TMI root causes -Reply -Reply

["Donald C. Kosloff" <DCK@nrc.gov>]

Replay of TMI occured at Davis-Besse on June 9, 1985 (NURGEG 1154) with
different complications.  The symptom based procedures caused the operators to
shut the PORV block valve before anyone realized that the PORV had stuck open. 
I know because I discovered that the PORV had stuck open about a day later while
I was reviewing the sequence of events recorder.  Training and symptom based
procedures were also sufficient to allow the operators to restore cooling from an
unforseen sequence of failures and they were prepared to iniatiate another  backup
method of core cooling (beyond the design basis) if their initial plan to restore
cooling would have failed.   All within about 11 minutes of the loss of feedwater. 
However,  based on my minimal simulator experience,  if you present the TMI
scenerio to operators early in their simulator training, I am sure that some of them
will simulate its duplication.