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Radiation alert as blast hits nuke reactor

Japan's nuclear safety agency says a fire in a reactor at a crippled nuclear power plant in tsunami-ravaged north-eastern Japan has been extinguished, but an alert is still in place as radiation spews out.Radiation levels near the Fukushima No.1 plant are now harmful to human health, Japan's Government says.“There is no doubt that unlike in the past, the figures are the level at which human health can be affected,” chief Government spokesman Yukio Edano said.In Tokyo authorities also said higher than normal radiation levels had been detected in the capital, the world's biggest urban area, but not at harmful levels. Tens of thousands of people have already been evacuated from a zone within a radius of 20km from the Fukushima No.1 plant, 250km north-east of Tokyo.But Prime Minister Naoto Kan urged people living within 10km of the exclusion zone around the plant to stay indoors.Earlier today a blast hit the plant's number-two reactor.Mr Edano later said there was also an explosion which started a fire at the number-four reactor.Although the number-four reactor was shut for maintenance when the quake and tsunami struck last Friday, “spent nuclear fuel in the reactor heated up, creating hydrogen and triggered a hydrogen explosion”.He said radioactive substances were leaked along with the hydrogen.FULL COVERAGE
“Please keep in mind that what is burning is not nuclear fuel itself,” Mr Edano said. “We'll do our best to put out or control the fire as soon as possible.”Similar hydrogen blasts had hit the number-one and number-three reactors on Saturday and Monday.Buildings housing four of the six reactors at the plant, which opened in 1971, have now been hit by explosions.Mr Edano said radioactive substances might spread outside the 20-30km area but would dissipate the farther they spread.It was still unclear whether the container sealing the number-two reactor had been breached.The plant operator initially told the nuclear safety agency that it had not been holed, but later said it was still checking for any breach. Japan is frantically battling a nuclear emergency after Friday's massive earthquake and tsunami cut power to the 40-year-old plant and knocked out cooling systems. Officials have struggled to prevent meltdowns at the damaged reactors, saying fuel rods may have been critically damaged by overheating.But they have not reported the kind of radiation leakage that would accompany a major meltdown.The continuing nuclear crisis has unnerved regional residents already struggling with the aftermath of the quake and tsunami.The troubles at the Fukushima Dai-ichi complex began when Friday’s massive earthquake and tsunami in Japan’s north-east knocked out power, crippling cooling systems needed to keep nuclear fuel from melting down.The nuclear crisis compounded the immense challenges faced by the Tokyo Government, already struggling to send relief to hundreds of thousands of people along the country’s quake and tsunami-ravaged coast where at least 10,000 people are believed to have died.The official death toll now stands at 2,400.Earlier, a top Japanese official said the fuel rods in all three of the most troubled nuclear reactors appeared to be melting.Of all these troubles, the drop in water levels at Unit 2 had officials the most worried.“Units 1 and 3 are at least somewhat stabilised for the time being,” Nuclear and Industrial Agency official Ryohei Shiomi said. “Unit 2 now requires all our effort and attention.”Workers managed to raise water levels after the second drop on Monday night, but they began falling for a third time, according to nuclear agency official Naoki Kumagai. They are now considering spraying water directly on container to cool it. The head of the International Atomic Energy Agency said the Japanese government has asked the agency to send experts to help.


In some ways, the explosion at Unit 3 was not as dire as it might seem.The blast actually lessened pressure building inside the troubled reactor, and officials said the all-important containment shell - thick concrete armour around the reactor - had not been damaged. In addition, officials said radiation levels remained within legal limits, though anyone left within 20km of the scene was ordered to remain indoors.“We have no evidence of harmful radiation exposure,” deputy Cabinet secretary Noriyuki Shikata said.Fukushima prefectural officials said, however, that 190 people have been exposed to some radiation from the plant. Nuclear safety officials said monitoring devices around the plant briefly showed radiation levels six times the legal limit, but they have since gone down.On Saturday, a similar hydrogen blast destroyed the housing around the complex’s Unit 1 reactor, leaving the shell intact but resulting in the mass evacuation of more than 185,000 people from the area.Officials were clearly struggling to keep ahead of the crisis and prevent a worst case scenario: a complete reactor meltdown.In that case, the uranium core can melt through the outer containment shell, releasing radioactive byproducts like iodine and cesium. That endangers the environment and people nearby.Late last night, the chief government spokesman said there were signs that the fuel rods were melting in all three reactors, all of which had lost their cooling systems in the wake of Friday’s massive earthquake and tsunami“Although we cannot directly check it, it’s highly likely happening,” Chief Cabinet Secretary Yukio Edano said.


Some experts would consider that a partial meltdown. Others, though, reserve that term for times when nuclear fuel melts through a reactor’s innermost chamber but not through the outer containment shell.Officials held out the possibility that, too, may be happening.“It’s impossible to say whether there has or has not been damage” to the vessels, Kumagai, the nuclear agency official, said.The Monday morning explosion at the Fukushima Dai-ichi plant’s Unit 3 injured 11 - seven plant workers and four military personnel. It came as authorities were trying to use seawater to cool the complex’s three reactors.While four Japanese nuclear complexes were damaged in the wake of Friday’s twin disasters, the Dai-ichi complex, which sits just off the Pacific coast and was badly hammered by the tsunami, has been the focus of most of the worries over Japan’s deepening nuclear crisis. All three of the operational reactors at the complex now have faced severe troubles.Operators knew the seawater flooding would cause a pressure buildup in the reactor containment vessels - and potentially lead to an explosion - but felt they had no choice if they wanted to avoid complete meltdowns. Eventually, hydrogen in the released steam mixed with oxygen in the atmosphere and set off the two blasts.Japan’s meteorological agency did report one good sign. It said the prevailing wind in the area of the stricken plant was heading east into the Pacific, which experts said would help carry away any radiation.