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Mihama: Safety in doubt

August 8, 2016

EDITORIAL: Extending life of Mihama nuclear reactor raises doubts on safety


The life of another aging nuclear reactor in Japan is about to be extended.

The Nuclear Regulation Authority (NRA) has endorsed the draft inspection report for the No. 3 reactor at Kansai Electric Power Co.’s Mihama nuclear plant in Fukui Prefecture. The reactor will have been in service for 40 years at the end of November.

Two more NRA approvals will pave the way for an extension of the reactor’s commercial operations by up to 20 years.

The law stipulates that nuclear reactors that have been operating for four decades or longer should be shut down in principle to prevent unpredictable accidents. Extended operations of reactors beyond the legal 40-year life span are supposed to be exceptions.

In June this year, however, the NRA gave the green light to extend operations of the Nos. 1 and 2 reactors at Kansai Electric Power’s Takahama nuclear plant, also in Fukui Prefecture. The two reactors have been operating for more than 40 years.

Just two months later, the NRA appears ready to renew the license of the No. 3 reactor at the Mihama plant.

The disaster at the Fukushima No. 1 nuclear plant in 2011 underscored the need to wean society from its dependence on nuclear power as soon as possible. When areas affected by the triple meltdown are still struggling to recover, we should not ignore the vital lesson so casually.

The No. 3 reactor at the Mihama plant also has some unique problems that reinforce the case against extending its service.

First of all, the reactor is located close to a fault. This has led the NRA to raise the assumed standard intensity of shaking caused by an earthquake by 30 percent from the original estimate made by the utility.

The NRA’s inspection process is also questionable. After the assumed quake intensity was raised, Kansai Electric Power told the watchdog that it needs time to take additional safety measures.

In response to the utility’s request, the NRA postponed the final confirmation of the quake resistance of important facilities at the plant.

The NRA also adopted this approach for the Nos. 1 and 2 reactors at the Takahama plant. But putting off this vital part of reactor safety inspections, which should be done before making any license decision, is highly questionable.

Kansai Electric Power has decided to decommission the Nos. 1 and 2 reactors at its Mihama plant. The Osaka-based company has opted to apply for a license renewal for only the No. 3 reactor, partly out of consideration for the local communities that have long been living with nuclear power.

In addition, the No. 3 reactor’s output is relatively large, which has convinced the utility that extending its operations will pay off even if that requires taking costly additional safety measures.

But the company’s calculation may not add up. The expected cost of safety measures to enhance quake resistance has increased by nearly 40 billion yen ($390 million) from the original estimate. And the work required will be two years longer than originally expected and last until March 2020, according to the company.

That means the maximum period of extended operations will be 16 years.

The cost and work needed could increase further, making it necessary for the utility to spend even more money for a shorter extension of the reactor’s operations.

A recent series of court rulings have questioned the safety of nuclear reactors and suspended their operations.

If the No. 3 reactor at the Mihama plant receives approval to restart, local residents opposed to the plan will undoubtedly seek a court injunction or court ruling against the move.

Does the utility believe the reactor will generate expected profits even if it cannot be operated according to plans?

The No. 3 reactor was also hit by a fatal accident in 2004. High-temperature steam leaked from the reactor, killing or injuring 11 workers.

We must remember the principle at the root of the 40-year legal life span of nuclear reactors: Policy efforts should focus on minimizing the various risks involved in nuclear power generation. Plans to extend the life of the Mihama reactor should be reconsidered.

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