Thursday, April 28, 2011

Prompt Criticality

Today, on the 25 anniversary of the Chernobyl disaster, I have two reports on the spent fuel pools.  The first is a frightening report on the huge explosion in Reactor #3 from Arnie Gundeson.  He's the nuclear industry expert who was asked to investigate Three Mile Island, and after discovering a much more serious situation than was being reported, went on to become a nuclear watchdog.  His latest report, at:

shows a side by side comparison of the two explosions at Fukushima Dai-ichi: Reactor #1 and Reactor #3. The reactor #3 explosion was more powerful and shot straight up.  He posits that it was not the reactor vessel, and its fuel rods exploding here (the reactor is still in tact), but instead that a hydrogen explosion disrupted the spent fuel pool so much that the Uranium & Plutonium there went "Prompt Critical",  and instantly released huge energy, which was channelled upward by the walls of the topless spent fuel pool.  Prompt Critical reactions are a kind of super-critical reaction that happens in nuclear bombs, and also is what happened at Chernobyl.

This analysis is confirmed by a second nuclear expert in an interview on RT.  

The implication is that the Plutonium and Uranium in reactor #3's spent fuel pool was vaporized and shot up to become airborne, in contrast to the expectations I wrote about in my last post that U and Pu would remain mostly at ground level.  This is consistent with ongoing reports of Uranium and Plutonium fallout reaching the whole of the US, with detections occurring in Hawaii, California and New England in particular.    From what I've seen at the EPA website, there doesn't appear to be high levels of U or Pu...but then I'm not sure what level to be concerned with.

Finally...part of the solution?   Here is a figure from the Japanese press, translated into English by former SFSU student Joey Fedrow, who is currently living in Tohoku.  It shows a possible scheme for repairing spent fuel pools.  I assumed this was just for Reactor #4, but perhaps it could be used for other reactors at well.

One thing that is disconcerting is how slow TEPCO is moving to contain the damaged reactors.  At this stage (49 days in) at Chernobyl, they were already building the concrete sarcophagus.


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