The Nuclear Safety Commission made public its 2006 white paper on the safety of nuclear power last week. The fact that its publication came after two postponements shows that the safety of the nation’s nuclear power plants cannot be taken for granted. It will take tremendous efforts on the part of the government and power industry to regain the people’s trust in nuclear power generation.
The first postponement was caused by a series of data-falsification incidents and coverups concerning problems and accidents at hydraulic, thermal and nuclear power stations, which surfaced in and after the fall of 2006. The commission was forced to include a report on these irregularities in the white paper. The second postponement was caused by the July 16 major earthquake off Niigata Prefecture, which caused Tokyo Electric Power Co.’s Kashiwazaki-Kariwa nuclear power plant to automatically shut down.
The plant, equipped with seven reactors for generation of a total of about 8.21 million kW of electricity, is among the world’s largest nuclear power plants. It was hit by strong seismic tremors never experienced before at other nuclear power plants. Four of the reactors automatically shut down; the three others were undergoing checks at the time and not in operation.
An attachment at the beginning of the white paper mentions the commission’s view on the earthquake’s effects and countermeasures. The main text deals with the September 2006 revision of the guidelines for designing nuclear power plants, the first revision in 25 years, as well as the data irregularities.
In the attachment, the commission says that the magnitude-6.8 earthquake caused 64 problems at the Kashiwazaki-Kariwa nuclear power plant, 15 of which were related to radioactive material. The troubles included a fire at the transformer that supplies electricity to the No. 3 reactor, a leak of contaminated water from a water pool for nuclear fuel for the No. 6 reactor, and damage to actuator joints of the ceiling crane above the pressurized chamber of the No. 6 reactor. The commission says that although tiny amounts of radioactive materials leaked into the sea and air, there was no environmental contamination. Referring to the automatic shutdown of the plant, it says that the plant’s important safety functions of “stoppage, cooling and containment” at the time of an emergency worked properly.
Despite this, however, the commission has issued a reasonable warning that nothing should be taken for granted regarding the safety of nuclear power generation, especially the quake resistance of nuclear power plants. It also calls for a “humble stance” of rendering judgment on the basis of scientific knowledge and facts.
The Kashiwazaki-Kariwa plant was hit by tremors 2.5 times stronger than the strongest tremors assumed in the design guidelines. The commission stresses the importance of evaluating in detail the quake resistance of existing nuclear power plants, which were designed in accordance with old design guidelines, and determining how they measure up to the new design guidelines. But it refrains from calling for a review of the new guidelines. It only says that at this point it is impossible to discuss the need for such a review. The commission should heed the opinions of outside experts and the public.
In addition to listing the strongest presumed possible earthquakes as an important factor in the design of nuclear power plants, the new guidelines consider the risk of radioactive materials dispersing and causing radiation exposure to local residents in the event of an earthquake stronger than the assumed strongest earthquakes. The power industry should minimize the possibility of such a risk by increasing the quake resistance of nuclear power plants.
The white paper reports that coverups and falsified information have surfaced concerning 316 kinds of problems at all types of power stations. Of them, 98 have occurred at nuclear power plants. The severest case was the coverup of a criticality accident at the No. 1 reactor of Hokuriku Electric Power Co.’s Shiga nuclear power plant on June 18, 1999, that was caused by operator error. At the end of the white paper, commission chairman Atsuyuki Suzuki says that these irregularities show that power companies carry the primary responsibility for the safety of nuclear power plants. He says that for the sake of transparency, power companies must fully explain safety problems to the public.
He also says that since trouble at nuclear power plants is inevitable, the important thing is to check for problems and errors around the clock to prevent minor mishaps from causing a major accident. The Niigata quake shows that the government and power companies’ responsibility to operate the 55 power reactors safely in this quake-prone country has deepened all the more.
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