ML13078A247

03/21/2013 Licensee Meeting Slides Re Joseph M. Farley Nuclear Plant NFPA 805 Fire Modeling LAR Submittal - Session 2 (3/20)

ML13078A247
Person / Time
Site:	Farley
Issue date:	03/19/2013
From:	Jo Y Southern Co, Southern Nuclear Operating Co
To:	Division of Operating Reactor Licensing
Brown E
Shared Package
ML13078A284	List: ML13078A245 ML13078A246 ML13078A247 ML13078A248 ML13078A250 ML13078A251 ML13078A252 ML13078A253 ML13078A255
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Download: ML13078A247 (15)

Text

FNP NFPA 805 LAR AUDIT March 20, 2013 Session 2 - LAR and LIC 109 Sensitivity Studies Young Jo

Objectives To clarify CDF and CDF estimates reported for the Farley NFPA 805 sensitivity cases A

Agendad Farley NFPA 805 LAR Time Line Farley Fire PRA and Sensitivity Analysis Time Line Explanation of CDF and CDF Calculations in Sensitivity Cases 2

F l NFPA Farley NFPA-805805 LAR Timeline Ti li NFPA-805 Submittal - September 25, 2012 NRC Acceptance Review Questions -

December 12, 2012 SNC Acceptance Review Response - December 20, 2012 NRC LAR Acceptance p - Januaryy 24,, 2013 Pre-LAR Audit Presentations - March 19~21, 2013 LAR Audit - Week of March 25, 2013 3 Round 1 RAIs Issued - April 2013

Farley Fire PRA and Sensitivity Analyses Time Line Fall 2009 Oct 2011 Spring 2012 Jun 2012 Sep 2012 Dec 2012 Farley Farley Approval NRC Farley Fire PRA LIC 109 Fire PRA of four Letter: NFPA Project Sensitivity Peer UAMs endorsing 805 LAR Ki k off Kick ff analysis R i Review b EPRI by approved Submittal expert UAMs (Sensitivity panel except analyses

((one electrical included 4

approved cabinet with a factor dissent)

Fire PRA RAI (draft)

In Enclosure 6 to the supplement dated December 20, 2012( Agency wide Document Access and Management System Accession Number ML12359A050), both the total and delta core damage frequency (CDF) results are actually lower than previously reported in the September 25, 2012 submittal, when only the credit for the electrical cabinet factor was removed. With the additional removal of credit for the main control room (MCR) very earlyl warning i fifire d detection t ti system t (VEWFDS)

(VEWFDS), it iis expected that these CDF results would increase, consistent with the increases in the large early release frequency (LERF) values.

Provide an explanation of the reasons for the divergent results, including the key modeling assumptions that are causing the divergence.

5

Sensitivity Studies for Farley NFPA 805 To ensure ens re Farle Farley NFPA NFPA-805 805 risk insights are valid:

1) LAR Sensitivity Analysis:

• Removal of crediting electrical cabinet factor

2) LIC 109 Sensitivity Analysis:

• Removal of crediting electrical cabinet factor and

• Removal of crediting Very Early Warning Fire Detection System (VEWFDS) for cabinets in the Main Control Room (MCR) 6

Sensitivity Studies for Farley NFPA 805 Process for performing sensitivity analyses:

1)) Factor of interest was removed

2) NUREG/CR 6850 based refinements were applied to assess realistic risk

3) CDF and CDF were recalculated 7

Sensitivity Studies for Farley NFPA 805 LIC 109 LAR sensitivity sensitivity (Dec.

LAR base (Sept 2012) 2012)

Crediting electrical cabinet factors Yes No No p

Creditingg incipient detection for MCR Yes Yes No Refined manual suppression No Yes Yes Refined Main Control Board fire scenarios (APP L) No No Yes More realistic HGL probabilities No No Yes Refining selected fire scenarios using refined circuit analysis No No Yes Correcting some anomalies in fire ignition frequencies in certain scenarios No No Yes 8

S Sensitivity iti it Studies St di for f Farley F l NFPA 805 CDFs and CDFs relative LAR Base case values 1.40 CDF delta CDF 1 30 1.30 1.20 1.10 1.00 LAR Base LAR Sensitivity LIC 109 Sensitivity (note) Graph is based on as reported values in the LAR andd iin th the R Response tto LIC 109 RAI RAIs 9

Revised e sed Se Sensitivity s yS Studies ud es for o Farley a ey NFPA 805 (3/4/2013)

To compare CDFs and CDFs after applying the same refinements to both sensitivity cases:

• Refined manual suppression

• Refined Main Control Board fire scenarios (App. L)

• More realistic HGL probabilities

• R fi i selected Refining l t d fifire scenarios i using i refined fi d circuit i it analysis results

• Correction of anomalies in fire ignition g frequencies q

in certain scenarios 10

Revised Sensitivity Studies for Farley NFPA 805 (3/4/2013)

LAR sensitivity LIC 109 sensitivity LAR base (Sept 2012) (Dec. 2012)

Crediting electrical cabinet factors Yes No No Crediting incipient detection for MCR Yes Yes No Refined manual suppression No Yes Yes Refined MCB fire scenarios (APP L) No Yes Yes More realistic HGL probabilities No Yes Yes Refining selected fire scenarios using No Yes Yes refined circuit analysis Correcting some anomalies in fire ignition No Yes Yes frequencies in certain scenarios (*)

(*) one more anomaly in ignition frequency was corrected in Cable Spreading Room HGL scenario In the revised sensitivity studies 11

Revised Sensitivityy Studies for Farleyy NFPA 805 (3/4/2013)

CDF and CDFs d CDFs CDF relative l ti LAR B Base case values l 1.4 CDF delta CDF 1.3 12 1.2 1.1 1

LAR Base Rev. LAR Sensitivity Rev LIC 109 Sensitivity (note) Graph is based on revised sensitivity analyses on 3/4/2013 12

Additional Candidates for Refinement Refinement of Hot Gas Layer treatment Incorporate findings from additional walk down:

• Example) some cabinets in the Cable Spreading Room are found to be sealed (fire will not spread out of the cabinet) 13

Summary Farley Fire PRA was developed based on the state-of-the-art t t f th t methodologies th d l i available il bl iin 2010

~ 2012 time frame SNC believes that the methods used are technically adequate for the application 14

Summary Sensitivity analyses were performed for addressing dd i th the methods th d nott accepted t d by b the th staff The results from the sensitivity analyses demonstrate that conclusions documented in the LAR are valid 15