Jul 18, 2007, 10:03 GMT
Tokyo - Tokyo Electric Power Co (TEPCO) underestimated the amount of radiation leakage discharged into the ocean from No 6 reactor at its Kashiwazaki-Kariwa nuclear power plant after a powerful earthquake hit the northern Japanese province of Niigata Monday, local media reported Wednesday.
The company corrected the radiation leak from 60,000 becquerel to 90,000 becquerel but still said the level 'falls below the safety standard set by the state and there is no safety problem.'
TEPCO blamed the calculation errors for under-reporting the amount of radiation.
'We are sorry for a simple calculation mistake,' a TEPCO official said.
TEPCO has found a total of nearly 50 accidents and problems at the Kashiwazaki-Kariwa plant since the 6.8-magnitude earthquake that killed nine, injured more than 1,000 and displaced nearly 10,000 people in the region Monday.
Kashiwazaki city government on Wednesday ordered the troubled TEPCO to effectively suspend the use of all seven nuclear reactors at the Kariwa power station.
Mayor Hiroshi Aida issued the emergency order based on the fire-defence law, saying, 'Safety of the nuclear power station cannot be assured at this point.'
It was the first time a municipal government ordered a nuclear power company to halt operations since Tsuruga City in Fukui prefecture ordered the emergency shutdown of the Monju plant in 1995.
The Japanese central government had already instructed the company to suspend operations of all seven reactors until safety could be assured.
Meanwhile, the trade ministry told TEPCO officials to analyze the cause of the problems and explain the delay of countermeasures, while urging other nuclear power operators to consider setting up their own fire-fighting systems and improve communications.
'We think that the announcement was delayed, and we think that this is a very serious problem,' Akira Fukushima, deputy director of nuclear and industrial safety agency, said at a press conference.
Radioactive water from the No 6 reactor escaped into the sea and a fire broke out at an electrical transformer at the Kashiwazaki-Kariwa plant shortly after the quake.
The company also reported on Tuesday radioactive material such as cobalt-60, iodine and chromium-51 at its main exhaust pipe of the plant's No 7 reactor.
A company spokesman said Tuesday the radiation was lower than the annual exposure limit for people and unlikely to cause any environmental hazard.
Also at the Kashiwazaki-Kariwa plant's waste-handling facility, some 100 storage drums toppled over during the quake and the lids of at least three drums were found open, officials admitted. The company was also investigating whether there was any radioactive release from the drums.
At the No 2 reactor, 800 litres of oil for water pump turbines also leaked out.
The ground motion measured at the Kashiwazaki-Kariwa nuclear plant after the quake was apparently significantly more intense than had been taken into account when the plant was constructed.
The government inspected the plant perimeter Tuesday and found some damage to the foundation and estimated the jolt also damaged the facilities within the perimeter, according to Jiji Press.
The earthquake-resistance guidelines for the nuclear facilities were revised last year and the government has instructed nuclear power operators to inspect their building designs to follow the guidelines, Fukushima said.
Japanese Chief Cabinet Secretary Yasuhisa Shiozaki said Wednesday that the government would reconsider the condition of the nuclear power plant building sites.
The world's third-largest nuclear country plans to build 13 nuclear plants by the 2018 fiscal year, two of which are already under construction.
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