A partial meltdown is likely under way at a second nuclear reactor, a senior Japanese official has said, as operators frantically tried to prevent a similar threat from a nearby unit at the same facility following a devastating earthquake and tsunami that may have killed as many as 10,000 people.
Chief Cabinet Secretary Yukio Edano told reporters on Sunday that a partial meltdown in Unit 3 of the Fukushima Dai-ichi power plant is "highly possible".
"Because it's inside the reactor, we cannot directly check it but we are taking measures on the assumption of the possible partial meltdown," he said.
About 170,000 people have been ordered to evacuate the area covering a radius of 20km around the plant.
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A meltdown refers to a very serious collapse of a power plant's systems and its ability to manage temperatures. A complete meltdown would release uranium and dangerous byproducts into the environment that can pose serious health risks.
Edano warned of the risk of a second explosion at the Fukushima plant on Sunday, a day after a blast destroyed the building housing another reactor.
However, he said the reactor would withstand it and there would be no adverse affect on the health of nearby residents.
Japan dealt with the nuclear threat as it struggled to determine the scope of the earthquake, the most powerful in its recorded history, and the tsunami that ravaged its northeast on Friday with breathtaking speed and power.
Hundreds of bodies were recovered on Sunday and Naoto Takeuchi, chief of Miyagi prefecture's policy force, said the death toll could top 10,000. He told state broadcaster NHK he had "no doubt" of that number of fatalities just in his prefecture - the region hardest hit by Friday's disaster.
Strong aftershocks continued to shake Japan's main island as the search pressed on for survivors.
Thousands of people have been taken to emergency shelters along the northeastern coast.
Preventing meltdown
The quake and tsunami damaged three reactors at the Fukushima Dai-ichi nuclear plant, which lost their cooling functions necessary to keep the fuel rods working properly.
Operators released slightly radioactive air from Unit 3 on Sunday, while injecting water into it as an effort to reduce pressure and temperature to save the reactor from a possible meltdown, Edano said.
He said radiation levels briefly rose above legal limits, but that it has since declined significantly.
On Saturday, an explosion destroyed the building housing the Unit 1 reactor, but not the reactor itself, which is enveloped by stainless steel 15cm thick.
The cause of the blast was apparently a reaction of hydrogen and oxygen as some hydrogen gas was released to relieve pressure inside the reactor.
Officials have said that radiation levels at Fukushima were elevated before the blast. At one point, the plant was releasing each hour the amount of radiation a person normally absorbs from the environment each year.
Workers in protective clothing were scanning people arriving at evacuation centres for radioactive exposure.
Officials said 22 people were known to have been exposed to radiation.
Virtually any increase in dispersed radiation can raise the risk of cancer, and authorities were planning to distribute iodine, which helps protect against thyroid cancer.
It is the first time Japan had confronted the threat of a significant spread of radiation since the greatest nightmare in its history, a catastrophe exponentially worse: the 1945 atomic bombings of Hiroshima and Nagasaki by the United States, which resulted in more than 200,000 deaths from the explosions, fallout and radiation sickness.
URL du billet: http://english.aljazeera.net/news/asia-pacific/2011/03/20113130540539552.html
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