ML12101A018
| 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: |
| References | |
| TAC ME7750 | |
| Download: ML12101A018 (18) | |
Text
SNC/NRC MEETING Risk Managed Technical Specifications Initiative 4b 1
SNC/NRC MEETING APRIL 11, 2012
Agenda yIntroduction/Purpose yOverview of the Project yTechnical Issues Discussion i
d i
i 2
yMeeting Summary and Action Item Review
Purpose 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 3
y Desired Outcome - NRC comments and feedback on SNCs technical approach
SNCs Risk Informed Journey - Fleet 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 4
{ 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 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 b S i i /E l E b
i d
5 y 4b Seismic/External Events treatment strategy submitted -
September 2011 y Vogtle fire model peer-reviewed - February 2012 y 4b LAR - 3rd quarter 2012
Initial LCO Selection EOOS 4+
Enhancement 4B Vogtle LAR Submittal Fire PRA Peer Review Enhanced A4 Procedure Changes/Training 6
Vogtle A4/4B Timeline Mar 2011 Jun 2011 Sep 2011 Dec 2012 Mar 2012 Jun 2012 Sep 2012 Dec 2012 Mar 2013 Jun 2013 EOOS Integrated Fire + Internal PRA Model 4B Procedure Training 4B Anticipated NRC Approval Sep 2013 EOOS Ready for Site-Specific Deployment for Enhanced A4 Key Changes Related to EOOS
- P6 to EOOS Automation
- CR Log to EOOS Automation
- EOOS 4+ Enhancements
Treatment of Seismic Risk 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 7
Analysis Approach is utilized for addressing Seismic Risk Internal Events Risk Fire Risk Seismic Risk Other External Events Risk Shutdown Risk Internal Events PRA Fire PRA Seismic PRA (includes Internal Flooding & Seismic LOOP)
FIVE Bounding Analysis Approach Updated IPEEE Screening N/A - At Power Only
Treatment of Seismic Risk y SNC submitted a Seismic Bounding Analysis Approach to NRC in September 2011 (ML112710169).
y Summary
{ Seismic risk within design basis:
8 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)
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 9
Treatment of Seismic Risk bounding CDF factor to the RICT Calculation
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 10 Treatment of Seismic Risk
{ 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 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 11
{ 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 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 12 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 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 directly correlated to a surrogate SSC 13 y
g 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 CRITERIA SSC GROUPS IN PRA IMPACT ON RICT IN EOOS FOR INOPERABLE CONDITIONS Reactor Coolant System Criterion 1: The SSC has no core damage or large early releases risk impact RCS Leakage Detection Systems NO No impact on CDF/LERF. EOOS calculates 30 day backstop Criterion 1: The SSC has no core damage or large early releases risk PZR Heaters NO No impact on CDF/LERF. EOOS calculates 30 day backstop 14 Note:
SSC categorization based on above Criteria are subject to change prior to LAR submittal since the resolutions are preliminary.
damage or large early releases risk impact calculates 30 day backstop Criterion 1: The SSC has no core damage or large early releases risk impact RCS Recirculation Fluid pH Control System NO No impact on CDF/LERF. EOOS calculates 30 day backstop Criterion 3: The SSC is added to the PRA model RCP seal injection needle valves YES Impact on CDF/LERF as calculated by EOOS Ultimate Heat Sink Criterion 2: The SSC is not modeled in PRA, but the SSC can be directly correlated to a surrogate SSC included in the PRA Nuclear Service Cooling Water (NSCW) basins with water temperature and/or water level NO Impact on CDF/LERF conservatively assumes unavailability of Nuclear Service Cooling Water train in EOOS
TS Functions Versus PRA Functions:
Disposition of Differences in VEGP RMTS Program CRITERIA SSC GROUPS IN PRA IMPACT ON RICT IN EOOS FOR INOPERABLE CONDITIONS Secondary Side Heat Removal Systems Criterion 3: The SSC is added to the PRA model MFRV bypass valves YES impact on CDF/LERF as calculated by EOOS Criterion 3: The SSC is added to the PRA model SG steam line sample isolation valves YES impact on CDF/LERF as calculated by EOOS Accumulators 15 Note:
SSC categorization based on above Criteria are subject to change prior to LAR submittal since the resolutions are preliminary.
Accumulators Criterion 2: The SSC is not modeled in PRA, but the SSC can be directly correlated to a surrogate SSC included in the PRA Accumulators Nitrogen supply NO Impact on CDF/LERF conservatively assumes unavailability of Accumulator Criterion 2: The SSC is not modeled in PRA, but the SSC can be directly correlated to a surrogate SSC included in the PRA Accumulator boron concentration not within limits NO Impact on CDF/LERF conservatively assumes unavailability of Accumulator
TS Functions Versus PRA Functions:
Disposition of Differences in VEGP RMTS Program CRITERIA SSC GROUPS IN PRA IMPACT ON RICT IN EOOS FOR INOPERABLE CONDITIONS Containment Systems Criterion 2: The SSC is not modeled in PRA, but the SSC can be directly correlated to a surrogate SSC included in the PRA Containment pressure NO Impact on CDF/LERF conservatively assumes unavailability of Containment Coolers in EOOS Criterion 2: The SSC is not modeled in Containment temperature NO Impact on CDF/LERF conservatively 16 Note:
SSC categorization based on above Criteria are subject to change prior to LAR submittal since the resolutions are preliminary.
Criterion 2: The SSC is not modeled in PRA, but the SSC can be directly correlated to a surrogate SSC included in the PRA Containment temperature NO Impact on CDF/LERF conservatively assumes unavailability of Containment Coolers in EOOS Refueling Water Storage Tank (RWST)
Criterion 3: The SSC is added to the PRA model RWST Sludge system isolation YES impact on CDF/LERF as calculated by EOOS Criterion 2: The SSC is not modeled in PRA, but the SSC can be directly correlated to a surrogate SSC included in the PRA RWST boron concentration not within limits, or RWST borated water temperature not within limits NO Impact on CDF/LERF conservatively assumes unavailability of RWST in EOOS
TS Functions Versus PRA Functions:
Disposition of Differences in VEGP RMTS Program CRITERIA SSC GROUPS IN PRA IMPACT ON RICT IN EOOS FOR INOPERABLE CONDITIONS Ventilation Systems Criterion 1: The SSC has no core damage or large early releases risk impact ESF room cooler and safety-related chiller train NO No impact on CDF/LERF. EOOS calculates 30 day backstop Criterion 1: The SSC has no core damage or large early releases risk Control Room Emergency Filtration System (CREFS) -
NO No impact on CDF/LERF. EOOS calculates 30 day backstop (CREFS 17 Note:
SSC categorization based on above Criteria are subject to change prior to LAR submittal since the resolutions are preliminary.
damage or large early releases risk impact Filtration System (CREFS)
Control Room Air Temperature Function calculates 30 day backstop (CREFS Isolation function is not in RMTS scope)
Criterion 1: The SSC has no core damage or large early releases risk impact Piping Penetration Area Filtration and Exhaust System NO No impact on CDF/LERF. EOOS calculates 30 day backstop
Summary and Action Item Review 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 18 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