[ RadSafe ] Fuel condition at TMI

[Jeff Terry]

Here is the link to the ANS description of TMI. 

http://www.ans.org/pi/resources/sptopics/tmi/whathappened.html

Sent from my iPhone

On Aug 4, 2011, at 3:09 PM, James Barnes <james.g.barnes at att.net> wrote:

> Dear all;
> 
> Have a very specific question about the fuel failure at TMI.
> 
> The sequence I recall is:
> 
> 1)    Reactor water levels dropped and tops of fuel bundles were exposed.
> 
> 2)    The Zircaloy fuel tubes overheated and cracked (with extensive melting of 
> the Zircaloy), releasing fission products to the reactor and auxiliary systems.
> 
> 3)    Fuel pellets were then mechanically dislodged from the fuel bundles and 
> fell down into the fuel assembly and reactor structures, and some quantity to 
> the bottom of the reactor vessel.
> 
> My question is this:
> 
> The fuel pellets themselves are generally uranium in a ceramic matrix 
> (correct?).  My sense is that ceramic matrices don't melt, they crack into 
> pieces ("sinter"; a point that the Wikipedia entry on ceramic fuels seems to 
> imply).  Thus, when the pellets were overheated and ejected, they tended to 
> crack into pieces and one got tiny pieces of fuel circulating in the system and 
> pieces of fuel pellets dropping into the reactor internals.
> 
> Was there ever any evidence that that actual fuel pellets themselves had 
> undergone melting.  If so, can any of you send me credible references to this 
> point?
> 
> Thanks,
> 
> Jim Barnes, CHP
> james.g.barnes at att.net
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