Newsgroups: sci.energy
From: John De Armond
Subject: Re: Nuclear Power and Climate Change
Message-ID: <-!zra_g@dixie.com>
Date: Thu, 07 Jan 93 10:32:57 GMT

wcarroll@encore.com (William Carroll) writes:


>No, it was in a "hot shutdown". According to FPL, the reaction was being
>maintained, but no energy was being supplied to the grid.

Hot shutdown has a specific meaning. That condition is when the reactor
is scrammed, the generator is tripped but reactor coolant temperature
is maintained by decay heat and/or reactor coolant pump heat input.

Hot standby is the condition where the turbine is tripped, the reactor
is making power and that power is being dumped to the condenser via
the bypass system.  Hot standby is not a normal condition since TMI
because the NRC now requires a turbine trip to cause a scram and because
reactor control is a bit touchy, particularly when coming down from
power and xenon is biting at your reactivity margin.  About the only
time hot standby is seen is during testing and if the operators think
the cause of the turbine or other trip will be remedied rapidly.
Remaining at power helps burn off xenon.

>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.

They were required by tech spec to proceed to cold shutdown, a process
that takes a few days, by the weather.  There was no damage to
plant systems.  The only damage was to the off-site evacuation sirens,
a system required by the NRC for operation.

>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.

There is a large difference in startup times due to limits on heat
rate.  The startup sequence is roughly, secure the residual heat
removal system and build primary system pressure while beginning
to establish water chemistry.  When the pressure reaches the
reactor coolant pump (RCP) net positive suction head (NPSH), start the
RCPs.  The approximately 10 MW of energy input by the RCPs brings the
primary temperature up to operating temperature, about 557 degrees
for a Westinghouse.  This takes a day.  Meanwhile the Chemical and Volume
Control System (CVCS) is reducing the concentration
of boric acid (neutron absorber) in primary coolant system from the
shutdown concentration to the startup concentration.  A steam bubble
is established and level control initiated in the pressurizer as the RCS
goes through 400 degrees.  At about this time feedwater from the steam
side is supplied to the steam generators and steaming commences.  Steam
is vented initially to the atmosphere and then to the turbine condenser.
This is hot standby.

After primary level, pressure and chemistry is established, the rods
are pulled according to the rod block sequence to put the reactor on
a 400 second period (power level doubles every 400 seconds.)  Power
level increases through about 12 decades until it reaches about 1%
of full output.  The turbine is spun and the generator synced to the line.
The neutron monitoring system is in the control loop and rod withdrawal
is programmed to increase power as measured by the neutron monitoring
system at a rate of 5% a minute up to the demand setpoint.  Boric acid
is reduced by the CVCS so that the rods are fully withdrawn which gives
the maximum shutdown margin upon scram.

Going from cold shutdown to hot shutdown takes from 13 to 24 hours.
Going from hot shutdown to power operation takes typically an hour.

(This is from memory so sue me if I forgot something.)

>Well, since the emergency systems are part of the nuke plant, and required
>for its operation, I would say that, yes, the nuclear plant was damaged. No,
>the containment buildings were not damaged. Or at least not to a newsworthy
>level.

The siren system is NOT a part of the plant other than there is a trip
button on the control panel.  A county evacuation plan is not part of
the plant either but the plant cannot operate by law without there being
one in place.

>The damage that required the plant to shutdown was the emergency systems.
>That was certainly not the only damage to the site. My impression was that
>FPL's facilities at Turkey point did not sustain significantly more damage
>than any of a number of other properties in the South Dade area. The plant
>did survive relatively intact.

The plant "survived" intact.  Period.

>So why should I believe Turkey Point is that much better designed than
>Homestead AFB?

Because we tell you it is.

John

Newsgroups: sci.energy
From: John De Armond
Subject: Re: Nuclear Power and Climate Change
Message-ID: <19zrz1j@dixie.com>
Date: Fri, 08 Jan 93 09:44:53 GMT

wcarroll@encore.com (William Carroll) writes:

>Thank you, John, for the excellent explantion.

Yer welcome :-)

>>The siren system is NOT a part of the plant other than there is a trip
>>button on the control panel.

>This is definitely NOT the impression given by news reports.

Media lie or mislead?  nah.. :-)

To expand on this a bit, the emergency siren system is designed to
make sure every person inside the 10 mile radius evacuation zone can
be warned of emergencies.  sirens are not mandated; Midland opted
for supplying a radio to every resident inside the area, but they
are the most common.  At almost every plant I've been involved with,
the sirens are triggered by radio, the rest were by dedicated phone
lines.  Each siren site contains a motor driven siren of from 10 to
50 horsepower, a radio receiver and controlling electronics.  each
siren is individually addressable plus there is an "all call" code
for simultaneously triggering them all.  (Interesting aside.
At TMI we had a real problem with a prankster.  They forgot to design
in a time stamp into the control protocol which enabled the prankster
to record the audio tones broadcast for the "all call" and then
drive around while playing them back through a low power transmitter.
He'd trigger 2 or 3 sirens at once.  They time out after 10 minutes
but it kinda degraded the public confidence  in the system.)

The central control and transmitter is located at the off-site
Emergency Operations Center for the simple reason that it might be necessary
to sound an alarm after the plant has become uninhabitable after an
accident.  There is a circuit - two redundant ones, actually - from
the EOC to the control room so the operators can trigger the sirens
AND so they can do routine testing which involves firing them off
once a week, typically at noon on Saturday.  At TMI, for example,
they just installed a couple of industrial grade pushbuttons in a box
and bolted it to the shift supervisor's desk.  This desk is located
inside the horseshoe control board area but not on the board.

>>>So why should I believe Turkey Point is that much better designed than
>>>Homestead AFB?

>>Because we tell you it is.

>But you admittedly have no more experience or knowledge of USAF specs than
>I have of either. I'm sure the AF felt just as good about the integrity of
>their hangars as you do about the integrity of a nuke plant. Frankly, I
>don't think anyone has the necessary experience weathering hurricanes to
>fell confident in their assumptions about what will happen in one.

My comment was semi tongue in cheek.  I actually do have a decent bit
of knowledge by virtue of seeing pretty detailed pictures of the
wrecked buildings on TV.  I can compare what I see to what I know
about regarding nuclear plants.  I've a real problem with any metal/sheet
metal building being called "hurricane proof".  I wonder if the USAF
really does call 'em hurricane proof or is this more "media enhancement"
of the facts.

Making a NP survive just about any natural disaster short of a volcano
is pretty easy.  Determine what the worst weather has been, double
that and then pour enough concrete to withstand it.  Make sure
all outside openings are either above the high water mark or equipped
with water-tight doors and away you go.   There is little practical limit
to what can be withstood using this method.  Hey, you ought to see
what constitutes earthquake-proofing the place.  :-)

John