Re: Nuclear Reactors & Blackout

[aek@vib.usr.pu.ru (Alexander Kopilovitch)]

John R. Strohm wrote:

> > Chernobyl
> > story began when scientist (physist, but without significant experience
> > with real working nuclear plants) was assigned to a commanding position.
> > He invented his owm method and procedure for testing. The result of that
> > testing immediately became (in)famous worldwide.

> ... this is an oversimplification.

Well, I'd not call that oversimplification, because I did not say (and did not
intend to say) that that single person was THE cause. As usual in catastrophes
there was several significant factors, and that "testing" was detonator only.
But that or likewise detonator was necessary for waiting catastrophe to happen
actually. And I did not intend to describe Chernobyl here or compare against
it, I simply pointed out that detailed knowledge and experience are significant
for making strong technical judgement, and provided example, which shows that
even scientific professionalism in one constituent domain may be not enough
for making such judgements about very complex critical systems.

>Part of the problem is that the people who designed the Chernobyl reactor
>had absolutely impeccable Party credentials, but did not know beans about
>reactor safety.  They designed a reactor with a positive void coefficient of
>reactivity, which creates a built-in thermal runaway hazard, and thermal
>runaway is EXACTLY what happened at Chernobyl.

Well, I heard about this. I did not try to learn those things myself, but I
have no grounds for not believing this theory. I lost interest for the reactor
side of that story when I saw the drawing - the plan of the plant's main building
(where all 4 reactors were located) - so much I was impressed with that
industrial architecture, it was something unbelievable for common sense.

The events overall around that story showed me that there was omnipresent
sense of relaxation around that doomed plant. You surely overestimate the role
of vulnerable reactor's design in that actual catastrophe. Yes, probably it
may be seen as the one of main factors, but no more.

You probably heard about the Soviet Union's rigid administrative system, so
you should wonder how it may happen that they in Chernobyl and Kiev did not
report to Moscow about the catastrophe. It was another nuclear power plant
(near Smolensk, several hundreds kilometers away), who discovered excess level
of radiation, checked themselves thoroughly, found nothing, and then alerted
Moscow.

Well, there were many other things in this story, perhaps worth of telling,
but then we'll go too far off-topic, so I will not continue this way.

> The Chernobyl design is illegal in the United States of America, for damned
> good reason.  Ed Teller, who wrote the law, figured that life would be
> simpler for everyone if reactors were simply not capable of thermal runaway
> at all.  So all U.S. reactors are required to be designed with a negative
> void coefficient of reactivity.

All that may be true, but I want to point on only one thing: that vulnerability
of reactor was far from enough for a catastrophe, at least in the *working*
general Soviet environment. It was only a potential for a catastrophe.

> The U.S. has yet to experience anything even remotely resembling a Chernobyl
> accident.

I think that no country except former Soviet Union has that precious experience.

> If you want more information, do a search on "void coefficent".  Here are a
> couple of starters:
> http://www.nrc.gov/reading-rm/basic-ref/glossary/void-coefficient-of-reactivity.html
> http://www.world-nuclear.org/info/chernobyl/voidcoef.htm

Thanks, perhaps some day (or night -:) I'll look there.



Alexander Kopilovitch                      aek@vib.usr.pu.ru
Saint-Petersburg
Russia