Japan needs to discharge a total of 11,500 metric tons of low-contaminated water into the ocean from a stricken nuclear power plant, a Japanese official said on Monday.
Koichiro Nakamura, a deputy director general of Japan's Nuclear and Industrial Safety Agency (NISA), said the measure was needed to "avoid a more serious risk," without elaborating.
He spoke at a news conference after he and other Japanese officials briefed member states of the International Atomic Energy Agency (IAEA) in Vienna about the crisis at the Fukushima Daiichi plant.
Plant operator Tokyo Electric Power Co (TEPCO) was forced on Monday to release low-level radioactive seawater that had been used to cool overheated fuel rods after it ran out of storage capacity for more highly contaminated water.
TEPCO said it would release more than 10,000 tonnes of water about 100 times more radioactive than legal limits in order to free storage capacity for more highly contaminated water.
Nakamura, citing information from the company, said the 10,000 tonnes needed to be dumped into the ocean to make storage space for higher-radioactive water now in reactor unit 2.
Another 1,500 tonnes was accumulated ground water in a drain pit of units 5 and 6.
"The total amount of water we need to discharge is 11,500 tonnes," he said, speaking through an interpreter.
NO EVACUATION ZONE CHANGE, FOR NOW
Jukka Laaksonen, chairman of the Western European Nuclear Regulators' Association and head of Finland's nuclear safety body, said normal sea water also contained radioactivity.
"In a few cubic kilometres of sea water you have much more radioactivity than what is being dumped from this accident," he told the same news conference. "It will not raise the total radioactivity of the sea water."
Officials attending the closed-door briefing said it did not provide new information about the crisis, partly because the emergency made it difficult to know exactly what was happening at the plant.
"There is a lot of information which is not available," Denis Flory, the head of the IAEA's safety department, said.
Lack of information, both from Japan and the IAEA, has been a frequent complaint voiced by diplomats and the media since the March 11 earthquake and tsunami severely damaged Fukushima and caused the worst nuclear accident since Chernobyl in 1986.
The head of the U.S. Nuclear Regulatory Commission, Gregory Jaczko, said there was no evidence of "recriticality" at the plant's spent fuel pools, in which a nuclear chain reaction would resume even though the reactors were automatically shut down at the time of the quake.
Nakamura said Japan was not planning to expand a 20-km (12-mile) evacuation zone around the plant now. "For the time being we are not going to. But it does not mean in the future we may (not) change that," he said.
http://www.reuters.com/article/2011/...7336L720110404