Japan steps up cooling operation

The aircraft dumped four loads before leaving the site in order to minimise the crews' exposure to radiation. On Wednesday, the helicopters were forced to abort a similar operation amid concerns over high radiation levels.

The BBC's Chris Hogg in Tokyo says the helicopters can carry an enormous amount of water but given the high winds it is difficult to know whether it has been dropped accurately.
Japanese government spokesman Yukio Edano said at a news briefing that nuclear experts were now investigating how effective the operation was.
Meanwhile, water trucks are on standby to spray more water on the reactors.
The operation was intended to help cool the reactors and also to replenish water in a storage pond with spent fuel rods.
Officials also said they were hoping that later on Thursday they would restore the power supply to the plant, which is needed for the cooling system and backup generators.
"If the restoration work is completed, we will be able to activate various electric pumps and pour water into reactors and pools for spent nuclear fuel," a spokesman for Tokyo Electric Power Company, which runs the plant, told the AFP news agency.
US President Barack Obama spoke to Prime Minister Naoto Kan on Thursday local time amid increasing US fears over the crisis.
The US has now chartered aircraft to help Americans leave Japan and authorised the voluntary departure of relatives of diplomatic staff.
The White House said Mr Obama conveyed "deep condolences" at the loss of life and said Washington was "determined to do everything possible to support Japan".
On Wednesday, Greg Jaczko, chairman of the US Nuclear Regulatory Commission (NRC), told a congressional energy and commerce subcommittee hearing in Washington that there appeared to be serious problems with attempts to cool the reactors.
"We believe that around the reactor site there are high levels of radiation."
He said it would be "very difficult for emergency workers to get near the reactors. The doses they could experience would potentially be lethal doses in a very short period of time".

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Fukushima Daiichi: What went wrong

• Reactor 1: Was first to be rocked an explosion on Saturday; fuel rods reportedly 70% damaged
• Reactor 2: There are fears a blast on Tuesday breached a containment system; fuel rods reportedly 33% damaged
• Reactor 3: Explosion on Monday; smoke or steam seen rising on Wednesday; damage to roof and possibly also to a containment system
• Reactor 4: Hit by a major blaze (possible blast) on Tuesday and another fire on Wednesday

• In graphics: Fukushima alert

US Energy Secretary Steven Chu said the situation appeared to be more serious than the partial meltdown at the Three Mile Island nuclear plant in Pennsylvania in 1979.

The head of the UN's atomic energy agency, Yukio Amano, is travelling to Japan in person to gather more information.
The US state department has urged Americans living within 80km of Fukushima Daiichi to leave the area - a much wider exclusion zone than the 20km advised by the Japanese government.
Mr Edano described the US approach as "conservative".
Britain has advised its nationals currently in Tokyo and to the north of the capital to consider leaving the area.
France has urged its citizens in Tokyo to leave the country or move south. Two Air France planes are due to begin evacuating French nationals later on Thursday.
In areas of the north-east badly hit by the tsunami, bitter winter weather has added to the misery of survivors, though more supplies are now reported to be reaching them.
The governor of Fukushima prefecture, where the badly damaged nuclear plant is located, has complained that evacuation centres lack basic necessities, including sufficient hot food.
About 450,000 people have been staying in temporary shelters, many sleeping on the floor of school gymnasiums.
The crisis has also continued to affect the markets - the benchmark Nikkei index fell 3.6% in early Thursday trading in Tokyo, shortly after the yen briefly hit the highest level against the US dollar since World War II.
On Wednesday, in a rare public appearance, Japan's Emperor Akihito said he was "deeply worried" about the crisis his country was facing.
TV stations interrupted programming to show the emperor describing the crisis facing the nation as "unprecedented in scale".

http://www.bbc.co.uk/news/world-asia-pacific-12768645