Education and science minister Hiroshi Hase said the Japan Atomic Energy Agency estimates it will cost around ¥300 billion to scrap the Monju fast-breeder reactor over 30 years.
The estimate was made by the agency in 2012 but had never been disclosed to the public.
The ministry has been in the middle of discussions about how to ensure safe operations of the trouble-prone experimental reactor in Tsuruga, Fukui Prefecture, after getting a warning from the Nuclear Regulation Authority last November.
The NRA said Monju needs a new operator and steps to guarantee its safety, including an option to close the facility if a new entity can’t be found to run it.
The decommissioning cost includes ¥130 billion for demolishing the reactor and ¥20 billion to remove the fuel, according to the ministry. If Monju continues operations, about ¥20 billion would be needed every year to maintain it.
The expected cost is “an uncertain figure estimated in the past” based on a variety of preconditions, Hase said at a news conference Tuesday. There is no plan to ask the agency to provide a new estimate, he added.
The cost estimates compare with about ¥36 billion to ¥85 billion required to close an ordinary reactor.
Kansai Electric Power Co. expects to spend a total of ¥68 billion to shut down two aging reactors at its Mihama plant in Fukui Prefecture.
A fast-breeder nuclear reactor operates in a more complex way using sodium as a coolant, making it more costly to decommission.
The government has spent more than ¥1 trillion on the Monju project as it seeks to recycle nuclear fuel to raise Japan’s energy self-sufficiency rate, which is currently around 6 percent.
A fast-breeder reactor can produce more plutonium than it consumes, and plutonium can be used as nuclear fuel for conventional and fast-breeder reactors by mixing it with uranium.
But Monju has a long track record of problems, starting with a major fire caused by a sodium leak in 1995. It has been idle much of the time since it first achieved criticality in 1994.