Japan may have lost race to save nuclear reactor (Guardian UK)

[jpak]

http://www.guardian.co.uk/world/2011/mar/29/japan-lost-race-save-nuclear-reactor

The radioactive core in a reactor at the crippled Fukushima nuclear power plant appears to have melted through the bottom of its containment vessel and on to a concrete floor, experts say, raising fears of a major release of radiation at the site.

The warning follows an analysis by a leading US expert of radiation levels at the plant. Readings from reactor two at the site have been made public by the Japanese authorities and Tepco, the utility that operates it.

Richard Lahey, who was head of safety research for boiling-water reactors at General Electric when the company installed the units at Fukushima, told the Guardian workers at the site appeared to have "lost the race" to save the reactor, but said there was no danger of a Chernobyl-style catastrophe.

<snip>

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.

<more>

[lapfog_1]

1. see China Syndrome

and, it's not Chernobyl, it's potential is much worse. If anything that stops the water from keeping the molten slag of fuel rods cool... it heats up and melts right through the floor all the way down to the water table. The resulting explosion as super heated nuclear material hits water will throw material dozens of kilometers in all directions (not to mention that some will make it into the upper atmosphere where it will be carried to who knows where - but west coast of US is very likely).

The worlds biggest "dirty bomb".

[flamingdem]

5. Possibly a worst case: hydrogen meets corium via water pools

From Reuters Q+A:

http://www.reuters.com/article/2011/03/29/japan-plant-i...

"If workers are unable to continue hosing operations, and if the nuclear fuel manages to melt through the bottom of the reactor and fall into a water pool below, this would result in a high temperature burst and a sudden release of a huge amount of hydrogen that could, in an unlikely "perfect storm" scenario, breach the containment vessel. "

comment:
With all the water dousing on site, water will pool in many locations. If these water pools come in contact with corium, or hydrogen collects in pockets, you have the source for an explosion & dirty bomb.

[godai]

2. Good article...bad news n/t

[flamingdem]

3. This is an analysis "follows an analysis by a leading US expert" - not a Tepco statement

so it's what they are implying with the radiation numbers but will not confirm?

Guess that means all work at the plant will be suspended due to threat of spikes or the current level of radiation?

[OKIsItJustMe]

15. NHK: Work at the site (Number 2 unit) is currently suspended.

http://www3.nhk.or.jp/daily/english/society.html

…

The most serious problem is puddles of highly radioactive water found in the basements of turbine buildings of the number 1, 2 and 3 reactors.

Radiation levels at the surface of water in the Number 2 unit are more than 1,000 millisieverts per hour. Work at the site is currently suspended.

…

The firm says there has been no major change in levels of highly radioactive water found on Monday in a tunnel called a trench outside the Number 2 turbine building. TEPCO is continuing to monitor the trench to prevent radiation from leaking outside.

…

[flamingdem]

4. Reuters Q+A link

From Reuters Q+A:

http://www.reuters.com/article/2011/03/29/japan-plant-idUSL3E7ES10P20110329?pageNumber=2

"If workers are unable to continue hosing operations, and if the nuclear fuel manages to melt through the bottom of the reactor and fall into a water pool below, this would result in a high temperature burst and a sudden release of a huge amount of hydrogen that could, in an unlikely "perfect storm" scenario, breach the containment vessel. "

comment:
With all the water dousing on site, water will pool in many locations. If these water pools come in contact with corium, or hydrogen collects in pockets, you have the source for an explosion & dirty bomb.

[FBaggins]

6. They "lost the race to save the reactor" very early in the timeline.

It's possible that some of the core got through the bottom of the RPV, and #2 is the most likely suspect (could help explain what happened to the torus), but that doesn't do much to the overall scenario... and is by no means a sure thing.

The rest of his analysis appears pretty good.

[OKIsItJustMe]

7. Once again, JAIF has been saying this for days, although they didn't use words like “meltdown”

http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=283989&mesg_id=284000

“It is presumed that radioactive material inside the reactor vessel would have leaked outside the containment vessel at unit-1, 2 and unit-3, based on the investigation of the water sampled at turbine building.”

[FBaggins]

8. I'd say that's a little different.

"Radioactive material" leaking out is not necessarily the same thing as molten portions of the core breaching the steel RPV containment.

[Fledermaus]

Arrrr! Captain Ahab, what be this molten goo creeping out of Unit 4?

[FBaggins]

12. You have the most incredibly active imagination I've seen in some time.

Have you ever considered writing fiction?

Oh... what am I saying. Of course you have! :rofl:

You really see "molten goo" in that photo, eh?

Amazing how well that thin piping stood up to a lava of molten metal, eh?

[Fledermaus]

13. Did you loose something?

[FBaggins]

14. Don't know... does it look "loose" to you?

Let me guess... that's the lid from #3 that somehow blew all the way over the #4, right?

[OKIsItJustMe]

9. Not necessarily, no

However, if they were speaking only of water, even contaminated water, isn't “material” rather an odd choice of words?

[FBaggins]

10. But they wouldn't be speaking of just water.

It's the core elements that the water caries out of the reactor that are dangerous.

If the core damage was significant, this could easily include things like plutonium.

isn't “material” rather an odd choice of words?

Not as odd as if you intended it to mean "corium". IMO.

[damntexdem]

11. Hey, look at the bright side: given where Japan is, there can't be a China Syndrome!

;-)

Of course, it might be an America Syndrome instead. But then, the glow will make it easier to look on the bright side.