Special to The Asahi Shimbun
Special to The Asahi Shimbun
As a scientist long involved in research and development of nuclear energy, I feel deep regrets for the trouble given to the public by accidents at reactors at the quake-stricken Fukushima No. 1 nuclear power plant.
The three towering principles for a nuclear power plant operator to deal with a powerful earthquake are "stop, cool and contain."
The operator of the plant, Tokyo Electric Power Co., managed to halt a nuclear reaction by inserting control rods at the initial stage.
But I wonder if the control rods were firmly inserted.
Even if an instrumental device shows that they are, the control rods' proper insertion should be verified with other means. But there has been no information available about them.
I find it troubling that no official announcement has been made so far about the position of the control rods although it is crucial in completely controlling a nuclear reaction.
To cool the nuclear reactor cores, TEPCO made the right decision to resort to the unprecedented method of pumping in seawater, although that step will force it to decommission those reactors.
But the decision came too late.
Every step TEPCO has taken is a day late and a dollar short. The release of information from TEPCO is even further behind.
The exposure of fuel rods at the No. 2 reactor for as long as several hours after the nuclear reaction had stopped should never have happened, even if it came two days after the stoppage.
The incident revealed TEPCO's lack of crisis-management ability.
TEPCO had no choice but to open valves to discharge vapor containing radioactive materials to prevent a wholesale rupture of the containment vessels of the nuclear reactors. The inevitable question now concerns the state of the pressure vessels and containment vessels.
We cannot make an accurate assessment of their state with the level of radioactivity in the surrounding area alone.
The vessels' ability to contain the radiation is apparently endangered, even if temporarily.
There were reports that a suppression pool at the No. 2 reactor was likely damaged, and radioactive substances may have leaked out from there.
Right now, the core's pressure vessel does not appear ruptured and thus the release of an enormous amount of radioactive materials into the atmosphere can be averted.
Nevertheless, we face a very grave situation.
As vice chairman of the Nuclear Safety Commission of Japan, an independent body, I took part in an operation to tackle a nuclear-criticality accident at JCO Co.'s uranium-processing plant in Tokai village in Ibaraki Prefecture in 1999. I was at the site.
The current government's approach is better than the one by its predecessor back then.
Prime Minister Naoto Kan and Chief Cabinet Secretary Yukio Edano are showing strong leadership in addressing the nuclear disaster.
In contrast, the Nuclear and Industrial Safety Agency (NISA), a regulator that oversees the nuclear power industry, does not seem to be fully functioning.
I have long questioned the wisdom of putting NISA under the oversight of the Ministry of Economy, Trade and Industry, which promotes nuclear power generation.
It seems that the negative effect of having NISA under the ministry has been unveiled in the unfolding event.
When the JCO accident occurred, many research institutes worked together with us in gathering various data.
All electric power companies cooperated by dispatching vehicles to monitor radiation levels.
We were able to ride out the crisis thanks to the full support, including advice and assistance, from people in the nuclear industry and other related sectors.
But in the current disaster, TEPCO and NISA seem to have taken on all the challenges by themselves, barely utilizing resources at other bodies.
They should have tackled the ongoing crisis while seeking help from the Nuclear Safety Commission of Japan and other bodies, but they have tried to cope with it alone.
And questions remain over the appropriateness of the steps they have taken.
The unfolding nuclear disaster has unveiled weaknesses in TEPCO's crisis-management system and a structural flaw in Japan's administrative policy to ensure the safety of nuclear power.
(This article was compiled from an interview by Satoshi Ozawa.)
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Kenji Sumita is professor emeritus at Osaka University. He specializes in nuclear engineering and radiation measurements. He served as vice chairman of the Nuclear Safety Commission of Japan.