jueves, 17 de marzo de 2011

Japan steps up cooling operation

 
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Professor Andrew Sherry explains the situation as helicopters spray water to cool nuclear reactors
Japan says it is stepping up efforts to cool overheating fuel at the tsunami-hit Fukushima Daiichi nuclear plant.
Helicopters dumped tonnes of water to try to prevent a meltdown of fuel rods, and media reports said water cannon had now joined in the operation on the ground.
Following the crisis, China suspended approval for new nuclear plants.
The confirmed death toll from Friday's 9.0 magnitude quake, which triggered the tsunami, has risen above 5,000.
Police say 5,178 are confirmed dead and another 8,606 people are still missing.
'Deep condolences' Japan's military CH-47 Chinook helicopters began spraying tonnes of water on reactors 3 and 4 at Fukushima, 220km (140 miles) from Tokyo, at 0948 local time (0048 GMT), officials said.
The attempt to use helicopters and water cannon to dump seawater on to the Fukushima power station is almost certainly unprecedented in more than half a century of nuclear power.
The water was not destined for the reactors themselves - they are contained within containment systems that are designed to be sealed tight and which appear to be intact, with the possible exception of a crack in a vessel attached to No 3 reactor.
The targets were cooling ponds situated above the reactors, which store fuel rods. The ponds in buildings 3 and 4 - and possibly more - are certainly short of water, possibly completely dry.
This means the rods get hot, increasing the chances of radioactive substances being released. It also exposes workers to radiation from the rods.
The positive development is that electric power may be restored to the plant in the coming hours, meaning pumps can be restarted - if they are still operational. 
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.
Video footage suggests the attempts were not very successful, with most of the water falling outside the target buildings.
Later military lorries on the ground joined in with water cannon, dousing reactor 3, the NHK TV network said.
Initially police crews had tried to spray the reactor but were forced to withdraw because they would have been exposed to high radiation levels. The military vehicles, unlike those of the police, are built to allow personnel to remain inside, NHK reported.
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 back-up 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.
 
Watch: Foreign nationals at Haneda Airport explain why they want to leave Japan
The US has also been asked to fly a drone over the site to help assess the situation.
The crisis has prompted China to suspend approval of new nuclear power stations and carry out checks on existing reactors.
China currently gets about 2% of its electricity from nuclear power, but is building more reactors than any other country in the world.
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".

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 
The head of the UN's atomic energy agency, Yukio Amano, is travelling to Japan to gather more information.
In Tokyo, our correspondent says that despite an air of superficial calm there are signs of unease under the surface.
Cash machines at one bank went down for a couple of hours on Thursday afternoon - prompting speculation that some people may be stocking up on reserves of cash in case the situation deteriorates.
Britain has advised its nationals currently in Tokyo and to the north of the capital to consider leaving the area, and to keep outside an 80km radius of the Fukushima plant, in line with US state department instructions.
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.
Fukushima map