27 Mars 2016
March 26, 2016
Shikoku Electric Power Co. has decided to decommission the No. 1 reactor at the Ikata nuclear power complex in Ehime Prefecture, as the reactor will have been in operation 40 years come September next year.
In the wake of the Fukushima No. 1 nuclear plant disaster, the government has set a new rule limiting the operational life of reactors to 40 years, in principle. An extension of up to 20 years can be granted by the Nuclear Regulation Authority (NRA). Ikata nuclear plant operator Shikoku Electric Power Co. had sought to have the No. 1 reactor's lifespan extended, but abandoned the idea after finding the enormous safety improvement costs would make it unprofitable to keep the reactor running.
Reactor pressure vessels are said to deteriorate in 40 years due to being bombarded by neutrons. From the viewpoint of ensuring nuclear plant safety, reactors over 40 years of age need to be decommissioned, regardless of their profitability. It is hoped that Shikoku Electric's decision will set a precedent for other power companies.
Five other reactors around the 40-year limit are already set to be decommissioned, including the No. 1 and 2 reactors at Kansai Electric Power Co.'s Mihama nuclear plant in Fukui Prefecture, and the No. 1 reactor at Kyushu Electric Power Co.'s Genkai nuclear station in Saga Prefecture -- decisions made in March last year. With the decommissioning of the Ikata plant's No. 1 reactor, the number of reactors in Japan will be reduced to 42.
The six reactors facing decommissioning are relatively small, with output in the 300,000 to 500,000 kilowatt range. More recent reactors can generate 1 million kilowatts each.
The decision over whether to decommission reactors is left up to each utility, and behind Kansai Electric and Kyushu Electric's decisions to decommission the aforementioned reactors also lay the issue of profitability. The smaller the output of a reactor is, the less profitable it is considering the massive cost of safety measures.
Meanwhile, Kansai Electric has applied to the NRA to extend the service life of the No. 1 and 2 reactors at the Takahama nuclear plant, and the No. 3 reactor at the Mihama plant, both in Fukui Prefecture. The utility decided that those reactors -- which can each generate about 800,000 kilowatts -- will be profitable enough even with the immense safety costs.
However, aging reactors are fraught with more problems than deteriorating pressure vessels. The longer it has been since a reactor entered operation, the fewer engineers there are who can pass down legacy technologies. Some experts point out that there is a limit to how much the safety of elderly reactors can be improved because their design concept itself is outdated. The question of decommissioning a reactor and its output and economic efficiency should be considered separately.
Furthermore, utilities face a host of other challenges to moving ahead with steady decommissioning. First and foremost, the final disposal site for the colossal amount of radioactive waste that will be generated by dismantling reactors has yet to be decided. There are not even regulatory standards for disposing of the severely contaminated inner components of reactors.
It is also imperative to secure storage locations for spent nuclear fuel generated by nuclear plants. Under the government's nuclear fuel cycle policy, spent fuel had been destined for the reprocessing plant in Rokkasho, Aomori Prefecture. However, the plant is under safety review by the NRA, and there is no prospect of it becoming operational anytime soon.
Power companies and the government need to overcome these challenges. Reactor decommissioning seriously affects regional economies and the finances of local governments dependent on nuclear plant hosting subsidies. The central government's support is indispensable in associating the decommissioning business with regional revitalization, among other measures.