In the country that gave the world the word tsunami, the Japanese nuclear establishment largely disregarded the potentially destructive force of the walls of water. The word did not even appear in government guidelines until 2006, decades after plants ? including the Fukushima Dai-ichi facility that firefighters are still struggling to get under control ? began dotting the Japanese coastline.
The lack of attention may help explain how, on an island nation surrounded by clashing tectonic plates that commonly produce tsunamis, the protections were so tragically minuscule compared with the nearly 46-foot tsunami that overwhelmed the Fukushima plant on March 11. Offshore breakwaters, designed to guard against typhoons but not tsunamis, succumbed quickly as a first line of defense. The wave grew three times as tall as the bluff on which the plant had been built.
Japanese government and utility officials have repeatedly said that engineers could never have anticipated the magnitude 9.0 earthquake that caused the sea bottom to shudder and generated the huge tsunami. Even so, seismologists and tsunami experts say that according to readily available data, an earthquake with a magnitude as low as 7.5 ? almost garden variety around the Pacific Rim ? could have created a tsunami large enough to top the bluff at Fukushima.
After an advisory group issued nonbinding recommendations in 2002, Tokyo Electric Power Company, the plant owner and Japan?s biggest utility, raised its maximum projected tsunami at Fukushima Daiichi to between 17.7 and 18.7 feet ? considerably higher than the 13-foot-high bluff. Yet the company appeared to respond only by raising the level of an electric pump near the coast by 8 inches, presumably to protect it from high water, regulators said.
The intensity with which the earthquake shook the ground at Fukushima also exceeded the criteria used in the plant?s design, though by a less significant factor than the tsunami, according to data Tokyo Electric has given the Japan Atomic Industrial Forum, a professional group.
Japan is known for its technical expertise. For decades, though, Japanese officialdom and even parts of its engineering establishment clung to older scientific precepts for protecting nuclear plants, relying heavily on records of earthquakes and tsunamis, and failing to make use of advances in seismology and risk assessment since the 1970s.
There is no doubt that when Fukushima was designed, seismology and its intersection with the structural engineering of nuclear power plants was in its infancy, said Hiroyuki Aoyama, 78, an expert on the quake resistance of nuclear plants who has served on Japanese government panels. Engineers employed a lot of guesswork, adopting a standard that structures inside nuclear plants should have three times the quake resistance of general buildings. ?There was no basis in deciding on three times,? said Aoyama, an emeritus professor of structural engineering at the University of Tokyo. ?They were shooting from the hip,? he added. ?There was a vague target.?