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Decommissioning of troubled fast-breeder reactor Monju would cost 300 billion yen

The Monju prototype fast-breeder reactor in Tsuruga, Fukui Prefecture, is pictured in this photo taken from a Mainichi helicopter on Oct. 7, 2015. (Mainichi)

The operator of Monju, a trouble-prone prototype fast-breeder nuclear reactor in Tsuruga, Fukui Prefecture, estimates that it would take at least 300 billion yen to decommission the reactor, the Mainichi Shimbun learned Feb. 15.

    This is the first time that Monju's decommissioning cost -- which is several times the cost of decommissioning regular nuclear reactors -- has come to light.

    The Nuclear Regulation Authority (NRA) has sought replacement of the reactor's operating body, the Japan Atomic Energy Agency (JAEA).

    Over 1 trillion yen has been pumped into the Monju reactor thus far, and even if it were reactivated, repairs and other maintenance costs would surpass another 100 billion yen. As such, massive costs would be required to either decommission or reactivate the reactor.

    The estimate was made in 2012. If decommissioning of Monju were to undergo the same procedures as the prototype nuclear test reactor Fugen, also in Tsuruga, it would take approximately 30 years and cost some 130 billion yen to dismantle the facility. It would cost an additional 20 billion yen to remove spent nuclear fuel, and some 150 billion yen for maintenance and management costs, such as electricity and labor. Estimated costs for the removal of spent nuclear fuel include temporary storage, but because no storage site has been decided, the cost of transporting spent fuel to such a site has not been included.

    In the case of ordinary nuclear reactors, such as the No. 1 and No. 2 reactors at Chubu Electric Power Co.'s Hamaoka nuclear plant in Shizuoka Prefecture, the cost of decommissioning both is expected to cost around 84 billion yen, while decommissioning both the No. 1 and No. 2 reactors at Kansai Electric Power Co.'s Mihama nuclear plant in Fukui Prefecture is estimated to cost around 68 billion yen.

    Because Monju is sodium-cooled, decommissioning costs are relatively higher than regular, water-cooled nuclear reactors. Furthermore, because the decommissioning technology for sodium-cooled reactors has yet to be established, funds for further research and development will also be needed. In response to numerous maintenance errors pointed out with the Monju reactor, the NRA advised the Ministry of Education, Culture, Sports, Science and Technology last November to propose an alternative operator to the JAEA. The NRA also demanded that if the ministry is unable to do so by around this coming summer, a fundamental review of Monju be conducted. The ministry set up a panel of experts late last year to consider a new operator for the troubled reactor.

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