facility of the government’s policy for nuclear fuel recycling, and the government said Japan would continue fast reactor development. It noted that the incidents at Monju had led to a "stagnation" in the fast reactor development, as well as increased costs. Plans for a research centre for nuclear technology to be developed in the area around the Monju site were announced. Alternative designs of FBRs would be explored. The government said it would "thoroughly utilise" the technology, knowledge and human resources Japan has already built up in fast reactor development. In addition, it will look for international cooperation to promote fast reactor development.