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Re: [Phys-l] Eartquaque in Japan



On 03/14/2011 09:34 AM, Bill Nettles wrote:
I have never understood why the electrical supply for nuclear power
plants must come from off-site grid. Yes, in general, run them on the
off-site grid, but allow the possibility to shift to local generation
rather than depending on diesel generators which get scheduled, but
short term testing. From what I've read, the diesels operated for
about an hour, then failed. Yeah, that's not surprising when they've
never been run for over an hour.

With the ability to shift to on-site generation (and I certainly
don't fully understand all the details of grid sync, etc, but it's
not an impossible shift to design), off-site grid failure still has 2
backups: diesel and on-site. The decay heat alone should generate
enough steam to run coolant pumps.

Am I missing something here?

Yes. The tsunami.

The diesels were working fine until the tsunami hit, about an
hour after the earthquake.

There is indeed a steam-driven backup generator, but it too
became inoperable after the tsunami hit.

Also: We don't know the details, but it seems very likely that
there was critical damage to other components, not just the
power supplies. Even now, days after the event, with plenty
of power available, they are having trouble with the cooling
on several different reactors.

============

It may be years before we know what went on. It seems likely
that the TEPCO guys don't fully understand what they are dealing
with. And if/whatever they do know, they're not telling us.
It's quite amazing how little reliable information is available.

Possibly of interest:
http://www.tepco.co.jp/en/press/corp-com/release/