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Re: [Phys-l] Nuclear Power



On 05/02/2011 08:53 AM, chuck britton wrote:
Last weeks tornados shut down all three reactors at the Browns Ferry
Power Plant in northern Alabama.
Downed transmission lines left virtually no load available so the
plant went into a cold shutdown state.
Seven of the eight diesel generators have fuel for one week to cool
the spent fuel storage pools and reactor cores.
More fuel is being trucked in.
The diesel generators can't provide enough power for 60% of the
warning sirens around the plant.

Good thing we don't get tsunamis in the Tenn. Valley ;-)

I agree with the sentiment.

Slight nit-pick on the terminology: The reactors scrammed, but
that is not the same as "cold shutdown". The reactors are currently
in a hot shutdown state. They are subcritical, but they are not cold.
Not by a long shot.

The point is that such a reactor doesn't reach the /cold/ shutdown
state until most of the "decay heat" has gone away ... which
doesn't happen until long after the reactor is turned off.

The standard terminology is not very expressive, and doesn't cover
all the possibilities. In particular, I have seen designs that
allow for "passive shutdown", meaning that you could turn off
the reactor and walk away, without any need for active cooling
and without fear of meltdown. Many of the research reactors
have this property. OTOH I doubt that any existing (or proposed)
power plants have this property.

And FWIW the official definition of "cold shutdown" doesn't
depend on whether active cooling is required. Sigh.
http://www.nrc.gov/reading-rm/basic-ref/glossary/cold-shutdown.html

Maybe what we need is a new term to designate the "passive walk-away"
state.

Good thing we don't get tsunamis in the Tenn. Valley ;-)

It's also a good thing we don't get huge floods in the Ohio /
Mississippi river valley, the sort of floods that might cut off
power and transportation for more than a week ... or inundate
the basement of a reactor building and take out all the switchgear
that controls the primary /and/ backup cooling.......

Oh, wait, nevermind. Oops.