ML12101A018

Meeting Slides - Meeting with Southern Nuclear Operating Company, Inc. to Discuss Risk-Informed Technical Specification Changes

ML12101A018
Person / Time
Site:	Vogtle
Issue date:	04/11/2012
From:	Southern Nuclear Operating Co
To:	Patrick Boyle Plant Licensing Branch II
Boyle P
Shared Package
ML12118A038	List: ML12052A149 ML12101A018 ML12117A324 ML12123A150
References
TAC ME7750
Download: ML12101A018 (18)

Text

Risk Managed Technical Specifications Initiative 4b 1

SNC/NRC MEETING APRIL 11, 2012

Agenda 2

y Introduction/Purpose y Overview of the Project y Technical Issues Discussion y Meeting i Summary and d Action i Item Review i

Purpose 3

y Purpose - Technical discussions on Vogtle pilot Risk Managed Technical Specifications (RMTS) program

{ Treatment of Seismic Risk

{ Comparison of TS Functions Versus PRA Functions

{ Treatment of Ventilation systems y Desired Outcome - NRC comments and feedback on SNCs technical approach

SNCs Risk Informed Journey - Fleet 4

y Achieve sustainable excellence through transitioning to risk-informed design and operation

{ Improved safety

{ Reduced forced outage rate

{ Enhanced on-line and outage work planning

{ Improved flexibility and regulatory predictability y 4b is a key component in our quest of achieving operational excellence Be the change you want to see in the world Gandhi

SNCs Risk Informed Journey - Vogtle 5

y Vogtle NRC Pilot for 4b - October 2010 y NRC Commissioners Meeting - February 2011 y Vogtle Seismic PRA Collaboration with EPRI - May 2011 y Vogtle NRC Pilot for 50.69 - June 2011 y 4b bSSeismic/External i i /E lE Events treatment strategy submitted b i d-September 2011 y Vogtle fire model peer-reviewed - February 2012 y 4b LAR - 3rd quarter 2012

Vogtle A4/4B Timeline 6

Enhanced A4 Procedure Changes/Training Initial LCO EOOS 4+ Fire PRA Peer 4B Vogtle LAR Selection Enhancement Review Submittal Mar 2011 Jun 2011 Sep 2011 Dec 2012 Mar 2012 Jun 2012 Sep 2012 Dec 2012 Mar 2013 Jun 2013 Sep 2013 EOOS Integrated 4B Procedure 4B Anticipated Fire + Internal Training NRC Approval PRA Model Key Changes Related to EOOS EOOS Ready for

• P6 to EOOS Automation Site-Specific

• CR Log to EOOS Automation Deployment for

• EOOS 4+ Enhancements Enhanced A4

Treatment of Seismic Risk 7

y TR NEI 06-09 permits bounding analyses or other conservative quantitative evaluations for risk contributors where the hazard group is not modeled in the baseline PRA.

y Seismic Risk is not in the PRA for VEGP, and a Bounding Analysis Approach is utilized for addressing Seismic Risk Internal Fire Seismic Other External Shutdown Events Risk Risk Risk Events Risk Risk Internal Fire Seismic PRA Events PRA PRA (includes Internal Bounding Updated N/A - At Flooding & Seismic FIVE Analysis IPEEE LOOP) Power Only Approach Screening

Treatment of Seismic Risk 8

y SNC submitted a Seismic Bounding Analysis Approach to NRC in September 2011 (ML112710169).

y Summary

{ Seismic risk within design basis:

LOSP contribution dominates seismic risk However, LOSP contribution from Internal and Fire events is significantly higher

{ Seismic risk beyond design basis:

SCDF assumed (in accordance with standard practice) to depend on the likelihood of a single seismic-induced failure leading to core damage.

Seismic-induced failures of equipment are assumed (in accordance with standard practice) to show a high degree of correlation (i.e. if one SSC fails, all similar SSCs will also fail)

Treatment of Seismic Risk 9

y Therefore, removing equipment from service (RICT calculations) has little impact on SCDF y To address any potential non-conservatism resulting from the above, SNC estimated seismic risk contribution by a bounding CDF factor to the RICT Calculation

Treatment of Seismic Risk 10 y Staff Report, Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States on Existing Plants, Safety/Risk Assessment, August 2010 has three screening values for Vogtle

{ Using 1989 EPRI: 2.6E-06

{ Using 1994 LLNL: 2E-05

{ Using 2008 USGS: 7.1E-06 y Using these surrogate analyses, NRC estimated a bounding total Seismic CDF (SCDF) of 2E-05/yr y The contribution of within design basis seismic hazard to CDF is significantly less than the internal events CDF

Impact of Within Design Basis Seismic Hazard 11 y The seismically-induced (unrecoverable) loss of offsite power frequency at 0.08g OBE versus total unrecovered LOOP frequency estimates

{ Total LOOP frequency (unrecovered) = 3.3E-02 x 6.5E-02 = 2.1 E-03/yr

{ Total Seismic LOOP frequency (RASP Handbook hazard data) = 9.5 E-05/yr

{ Seismically-induced LOOP < 5% contributor y As a result, within design basis seismic hazard does not significantly impact RICT for removing equipment from service (e.g. diesel generator) and is enveloped by the bounding seismic CDF factor

TS Functions Versus PRA Functions:

Disposition of Differences in VEGP RMTS Program 12 y Final Safety Evaluation for NEI 06-09 Requires the LAR Provide

{ Comparison of Technical Specification functions to PRA functions

{ Ensure LCO Conditions included are supported by CDF/LERF metrics y Process identifies any differences between TS and PRA functions

{ Provides justifications for PRA logic model

{ Offers resolutions for treatment of differences in VEGP RMTS Program y Each disposition of differences in VEGP RMTS Program are categorized based on the following criteria

TS Functions Versus PRA Functions:

Disposition of Differences in VEGP RMTS Program 13 y Criterion 1: The SSC has no core damage or large early release risk impact y Criterion 2: The SSC is not modeled in PRA, but the SSC can be directlyy correlated to a surrogate g SSC included in the PRA y Criterion 3: The SSC is added to the PRA model

TS Functions Versus PRA Functions:

Disposition of Differences in VEGP RMTS Program 14 IMPACT ON RICT IN EOOS IN FOR INOPERABLE CRITERIA SSC GROUPS PRA CONDITIONS Reactor Coolant System Criterion 1: The SSC has no core RCS Leakage Detection NO No impact on CDF/LERF. EOOS damage or large early releases risk Systems calculates 30 day backstop impact Criterion 1: The SSC has no core PZR Heaters NO No impact on CDF/LERF. EOOS damage or large early releases risk calculates 30 day backstop impact Criterion 1: The SSC has no core RCS Recirculation Fluid pH NO No impact on CDF/LERF. EOOS damage or large early releases risk Control System calculates 30 day backstop impact Criterion 3: The SSC is added to the RCP seal injection needle YES Impact on CDF/LERF as calculated by PRA model valves EOOS Ultimate Heat Sink Criterion 2: The SSC is not modeled in Nuclear Service Cooling NO Impact on CDF/LERF conservatively PRA, but the SSC can be directly Water (NSCW) basins with assumes unavailability of Nuclear correlated to a surrogate SSC included water temperature and/or Service Cooling Water train in EOOS in the PRA water level Note: SSC categorization based on above Criteria are subject to change prior to LAR submittal since the resolutions are preliminary.

TS Functions Versus PRA Functions:

Disposition of Differences in VEGP RMTS Program 15 IMPACT ON RICT IN EOOS IN FOR INOPERABLE CRITERIA SSC GROUPS PRA CONDITIONS Secondary Side Heat Removal Systems Criterion 3: The SSC is added to the MFRV bypass valves YES impact on CDF/LERF as calculated by PRA model EOOS Criterion 3: The SSC is added to the SG steam line sample YES impact on CDF/LERF as calculated by PRA model isolation valves EOOS Accumulators Criterion 2: The SSC is not modeled in Accumulators Nitrogen NO Impact on CDF/LERF conservatively PRA, but the SSC can be directly supply assumes unavailability of Accumulator correlated to a surrogate SSC included in the PRA Criterion 2: The SSC is not modeled in Accumulator boron NO Impact on CDF/LERF conservatively PRA, but the SSC can be directly concentration not within assumes unavailability of Accumulator correlated to a surrogate SSC included limits in the PRA Note: SSC categorization based on above Criteria are subject to change prior to LAR submittal since the resolutions are preliminary.

TS Functions Versus PRA Functions:

Disposition of Differences in VEGP RMTS Program 16 IMPACT ON RICT IN EOOS IN FOR INOPERABLE CRITERIA SSC GROUPS PRA CONDITIONS Containment Systems Criterion 2: The SSC is not modeled in Containment pressure NO Impact on CDF/LERF conservatively PRA, but the SSC can be directly assumes unavailability of Containment correlated to a surrogate SSC included Coolers in EOOS in the PRA Criterion 2: The SSC is not modeled in Containment temperature NO Impact on CDF/LERF conservatively PRA, but the SSC can be directly assumes unavailability of Containment correlated to a surrogate SSC included Coolers in EOOS in the PRA Refueling Water Storage Tank (RWST)

Criterion 3: The SSC is added to the RWST Sludge system YES impact on CDF/LERF as calculated by PRA model isolation EOOS Criterion 2: The SSC is not modeled in RWST boron concentration NO Impact on CDF/LERF conservatively PRA, but the SSC can be directly not within limits, or assumes unavailability of RWST in correlated to a surrogate SSC included RWST borated water EOOS in the PRA temperature not within limits Note: SSC categorization based on above Criteria are subject to change prior to LAR submittal since the resolutions are preliminary.

TS Functions Versus PRA Functions:

Disposition of Differences in VEGP RMTS Program 17 IMPACT ON RICT IN EOOS IN FOR INOPERABLE CRITERIA SSC GROUPS PRA CONDITIONS Ventilation Systems Criterion 1: The SSC has no core ESF room cooler and safety- NO No impact on CDF/LERF. EOOS damage or large early releases risk related chiller train calculates 30 day backstop impact Criterion 1: The SSC has no core Control Room Emergency NO No impact on CDF/LERF. EOOS damage or large early releases risk Filtration System (CREFS) - calculates 30 day backstop (CREFS impact Control Room Air Isolation function is not in RMTS Temperature Function scope)

Criterion 1: The SSC has no core Piping Penetration Area NO No impact on CDF/LERF. EOOS damage or large early releases risk Filtration and Exhaust calculates 30 day backstop impact System Note: SSC categorization based on above Criteria are subject to change prior to LAR submittal since the resolutions are preliminary.

Summary and Action Item Review 18 y SNC appreciates the opportunity to work with the NRC on this important RI application pilot project y SNC and NRC gained valuable insights on technical issues impacting 4b LAR y SNC communicated its commitment for implementing 4b fleet-wide

{ Improved safety

{ Reduced forced outage rate

{ Enhanced on-line and outage work planning

{ Improved flexibility and regulatory predictability y Action item review