From: dpe@inel.gov (Don Palmrose)
Subject: Re: Nuclear Power and Climate Change
Organization: INEL EG&G Idaho
Date: Wed, 6 Jan 93 20:51:39 GMT

In article <C0G5tF.IBB@encore.com>, wcarroll@encore.com (William Carroll) writes:
> 
> It was in a "hot shutdown". According to FPL, the reaction was being
> maintained, but no energy was being supplied to the grid. It was my
> impression that this is what the NRC requires in that type of situation.
> After the storm, they were required to take it to a "cold-shutdown" until
> the emergency systems had been repaired and inspected. The implication was
> that the reactor was now turned off and there was NO atom splitting going
> on. Then the reaction had to be initiated again. I am certainly no nuke
> eng, but reading reports led me to believe that there is a _significant_
> difference in the startup times between the "hot shutdown" case and the
> "cold shutdown" case. Perhaps Mr. De Armond, or some other netter with
> industry experience, could clarify the difference for us.
> 
> 
> William R. Carroll (Encore Computer, Ft. Lauderdale FL) wcarroll@encore.com
> 
> "We trained hard,  but it seemed that every time we were beginning to form
> up into teams, we would be reorganized.  I was to learn later in life that
> we tend to meet any new situation by reorganizing;  and a wonderful method
> it can be for creating the illusion of progress while producing confusion,
> inefficiency, and demoralization."	-Petronius Arbiter, 210 BC
> 
> 

FYI,  William R. Carroll (or do you prefer Bill?  For now I will use William) 
is basically right about the definitions for Hot Standby and Cold Shutdown. 

Hot Standby is the reactor is critical but not sending steam to the turbines
that produce electricity to send out to the grid.  Steam is still used to
power any steam turbines for auxiliary systems that may have them and site
electricity is either supplied from the grid or diesels.  Typically, the
reactor is at about 1% of total rated power.  To come back on-line is just
a matter of getting the steam piping to the large electric generator's 
turbines at the proper conditions and raising the level of auxiliaries needed
to support full power.

Cold Shutdown is when the control rods are driven back into the core.  William
is wrong in that all fissions are stopped.  There are fissions still occurring
but not at a rate or level to maintain a chain-reaction, this condition is
called sub-critical.  The steam side is completely shutdown unless they are
going to perform a cooldown.  The operators may even force cool the plant 
down to temperatures below 200F by taking steam off the steam generators and
filling the steam generators with water and at specified temperatures and 
system pressures, begin operating support systems designed to remove the 
reactor core's decay heat.  Because the plant is no longer at its normal
operating temperatures and pressures, to bring the plant back on-line with the
grid requires reversing the cold shutdown proceedure.  There are strict 
operating rules on how this and other operations are performed but since
from cold shutdown one must raise primary water temps by close to 400, this
will take time to become fully operational again.

Hope this helps.

Don Palmrose




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