Initial Japan Radiation Higher

Friday, May 25, 2012 @ 03:05 PM gHale

Radiation released in the first days of the Fukushima nuclear disaster was almost 2.5 times the amount first estimated by Japanese safety regulators, the operator of the crippled plant said in a report released Thursday.

Tokyo Electric Power (Tepco) said its own analysis conducted over the past year put the amount of radiation released in the first three weeks of the accident at about one-sixth the radiation released during the 1986 Chernobyl disaster.

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“If this information had been available at the time, we could have used it in planning evacuations,” said Tepco spokesman Junichi Matsumoto.

Because radiation sensors closest to the plant ended up knocked out by the March 11, 2011 quake and tsunami, the utility based its estimate on other monitoring posts and data collected by Japanese government agencies.

Tepco, which will now be nationalized in July in exchange for a Japanese government bailout, estimated meltdowns at three Fukushima reactors released 900,000 terabecquerels of radioactive substances into the air during March.

That was 2.5 times the amount of the first estimate by Japan’s Nuclear and Industrial Safety Agency in April last year and about 17 percent more than the highest estimate provided by the government safety agency.

The estimate came from measurements suggesting the amount of Iodine-131 released by the nuclear accident was three times higher than previous estimates, the utility said in the report.

Iodine-131 is a fast-decaying radioactive substance produced by fission that takes place inside a nuclear reactor. It has a half-life of eight days.

More than 99 percent of the radiation released by the accident came in the first three weeks, it added.

A series of hydrogen explosions and meltdowns hit the Fukushima Dai-ichi plant, which had six reactors, after the tsunami cut of power and cooling systems.

The World Health Organization (WHO) released its own study this week concluding residents around the Fukushima plant suffered up to 20 times normal background radiation in the first year after the accident. That was still within the WHO’s recommended emergency limit.

Officials expect it will take up to 30 years to decommission the Fukushima reactors. The accident has prompted a debate over the future of nuclear power in the resource-poor nation.

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