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Japanese nuclear disaster

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Q&A: Dangers posed by Japan's quake-hit atom plant

Sat Mar 12, 2011 10:53am EST

(Reuters) - Analysts and industry representatives gave different assessments of the potential dangers after an explosion blew the roof off one of Japan's nuclear power plants damaged in Friday's massive earthquake.

It underlined the fluid and unpredictable situation at the Fukushima Daiichi facility north of Tokyo, from which the Japanese government said radiation leaked.

The critical issue is what has happened or is happening with the reactor fuel -- which contains almost all the radioactivity in the plant -- and whether it is damaged.

"We don't know enough about what the status of the fuel is in the reactor core," Mark Hibbs of the Carnegie Endowment for International Peace said. "The issue is whether the core is uncovered, whether the fuel is breaking up or being damaged, or whether the fuel is melting."

WHAT HAPPENED AT THE PLANT?

The blast at the 40-year-old Daichi 1 reactor came as plant operator Tokyo Electric Power Co (Tepco) worked to reduce pressures in the core after the total loss of power needed to keep water circulating to prevent it from overheating.

It led to fears of a disastrous meltdown at the plant, which automatically shut down after the quake, even though the government insisted that radiation levels were low.

"The most probable (cause of the explosion) is the coolant, particularly if it's water, can overheat and turn to steam more rapidly than it was designed to cope with," said nuclear fuel technology professor Timothy Abram at Manchester University.

The cause and exact location of the blast still needs to e established, said nuclear physics professor Paddy Regan at the University of Surrey. "So far it looks like it's not the reactor core that's affected, which would be good news."

The World Nuclear Association, a London-based industry body, said the blast was probably due to hydrogen igniting and that this was unlikely to cause a big accident by itself.

"It is obviously an hydrogen explosion," communications director Ian Hore-Lacy said. "If the hydrogen has ignited, then it is gone, it doesn't pose any further threat."

HOW SERIOUS COULD IT BE?

Views differ. Stratfor, a risk consultancy, said the blast appeared to have caused a reactor meltdown, but this was contradicted by others who dismissed any comparisons with the 1986 Chernobyl nuclear disaster in Ukraine.

"The reactor fuel appears to have at least partially melted, and the subsequent explosion has shattered the walls and roof of the containment vessel," Stratfor said in an analysis.

"There have been reports of "white smoke," perhaps burning concrete, coming from the scene of the explosion, indicating a containment breach and the almost certain escape of significant amounts of radiation."

But Abram, the Manchester professor, said it was unlikely it would develop into anything more serious, even though this would depend on the integrity of the fuel.

He believed it would be "pretty unlikely" that the fuel itself had been significantly damaged, but if this had happened, some radioactive material might be released into the plant's primary circuit.

In comments that appeared to back up this view, Japan's top government spokesman said the plant's concrete building collapsed in the blast, but the reactor container inside did not explode.

The spokesman said Tepco, the operator, planned to fill the leaking reactor with sea water to cool it down and reduce pressure.

Carnegie's Hibbs said: "If they are suggesting that the reactor vessel is intact and that they have a way to get cold water into the core of the reactor to cool that core down, that is very good news indeed."

(Writing by Fredrik Dahl; Editing by Matthew Jones)
 
Wouldn't UAVs be very helpful in surveying the damage from air in such a situation? Just a thought.
 
This disaster came at a bad time for Libya rebels. World attention will be diverted.
 
i agree no name


there is now a third reactor having problems, they are finding trouble finding another water source for it..

they are scanning all evacutees for radiation also
 
It seems we had what nuclear designers said for years was extremely unlikely: a hydrogen explosion in a high-humidity environment. That was enough to shatter the concrete of the containment building. The concrete from the top of the containment then falls on top of the reactor. The fuel assemblies are further damaged but the control rods may have shattered. These changes in the reactor geometry may lead to pockets of uncooled fuel or even criticality in the core, leading to a partial core melt.
 
Twitter reports radiation increasing, fuel rods 3' above coolant water. Core melt appears to be under way.
 
Reports that F-1 #3 cooling system is failing. This reactor is larger than F-1 #1 and has a uranium-plutonium core. Consequences of a nuclear accident at this unit are potentially greater than a core melt.
 
The hydrogen explosion blew apart the containment building of #1. Haven't you seen the video? They're dumping in seawater now. I guess nobody will be fishing that part of the Pacific for some time....

#3's containment is intact - for now. link
 
I have a bad feeling about this.... Hope everyone has been evacuated and there is no human radiation exposure. Dumping sea water is the last resort that the Japanese have and they are fast running out of options.
 
The hydrogen explosion blew apart the containment building of #1. Haven't you seen the video? They're dumping in seawater now. I guess nobody will be fishing that part of the Pacific for some time....

#3's containment is intact - for now. link

As I understand it a crack in the inner core caused an explosion of the "wet" part of the reactor core. I am wondering if there is an update on the status of the inner core containment.


I have a bad feeling about this.... Hope everyone has been evacuated and there is no human radiation exposure. Dumping sea water is the last resort that the Japanese have and they are fast running out of options.

The science talking heads on TV say using sea water as emergency coolant is unprecedented and may be a sign that the situation isn't under control.
 
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