In a message dated 9/10/2011 8:26:06 P.M. Eastern Daylight Time,
Spinozalens@aol.com writes:
In a message dated 9/10/2011 7:46:19 P.M. Eastern Daylight Time,
jsd@av8n.com writes:
Looking at the big picture, and trying to guess what motivates
the questions, I think the answer to the underlying question
is that the plants aren't particularly well designed. They
just didn't pay much attention to the blackout scenario. I
am not an expert, but I reckon that for very little cost they
could have added a 1 MW turbine (and a 1 MW dummy load) so
that as long as there was steam in the system they could
operate in safety *and comfort* while disconnected from the
grid.
))))))))))))))))))))))
BZ
Internal loads are more like 50MWe for a 1000 MWe plant. . There actually
is no reason to keep the reactor critical and at power during a black out.
This is not a safe condition, safe in this case is the reactor scrammed
and
the emergency systems working to bring the plant to cold shutdown. To
try
to keep the plant running under a blackout condition is crazy. Also
large
plants don't enjoy very stable control at very low power. The best your
turbine idea could accomplish is to prevent a reactor shutdown until the
diesels come up to speed. It would be a much more expensive way to get
the plant
in a shutdown condition with little or no gain in plant safety.
)))))))))))))))))))))))))))))))))))))))))
I'm not saying this would be completely trivial. I can
think of several devilish details that would need to be
addressed, but that's what design engineers do for a living.
In show business, and in politics, there is a proverb that
says you should never believe your own press clippings. I
reckon the same rule should be applied to this industry. It
appears they believed their own hype and assumed blackouts
would be so rare as to be not worth worrying about. By way
of contrast, the airline industry assumes that crashes will
be very rare ... but they plan for them anyway. Not only
did Sully Sullenberger know how to ditch a plane in the
Hudson, the cabin crew knew exactly how to get everybody
off the plane afterwards in less than 90 seconds.
))))))))))))))
This is not right. Station blackouts are classified as one of the most
likely events. Nuclear plants are designed to handle a station blackout
and
have done so numerous times without incident. The situation is Japan was
out side the design analysis and its very justifiably to criticize this
failing, that's never supposed to happen. Also the early GE containments
has
long been known to be problematic, that's another very justifiable
criticism.
But your general statement is just plain wrong.
Bob Zannelli
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To make this easier to understand I give you a scenario. . You have a
1000 MWe plant in a black out condition, the reactor is at 5% power , you are
supplying all internal loads using the reactor. Now how do you shut down?
You can't reduce power , because the reactor is supplying internal loads.
It's not a good situation to hold at 5% power with xenon building fast ,
shutting down the nuclear fission., what can you do, keep pulling control
rods ( BWR) or dilute boron in the primary fighting to keep the plant
critical.(PWR) Your only real choice. . Start the safety systems and scram the
reactor.