18 Mai 2013
May 18, 2013
Overly optimistic assumptions about the safety of nuclear power plants can result in huge damage if a disaster actually takes place. That is one of the most important lessons that should be gleaned from the devastating accident that occurred in 2011 at the Fukushima No. 1 nuclear power plant.
The Nuclear Regulation Authority (NRA), which has been created to improve the nation’s nuclear safety regulations in line with the lessons learned, is completely right in demanding that nuclear power facilities be prepared for the greatest safety risks that can be assumed based on latest scientific knowledge.
But Kasai Electric Power Co. is behaving in a way that is difficult to understand because it goes against this point of view.
The utility is showing reluctance to comply with the nuclear watchdog’s requests concerning the safety of the No. 3 and 4 reactors at the company’s Oi nuclear plant in Fukui Prefecture. The two reactors are the only ones in Japan that are currently online.
There are two seafloor faults near the Oi plant and also an inland fault about 10 kilometers from the facility. Recent research has pointed to the possibility that the three faults can be linked within a bay located at a halfway point between them.
If linked, the three faults, which are all active, have a total length of 63 kilometers and could cause a more powerful earthquake than previously assumed.
The No. 3 and 4 reactors at the Oi plant are scheduled to remain in operation until September under provisional safety standards set after the Fukushima nuclear disaster.
The NRA, which plans to introduce tougher nuclear safety standards in July, has asked Kansai Electric Power to review the current estimates of the strength of possible quakes that could hit the Oi plant, under the assumption that an earthquake can be caused by movements occurring simultaneously along all the three faults. The utility, however, has rejected this request, which was made in line with the basic principles of the new regulatory standards.
Kansai Electric claims that its own research has shown there is little possibility of a quake involving all three faults.
But an independent expert who was consulted by the NRA said the possibility of such a quake cannot be ruled out.
Before the two reactors at the plant were restarted last year, Kansai Electric, on the instructions of the government, estimated the magnitude of a quake linked to all the faults.
The utility says the estimated magnitude was not large enough to raise concerns about a severe accident.
Now that new safety standards are to be introduced, however, there is a strong case for re-evaluating the risk just to be doubly sure.
There are also safety concerns about other nuclear power plants due to possible earthquakes on multiple faults.
The safety inspection of the two reactors at the Oi plant is drawing attention of other utilities as well because it is seen as a precedent.
That only reinforces the case for strictly dealing with the issue according to the NRA’s safety-first policy, which adopts the principle of erring on the side of safety. This principle should be firmly established through the safety inspection of the Oi plant.
Moreover, the decision to restart the two reactors at the Oi plant was a special measure taken in consideration of Kansai Electric’s heavy dependence on nuclear power generation in ensuring a stable power supply.
At that time, the president of the utility promised to take additional steps to confirm the safety of the plant according to new safety standards when they were introduced. The company should act responsibly and make every possible effort to match words with actions.
NRA Chairman Shunichi Tanaka has indicated his intention to suspend the operation of the Oi plant if a problem that raises serious safety concerns is discovered.
Although the summer season of peak demand for electricity is approaching, the NRA should not forget that its mission is to ensure the safety of nuclear facilities.
The nuclear watchdog should carry out a rigorous safety inspection of the plant while giving thought to the efforts of Japanese people to cut power consumption.
--The Asahi Shimbun, May 18