Chubu Electric Power Co. has announced a plan to decommission two aging reactors at its Hamaoka Nuclear Power Station in Shizuoka Prefecture and build a new reactor as a replacement. The decision to decommission the No. 1 and No. 2 boiling water reactors with a combined output of 1.38 million kW is reasonable. But the decision to build a new advanced boiling water reactor with an output of 1.4 million kW is questionable. The nuclear-power station is situated over a cluster of potential hypocenters for the magnitude-8 “Tokai Earthquake,” which could happen anytime.

The No. 1 reactor started operation in March 1976 but has been shut since 2001 when a steam pipe was broken. Water leakage also occurred at the bottom of its pressurized vessel, casting doubts on its safety. The No. 2 reactor started operation in November 1978 but has been idle since 2004 due to a series of troubles.

The Hamaoka nuclear-power complex, with five reactors, has a total output of about 5 million kW and is Japan’s second-largest nuclear complex. In July 2003, local residents filed a lawsuit seeking permanent closure of the No. 1 to No. 4 reactors. In September 2004, the power company announced a plan to replace the shroud structure surrounding the No. 1 and No. 2 reactors’ cores. But this work has not progressed.

The Shizuoka District Court turned down the residents’ lawsuit in October 2007. It is now before the Tokyo High Court. Since it will take about 10 years and ¥300 billion to make the No. 1 and No. 2 reactors quake-proof, the power company decided to replace them with a new reactor, which is expected to cost about ¥400 billion.

The Hamaoka No. 1 and No. 2 reactors are among the nation’s 17 reactors that started operation 30 or more years ago. They account for about one-third of the nation’s 55 reactors. The decommissioning of aging reactors will become a big issue since sites for storing high-level nuclear wastes have yet to be found. Chubu Electronic Power Co. will also have a difficult time because it has to secure a new site adjacent to the No. 5 reactor to build the new reactor.

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