-----Original Message-----
From: Jacobus, John (OD/ORS) [mailto:jacobusj@ors.od.nih.gov]
Sent: Thursday September 27, 2001 10:32 AM
To: Franta, Jaroslav; radsafe@list.vanderbilt.edu
Subject: RE: NRC News release on Terrorists.
Jaro,
Do you think the burning fuel would cause structural failure?
-- John
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What burning fuel ? ...at Chernobyl, it was the graphite moderator that was burning -- later, globs of MELTED fuel ("corium") flowed in various parts of the basement (some of the fuel got blown into the surrounding countryside during the initial powerful nuclear excursion and resulting steam explosion...).
At TMI, the MELTED fuel didn't get anywhere -- it collected at the bottom of the pressure vessel, not even causing any thinning of the thick steel pressure vessel.....
There was apparently some oxidation of the zirconium fuel cladding - along with hydrogen gas formation - but as far as I know, the UO2 (already an oxide) remained what it was....
Also, I think its important to remember that PWR scram rods have electromagnetic drives which are fail-safe -- cut the power supply, and they drop into the core (with springs assisting gravity). So the only concern would be radioactive decay heat, which if interrupted, can cause a TMI-type accident.
Jaro