Japan stands on brink of nuclear meltdown
Source: Agencies |
March 15, 2011, Tuesday
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Print Edition
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WATER levels dropped precipitously inside a stricken Japanese nuclear reactor yesterday, twice leaving the uranium fuel rods completely exposed and raising the threat of a meltdown, hours after a hydrogen explosion tore through a building housing a different reactor.
Water levels were restored after the first decrease but the rods remained exposed late last night after the second episode, increasing the risk of the spread of radiation and the potential for an eventual meltdown.
The cascading troubles in the Fukushima Dai-ichi plant compounded the immense challenges faced by the Tokyo government, already struggling to send relief to hundreds of thousands of survivors along the country's quake and tsunami-ravaged coast.
Later, a 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 stabilized for the time being," said Nuclear and Industrial Agency official Ryohei Shiomi. "Unit 2 now requires all our effort and attention."
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 had not been damaged. In addition, officials said radiation levels remained within legal limits, though anyone left within 20 kilometers of the scene was ordered to remain indoors.
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.
The chief government spokesman said there were signs 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 told reporters.
Some experts would consider that a partial meltdown. Others reserve that term for times when nuclear fuel melts through a reactor's innermost chamber but not through the outer containment shell.
By contrast, a complete reactor meltdown, where the uranium core melts through the containment shell, would release a wave of radiation and result in major, widespread health problems.
Yesterday morning's explosion at the Fukushima Dai-ichi plant's Unit 3 injured 11 workers and came as authorities were trying to use sea water 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.
Meanwhile, 17 United States military personnel involved in helicopter relief missions were found to have been exposed to low levels of radiation after they flew back from the coast to an aircraft carrier about 160 kilometers offshore.
Officials said the exposure was roughly equal to one month's normal exposure to natural background radiation, and the 17 were declared contamination-free after scrubbing with soap and water.
Water levels were restored after the first decrease but the rods remained exposed late last night after the second episode, increasing the risk of the spread of radiation and the potential for an eventual meltdown.
The cascading troubles in the Fukushima Dai-ichi plant compounded the immense challenges faced by the Tokyo government, already struggling to send relief to hundreds of thousands of survivors along the country's quake and tsunami-ravaged coast.
Later, a 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 stabilized for the time being," said Nuclear and Industrial Agency official Ryohei Shiomi. "Unit 2 now requires all our effort and attention."
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 had not been damaged. In addition, officials said radiation levels remained within legal limits, though anyone left within 20 kilometers of the scene was ordered to remain indoors.
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.
The chief government spokesman said there were signs 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 told reporters.
Some experts would consider that a partial meltdown. Others reserve that term for times when nuclear fuel melts through a reactor's innermost chamber but not through the outer containment shell.
By contrast, a complete reactor meltdown, where the uranium core melts through the containment shell, would release a wave of radiation and result in major, widespread health problems.
Yesterday morning's explosion at the Fukushima Dai-ichi plant's Unit 3 injured 11 workers and came as authorities were trying to use sea water 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.
Meanwhile, 17 United States military personnel involved in helicopter relief missions were found to have been exposed to low levels of radiation after they flew back from the coast to an aircraft carrier about 160 kilometers offshore.
Officials said the exposure was roughly equal to one month's normal exposure to natural background radiation, and the 17 were declared contamination-free after scrubbing with soap and water.
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