ML13078A247
| 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: |
| References | |
| Download: ML13078A247 (15) | |
Text
FNP NFPA 805 LAR AUDIT March 20, 2013 Session 2 - LAR and LIC 109 Sensitivity Studies Session 2 LAR and LIC 109 Sensitivity Studies Young Jo
Objectives To clarify CDF and CDF estimates reported for To clarify CDF and CDF estimates reported for the Farley NFPA 805 sensitivity cases A
d Agenda 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 805 LAR Ti li Farley NFPA-805 LAR Timeline NFPA-805 Submittal - September 25, 2012 NRC Acceptance Review Questions NRC Acceptance Review Questions -
December 12, 2012 SNC Acceptance Review Response - December SNC Acceptance Review Response December 20, 2012 NRC LAR Acceptance - January 24, 2013 p
y Pre-LAR Audit Presentations - March 19~21, 2013 3
LAR Audit - Week of March 25, 2013 Round 1 RAIs Issued - April 2013
Farley Fire PRA and Sensitivity Analyses Farley Fire PRA and Sensitivity Analyses Time Line Fall 2009 Oct 2011 Sep 2012 Dec 2012 Jun 2012 Spring 2012 Farley Fire PRA Project Ki k ff Farley Fire PRA Peer R
i Farley NFPA 805 LAR LIC 109 Sensitivity analysis NRC Letter:
endorsing Approval of four UAMs b EPRI Kick off Review Submittal (Sensitivity analyses included analysis approved UAMs except electrical by EPRI expert panel (one 4
included electrical cabinet factor
(
approved with a dissent)
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)
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) l i
fi d t ti t
(VEWFDS) it i (MCR) very early warning fire detection system (VEWFDS), it is 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
To ens re Farle NFPA 805 risk insights are Sensitivity Studies for Farley NFPA 805 To ensure Farley NFPA-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 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
Sensitivity Studies for Farley NFPA 805 Sensitivity Studies for Farley NFPA 805 LAR base LAR sensitivity (Sept 2012)
LIC 109 sensitivity (Dec.
2012)
LAR base (Sept 2012) 2012)
Crediting electrical cabinet factors Yes No No Crediting incipient detection for MCR Yes Yes No g
p Refined manual suppression No Yes Yes Refined Main Control Board fire scenarios (APP L)
No No Yes scenarios (APP L)
No No Yes More realistic HGL probabilities No No Yes Refining selected fire scenarios using refined circuit analysis No No Yes refined circuit analysis No No Yes Correcting some anomalies in fire ignition frequencies in certain scenarios No No Yes 8
S iti it St di f
F l
NFPA 805 Sensitivity Studies for Farley NFPA 805 CDFs and CDFs relative LAR Base case values 1 30 1.40 CDF delta CDF 1.20 1.30 1.10 (note) Graph is based on as reported values in the LAR d i th R
t LIC 109 RAI 1.00 LAR Base LAR Sensitivity LIC 109 Sensitivity 9
and in the Response to LIC 109 RAIs
Revised Sensitivity Studies for Farley NFPA e sed Se s y S ud es o a ey 805 (3/4/2013)
To compare CDFs and CDFs after applying the same refinements to both sensitivity cases:
Refined manual suppression Refined manual suppression Refined Main Control Board fire scenarios (App. L)
More realistic HGL probabilities R fi i l
t d fi i
i fi d i it Refining selected fire scenarios using refined circuit analysis results Correction of anomalies in fire ignition frequencies g
q in certain scenarios 10
Revised Sensitivity Studies for Farley NFPA 805 (3/4/2013)
LAR sensitivity LIC 109 sensitivity LAR base LAR sensitivity (Sept 2012)
LIC 109 sensitivity (Dec. 2012)
Crediting electrical cabinet factors Yes No No Crediting incipient detection for MCR Yes Yes 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 refined circuit analysis No Yes Yes Correcting some anomalies in fire ignition Correcting some anomalies in fire ignition frequencies in certain scenarios (*)
No Yes Yes
(*) one more anomaly in ignition frequency was corrected in Cable Spreading Room HGL scenario In the revised sensitivity studies 11 In the revised sensitivity studies
Revised Sensitivity Studies for Farley y
y NFPA 805 (3/4/2013)
1.4 CDF CDFs and CDFs relative LAR Base case values 1 2 1.3 delta CDF 1.1 1.2 1
LAR Base Rev. LAR Sensitivity Rev LIC 109 Sensitivity 12 (note) Graph is based on revised sensitivity analyses on 3/4/2013
Additional Candidates for Refinement 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 Room are found to be sealed (fire will not spread out of the cabinet) 13
Summary Farley Fire PRA was developed based on the t t f th t
th d l i
il bl i
2010 state-of-the-art methodologies available in 2010
~ 2012 time frame SNC believes that the methods used are SNC believes that the methods used are technically adequate for the application 14
Summary Sensitivity analyses were performed for dd i
th th d t
t d b th addressing the methods not accepted by the staff The results from the sensitivity analyses The results from the sensitivity analyses demonstrate that conclusions documented in the LAR are valid LAR are valid 15