ML080640562

Observation of the Diablo Canyon Fire PRA Peer Review Process Pilot

ML080640562
Person / Time
Site:	Diablo Canyon
Issue date:	03/05/2008
From:	Parry G NRC/NRR/ADRA/DRA
To:	Cunningham M NRC/NRR/ADRA/DRA
References
Download: ML080640562 (3)

Text

March 5, 2008

MEMORANDUM TO: Mark A. Cunningham, Director Division of Risk Assessment Office of Nuclear Reactor Regulation

FROM: Gareth W Parry, Senior Advisor for PRA /RA/ Division of Risk Assessment Office of Nuclear Reactor Regulation

SUBJECT:

OBSERVATION OF THE DIABLO CANYON FIRE PRA PEER REVIEW PROCESS PILOT

Ray Gallucci (NRR), JS Hyslop (RES), Gareth Parry (NRR), and Steve Nowlen (SNL) observed a pilot application of NEI 07-12, "Fire Probabilistic Risk Assessment (FPRA) Peer Review Process Guidelines, Draft Version F" at the Diablo Canyon Nuclear Plant from January 28, 2008 through January 31, 2008. The peer review was performed against the ANSI/ANS-58.23-2007 Fire PRA Standard. The peer review team, which consisted of six members, was assembled by the Pressurized Water Reactor Owners' Group (PWROG). Also present were two industry observers, and a process observer. This activity was classified as a pilot of the Fire PRA Peer Review Process, as proposed in NEI 07-12, and not a full peer review of Diablo Canyon's Fire PRA, since the Diablo Canyon fire PRA is still in development. For example, only three fire areas have had detailed fire modeling, and many areas have been treated in a conservative manner. Consequently, a number of the Standard elements could not be assessed, while others could not be assessed completely. Nonetheless, the exercise was considered to have assessed the review process itself. One issue that was identified with the process related to how to address those supporting requirements of the ASME internal events standard that are incorporated by reference in the fire PRA standard.

Several important insights were identified with regard to the ANSI/ANS-58.23-2007 Fire PRA Standard (also Part 3 of the combined ASME/ANS PRA Standard, ASME/ANS RA S-2008) and NUREG/CR-6850, "EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities", which is being as a reference for performing fire PRAs. Even with three of the fire PRA standard writing group present, there were some problems in interpretation of the standard. Furthermore, some potential problems were identified with NUREG/CR-6850 relating to how the guidance in that document was being interpreted, and a minor inconsistency was noted in the way in which the term reactor year is defined when compared with the definition in the ASME PRA standard.

M. Cunningham This results in slightly conservative initiating fire frequencies. Other methodological issues were also identified, relating to the incompleteness of the guidance in NUREG/CR-6850, including how to estimate the total probability of a spurious actuation of a component when there is more than one target cable that could cause the actuation.

These issues appear to be ones that are amenable to reasonably short term resolution.

ML080640562 NRR-105 OFFICE NRR/DRA NRR/DRA NAME GParry MCunningham DATE 3/4/08 3/5/08