Fukushima: Worse Than a Disaster

[AtheistCrusader]

33. The containments are compromised. No doubt there. They are leaking water.

But these are likely cracks, damage from the explosion in the condenser torus, and connecting pipes that were destroyed by the quake. The water doesn't drain fast enough to suggest it's all going right out a hole in the bottom.

When the cores melted (reactor 1 the worst/hottest) all that material splashed to the catchment at the bottom of the containment. When that happened, it stopped being critical, meaning no longer actively producing heat by fission. All it adds at that point is the decay heat of the fuel itself. The conditions for it to remain critical were gone.

The fuel landed on a platform designed to separate the fuel, add poisons (boron) that prevent criticality, and generally soak up heat. Steel, seven meters of concrete, etc. The fuel likely burned something like 70cm into the concrete in places, if I recall the report correctly. That further poisons the fuel with impurities, like steel and concrete. It would quickly reach a state like the 'foot' of corium under the reactor in Chernobyl. A slagged mess of incredibly radioactive crap. You see the 'foot' (below) in Chernobyl, because the RBMK reactor that exploded had no containment at all. Nothing to catch the slagged, molten corium, and contain it.

The containments on reactors 1-3 should have done better. They should be water-tight, and keep the contamination inside. They failed in that regard. Spectacularly so. But they did not fail to contain the core material itself. If the cores had remained critical, in the bottom of the catchment, then yes, they would eventually burn their way through all that concrete and steel, and escape from the bottom. But that kind of fuel can't work that way. It has to be in the geometric config of the core before it melted, and it needs a neutron moderator to truly run at full power/temp or runaway beyond that point.

Chernobyl unit 4 was a 3.2mw reactor, and when it exploded, the last instrument showed 33mw of thermal output (Almost 10x the design limit). It had no containment at all, and here is the lowest level of the basement where the corium halted and solidified, and remains today:



Fukushima Dai-Ichi is worse than 3 mile island by a lot, but the cores more closely resemble the state of TMI than Chernobyl unit 4. TMI's core only partially melted, and didn't escape the reactor pressure vessel, but did stay inside the containment.