24 Mars 2013
March 22, 2013
A power blackout at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant resulted in a long stoppage in the circulation of water that cools spent fuel in several pools.
If the blackout had continued for days, the heat that the spent fuel constantly emits could have caused water in the cooling pools to evaporate, potentially resulting in accidents such as meltdowns and hydrogen explosions.
Fortunately, power was restored before it was too late, and the rise in water temperature did not go beyond 6 degrees at most.
But many people must have been alarmed.
The incident drove home the reality that even two years after the March 2011 disaster, the accident is still not over. Anxiety will continue until all fuel is removed. This is to be expected in a nuclear disaster.
Once again, the government and TEPCO are urged to step up efforts to eliminate unstable factors one by one.
The crippled nuclear reactors themselves have been fitted with backup power sources because even a short shutdown of cooling systems could cause them to return to the state of two years ago. But the fuel pools have no backup power sources.
Although the cause of the blackout has yet to be established, the possibility has arisen that a small animal, such as a rat, short-circuited a switchboard.
In building management, it is common practice to cover electrical systems with special nets to protect them from rodents. Such measures were not taken for the temporary switchboard, which was installed in May 2011, that caused the blackout.
Radiation levels in the nuclear complex remain high. The dose near the accident site is about 300 microsieverts per hour and workers are required to wear special protective clothing and full-face masks.Their work hours are restricted.
Priority is given to urgent work such as reinforcing pipes to cool reactors. Lower-priority tasks are inevitably put off.
But that is all the more why "such situations can happen again in the future," as Shunichi Tanaka, chairman of the Nuclear Regulation Authority, put it.
We must learn lessons from the incident so that we can deal calmly with future emergencies, by being prepared with a specially formed task force equipped with response measures.
What is troublesome is that conditions at the site change daily because of the various maintenance projects under way. This time, too, the blackout had a greater impact because two power networks that are usually independent from each other had been connected together. This was because of ongoing work to reinforce tsunami preparedness.
When multiple maintenance projects take place simultaneously, the risk of accidents rises. Therefore, what is indispensable is a system to constantly monitor the entire nuclear power plant as a whole.
Be that as it may, why did it take as long as three hours for TEPCO to inform media organizations about the blackout? Although the company had immediately reported the situation to the relevant central and local governments, if it is to inform the public at nighttime, it needs to do it through the media.
The mayor of Minami-Soma requested that TEPCO promptly pass on information.
The nuclear crisis is still ongoing. TEPCO should not forget that many people are watching closely.
--The Asahi Shimbun, March 22