RE: Errors in NRC TMI Factsheet

[Doug Aitken <daitken@sugar-land.oilfield.slb.com>]

Norm Cohen Quoted;

"It was only by luck that the reactor walls were not breached. The industry

conjectured that voids in the coolant prevented molten fuel from burning

through the reactor walls. It is not known if these voids will form to

prevent a total meltdown in future accidents. "



In Reply, Dukelow, James S Jr wrote:

<<It was actually not luck, but a previously unanalyzed aspect of heat 

transfer during the accident.

As the molten core materials (corium) dropped into the lower reactor vessel 

head, it contacted the relatively cool lower RV head and froze. The frozen 

corium was a mixture of metals and metal oxides (mostly metal oxides). As 

such, it was a ceramic material and had a relatively low heat transfer 

coefficient. The molten corium was enclosed in a "cup" of frozen corium. 

The small flow of heat through the frozen corium was easily conducted to 

the outside of the lower RV head by the metal in the head (which has a high 

heat transfer conductivity). This combination of low heat flow through the 

frozen corium and easier heat flow through the metal head kept the 

temperatures in the head low enough to prevent melting.

This previously unanalyzed phenomena is being incorporated into the design 

of next generation reactors as a passive safety feature. It has been 

thoroughly analyzed by reactor vendors and others and accepted by the NRC 

during its review of the new designs.>>



IMHO, The difference between "Luck" and "a previously unanalyzed aspect of 

heat transfer during the accident" is somewhat slim!



While the "after-the-fact" analysis of what happened shows a fortuitous 

combination of circumstances prevented a major disaster, there is no way 

that the professional community should clad this event in an aura of 

"science" (or obfuscation?). This is the sort of thing that can alienate 

the layman!



So in this instance, I am afraid that the honest answer would be "Yes, we 

got lucky. But we understand what happened and can incorporate this into 

future design to improve overall safety."



<Just a comment from a non-professional in the nuclear field, but a fair 

experience in safety management>

Doug

Doug Aitken		Schlumberger Drilling and Measurements QHSE 

Advisor

Phone (Sugarland):   	281 285-8009

Phone (Home office): 	713 797-0919	

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Mail: 	300 Schlumberger Drive MD2, Room 111

	Sugar Land, TX 77478









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