ML12117A324

4/11/12 Meeting Summary - Summary of Meeting with Southern Nuclear Operating Company, Inc, on Technical Specifications Risk-Informed Initiative 4B

ML12117A324
Person / Time
Site:	Vogtle
Issue date:	05/02/2012
From:	Patrick Boyle Plant Licensing Branch II
To:	Southern Nuclear Operating Co
Boyle P
Shared Package
ML12118A038	List: ML12052A149 ML12101A018 ML12117A324 ML12123A150
References
TAC ME7750
Download: ML12117A324 (22)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 May 2,2012 LICENSEE: Southern Nuclear Operating Company, Inc.

FACILITY: Vogtle Electric Generating Plant, Units 1 and 2

SUMMARY

OF APRIL 11,2012, MEETING WITH SOUTHERN NUCLEAR OPERATING COMPANY, INC., ON TECHNICAL SPECIFICATIONS RISK-INFORMED INITIATIVE 4B (TAC NO. ME7750)

On April 11, 2012, a Category 1 public meeting was held between the U.S. Nuclear Regulatory Commission (NRC) and representatives of Southern Nuclear Operating Company, Inc. (SNC, the licensee) at NRC Headquarters, One White Flint North, 11555 Rockville Pike, Rockville, Maryland. The purpose of the meeting was to discuss Technical Specification Risk Informed Initiative 4b Limiting Conditions for Operation, Risk-Informed Completion Times (4b). A list of attendees is provided as Enclosure 1.

The licensee presented information (See Enclosure 2)

The staff discussed with the licensee their planned license amendment request for this initiative with the following areas of interest:

• Based on SNCs examples which successfully highlighted possible issues that might arise during the review of the pilot application, in addition several issues were identified as important topics for further discussions. SNC stated that they will internally evaluate these issues with respect to their inclusion in the 4b pilot The NRC staff indicated that pilot applications may be accepted for review even when they include issues that need further discussions, and that the review process may be the best vehicle to resolve many issues.

• The NRC staff questioned the apparent reliance on full correlation assumed for seismic induced failures of redundant systems, structures and components (SSCs) to support the use of the total seismic risk as a conservative estimate of the maximum increase in seismic risk in allowed outage time (AOT) calculations.

SNC indicated that there were other factors that also supported the use of total seismic risk as the maximum increase.

• There was an extensive discussion on how the AOTs for SSCs whose failures do not contribute to core damage or large early release might be included in the proposed implementation of 4b at SNC. Including such SSCs was not previously envisioned under 4b.

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• SNC provided an example of extending the time that a limiting conditions for operation (LCO) might be exceeded (e.g., cooling basin water temperature limits) in the proposed implementation of 4b at SNC. It was unclear how the range and magnitude of such changes could be characterized so the NRC staff review and SNC implementation could be accomplished.

• The NRC staff questioned SNC plans to allow changes in the probabilistic risk assessment model input data while calculating AOTs. It was unclear how the range and magnitude of such changes could be characterized so the NRC staff review and SNC implementation could be accomplished.

• The licensee indicated that the 4b initiative would not be an implementation of Technical Specification Task Force (TSTF) TSTF-505, "Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b."

Members of the public were in attendance. Public Meeting Feedback forms were available but no comments were received.

Please direct any inquiries to me at 301-415-3936.

Patrick G. Boyle, Project Manager Plant Licensing Branch, 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-424 and 50-425

Enclosures:

1. List of Attendees

2. Licensee Handouts cc w/encls: Distribution via Listserv

LIST OF ATTENDEES APRIL 11. 2012. MEETING WITH SOUTHERN NUCLEAR COMPANY RISK-INFORMED INITIATIVE 4B LIMITING CONDITION OF OPERATIONS. RISK-INFORMED COMPLETION TIMES ATTENDEE REPRESENTING Patrick G. Boyle NRC-DORL Jigar Patel NRC-DRA  !

Bob Martin NRC-DORL I I Ken McElroy SNC - Risk-Informed Engineering i Erin Anners SNC - Licensing

• Jack Stringfellow SNC -- Licensing Biff Bradley NEI Anees Farruk SNC - Risk-Informed Engineering

• Donnie Harrison NRC-DRA Stephen Dinsmore NRC-DRA Doug True ERIN Via Phone I

Ameren - Callaway Plant, Regulatory Roger Wink Initiatives Lesa Hill SNC -- Licensing Nancy Salgado NRC--DORL Mike Cain NRC - SRI, Plant VogUe Amir Afzali SNC - Risk-Informed Engineering Mark Ajluni SNC - Licensing Enclosure

Enclosure 2 Vogtle Electric Generating Plant, Units 1 and 2 Final Meeting Slides ADAMS Accession No.: ML12123A150

Risk Managed Technical Specifications Initiative 4b 1

SNC/NRC MEETING APRIL 11, 2012

Agenda 2

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

Purpose 3

Purpose - Technical discussions on Vogtle pilot Risk Managed Technical Specifications (RMTS) program Treatment of SSCs unavailability included in the scope of 4b Treatment of Seismic Risk Desired Outcome - NRC comments and feedback on SNCs technical approach

SNCs Risk Informed Journey - Fleet 4

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 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

Vogtle NRC Pilot for 4b - October 2010 NRC Commissioners Meeting - January 2011 Vogtle Seismic PRA Collaboration with EPRI - May 2011 Vogtle NRC Pilot for 50.69 - June 2011 4b Seismic/External Events treatment strategy submitted -

September 2011 Vogtle fire model peer-reviewed - February 2012 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 SSCs Unavailability in 4B 7

Final Safety Evaluation for NEI 06-09 requires the LAR to:

Justify any differences between TS functions and PRA functions success criteria Ensure LCO Conditions included are supported by CDF/LERF metrics Demonstrate treatment of SSCs unavailability impacted by LCO Conditions by concluding Has no impact on CDF/LERF Impact bounded by a surrogate SSC modeled in PRA, or Represented by a PRA a basic event(s)

Treatment of SSCs Unavailability in 4B is justified based on the following criteria that reflects the above NEI 06-09 guidelines

Treatment of SSCs Unavailability in 4B-Justification Criteria 8

Criterion 1: The SSC has no core damage or large early release risk impact Criterion 2: The SSC is not modeled in PRA, but the SSC can be directly correlated to a surrogate SSC included in the PRA Criterion 3: The SSC is added to the PRA model

Treatment of SSCs Unavailability in 4B:

Criterion 1 Example 9

Criterion 1: The SSC has no core damage or large early release risk impact Ventilation Systems SSCs TS LCO Condition Example One ESF room cooler and safety-related chiller train Inoperable ESF room cooler and safety-related chiller unavailability is not in PRA logic model because it does not impact CDF/LERF based on documented heat up analysis As a result, EOOS calculates a 30 day Backstop when ESF room cooler and safety-related chiller train become unavailable

Treatment of SSCs Unavailability in 4B -

Criterion 2 Example 10 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 water temperature and/or water level TS LCO Condition Example One or more Nuclear Service Cooling Water (NSCW) basins with water temperature and/or water level not within limits.

Nuclear Service Cooling Water (NSCW) basins water temperature and/or water level unavailability is not in PRA logic model because it does not impact mitigation of CDF/LERF or has a negligible impact As a conservative assumption, for calculating RICT, impact on CDF/LERF assumes unavailability of Nuclear Service Cooling Water train as a surrogate in EOOS

Treatment of SSCs Unavailability in 4B -

Criterion 3 Example 11 Criterion 3: The SSC is added to the PRA model RWST Sludge system isolation TS LCO Condition Example:

One or more sludge mixing pump isolation valves inoperable.

Sludge mixing pump isolation valves unavailability is not in PRA logic model but the logic model was revised to include Sludge mixing pump isolation valves Impact of sludge mixing pump isolation valves unavailability on CDF/LERF is calculated by EOOS

Treatment of Seismic Risk 12 When a hazard group is not modeled in the baseline PRA, NEI 06-09 permits use of bounding analyses or other conservative quantitative evaluations to determine risk impacts.

Seismic Risk is not in the PRA for VEGP, and a Bounding Analysis approach is utilized for addressing Seismic risk impacts Internal Fire Seismic Other External Shutdown Events Risk Risk Risk Events Risk Risk Internal Fire Seismic PRA Events PRA PRA Bounding Updated (includes Internal N/A - At

+ Flooding ) Analysis IPEEE Power Only Approach Screening

Treatment of Seismic Risk 13 SNC submitted a Seismic Bounding Analysis Approach to NRC in September 2011 (ML112710169).

ML112710169 categorizes seismic risk into two types of contributions Seismic risk within design basis Seismic risk beyond design basis ML112710169 discusses a Generic approach, and VEGP -specific application for treating the impact of both contributions of seismic risk in RICT calculations

Treatment of Seismic Risk - Within Design Basis 14 Significance of VEGP Seismic risk within design basis Total unrecovered LOSP frequency = 3.3E-02 x 6.5E-02 = 2.1 E-03/yr Total Seismic LOSP frequency (RASP Handbook hazard data) = 9.5 E-05/yr Seismically-induced LOSP < 5% contributor The unrecovered seismically-induced loss of offsite power frequency is a small fraction of the total unrecovered LOSP frequency As a result, within design basis seismic hazard does not significantly impact RICT for removing equipment from service (e.g. diesel generator) and is bounded by the internal events CDF

Treatment of Seismic Risk - Beyond Design Basis 15 Significance of VEGP Seismic risk beyond design basis:

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

Seismic CDF (SCDF) is assumed to depend on the likelihood of a single seismic-induced failure leading to core damage (i.e. single limiting plant fragility convoluted with the seismic hazard).

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

Treatment of Seismic Risk -

Basis for Bounding SCDF factor 16 Staff Report, Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States on Existing Plants, Safety/Risk Assessment, ML100270639, August 2010 has three screening values for VEGP Using 1989 EPRI: 2.6E-06 Using 1994 LLNL: 2E-05 Using 2008 USGS: 7.1E-06 Using these surrogate analyses, NRC estimated a bounding total SCDF of 2E-05/yr for VEGP which is the bounding SCDF factor applied to the RICT Calculation

Summary and Action Item Review 17 SNC appreciates the opportunity to work with the NRC on this important RI application pilot project SNC and NRC gained valuable insights on technical issues impacting 4b LAR 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 Action item review

PKG ML12118A038 Meeting Notice ML12052A149 Meeting Summary ML12117A324 Slides ML12101A018 Final Slides ML12123A150 OFFICE DORULPL2-1/PM DORULPL2-1/LA* DORULPL2-1/BC DORULPL2-1/PM NAME PBoyle SFigueroa NSalgado PBoyle DATE 05/02/12 04/27/12 05/02/12 05/02/12

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