Japanese Nuclear Power and the Wrath of Nature

Abstract

Japan, perched on the so-called Pacific "Ring of Fire," is one of the most seismically unstable countries. In the 20 th Century, about 158,280 persons died there in nine major earthquakes, with Richter magnitude 6 and above. The Japanese had that in mind when building 55 nuclear reactors for 17 nuclear power plants, which supply the country with 34.5% of its electricity. They made them sturdy enough not to release any dangerous radioactivity outside the plant limits, even due to the worst earthquakes. The quake of March 11 2011, of magnitude 9.0, the greatest in the Japan history, proved that the plants operated almost as expected. No dangerous radioactivity was reported to escape from the destroyed Fukushima nuclear power plants into the environment outside the plants' limits, and nobody was seriously harmed by radiation among the public. However, even though the power plants evidently withstood the 9.0 magnitude earthquake, they appeared to be sensitive to the enormous tsunami, with the waves up to 7 meters high, which flooded their emergency diesel power generators, intended to provide backup power for the pumps that cooled the reactor core. This was evidently an effect of the poor original design of the 40-year-old power plant, as the generators were located just behind a sea wall on low-lying coastal ground. The tsunami overwhelmed the 6-meter high barrier. The result was an overheating of the cores of the reactors. Like Chernobyl 25 years ago, Fukushima now brings important lessons for the only 56-years-old nuclear power. In the heavily affected prefectures of Miyagi, Fukushima, and Ibaraki, there are 11 nuclear power reactors. Those which operated during the earthquake were automatically shut down when tremors started, and the crews started standard procedures of cooling the "residual heat," i.e., pumping the water to the pressure vessels of the reactors. However, after an hour, the emergency power generators at Fukushima Daiichi plant were destroyed by the tsunami; the high pressure emergency cooling was lost, and before the mobile generators were supplied, the temperature of the core in the Unit 1 reactor increased to a level where the zirconium cladding of the fuel rods reacted with water, producing hydrogen gas. When the gas was released from * Zbigniew Jaworowski was a multidisciplinary scientist who has published more than 300 scientific papers, four books, and scores of popular science articles. He has been a member of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)since 1973, and served as its chairman from 1980-1982. His recent article , "Observations on Chernobyl After 25 Years of Radiophobia" is available here: www.21stcenturysciencetech.com/Articles_2010/Summer_2010/Observations_ Chernobyl.pdf Zbigniew Jaworowski died on the 12 of November 2011 in Poland at the age of 84.