Japan doubles Fukushima radiation leak estimate

Posted by on Jun 07, 2011 | Comments Off on Japan doubles Fukushima radiation leak estimate

apan has more than doubled its estimate of radiation that escaped from the tsunami-hit Fukushima nuclear plant in the first week after the disaster.

Japan’s nuclear safety agency also said meltdowns took place in three reactors more quickly than earlier believed.

The assessment comes as an expert panel begins an inquiry into the crisis.

The plant’s operator is hoping to shut down the facility by January, although there is concern it may take longer – the plant is still leaking radiation.

More than 80,000 local residents living within a 20km (12 mile) radius of the plant have been evacuated from their homes. A voluntary evacuation policy is operating in the area 20-30km from the plant.

Some towns further away have also been affected.

Japan’s Chief Cabinet Secretary Yukio Edano says more evacuations are being considered. Monitoring shows the lie of the land and wind patterns may be causing a build-up of radiation in other areas.

Brace for criticism

Japan’s Nuclear and Industrial Safety Agency (Nisa) now says 770,000 terabecquerels escaped into the atmosphere following the 11 March disaster – more than double its earlier estimate of 370,000 terabecquerels.

BBC map

Although the amount is just 15% of the total released at Chernobyl in Ukraine in 1986 – the world’s worst nuclear disaster – it suggests the contamination of the area around the plant is worse than first thought, says the BBC’s Roland Buerk in Tokyo.

The safety agency also says that in reactor No 1, molten nuclear fuel dropped to the bottom of the pressure vessel within five hours of the earthquake – 10 hours earlier than initially estimated by operator Tepco.

Nisa also says a meltdown damaged the No 2 reactor after 80 hours, and the No 3 reactor 79 hours after the tsunami knocked out the plant’s cooling systems.

The revision, nearly three months into the crisis, is likely to increase criticism in Japan that the plant’s operator and the government were too slow to release information, our correspondent says.

The findings were released as an independent 10-member expert panel begins an investigation into the causes of the nuclear accident.

An investigation by the UN’s nuclear watchdog, the IAEA, has already pointed out a key failure – admitted by Japan – to plan for the risk of waves crashing over the sea wall and knocking out the plant’s back-up generators.

Even though a major faultline lies just offshore, the sea wall at Fukushima was less than 6m (20ft) high. The height of the tsunami wave was about 14m.

In its draft report, the IAEA said continued monitoring of the health and safety of the nuclear workers and the general public was necessary.

The report also emphasised the importance of independent regulators in the nuclear industry.

In Japan, the nuclear safety agency is part of the industry ministry, which promotes nuclear power.

A draft report obtained by Japanese broadcaster NHK – to be submitted to the IAEA Ministerial Conference on Nuclear Safety later this month – outlines plans to split the two bodies.

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