More serious than a meltdown — Possibility that fuel had a “melt through” at all 3 reactors

[FourScore]

Melted Fuel at Fukushima May Have Leaked Through, Yomiuri Says
By Go Onomitsu - Jun 7, 2011 2:02 AM ET

The melted fuel at Tokyo Electric Power Co.’s Fukushima Dai-Ichi nuclear power station may have leaked through the pressure vessels of the Nos. 1 to 3 reactors, the Yomiuri newspaper reported.

The Japanese government will submit a report to the International Atomic Energy Agency that raises the possibility the fuel dropped through the bottom of the pressure vessels, a situation described as a “melt through” and considered more serious than a “meltdown,” according to the report, which cited the document.

http://www.bloomberg.com/news/2011-06-07/melted-fuel-at-fukushima-may-have-leaked-through-yomiuri-says.html

[yella_dawg]

1. Molten metal + concrete equals bomb.

Every time, no exceptions. If the rods melted, then they burned through the containment vessel.

[dixiegrrrrl]

2. Can you expand on that for me, pls?

Assuming they did burn thru the containment vessel, what will happen next?

[JuniperLea]

4. + hit water table...

Which is right there since this is an island nation and the reactors are at sea level.

Nuclear sauna... and it will be visible... and probably loud.

[damntexdem]

3. I thought the the major danger of a meltdown WAS a melt through.

Resulting in all sorts of both contamination of the environment and chemical reactions involving explosions that further spread that contamination.

[Rageneau]

5. Only thing I'm sure of at this point is that the very worst is going to happen.

I wondered aloud back on Day One how bad this situation would be if it turned out to be as bad as it could possibly be. I fear we're going to find out.

[izquierdista]

6. Think down, not up.

This material is going to continue to sink until it hits something impermeable. At this point, groundwater contamination is the least of their worries, that's already a given, the problem should be recast as how to limit the spread of groundwater plumes. What they need to do is start building a geologic high-level waste repository on site and figure out how they can dump stuff into it, the most radioactive material first.

Maybe it's time to revisit Operation Plowshare (http://en.wikipedia.org/wiki/Operation_Plowshare) and create and underground cavern that all of the "meltthrough" can drop into. That assumes that the geology of the site is conducive to such an effort. The more alluvium there is under the site, the deeper it will have to be.

There is a new effort at Chernobyl to repair the concrete cap with a containment building. Here is a video of their plan: http://www.youtube.com/watch?v=jvEDVuGOJ6Y It should be noted that they still have a concrete bottom containment to work with, otherwise the Dneiper would be hopelessly contaminated by now.

Once they accept what has happened, the people in charge of Fukushima need to stabilize it with neutron absorbers and cover it over with concrete. That is the "up" part of the problem. The "down" part of the problem is what I mentioned earlier and depends on the geology of the area. It could be that there is nothing they can do but let another Oklo type reactor form (http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor) which would continue to cook away for another few hundred thousand years.