From: jgd@dixie.com (John De Armond)
Newsgroups: sci.energy
Subject: Yack's daemons (was Re: Nuke Stupidity Rebuttal)
Date: 28 Sep 92 07:39:09 GMT
Organization: Dixie Communications Public Access.  The Mouth of the South.

yodaiken@chelm.cs.umass.edu (victor yodaiken) writes:

>>My point is this:  I don't see how the kind of scenario you're so concerned
>>with can occur without some kind of release of highly radioactive material
>>from the reactor.  And as far as I know (this could be sheer ignorance on
>>my part, of course), the only way such a release can occur is when the
>>containment is breached.  After all, the *job* of the containment is to
>>prevent such a release, yes?

Let's take a look at what our resident armchair reactor engineer, yackadamn
proposes:

>Well, that's the big question isn't it? What if a TMI style
>screwup happens at an older plant and when they finally start 
>cooling it the reactor vessel splits open due to the loss of 
>ductility associated with nuclear radiation, 

If you're going to walk the walk, at least talk the talk.  The theoretical
problem is called Neutron-Enhanced Nil Ductility Elevation or simply 
Neutron embrittlement.  Not a problem, of course, since a) all reactors are
now charged with fuel enrichments that minimizes neutron irradiation of
the pot and b) since the problem has been identified, all cooling water 
including the passive accumulator cooling system is heated at all times
to a temperature above the theoretical worst case nil ductility point.  End
of problem.  As long as we're postulating, we can also postulate that the
same core melt that would set up the conditions for nil ductility failure
would also heat the pot hot enough to anneal out the neutron induced defects.
As long as we're postulating.

But let's assume for the sake of argument that the pot breaks.  What then?
Well either the bottom of the pot falls off or it stays partially in place.
If it falls off, it falls into the reactor sump and is cooled by the couple
of million gallons of water present.  If it stays in place, it is cooled
by the safety injection system, HPSI, LPSI, passive accumulator, concensate
cooling system, and/or river water system.  Yeah, we really do think
of these kinds of things when we design the multiply redundant safety 
systems.

>suppose that the
>plant has a weaker containment dome than did TMI (which was 
>especially strengthened due to the nearby airport), 

No it wasn't.  All containment buildings must withstand the impact of 
the largest known aircraft that would be flying in the area.  Most all
FSARs I've read use the 747 as the prototypical crasher.

>suppose that a
>venting valve from containment is stuck open, 

Then the operator would simply close one of the other redundant valves
in the train.  All containment penetrations have two valves inside and 
two valves outside, all in series and all designed to fail closed.

>or that there is a
>lightening strike and the operators lose instrument power, 

Then the PWR plant would cool on natural circulation until power was restored.
Natural circ cooling is a test performed ALL PWRs.  BWRs are cooled by
first the HPSI and then the LPSI pumps.  Both are steam driven turbine
pumps that require no outside power to function.  I startup tested these 
pumps at Browns Ferry NP, Unit III.  One of the tests performed is to 
rack out the control panel power breakers and verify the pumps operate
normally and that all valves fail in the proper direction.  Note too
that all components including the heat sink are located inside the secondary
containment building so containment isolation does not affect their 
operation.  (I've saved the definitions of the acronyms for later in
order to watch Yackadamn stumble over these new-to-him terms.)

>or that
>someone panics and opens a venting pipe 

Then the SRO, the shift supervisor or the STA, all of which are licensed and
all of which are required to be in the control room at all times, 
would override the operator and close the valve.  Since only the shift 
supervisor, with the agreement of either an SRO or STA can override 
a written procedure, "someone panics" would not happen.  If a sudden
fit of insanity should overtake one of the operators, the armed guard
posted at the entrance to the control room would remove him.


>or that the turbine cracks and
>sends a large metal fragment through the containment wall

A massive turbine failure with half the largest wheel escaping at best
velocity and penetration angle is a design-basis accident that is planned for.
Half the wheel is used because if a fragment constitutes more than half,
it won't be able to escape the shaft.  No credit is taken in the analysis
for the fragment penetrating the turbine casing (about 6" thick alloy 
steel), the turbine building or aero drag during its trip.  Gee, Yack,
maybe you outta actually READ an FSAR sometime.
In other words, the turbine cannot penetrate the containment.


...., suppose
>its(sic) a BWR plant and the rods won't withdraw, 

BWR rods insert from the bottom for shutdown, therefore your pretend is 
irrelevant.  Assuming you knew enough to correctly phrase the hypothetical, 
since each rod and associated drive in a BWR is a separate system, with 
banks of drives located in at least 4 physically separated areas, and 
since the rod insertion is a passive process driven by reactor pressure, 
"rods" can't fail to insert.  A rod MIGHT.  "Rod Ejection" accidents,
as these events are known as, are planned for.

But let's pretend that something could happen to cause a massive failure
to insert.  The RO would simply lift the cover on the Standby Liquid 
Control system  activation button and press it.  This would fire explosive-
activated valves and start up a DC motor driven pump, driven from
batteries in the same room, that injects a concentrated boric acid solution
into the reactor to shut it down.  If that failed, he'd simply lift 
the cover on one of the other three of the quadruply redundant trains
and fire it.  If all of those failed, he'd just sit back and let HPSI
do its thing.  As soon as the pressure drops in the reactor with the recirc
pumps off, steam voiding automatically shuts down the nuclear reaction.  
The operator might occasionally trim the pressure control to keep the 
cladding below the ignition point but other than that, not much to do.

>and the cladding catches fire

The cladding burned at TMI.  HoHum.  Oh, maybe a few thousand people we
somehow missed died because of this.

>or that a fuel barge tips over on the cooling water intake or  .... 

All plants are required to impound enough cooling water inside the compound
to achieve cold shutdown.  Assuming by "fuel" you mean diesel, the fish 
might not like it.

>Is the probability of all this equivalent to the probability of a meteor
>strike? If so, what's the evidence?

Well.. Let's see.  Meteors strike the earth every day.  None of your
fantasy has ever happened so one can step out on a limb and say
that the probability of your fantasy is a bit less than a meteor strike.

>>regard?  Why is it that your decisions with respect to transportation
>>(to name one example) are not similarly based primarily on the spectacular?

>We have to make decisions about what we think are credible scenarios and
>what we think are worthwhile risks. 

In the venerable words of Tonto, "What's this WE shit, white man?"

[The rest of Yackadamn's interminable anal discharge mercifully deleted]

Yack, you've again ventured out of your normal demagoguery and have tried
to act like you know something about nuclear power.  As usual you failed
miserably.  Maybe you ought to stick to safe areas like telling us how
you quake in the night from your fear of nuclear power.

John

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