ML031110452

E-mail from G. Demoss to S. Long, Regarding Davis Besse

ML031110452
Person / Time
Site:	Davis Besse
Issue date:	08/12/2002
From:	Demoss G Office of Nuclear Regulatory Research
To:	Long S Office of Nuclear Reactor Regulation
References
FOIA/PA-2003-0018
Download: ML031110452 (1)

Text

I.Gary Demoss - Davis Besse P;=

From: Gary Demoss e6c To: Steven Long / il /&iG Date: 8/12/02 3:56PM

Subject:

Davis Besse Steve, I've taken a quick look at your Predecisional Draft SDP per you request and have comments on each rupture type.

As-found cavity - Medium LOCA -

1. In the section entitled "CCDF for LOCAs", you seem to state that you will use the licensee's restated CCDP, but use the CCDP from the Davis-Besse IPE.

2. The model is operating way out on the tail of a statistical distribution. Probably the best that can be done, but this should be made clear to the reader.

Enlarged cavity - Large LOCA -

1. The use of the probability that Davis-Besse could have achieved more years of operation by February 16, 2002 as the initiating event frequency is not consistent with an ASP analysis.

2. The second tier assumptions associated with the initiating event frequency would have to include no NRC action, no adequate inspections, no leakage greater than 1 gpm, and no small or medium LOCA before the large LOCA. You qualitatively addressed all these issues, but they appear to add a significant amount of doubt as to the likelihood that this event could have led to a large LOCA.

3. I don't have a good suggestion for quantitatively resolving items 1 and 2. I think that we should look into possible models that incorporate the approach that was taken for the As-found cavity in conjunction with a growing cavity size. Additionally, we could consider attempting to quantitatively address the human reliability of the inspections. It certainly won't be easy.

Nozzle eiection - Medium LOCA

1. In the section entitled "CCDF for LOCAs", you seem to state that you will use the licensee's restated CCDP, but use the CCDP from the Davis-Besse IPE.

I will be in Richmond starting tonight. If you have any questions or time to discuss this, feel free to call me in my hotel room tomorrow morning between 6:30 and 8:00 at 804-965-9500, or anytime later in the week.

Gary DeMoss CC: Don Marksberry; Michael Cheok; Stephen Dinsmore I\2