Hamaoka 1 and 2 are both boiling water reactors, starting up in 1973 and 1978, respectively. Unit 1 had a capacity of 540 MWe while unit 2’s capacity was 840 MWe. Chubu decided to close both units in January 2009 as they required expensive modifications to meet seismic standards imposed after the July 2007 Niigata Chuetsu offshore earthquake.
The utility submitted a decommissioning plan for Hamaoka 1 and 2 in June 2009, which was subsequently revised in September of that year. The overall plan divided the decommissioning of the two units into four stages. The first stage is for preparations for dismantling work at the units, while the second stage covers the dismantling and removal of equipment surrounding the reactors. The third stage is for the dismantling of the reactors themselves, while the fourth covers the demolition of buildings at both units.
The plan was approved by the Ministry of Economy, Trade and Industry in November 2009, when Chubu began stage 1 of the decommissioning programme.
Having completed stage two work at both units, on 18 December last year the Nuclear Regulation Authority approved Chubu’s application to move to the third stage of decommissioning at the units.
Chubu announced on 17 March that it had removed the upper lid of the pressure vessel of unit 2, marking the start of the dismantling of the reactor itself. As well as the reactor pressure vessel, the reactor internals and radiation shielding surrounding the vessel will be dismantled.
Hamaoka 1 and 2 are the first two commercial nuclear power reactors in Japan to enter the reactor dismantling phase.
Chubu plans to dismantle units 1 and 2 over a period of about 12 years, starting with the reactor of unit 2 first. The decommissioning of the two reactors is expected to be completed in fiscal 2042 after the reactor buildings are demolished.
