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Jon Elson[_3_]

wrote:

On Wed, 27 Jun 2012 14:31:00 -0500, Jon Elson
wrote:

It is totally amazing that nothing was done, even though they had
meetings on the risks and what could be done to mitigate them.

Jon
And the cooling water pumps run off the grid? instead of off the
reactor.
The turbo-alternator exciter can become unstable under extremely light
loads,
like trying to self-power the plant. The Chernobyl disaster was caused
by trying to power the reactor off alternator inertia for a minute while the
Diesel generators came up to speed. A special exciter was installed to
operate at light load. The alternator slowed down, the line frequency
dropped, and the cooling pumps slowed down. Due to the insane design
of a VERY dangerous plutonium production reactor repurposed as a commercial
power plant, it has a positive void coefficient, ie. if the cooling water
boils, the reaction rate goes UP!

So, we use fast-start generators and UPS-like back up power for the cooling
pumps, plus huge amounts of water in the reactor and negative void
coefficients to guarantee thermal stability.

And the backup generator was in the basement, where it
flooded even before the reactor gave any trouble. Pretty poor design,
when it comes to failsafe. But it was Japanese engineering, so of
course nothing would ever go wrong.
Yes, so MANY poor decisions a disaster was inevitable. Even a major
water leak in the plant could have flooded critical safety systems.

Also, the tsunami knocked out the sea water pumps, and 5 of 6 emergency
Diesels were water-cooled.

Jon