Chubu Electric Power Co., which serves central Japan around Nagoya, decided Monday to suspend all operations at its Hamaoka nuclear power plant in Shizuoka Prefecture in response to Prime Minister Naoto Kan’s call Friday for the suspension for safety reasons.

His call came about a week after Chubu had disclosed a plan to resume by July the operation of the power plant’s No. 3 reactor, which has been undergoing regular checks since November 2010.

Mr. Kan acted rather quickly, apparently because the firm disclosed the plan while the nuclear crisis at Tokyo Electric Power Co.’s Fukushima No. 1 nuclear power plant is still going on.

Because the Hamaoka plant sits inside a zone where a magnitude-8 earthquake — referred to as the Tokai Earthquake — is expected to occur with high probability, Chubu’s decision appears reasonable. But the suspension of operations will continue only for about two or three years — until a bulwark 15 meters or more in height from sea level is erected behind a 10-to-15- meter-high dune facing the sea in front of the plant.

Although Chubu’s decision will cause power shortage, serious discussions must be held over whether the construction of the bulwark can justify resumption of the Hamaoka plant operations. Hamaoka is Chubu’s only nuclear power plant and has provided about 12 percent of the utility’s total power supply.

The operation of its Nos. 1 and 2 reactors ended permanently in 2009. While the No. 3 reactor has been under regular checks, the operations of Nos. 4 and 5 reactors have continued. But their operations will end within several days. Chubu has a plan to start building the No. 6 reactor in 2016.

Chubu’s decision will cause power shortages and may affect the whole Japanese economy. Still the power shortage problem should not distract attention from safety questions.

In 2005, Chubu started work to raise the Hamaoka’s resistance to seismic shocks. It now can endure shocks with an acceleration of 1,000 gals (one gal is equal to an acceleration of one centimeter per second per second). Chubu reportedly assumes that the plant can withstand a magnitude-8.5 quake. The company appears to think that once the bulwark is completed, there will be no safety problems with Hamaoka.

But the possibility should not be ruled out that strong tremors may make insertion of control rods into reactor cores difficult or may break pipes that play important roles in cooling the reactors. Attention also must be paid to what Mr. Kiyoo Mogi, professor emeritus of seismology at the University of Tokyo and former chairman of the government’s Coordination Committee for Earthquake Prediction, said in an interview with Tokyo Shimbun. His points include: (1) it is unpredictable what will happen if seismic forces concentrate on a structurally weak section of a reactor; (2) the possibility cannot be excluded that the Tokai Earthquake may occur together with two other expected major earthquakes (Tonankai and Nankai earthquakes); and (3) even a magnitude-7 earthquake, if it happens directly underneath the Hamaoka plant, could cause dreadful consequences.

Another seismologist, Mr. Katsuhiko Ishibashi, professor emeritus at Kobe University, says that the Tokai Earthquake will raise the site of the Hamaoka plant by one to two meters, making it uneven. This may destroy the planned bulwark.

There is also no guarantee that the bulwark can withstand strong tsunami. Also tsunami could hit the plant from two rivers flowing on either side of the plant.

It also must be remembered that backup power sources the power firms have newly installed to cope with a situation in which all the outside and emergency power sources have become out of use are not powerful enough to sufficiently cool reactors and put them in a stable condition. The Hamaoka plant is no exception.

Although Mr. Kan’s call led Chubu to suspend the Hamaoka plant operations, he must be criticized for not presenting a clear grand policy on energy. After seeing the accidents at the Fukushima No. 1 plant, no municipality will accept nuclear power plants in their areas. Japan will have no alternative but to push serious power-saving efforts across the nation and to gradually reduce dependence on nuclear power generation, which accounts for about 30 percent of Japan’s power supply. Use of old reactors should be stopped and other reactors should be subjected to strict safety checks.

A logical path should be to increase utilization of renewable energy sources, including solar, geothermal, wind and tidal powers, and other energy sources whose carbon dioxide emissions are relatively small, although renewable energy sources currently account for a negligible portion of Japan’s energy supply.

The current monopolistic electricity market should give way to the dispersal of small-sized energy generation and supply entities across the nation, which also means flexibility and a dispersion of risks. This path is not an easy one. But Mr. Kan should realize that political leadership with a vision can change the inertia and mindset of the power industry and electricity users.

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