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Merged nuclear power safe?

Claims that the evidence points to a meltdown of reactor two through the reactor container, but not the outer container, although that may be damaged.
At least part of the molten core, which includes melted fuel rods and zirconium alloy cladding, seemed to have sunk through the steel "lower head" of the pressure vessel around reactor two, Lahey said.
"The indications we have, from the reactor to radiation readings and the materials they are seeing, suggest that the core has melted through the bottom of the pressure vessel in unit two, and at least some of it is down on the floor of the drywell," Lahey said. "I hope I am wrong, but that is certainly what the evidence is pointing towards."
The major concern when molten fuel breaches a containment vessel is that it reacts with the concrete floor of the drywell underneath, releasing radioactive gases into the surrounding area. At Fukushima, the drywell has been flooded with seawater, which will cool any molten fuel that escapes from the reactor and reduce the amount of radioactive gas released.
Lahey said: "It won't come out as one big glob; it'll come out like lava, and that is good because it's easier to cool."
The drywell is surrounded by a secondary steel-and-concrete structure designed to keep radioactive material from escaping into the environment. But an earlier hydrogen explosion at the reactor may have damaged this.
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http://www.guardian.co.uk/world/2011/mar/29/japan-lost-race-save-nuclear-reactor
 
The Grauniad said:
At Fukushima, the drywell has been flooded with seawater, which will cool any molten fuel that escapes from the reactor and reduce the amount of radioactive gas released.
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I don't like to introduce the C word, but wasn't it the molten fuel falling into a pool of water that caused the colossal explosion at Chernobyl? The expectation seems to be that it's going to be oozing out slowly rather than all falling out in one lump, but what are the chances of it all going even more wrong?
 
richardm said:
I don't like to introduce the C word, but wasn't it the molten fuel falling into a pool of water that caused the colossal explosion at Chernobyl? The expectation seems to be that it's going to be oozing out slowly rather than all falling out in one lump, but what are the chances of it all going even more wrong?
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My understanding of the Chernobyl incident is that there was an unrestrained chain reaction leading to excessive steam buildup in the reactor. This reaction was not caused simply by molten fuel falling into the water, but by a bit more complex situation (steam pockets around the fuel rods caused the fuel rods to further increase in temperature resulting in increasing steam pockets, and so on).

Wikipedia seems to have a pretty good run down on the incident (not sure exactly how accurate it is, of course, so YMMV).
 
richardm said:
I don't like to introduce the C word, but wasn't it the molten fuel falling into a pool of water that caused the colossal explosion at Chernobyl? The expectation seems to be that it's going to be oozing out slowly rather than all falling out in one lump, but what are the chances of it all going even more wrong?
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It can't be Chernobyl, but they seem to be trying to find out how close they can push their much better technology towards a Chernobyl rating. I have seen people calling it a six now.
 
richardm said:
I don't like to introduce the C word, but wasn't it the molten fuel falling into a pool of water that caused the colossal explosion at Chernobyl? The expectation seems to be that it's going to be oozing out slowly rather than all falling out in one lump, but what are the chances of it all going even more wrong?
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No, the initial explosion was due to a flash reaction , where the reactor power output suddenly increased a dozen time the maximum rated output followed by a steam explosion. At least that is what the simulation says since no instrument could register it.

There were a secondary concern of steam explosion when the corium reach a water table below, but my understanding of the design of Fukushima is that within the basement the corium will be spread enough, and of a different nature and quantity than what was produced at Chernobyl, whereas at chernobyl there were huge amount of it.
 
a_unique_person said:
It can't be Chernobyl, but they seem to be trying to find out how close they can push their much better technology towards a Chernobyl rating. I have seen people calling it a six now.
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From the definition I have seen (significant release of at least 0.1% of the core material) that does not seem to be meeting the requirement.
 
JihadJane said:
What would happen if a Fukushima meltdown hit the water table?
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I said it WAY above discussing the worst case scenario, which this nearly is; You have to sink coffer dams all around the site down to well below the water table, and then you sink wells and pump. You have to pump it dry continuously for years. You need barge away all that water for very expensive processing.
 
Small digression. Here is where I spent all my holidays as a child - in the house behind this street view. What's that on the mainland, visible straight ahead if you zoom in?

Hunterston nuclear power station.

It was built just before I remember. I don't have any memories of that coastline unsullied by the power station. I do have memories of admiring the way it was all lit up at night. "Like fairy-land!"

I don't ever recall being at all worried by it. Now, though, I do think, what if some time in the future we say the word "Hunterston" in the same breath as Three Mile Island and Fukushima?

Rolef.
 
Could this be true? It seems too ridiculous to be true. Maybe it was a bad joke. Some animes have a twisted sense of humor.
I've never heard of this source:

http://www.speakoz.com/english-directory/lesson-plans/plutonium.html

The Story of Plutonium starring ‘Mr Pluto’ aka ‘Plutonium Boy’
Broadcast in 1993/1994 in Japan

‘The Story of Plutonium’ was an 11-minute promotional video distributed to Japanese schools and broadcast on TV, showing how safe and friendly Plutonium was. An anime character ‘Mr Pluto’ flew about the video sprouting ‘facts’ and even encouraged a boy to drink a glass of water laced with Plutonium, saying that there’s nothing to be afraid of and Plutonium is safe to eat. The cartoon character wore a bright green hat with a friendly PU sign on the front and was aimed at kids. The cartoon boy, who drank the water, happily visited the toilet afterwards saying “Feels great! All fresh!” In reality, Plutonium is so dangerous that micrograms of it can cause cancer.

The government-owned nuclear fuel company (PNC) distributed the video to prepare the Japanese public for the start-up of the plutonium-fueled Monju prototype breeder reactor in the Fukui prefecture. It was in response to the overwhelming protests against the building of the reactor.
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I get the feeling that important parts of this story have been changed or made up. Skeptics, please help!

ETA: Found this on Youtube. (it's in Japanese)


ETA2::eye-poppi
It seems to be more or less what that article says. But it's late and I have to go to bed now. I don't have time to watch the whole thing now.
 
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