Reflection on the Fukushima accidents

Sixteen months have passed since the severe nuclear accidents in the nuclear power plant in Fukushima, operated by TEPCO. In Japan, and in all over the world to some extent, rather hysterical opposition against nuclear energy is still raging. It is understandable, considering the fact that nuclear technology is beyond understanding of the general public. I have studied the accidents extensively and now feel that I would not be afraid of living just outside the nuclear plant fances, because negligibly small is the probability that similar accidents should be repeated and that I would be able to safely flee from the accidents in case they should ever happen at all.

Some people argue that the accidents in Fukushima were as bad as those in Chernobyl in 1986. Both were classified as the Level 7 disasters. The level 7 in the international scale is the highest level, while other lower levels are defined according to the amount of radioactivity released into the ambience. Difference of one level corresponds to ten times difference of the released radioactivity. Actually Chernobyl accidents released roughly ten times radioactivity of that in Fukushima accidents. If higher levels had been defined, Fukushima accidents should have been a Level 7 disaster while Chernobyl ones should have been a Level 8 disaster.

Soon after the Fukushima accidents, I wrote that a certain areas nearest to the nuclear plant might become uninhabitable for decades. A friend of mine, who had been in the nuclear manufacturing industry, fiercely opposed to my opinion, and said that such things should not happen at all. From this and other conversations, I realised that the more knowledgeable people were in nuclear technologies, the more optimistic those people were. Therefore, by extention of inference, it is quite understandable that the general public is hysterical about nuclear accidents. A slogan of an anti-nuclear demonstration read "Life is more important than prosperity". That slogan forgets the fact that although as many as 27 thousand people perished because of the earthquake and tsunami, no one has ever become sick or dead because of the spread radioactivity in Fukushima. In Chernobyl, many boys and girls sufferred from thyroid carcinoma because they continued to drink contaminated milk. That didn't happen in Fukushima. Other sickness has not been reported in the Chernobyl case. I believe, therefore, there will happen practically no illness or casualties caused by radioactivity in Fukushima.

I extensively studied the accidents in Fukushima and have summarized the causes of accidents as follows;

(1) I believe that the nuclear plant successfully endured the once-in-thousand-years earthquake, and that although all electrical powers into the plant went out, the emergency power generators started automatically. Then, however, the once-in-thousand-years tsunami attacked and flooded all emergency power generators. The plant must have been controlled if (a) tsunami should have been smaller, or (b) if the emergency generators should have been placed on higher grounds, or (c) if separate mobile generators should have been prepared on higher grounds near the site. At least, (c) has been already realized in all nuclear plants in Japan. The essential mistake here is that no body including TEPCO people has anticipated or believed in tsunami of such height.

(2) If sea water had been immediately pumped into the reactor by fire engines, the plant must have been controlled. But pumping sea water would mean abolishing the reactors, and no one could quickly decide it. Since no one anticipated the no power situation, no one discussed the countermeasures for it in advance.
But discussions and considerations are virtually of no cost, and, therefore, those should have been done. The reasonable conclusion of such discussions would have been "pump sea water", and it would have been included in the operation manual. A single line of instruction "pump sea water" in the operation manual must have avoided spread of radioactivity. Now people are wise enough to be prepared for pumping sea water if necessary.

(3) Most of the released radioactivity into the water was caused by fissures of the No. 2 reactor in the excessive presure, and most of radioactivity spread into the atmonphere was from hydrogen explosion of the buildings for the 1st, 3rd and 4th reactors. The No. 4 reactor was not loaded with nuclear fuel at all, but why did its building explode ? The reason for explosion was as follows.
Internationl community of nuclear technologies concluded at some time in the past that reactors should have "vent" facilities, which would release the excessive pressure of the reactor in case of accidents. TEPCO didn't believe that vent facilities were necessary, because TEPCO didn't believe in accidents, but the Government forced TEPCO to add "vent" facilities. TEPCO accepted but added nominal minimum facilities; One chimney was shared by two reactors. Namely, No.1 and No. 2 shared a chimney, while No. 3 and No. 4 shared another. The chimneies were used also to vent the atmosphere inside the buildings through valves to prevent backward flow. This prevention was later found incomplete. Venting routes had filters to capture radioactivity, but those filters worked only with electric power, because TEPCO didn't believe in no power situation.
During the accidents, venting had to be done. But hydrogen-rich exhaust flowed back through defective valves into the buildings, which then exploded. Because the filters didn't work in the blackout, huge amount of radioactivity was spread by explosions. No. 4 building exploded because of the vent of No. 3 reactor.
If (a) More robust vent facilities had been installed, or if (b) accumulation of hydrogen in the buildings had been avoided by vent valves at the ceilings, or if (c) better filters had been installed, the accidents would have been much lighter.

(4) No.2 reactor got fissures while TEPCO was taking time to find out how to vent without electric power. People should know now, after the accidents, how to do it.

(5) Vent, and unexpected explosion which followed, must have been done considering the wind directions. There was an elaborate simulator named SPPEDI developed and operated by the Government, but it was not known among concerned organizations, and therefore, not used in the accidents, because everyone didn't believe in accidents.

(6) The Government had subsidized and developed robots for high-radioactivity environment. But those were not taken up or used by anybody, because no one believed in accidents. When accidents really occurred, those developed robots had been already scrapped. If some of the robots had survived, countermeasures to address the accidents must have been quicker and easier.

Because of the reasons stated above, I believe that the probability of similar accidents with equivalent severity will be much smaller now, and I will not be afraid of living near a nuclear power plant.

End