Unit
5 was checked first to prove the process. We know the core is there
because Units 5 and 6 did not lose power, and so had no core damage.
Unit 2 core obviously had a great deal of melting, if not totally melted.
The
radioactive decay of the atom splitting pieces that produces that heat
that causes melting, decreases continuously with time. (I guess this was
why the name “decay” was chosen. This relates what is happening to
processes with which people are familiar.)
Because
the heat generation always decreases and never again increases, your
words that a meltdown might occur again are not right.
In
the terrible, gross, Chernobyl accident, the mixture of molten fuel and
molten/burning graphite flowed for a while out broken pipes, then
solidified. The pictures are dramatic. The formations were dubbed
“elephants feet.” You can find them on line. http://nautil.us/blog/
At
Unit 2, based on the findings, I expect that molten core mass will have
melted through the reactor vessel, and solidified somewhere below it.
In the MK I BWR design, the reactor vessel sits on a tall collar,
because the control rod drives stick out from the bottom of the vessel.
(I’ve stood under them) The collar sits on the inside of the “upside
down light bulb” shaped primary containment. There is a flat concrete
floor poured in the bottom of the bulb that provides a working surface.
The “bulb” sits on a large solid concrete pedestal that is not quite
as big around as the bulb. The pedestal sits on the floor of the
reactor building, which is the secondary containment. Around the
pedestal is the Suppression Pool-the torus – doughnut shaped. It is
about half filled with water and connected to the bulb.
I
expect all the core to have cooled and solidified long ago – first days
– and be in the bottom of the bulb and perhaps on the floor of the
reactor building. All the concrete and steel soaks up heat being
generated from the molten core mass, and speeds up the cooling.
Howard Shaffer
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