ML030840378
| ML030840378 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 08/12/2002 |
| From: | Long S Office of Nuclear Reactor Regulation |
| To: | Marksberry D Office of Nuclear Regulatory Research |
| References | |
| FOIA/PA-2003-0018 | |
| Download: ML030840378 (1) | |
Text
Stxff Long - Re: Frequency of exceeding >2SOOpsig at DB Page 14 From:
Steven Long U'A P To:
Don Marksberry Date:
8/12102 5:04PM
Subject:
Re: Frequency of exceeding >2500psig at DB
- Don, Well, that's ceratainly less than 1 E-5/year!
But, I'm not so sure it's a good estimate for LOFW ATWS Especially for a B&W plant, the ICS may make the conditional probability of LOFW given an ATWS a bigger contributor than the frequency of LOFW combined with the random probability of an ATWS. At least, it's a second path you haven't estimated Steve
>>> Don Marksberry 08/12/02 03:53PM >>>
- Steve, The updated frequency of total loss of main feedwater with failure of RPS (i.e., ATWS) is as follows:
Frequency of total loss of main feedwater at Davis Besse (8.OE-2/critical year)(0.79 critical year/calendar year) = 6.3E-2/calendar year From NUREG/CR-5750, Tables G-10 and H-3 Probability of RPS failure = 1.6E-6/demand From NUREG/CR-5500, Vol 11, Reliability Study: Babcock & Wilcox Reactor Procection System, 1984-1998, Table 3-4.
The frequency of total loss of main feedwater with failure of RPS (6.3E-2/calendar year)(1.6E-6) = 1 E-7/calendar year L6Ki-RFFi&4-uýiiRý of excee in psig a age