World is ignoring most important lesson from Fukushima nuclear disaster
Fukushima's most important lesson is this: Probability theory (that disaster is unlikely) failed us. If you have made assumptions, you are not prepared. Nuclear power plants should have multiple, reliable ways to cool reactors. Any nuclear plant that doesn't heed this lesson is inviting disaster.
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In Japan, the Atomic Energy Safety Commission made at fatal mistake by relying casually on this probability theory. They said that the probability of long-term stoppage of external electric supply “in a country like Japan” is so unlikely that we do not have to assume it might take place. So, while they insisted on having three emergency generator sets per reactor, they did not think of a situation of the disruption of the external electricity supply from Japan’s main grid.Skip to next paragraph
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Fukushima No.1 had five different paths for the grid to come in, but all of them were destroyed by the powerful earthquakes 45 minutes prior to the tsunami. Had only one line remained active, we would have had no problems.
Had the commission made no assumptions about the external energy supply and built solar, wind, gas turbine, or even small LNG power stations on site for the six gigantic reactors, this accident could have been avoided.
Another fatal assumption was about the tsunami’s power and height. Historically, they say, the maximum height observed along the eastern shores of Japan was 10 meters. The probability of 15-meter tsunami hitting the Japanese coast is so low that you do not have to assume such a disaster because it is likely to take place once in 10,000 years. What we learned in Fukushima is that when something like that happens, the probability is 100 percent. It does not matter what the theoretical probability is.
Yet another false assumption involved the containment vessel, an invention of nuclear engineers to assure nearby inhabitants that, if there were an unimaginable accident and fission products leaked out of the core, they would be confined inside and not leak out into the external environment. This long-held myth was also broken by Fukushima No.1, as the molten fuel dropped through the pressure vessel and the “nuclear lava” melted the bottom of the containment vessel, leaking a huge amount of fission gasses and particles to the air and water.
Assumptions and probability are for the theoretical dreamers. If you have a hot reactor, soaked in water and without power to circulate the coolant, then you still have to cool it no matter what. If you cannot equip the facility with a reliable last resort of power and heat sink, you should not operate the nuclear plant to begin with. That is the lesson of Fukushima.
My recommendation is very simple. We should not assume anything in the design of a nuclear reactor. We should be prepared to cool down a reactor and bring it to cold shutdown with at least one reliable power supply and heat sink. This means that the emergency power should be provided in multiplicity of means and locations, and the heat sink should not depend on prevailing water alone, but on air and alternative water reservoirs.
If this is established then the reactor can be safe not only against natural disasters but also man-made damage.
Any nuclear plant operator anywhere in the world who does not heed these lessons from Fukushima is inviting the kind of disaster we have experienced in Japan.
Kenichi Ohmae, an MIT-trained nuclear engineer also widely regarded as Japan’s top management guru, is dean of Business Breakthrough University. He was a founder of McKinsey & Co.’s strategic consulting practice and is the author of many books, including “The Borderless World.”