Quote:
Originally Posted by CraigS
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Hi Craig,
Thanks for the link to the IAEA Fukushima status page.
The confirmation that, for Unit 4, "All fuel had been removed from the reactor core for
routine maintenance before the earthquake and placed into the spent fuel pool",
and that "a portion of the building's outer shell was damaged" is consistent with the US
NRC reporting and a set of facts of considerable concern.
That unit had a output capacity of 1100 MW of power. The source of that power
was purely from its fuel rods when in a controlled fission state. Now those fuel
rods, the potential source of all that energy, are inconveniently sitting
outside
the primary containment vessel effectively out in the open. Separated by space gaps,
they currently do not form a critical assembly, but they are rising in temperature
hour by hour. If they should catch fire and melt (and they eventually will if they cannot be cooled),
they may form a conglomerated mass and a fission reaction will begin again releasing
even more energy. So there is a real race against time here probably over the next few weeks.
The pool structures are said to be made of concrete lined with "a thin
stainless steel liner". One concern from TEPCO has been that the concrete on
Unit 4's pool has partially fallen away leaving only the stainless steel liner.
It would be interesting to learn of a link to an authoritative source as to whether it is
believed the thin stainless steel liner of the cooling pool will be sufficient or not
to hold the rods in the spent pool, should the worse occur and the rods melt.
One can only hope that Unit 4's pool is watertight and that, if it is not too late,
water can be added to it. Should a cladding fire occur, water is not the
correct material to pour on it. In that eventuality, they may have to start dropping
large amounts of sand on it, possibly mixed with boron, which acts as a neutron
poison. Hopefully this will not occur, but suffice to say, it would be an act of
desperation.
Yesterday, France flew out 95 tonnes of boron destined for Japan.
See
http://www.straitstimes.com/Breaking...ry_646202.html