| The Yomiuri Shimbun
This is the second installment of a three-part series examining how earthquake-prone Japan can coexist with nuclear power plants, a concern that has surfaced in the wake of the July 16 earthquake in the Chuetsu region of Niigata Prefecture--the first temblor anywhere in which a fault line ran beneath a nuclear power plant. Following last Monday's earthquake, the asphalt-paved grounds of Tokyo Electric Power Co.'s Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture bulge and sag, blocking people's path. Immediately after the Niigata Prefecture Chuetsu Offshore Earthquake occurred, Shizuo Suda, deputy manager of the fire prevention division at Kashiwazaki Fire Department, entered the plant to inspect an electric transformer that had caught fire. After observing the scene, Suda became very concerned about the possibility of a secondary disaster occurring. He had never imagined that an earthquake would bring about such terrible destruction, and he thought to himself that if oil leaked from an underground pipe and ignited, there would be no remedying the situation. Suda's report to the Kashiwazaki municipal government indicating the seriousness of the situation at the plant prompted the municipal government to issue an emergency order to TEPCO instructing it to shut down the plant. Yumio Ishii, president of the Japan Society of Civil Engineers, said Friday: "I strongly feel we were lucky the disaster wasn't worse than it was. The quake-resistance standards for nuclear power plants definitely need to be reviewed." The late Nobu Kitamura, a prominent geologist and professor emeritus at Tohoku University, conducted research into faults across the country in the 1960s and '70s. He once described the Japanese archipelago, which is situated in a seismogenic zone, as follows: "If I throw a stone from here to there, countless faults lie underground in the space between. That's where Japan is located." Last Monday's quake, in which fault lines directly underneath the nuclear power plant shifted, showed Kitamura's description was no exaggeration. Japan is the only country located on four plates edging toward each other and many fault zones. Among 31 nations and regions that have nuclear power plants, Japan is the most at risk of being hit by earthquakes. Japan introduced nuclear power technology from Europe and the United States 50 years ago. The history of Japan's nuclear power industry has been a struggle against earthquakes. Inside a nuclear reactor, control rods designed to serve as brakes move between nuclear fuel rods that are assembled precisely spaced apart. (suite)
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If the spacing changes even slightly due to an earthquake, the control rods will cease to function as brakes. Japan Atomic Power Co.'s Tokai nuclear power station in Tokaimura, Ibaraki Prefecture, is the nation's first commercial nuclear power plant. A graphite reactor, imported from Britain, a nation that not face the threat of serious earthquakes, was used for the power plant. At the time of introducing the reactor, questions regarding its quake-resistance capabilities were voiced by many experts, forcing the company to make changes in the construction plan, including improvements to the graphite layers surrounding the fuel rods. The technology for light water reactors, which was used in many plants later, was imported from the United States, which has seismogenic zones on its Pacific Coast. Although those reactors were designed for optimum quake resistance, the United States is blessed with many choices for locating its nuclear plants, so it does not have to worry so much about making its nuclear plants capable of withstanding very strong quakes. Japan, however, had to develop the strictest quake-resistant standards for its nuclear power plants. But the tremors of the Niigata Prefecture Chuetsu Offshore Earthquake exceeded those standards. Seismic research has advanced significantly in the past half century. But it was only after the Great Hanshin Earthquake in 1995 that active faults in various regions earned serious attention. Also, it was not until the 1980s that understanding of the process of liquefaction began to deepen. Seismology is still developing, and quake-resistance standards for nuclear power plants always need to be reviewed. It is said that the cost of building one nuclear power plant in Japan is 300 billion yen--the highest in the world--as expenses for quake-resistance measures are high. In the electric power industry, many are reluctant to adopt strict antiseismic measures, saying costs will skyrocket if standards are made rigorous. Mitsumasa Hirano, chief secretary of the Japan Nuclear Energy Safety Organization said, "People have become to understand the uncertainty of seismology, and the social perception toward risk has changed since the Great Hanshin Earthquake." Electric power companies have been making efforts to balance cost and safety in setting quake-resistance standards for nuclear power plants, but it is not acceptable to delay the implementation of antiseismic measures simply because doing so will be expensive. |