Carl Denk wrote:

> As a non-nuclear person, I need to make some assumptions:
> 1: Even with the control rods in place, the fuel generates some heat.
> That quantity of heat needs cooling to prevent boiling the very clean
> water inside the reactor, this may take some time (days??) without
> outside cooling. The water slowly heats, and there is insufficient heat
> radiation/conduction to dissipate the heat.

Not exactly.  The fuel rods don't generate enough heat to boil water
unless there is a reaction going on.  However, once the reaction is in
started the reaction itself creates a ton of heat, and some of the
reaction byproducts also generate heat, but a lot less.  Once the reaction
is stopped they get consumed after a few days, but for a few days there is
still quite a bit of heat being generated, but nothing like the amount
when the reaction is progressing.

> 2: Normally the reactor water is cooled by a second water cooling
> system, using a heat exchanger to move the heat between the 2 waters.
> The 2nd cooling system could be dissipating the heat with a cooling
> tower (didn't see any here), taking sea water, adding heat to it, and
> sending back to the sea, or some other method.

The F-D reactor is a BWR, you describe a PWR.  There is no secondary loop
in a BWR.  the problem with sea water is that the contaminants can be made
radioactive, and they may take a lot of time for the radiation to
dissapate.  With the pure water the half life of the irradiated products
is very short.  Sea water is also horribly corrosive so likely it did a
lot of damage.

> 4: Without cooling, thing of a pot of water on the stove. With enough
> heat at the bottom, bubbles of steam rise to the surface, even though
> the biggest part of the water is not near boiling.

Pressure keeps it from boiling until it reaches the turbines.

[clip]

> 6: There was reports that the reactor facility was short of electric
> power. As strange as it sounds, it is possible that the voltages
> produced at the nuclear site need to go off site, to a
> transformer/switchgear yard, reduced in voltage, and then return to the
> nuclear site to power controls, pumps, etc. Several years ago, in
> Western, Ohio, USA, at the Davis Besse nuclear generating plant. A small
> tornado took out a single moderate voltage electric line going to the
> plant. The plant was shut down for several weeks, until the electric
> wires could be replaced, and the unit brought back on line properly

Once the control rods are dropped, the plant is no longer generating
electricity.  However, numerous safety systems require electricity.  For
that reason, U.S. plants are not permitted to keep operating unless there
are at least two independent outside sources of power in addition to any
onsite generating capacity (batteries, diesel generators, etc.)  Japanese
rules appear to be similar.

There was a SCRAM at the E. Fermi II plant last year simply because one of
the two outside sources of power went away.  When they investigated they
discovered more serious damage, but the shutdown was caused by having only
one outside power source.

--McD





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