[ RadSafe ] Melting a reactor??

[Doug Huffman]

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The statement, "shut off a reactor" begs the question, modus ponens,
what does shutting off a heat source like a reactor mean?  It continues
to produce heat from sub-critical fission while 'shut-off'.

It has been a while, but I may recall that various alloys and chemical
reactions all occur at elevated temperatures of a magnitude achieved in
a loss of coolant accident.  Even in a LOCA there is plenty of hydrogen
available for hydriding chemical reactions.  ZrH2 autoignition occurs by
300C.

A critical mass is never safe.  Carefully managed, it's benefit is worth
the risk that is comparable to that enjoyed in everyday life.

"The cooling system" is integral to the whole design of a modern
facility and has been shown empirically robust.  The worst experience
caused only an arguable marginal increase in morbidity/mortality.
Remember that we argue radiation hormesis.

On 1/2/2011 20:15, Steven Dapra wrote:
> Jan. 2
> 
>     This quote is from an editorial page article written by Charles
> Faddis and published in the NY Times.
> 
> "But there's no way to quickly shut off a reactor: the heat that builds
> up inside it is so intense that even if something goes wrong, cooling
> water must continue to circulate through its systems for days before it
> is safe.
> 
> "If the cooling system malfunctions, even if the rest of the plant is
> operating safely, the heat will literally melt the reactor and its
> concrete containment shell, releasing radioactive gas into the
> atmosphere  in other words, a partial nuclear meltdown like that at
> Three Mile Island in Pennsylvania in 1979."
> 
>     Is it true that reactor heat will melt the containment vessel
> ("shell")?
> 
>     The link to the Faddis' NYT article is:
> 
> http://www.nytimes.com/2010/05/06/opinion/06Faddis.html?_r=1
> 
> Steven Dapra
> 
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