This image shows the first waters of the tsunami breaching the Fukushima power plant's buildings
Japan
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.
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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