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In Memoriam
Experts describe Japanese efforts to prevent meltdown at a quake-damaged nuclear reactor as "a sign of desperation".
Fears that one of Japan's nuclear reactors could go into meltdown have escalated after the operator of a quake-hit facility said water levels, which cool the plant, were almost empty.
Earlier officials said fuel rods that the Fukushima Daiichi complex's No.2 reactor had been temporarily exposed to the air, which can cause a meltdown.
Al Jazeera looks at Japan's nuclear situation and the possible outcomes.
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What area is affected?
Nine nuclear units, all boiling water reactors along Japan's northeastern coast, are under states of emergency. The three at Fukushima Daiichi, three at the nearby Fukushima Daini complex and another three at Onagawa.
Units 1 and 3 at the Fukushima Daiichi plant have been hit by explosions, while unit 2 has seen cooling water levels drop dramatically. At Daini, units 1,2 and 4 have experienced increased pressure inside their containment vessels, the area which holds the nuclear material.
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Engineers are using firefighting equipment to force sea water into the chambers, a task described by an American official in the New York Times as "trying to pour water into an inflated balloon".
Justin Dargin, a nuclear energy analyst from Harvard University, told Al Jazeera that the procedures Japanese authorities have been using so far are untested, a sign of desperation.
"That just shows how extreme the situation is, and the government is attempting to do whatever it can to try and mitigate what is looking like a partial meltdown," he said.
Some levels of radiation have already been released into the atmosphere from a method known as "feed and bleed", where engineers vent hydrogen from the plant to prevent pressure build ups.
Some 180,000 people have been evacuated from around the two Fukushima complexes, but it is feared 160 of those may have been exposed to levels of radiation.
What are the possible outcomes?
If the temperature inside the Fukushima reactor vessel continues to rise to 2,200 Celsius, then the uranium fuel pellets would start to melt.
Dargin said if the nuclear rods "are exposed for a certain duration of time then we could have a full meltdown, as opposed to a partial meltdown.
"When that happens we can have quite a disaster in the sense of radioactivity that would be leaked into the surrounding areas."
If fuel rods do begin to melt, the fuel could eat through the bottom of the reactor vessel, a thick steel container, then through the containment building and into the environment. There is a possibility that if this happened, another explosion could occur, sending particles even further into the air.
Dargin said the reactor at unit 1 is about 40 years old, and has not been reinforced to the level which would be able to withstand this recent earthquake.
"The situation does not look good. On the one hand while the government is trying to get this situation under control ... they have staff there but they are being exposed to radiation."
He said the current "feed and bleed" method, which sees the reactor flooded with seawater and the steam released, could go on for several months, if not a year.
"So what we're going to see is that people are going to have to evacuate for a long time. The worst case scenario is that we'll see a full-scale meltdown, but hopefully that won't happen, because Japanese authorities are working around the clock."
Read more at:
http://english.aljazeera.net/news/asia-pacific/2011/03/201131413138549692.html
Fears that one of Japan's nuclear reactors could go into meltdown have escalated after the operator of a quake-hit facility said water levels, which cool the plant, were almost empty.
Earlier officials said fuel rods that the Fukushima Daiichi complex's No.2 reactor had been temporarily exposed to the air, which can cause a meltdown.
Al Jazeera looks at Japan's nuclear situation and the possible outcomes.
(snipped)
What area is affected?
Nine nuclear units, all boiling water reactors along Japan's northeastern coast, are under states of emergency. The three at Fukushima Daiichi, three at the nearby Fukushima Daini complex and another three at Onagawa.
Units 1 and 3 at the Fukushima Daiichi plant have been hit by explosions, while unit 2 has seen cooling water levels drop dramatically. At Daini, units 1,2 and 4 have experienced increased pressure inside their containment vessels, the area which holds the nuclear material.
(also snipped)
Engineers are using firefighting equipment to force sea water into the chambers, a task described by an American official in the New York Times as "trying to pour water into an inflated balloon".
Justin Dargin, a nuclear energy analyst from Harvard University, told Al Jazeera that the procedures Japanese authorities have been using so far are untested, a sign of desperation.
"That just shows how extreme the situation is, and the government is attempting to do whatever it can to try and mitigate what is looking like a partial meltdown," he said.
Some levels of radiation have already been released into the atmosphere from a method known as "feed and bleed", where engineers vent hydrogen from the plant to prevent pressure build ups.
Some 180,000 people have been evacuated from around the two Fukushima complexes, but it is feared 160 of those may have been exposed to levels of radiation.
What are the possible outcomes?
If the temperature inside the Fukushima reactor vessel continues to rise to 2,200 Celsius, then the uranium fuel pellets would start to melt.
Dargin said if the nuclear rods "are exposed for a certain duration of time then we could have a full meltdown, as opposed to a partial meltdown.
"When that happens we can have quite a disaster in the sense of radioactivity that would be leaked into the surrounding areas."
If fuel rods do begin to melt, the fuel could eat through the bottom of the reactor vessel, a thick steel container, then through the containment building and into the environment. There is a possibility that if this happened, another explosion could occur, sending particles even further into the air.
Dargin said the reactor at unit 1 is about 40 years old, and has not been reinforced to the level which would be able to withstand this recent earthquake.
"The situation does not look good. On the one hand while the government is trying to get this situation under control ... they have staff there but they are being exposed to radiation."
He said the current "feed and bleed" method, which sees the reactor flooded with seawater and the steam released, could go on for several months, if not a year.
"So what we're going to see is that people are going to have to evacuate for a long time. The worst case scenario is that we'll see a full-scale meltdown, but hopefully that won't happen, because Japanese authorities are working around the clock."
Read more at:
http://english.aljazeera.net/news/asia-pacific/2011/03/201131413138549692.html