ML031530354

E-mail from S. Long to J. Chung, Regarding Large LOCA Treatment in Revision 3i SPAR Models

ML031530354
Person / Time
Site:	Davis Besse
Issue date:	04/01/2002
From:	Long S Office of Nuclear Reactor Regulation
To:	Chung J, O'Reilly P Office of Nuclear Reactor Regulation, Office of Nuclear Regulatory Research
References
FOIA/PA-2003-0018
Download: ML031530354 (1)

Text

SteLCn - Re: Large LOCA Treatmi n Revisio '3WiSPAR ModelsPage1 From: 1 j2f-Steven Long vj To: N.Jin Chung; Patrick O'Reilly I Date: 4/1/02 7:20AM

Subject:

Re: Large LOCA Treatment in Revision 3i SPAR Models Pat and Jin, The Davis Besse IPE submittal dated February 1993 clearly states in multip;le places that the medium LOCA in their model is between 0.02 and 0.5 square feet. Tha this equivalent to break diameters between 2 inches and 9 inches. Since Davis Besse has a unique combination of ECCS and RCS characteristics (B&W RCS with intermediat-head Si pumps), I don't think we are in a very good position to argue with them unless we have plant-specific thermal-hydraulic calculations that show they don't need the SI pumps for breaks as large as 6-inches to 9-inches in diameter. They claim that the 9-inch diameter is the "smallest break that could be accommodated soley by the LPI and core flood tanks."

Anyway, that was a 1993 submittal, so we have asked the plant for current info, in case their thinking has changed. I wil make sure that both of you get the info when I do. It might be appropriate to change the notes in the Davis Besse SPAR manual.

Steve

>>> Patrick O'Reilly 03/28/02 01 :34PM >>>

I told you that I would check with INEEL and confirm the source(s) of the data that form the basis for the treatment of large break LOCAs in the Revision 3i SPAR models. I spoke to Bob Buell, who is the Pi for the Revison 3 SPAR model development project at INEEL, and here is what he told me.

As identified in the footnotes to Table B-1 in the Davis-Besse Revision 3i SPAR model users manual, the large LOCA initiating event frequency which is used in developing the Revision 3 SPAR models comes from the RES-sponsored Initiating Event Report, NUREG/CR-5750, Rates of Initiating Events at U.S.

Nuclear Power Plants, 1987-1995, Table 3-1, published in February 1999. The value that is incorporated in the model is actually the per hour occurrence probability, 5.7E-1 0.

The large LOCA break size criterion was determined from the results of a review of information published in several sources, including FSARs, the Daily Events Analysis Manual, plant PRAs, topical reports, and IPEs, to name a few. The consensus of these sources indicated that the range of large LOCA break sizes was about 5 in. in diameter and greater. So that is the size that was selected as the break criterion.

As I said, the basis came from a number of sources, of which IPEs were only one source. The 5-inch diameter criterion has been used for all PWR Revision 3 SPAR models, regardless of NSSS vendor.