ML17069A391

Periodic Schedule Update for Revision of Loss-of-Coolant Accident Mass and Energy Release Calculations Related to Containment Integrity Response Analyses

ML17069A391
Person / Time
Site:	Sequoyah
Issue date:	03/10/2017
From:	Shea J W Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CNL-17-041, TAC MF2446, TAC MF2447
Download: ML17069A391 (4)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-17-041 March 10, 2017 10 CFR 50.4 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Sequoyah Nuclear Plant, Units 1 and 2 Renewed Facility Operating License Nos. DPR-77 and DPR-79 NRC Docket Nos. 50-327 and 50-328

Subject:

Sequoyah Nuclear Plant, Units 1 and 2 - Periodic Schedule Update for Revision of Loss-of-Coolant Accident Mass and Energy Release Calculations Related to Containment Integrity Response Analyses

References:

1. Letter from TVA to NRC, "Sequoyah Nuclear Plant, Units 1 And 2 - Application to Modify Ice Condenser Technical Specifications to Address Revisions in Westinghouse Mass and Energy Release Calculation (SQN-TS-12-04)," dated July 3, 2013 (ML13199A281) 2.Letter from TVA to NRC, CNL-15-020 "Supplement to the Application to Modify Ice Condenser Technical Specifications t o Address Revisions in Westinghouse Mass and Energy Re lease Calculation (SQN-TS-12-04) and Response to NRC Requests for Additional Information," dated April 10, 20 15 (ML15117A566) 3.Electronic Mail from NRC to TVA, "Sequoyah Nuclear Plant, Units 1 and 2, Related to License Amendment Request to Revise Technical Specifica tion on Ice Condenser Ice Mass (TAC Nos. MF2446 and MF2447)," dated

July 13, 2015 4.Final Safety Evaluation for Westinghouse Electric Company (Westingho use)Topical Rep ort (TR) WCAP-17721-P, Revision 0, And WCAP-17721-NP, Revision 0, "Westinghouse Containment Analys is Methodology - PWR

[Pressurized Water Reactor] LOCA [Loss-Of-Coolant Accident

] Mass And Energy Release Calculation Methodology," dated August 24, 2015 (ML15221A005) 5.Letter from TVA to NRC, CNL-16-049, "Sequoya h Nuclear Plant, Units 1 and 2 - Withdrawal of Application to Modify Ice Condenser T echnical Specifications to Address Revisions in Westing house Mass and Energy Release Calculation (SQN-TS-12-04)," dated September 19, 2016 (ML16264A456)

U.S. Nuclear Regulatory Commission CNL-17-041

Page 2 March 10, 2017

By letter dated July 3, 2013 (Reference 1), Tennessee Valley Authority (TVA) submitted license amendment request (LAR) SQN-TS-12-04 for Sequoyah Nuclear Plant (SQN), Units 1 and 2. The proposed changes were to revise SQN Units 1 and 2 Technical Specifications (TSs) 3/4.6.5, "Ice Condenser," to increase the total ice weight from 2,225,880 pounds to 2,540,808 pounds.

The Reference 1 LAR was submitted to address the issues raised in Westinghouse Nuclear Safety Advisory Letter (NSAL) 11-5, "Westinghouse LOCA Mass and Energy Release Calculation Issues." The issues identified in NSAL-11-5 affected plant-specific loss of coolant accident (LOCA) mass and energy (M&E) release calculation results that are used as input to the containment integrity response analyses. The changes in the LOCA M&E release calculations and the associated changes to the SQN containment integrity response analyses resulted in TS Limiting Condition for Operation 3.6.12 being non-conservative with respect to the required total ice weight.

The Reference 2 LAR supplement proposed changes to address issues raised in Westinghouse Nuclear Safety Advisory Letter (NSAL) 14-2, "Westinghouse Loss-of-Coolant Accident Mass and Energy Release Calculation Issue for Steam Generator Tube Material Properties." The issues identified in NSAL-14-2 also affected plant-specific LOCA M&E release calculation results that were used as input to the SQN containment integrity response analyses.

On July 13, 2015 (Reference 3), TVA received a request for information regarding Westinghouse InfoGram IG-14-1, dated November 5, 2014, which stated that the LOCA M&E release analysis methodology used a reactor coolant system (RCS) stainless steel volumetric heat capacity value that was lower than the ASME values.

To address the issue identified in IG-14-1, TVA is revising the LOCA M&E release calculations and the associated SQN containment integrity response analyses utilizing the new Westinghouse WCOBRA/TRAC model, which is based on WCAP-17721-P, "Westinghouse Containment Analysis Methodology - PWR LOCA Mass and Energy Release Calculation Methodology" (Reference 4). The revised LOCA M&E release calculations and the associated SQN containment integrity response analyses are expected to be completed by May 2018.

In a letter dated September 9, 2016 (Reference 5), TVA withdrew LAR SQN-TS-12-04 and committed to provide periodic updates every six months to NRC regarding the progress of the

revised analysis. A new LAR will be submitted using the revised analyses, if necessary. In that letter, TVA committed to provide the first six-month update by February 28, 2017. In a phone call on February 24, 2017, with the NRC SQN Project Manager, TVA was granted two additional weeks to provide the update. The enclosure to this letter includes the first six-month update.

Page E-1 Enclosure Sequoyah Nuclear Plant, Units 1 and 2 Periodic Schedule Update for Revision of Loss-of-Coolant Accident Mass and Energy Release Calculations Related to Containment Integrity Response Analyses The table below includes completed and future milestones for the revised loss-of-coolant accident (LOCA) mass and energy release calculations and associated containment integrity response analyses utilizing the new Westinghouse WCOBRA/TRAC model.

Phase 1 Target Milestones Schedule Date 1 Project Customer Kickoff June 2016 (Complete) 2 Input Request Letter to TVA August 2016 (Complete) 3 TVA issuance of analytical input summary (AIS) September 2016 (Complete) 4 Completion of WCOBRA/TRAC Model July 2017 5 Issuance of preliminary containment response results November 2017 6 TVA issuance of Phase 2 guidance on margin allocation December 2017 Phase 2 Target Milestones Schedule Date 7 Issuance of draft LOCA M&E and Containment Integrity analysis report March 2018 8 TVA provides comments on draft Containment Integrity analysis report April 2018 9 Issuance of final Containment analysis report plus FSAR, Accident Analysis Parameter Checklist, Technical Specification markups (if necessary) May 2018