Damage to a nuclear power station run by Tokyo Electric Power Co. from a July 16 earthquake “appears less than expected,'' the International Atomic Energy Agency said after a three-day examination.
A team of inspectors “has concluded that plant safety features performed as required during the earthquake,'' the IAEA, as the United Nations nuclear watchdog is known, said in an Aug. 14 statement on its Web site. “Damage from the earthquake appears to be limited to those sections of the plant that would not affect the reactor or systems related to reactor safety.''
The epicenter of the magnitude 6.8 earthquake was 9 kilometers from the Kashiwazaki Kariwa station, causing radiation leaks and a fire. Japan's government aims to ease public concern about safety by allowing the IAEA to inspect the damage and share its analysis with plant operators and regulators.
Six IAEA experts, led by Philippe Jamet, director of the agency's installation nuclear safety division, visited the Kashiwazaki Kariwa nuclear station, the world's biggest, from Aug. 6 to Aug. 9. The team's report will be released “within a few days,'' according to the statement.
“The team conducted a three-day physical examination covering the complex of seven units, as well as analysis of instrument logs and other records from the time of the event,'' the statement said.
The earthquake shook the plant more than it was designed to withstand, the Tokyo-based utility said July 30. In one case, the vibration was more than threefold the maximum assumed in the plant's design.
`Robustness in Design'
“However, as with most nuclear plants, additional robustness in design had been incorporated into plant structures, systems and components,'' the statement said. “ The IAEA team said these conservative seismic design measures probably explain why damage was less than it could have otherwise been expected.''
Still, physical stresses from the earthquake could affect the “long-term safe operation'' of some of the components of the station, the IAEA said. Further analysis of such components may be needed to determine “whether they should be replaced earlier'' than anticipated, it said.
The facility has seven reactors with a generating capacity of 8,212 megawatts. Three of the seven reactors were shut for maintenance when the tremor hit Niigata prefecture. Japan has 55 reactors that generate about one-third of the country's electricity, making the nation the third-largest nuclear power producer in the world.
