Welcome to European Tribune. It's gone a bit quiet around here these days, but it's still going.
We now have TWO confirmed LOCA's and subsequent H2 explosions at the Fukushima complex. To make a big H2 boom, you have to make a lot of H2, which evidently comes from this reaction:

Zr + 2 H2O  -->  ZrO2 + 2 H2

So this means that lots of Zr fuel cladding has turned into zirconia and lots of H2, and that the really hot UO2 fuel pellets (self heating due to daughter products radioactive (via beta emission) decay) are now exposed to hot steam and some nasty "daughters" are puking out of the system via the steam vents.

I thought one known mechanism for hydrogen production was dissociation of cooling/moderator water by neutrons or gamma rays from the nuclear reaction. Can than not possibly produce enough H2 for the kinds of explosions we've seen without assuming the Zircon alloy fuel cylinders have begun to disintegrate?

So, in what may be my last act of "advising", I'll advise you to cut the jargon. -- My old PhD advisor, to me, 26/2/11
by Carrie (migeru at eurotrib dot com) on Mon Mar 14th, 2011 at 05:19:22 PM EST
[ Parent ]
One ton of Zr can make about 88 lbs of H2, which is about 15,780 ft^3 of H2. That would probably be enough to take the roof off the buildings, especially as this would be uniformly distributed over a big area - like a fuel-air bomb. It would be ugly.

Ionizing water, or catalytically decomposing water at cherry red temps would make both H2 and O2 which could also recombine, especially with all that ionizing radiation. Maybe some ionizing radiation from a "hot" isotope of Xe or I2 kicked off the explosion that blew off the roof...or maybe just a motor or a switch that was not rated" explosion-proof".


by nb41 on Mon Mar 14th, 2011 at 11:00:31 PM EST
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Checking some other sources like this one, I see that the zirconium reaction is indeed considered the primary source of hydrogen gas during meltdowns, and radiolysis as source of hydrogen gas poses more a problem of accumulation.

I also read that after Chernobyl, to prevent hydrogen gas explosions, plant safety plans foresee the flooding of the vessel with nitrogen so that there is no oxygen to react with. Hence the explosion only outside after venting.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Tue Mar 15th, 2011 at 07:09:09 AM EST
[ Parent ]


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