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Re: [Phys-l] Nuclear Power and the Grid



In a message dated 9/11/2011 10:53:04 A.M. Eastern Daylight Time,
jsd@av8n.com writes:

On 09/10/2011 05:25 PM, Spinozalens@aol.com wrote:

To try
to keep the plant running under a blackout condition is crazy.

That wasn't what I was suggesting.

))))))))))))))

BZ

OK

))))))))))))))))



I was talking about something along the lines of the reactor core
isolation cooling system (RCIC), which does useful things with the
residual decay heat. If it is so crazy, why did GE provide such a
system in the Mark I reactor design, as used at Fukushima and many
other places?
_http://www.google.com/search?q=ge+"mark+i"+rcic_
(http://www.google.com/search?q=ge+"mark+i"+rcic)

))))))))))))))))))))

BZ

I wrote about RCIC in one of my posts. I never said that you couldn't do
something useful with decay heat. I said you don't want to keep the plant
critical during a loss of off site power.

))))))))))))))))



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.

Perhaps I wasn't clear about the terminology. Please do not confuse
the following:
-- A "station blackout" is where the station itself, including the
control room and the coolant pumping systems, are without power.
This is not common, and the US NRC and others have known for years
that many scenarios involving a prolonged station blackout end in
disaster.
))))))))))))))

BZ

OK you mean a failure of all the power sources including emergency sources.
Nuclear plants are designed so this should never happen. If it does happen
, then yes for current nuclear power plants disaster is quite likely. I
was just talking about total loss of the power grid. This total loss of all
power sources is exactly what happened at the Japanese plants, this was a
design failure related to an extraordinary event. Such events are never
supposed to happen.

)))))))))))))))))))))


-- A regional blackout is a much less dire situation. It means that
the plant cannot obtain power from the grid, but the control room and
the pumps et cetera can operate from the on-site diesel generators.
We agree this has happened numerous times without leading to disaster.
OTOH this is *not* what the NRC calls a station blackout, and not
what I was talking about.

))))))))))

BZ

OK

)))))))))))))



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.

My general statement was that the plants weren't very well designed.
You agree that the design is in several ways "problematic" but disagree
with the general statement? What's wrong with this picture? Even if
I'm wrong about the number of MW required to operate the station, I stand
by the general statement. These plants weren't all that well designed.


)))))))))))))

BZ

I make a distinction between a plant poorly designed and a new and better
technological approach for the utilization of nuclear energy. However,
it's true , in my opinion, that bad engineering was involved with the
disaster in Japan. Other light water reactors have better designed containments,
and perhaps are better designed to cope with extraordinary events but I am
more than willing to concede that design failures of the Japanese plants
were instrumental in the accident.

)))))))))))))


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

As another bit of evidence supporting that general statement, consider all
the upgrades that the US NRC has required Mark I plants to install over the
years, at a cost of billions of dollars per plant. Note that "regulatory
capture" (where the industry controls the regulators and not vice versa) is
even more of a problem in Japan than in the US, and the Japanese regulators
did not require the same level of upgrades, leaving it to the discretion of
the operating companies, since "they were in the best position to know"
what
needed doing. At least one of these upgrades, namely hardening the vent
stack, by all accounts would have prevented at least one of the explosions
at Fukushima. This should be an obvious lesson for those who are
demanding
"deregulation" in the US ... as if the Deepwater Horizon were not lesson
enough.

)))))))))))))0

BZ

I am not familiar with the details of this but in general what you write
sounds reasonable and not surprising

))))))))))))))))))))



As yet another example supporting my general statement: There are
conflicting
stories about this, but the impression I get is that at Fukushima, after
the
diesel generators failed, operators ran the coolant pumps from batteries
for
several hours. It was only after the batteries were exhausted that cooling
stopped and losses of many trillion yen were incurred.

At this point the question arises, what about the RCIC? The story is that
without battery power, they were unable to control the valves to run the
RCIC. If any part of this story is true, this is some verrry badly
designed
hardware *and* some verrry badly designed operating procedures. It
boggles
the mind.

))))))))))))))0

BZ

Again I don't know the details here. It wasn't my intention to defend
the Fukushima accident, just to offer some clarification on nuclear plants
and station blackouts. You may well be correct on this.

))))))))))))))))))))



-- The RCIC hardware should have been fail-safe. It should have been
operable, somehow, without battery power.

))))))))))))0

BZ

Without power to instruments and control systems things go south rather
quickly. I would say instead that the plants should have been designed to
withstand the triggering event and make it possible for operators to get
these reactors to safe shutdown.

)))))))))))))))))





-- Hours earlier, when it was obvious that it would be days (not hours)
before anyone would be able to bring in help from outside, the operators
should have started husbanding battery power. They should have switched
off the electrically driven pumps and used the battery power to control
the RCIC. Controlling a valve takes a lot less power than driving a pump.
I don't know for sure, but it seems plausible that this would have
increased
the battery lifetime by orders of magnitude. The hypothesis is that they
could have operated the RCIC for days, buying them enough time to bring in
pumps and generators from outside, time to figure out what was going on,
time to let the residual decay heat in the core taper off, et cetera.
This could have led to a very different outcome.

Note that hooking up external power is a lot easier if you do it /before/
the plant explodes and spreads high level radioactivity all over the site.

Even if we don't understand the details, we know that the RCIC was
intended
to be a last-ditch cooling system, but turned out to be not operable under
last-ditch conditions. This is not something to be proud of.
))))))))))))))))))))))

I agree.

Bob Zannelli


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