ML13108A107

Commitment to Install Improved Flood Mitigation Systems

ML13108A107
Person / Time
Site:	Watts Bar, Sequoyah
Issue date:	04/16/2013
From:	Swafford P Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML13108A107 (8)

Text

Tennessee Valley Authority, 1101 Market Street, LP 3R, Chattanooga, Tennessee 37402 Preston D. Swafford Executive Vice President and Chief Nuclear Officer April 16, 2013 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 Facility Operating License Nos. DPR-77 and DPR-79 NRC Docket Nos. 50-327 and 50-328 Watts Bar Nuclear Plant, Unit 1 Facility Operating License No. NPF-90 NRC Docket No. 50-390 Watts Bar Nuclear Plant, Unit 2 Construction Permit No. CPPR-92 NRC Docket No. 50-391

Subject:

Commitment to Install Improved Flood Mitigation Systems Since 2008, Tennessee Valley Authority (TVA) has been updating the flood hazard analyses for the Watts Bar Nuclear Plant (WBN), Sequoyah Nuclear Plant (SQN) and Browns Ferry Nuclear Plant (BFN). TVA and the NRC have discussed these efforts and related activities to improve flood hazard protection at SQN and WBN in several public meetings, including meetings dated July 7, 2010, and March 29, May 31, December 3, and December 13, 2012.

These efforts have also been the subject of correspondence from TVA to the NRC including, in part, letters dated March 21, 2011, June 13, July 19, August 10, and October 30, 2012, and January 18, 2013. The subject meetings and correspondence have been principally related to the current licensing bases for SQN and WBN with some limited discussions related to BFN. In addition to analyses and improvements associated with the existing licensing bases, TVA is conducting the comprehensive flood hazard reanalysis required by the NRC in its letter issued March 12, 2012, pursuant to 10 CFR 50.54(f), to all power reactor licensees and holders of construction permits in active or deferred status.

TVA has worked diligently since 2011 to develop a strong, comprehensive strategy to mitigate beyond-design-basis events, taking into account the significant lessons from the printed on recycled paper

U.S. Nuclear Regulatory Commission Page 2 April 16, 2013 March 2011 event at the Fukushima Dai-ichi nuclear plant. However, with respect to current requirements associated with design basis floods, TVA acknowledges that its efforts to update the current licensing basis as well as efforts to ensure compliance with the current licensing basis requirements have not always been timely, and in some cases, not sufficiently rigorous. Additional insights in this regard are discussed in Enclosure 1.

TVA considers that the current licensing basis approach to external flood hazards represents a sufficient bases for supporting a finding that the design and operation of SQN Units 1 and 2 and WBN Unit 1, and proposed design and operation of WBN Unit 2, provide adequate protection against design basis floods. The current licensing basis for SQN Units 1 and 2 and WBN Unit 1, and the proposed licensing basis for WBN Unit 2, are described in the SQN Updated Final Safety Analysis Report, WBN Unit 1 Updated Final Safety Analysis Report, and the WBN Unit 2 Final Safety Analysis Report, respectively, as supplemented by the improvements described in TVA's letter dated June 13, 2012.

To provide additional margin and improve protection against flood hazards moving forward, TVA assessed the merits of additional flood hazard mitigating capability at its nuclear plants.

Based on our assessment, TVA commits to improve the ability to mitigate the consequences of potential flooding hazards at both SQN and WBN. Enclosure 1 to this letter provides a design approach for an improved flood mitigation system at each facility and forms the basis of TVA's commitment. Enclosure 1 also includes specific milestones for the implementation of the planned systems. TVA will complete implementation of the improved flood mitigation systems at SQN Units 1 and 2 and WBN Units 1 and 2 by December 31, 2016.

Finally, in addition to the improved flood mitigation systems discussed in this letter, TVA continues to design and implement the mitigation strategies as outlined in our February 28, 2013 response to the NRC Orders related to the Fukushima Dai-ichi event.

As discussed in Enclosure 1, TVA will provide additional details of the planned design and as appropriate, licensing strategy for the improved flood mitigation systems. TVA will be prepared to discuss additional details in the upcoming April 22, 2013 regulatory/pre-decisional enforcement conference or at the NRC's request. Written progress updates will be provided as discussed in Enclosure 1.

A list of commitments referred to in this letter is included in Enclosure 2.

If you have questions regarding this matter, please contact Joe Shea at (423) 718-9576.

Res etfully, resonD.Swaifford/

Enclosures:

1. Sequoyah Nuclear Plant and Watts Bar Nuclear Plant Flood Mitigation Initiatives Description and Commitment

2. List of Commitments cc: (see page 3)

U.S. Nuclear Regulatory Commission Page 3 April 16, 2013 cc: (w/Enclosures)

NRC Regional Administrator - Region II NRR Director - NRC Headquarters NRC Senior Resident Inspector - Sequoyah Nuclear Plant NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRR Project Manager - Sequoyah Nuclear Plant NRR Project Manager - Watts Bar Nuclear Plant, Unit 1 NRR Project Manager - Watts Bar Nuclear Plant, Unit 2

ENCLOSUREI Sequoyah Nuclear Plant and Watts Bar Nuclear Plant Flood Mitigation Initiatives Description and Commitment

Background

Since 2008, the Tennessee Valley Authority (TVA) has been updating the flood hazard analyses for the Watts Bar Nuclear Plant (WBN), Sequoyah Nuclear Plant (SQN) and Browns Ferry Nuclear Plant (BFN). TVA and the NRC have discussed these efforts and related activities to improve flood hazard protection at SQN and WBN in several public meetings, including meetings dated July 7, 2010 (Reference 1), and March 29 (Reference 2), May 31 (Reference 3), December 3 (Reference 4), and December 13, 2012 (Reference 5). These efforts have also been the subject of correspondence from TVA to the NRC including, in part, letters dated March 21, 2011 (Reference 6), June 13 (Reference 7),

July 19 (Reference 8), August 10 (Reference 9) and October 30, 2012 (Reference 10), and January 18, 2013 (Reference 11). The subject meetings and correspondence have been principally related to the current licensing bases for SQN and WBN with some limited discussions related to BFN.

Regulatory Responsiveness WVA acknowledges that efforts to update the current licensing basis, as well as efforts to ensure compliance with the current licensing basis requirements regarding flood protection have not always been timely nor sufficiently rigorous in recent years. Moreover, TVA's senior management did not provide effective leadership and responsiveness to these issues. Several recent root cause analyses have identified weaknesses in fully understanding the regulatory requirements associated with flood protection licensing bases throughout the fleet. Weakness with the urgency by which WVA responded to flood protection issues was also identified. Actions to address these weaknesses are underway.

In addition, actions to improve the WVA regulatory organization's ability to provide the leadership needed to accelerate broad changes in fleet regulatory behaviors and responsiveness are being further strengthened.

Improved Flood Mitigation System Design and Implementation To further improve protection against external flood hazards moving forward, WVA will design and install improved flood mitigation systems at SQN Units 1 and 2 and WBN Units 1 and 2. The installed systems will be in addition to the flood mode systems currently described in the Sequoyah Nuclear Plant Updated Final Safety Analysis Report UFSAR, Watts Bar Nuclear Plant Unit 1 UFSAR, and the Watts Bar Nuclear Plant Unit 2 Final Safety Analysis Report (FSAR), as supplemented by the improvements described in WVA's letter dated June 13, 2012.

The flood mitigation systems addressed in this letter will incorporate improvements to flood mitigation at SQN and WBN through the installation of new components and will utilize certain elements of the Fukushima Dai-ichi mitigation equipment (FLEX). The systems will provide for the following key safety functions:

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1. Reactor Decay Heat Removal: TVA will improve flood mode Reactor Decay Heat Removal by providing 1) a new source of clean water 2) new pumping capacity to feed the steam generators and 3) a path to reject decay heat either to the atmosphere or to another operating heat sink. Upon completion, this decay heat removal path will be used preferentially over the existing flood mode decay heat removal process of providing high pressure fire system water into the steam generators. High pressure fire water will continue to be the design basis water source for flood mode mitigation and will be utilized in the event the clean water source is unavailable.

2. RCS Makeup and Criticality Control: TVA will install additional reactor coolant system makeup by providing 1) a protected source of borated water and 2) a new injection pump.

These flood mitigation systems will not make additional enhancements to the existing spent fuel inventory makeup capability. TVA will provide for makeup to the spent fuel pool using elements of the FLEX mitigation strategy.

TVA also continues to develop and design the mitigation strategies as outlined in its letters dated February 28, 2013 for SQN and WBN in response to the NRC Orders related to the Fukushima Dai-ichi event. As stated earlier, some elements of the Fukushima Dai-ichi mitigation equipment (FLEX) will be credited as part of the improved flood mode mitigation systems. The improved flood mode mitigation systems do not replace the mitigation strategies provided in TVA's Fukushima Order response, however changes to the hardened structure described in our February 28, 2013 response for Watts Bar will likely be required.

As a result, as an interim measure, TVA will modify its approach to equipment storage at Watts Bar consistent with the guidance in NEI 12-06, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide, such that no one external event will reasonably fail the site FLEX capability. This will include storage of the 3.0 MWe diesels in two diverse locations until the hardened structure is completed. TVA will submit an updated strategy for FLEX equipment storage at Watts Bar on or before June 30, 2013.

TVA will implement the improved flood mitigation systems at SQN Units 1 and 2 and WBN Units 1 and 2 by December 31, 2016. TVA specifically commits to the implementation milestones in the table below:

Table of Improved Flood Mitigation System Milestones Milestone Milestone Description Completion Date Name 1

Hardened A Hardened Structure will be constructed on site that will meet or SQN:

Structure exceed NEI 12-06.

June 2015 Constructed 0

Seismic Design 2X SSE HCLPF Wind speed/Missile criteria 360 MPH WBN:

No less than 15 feet above current PMF levels November 2015 Will also store portable FLEX equipment 2

3.0 MWe The 3.0 MWe diesels are designed to provide extended coping in SQN:

Diesels accordance with NEI 12-06 guidance. Diesels with diverse and December 2015 (One per redundant distribution will be available onsite to reduce reliance on operating unit) off-site equipment.

WBN:

August 2014 E1-2 of 4

3 Install The system will be installed in the Hardened Structure and operable, SQN:

Hardened including having required training and procedures in place and take December 2016 Enhanced advantage of the FLEX 3.0 MWe diesel power.

Flood Mode Will provide a high quality water source available through System for the duration of a flooding event.

WBN:

Decay Heat 0

Will utilize a condensate recovery system to achieve December 2016 Removal service time for two operating units when relying on the clean water source.

0 Maintenance and testing will be developed in accordance with NEI 12-06.

4 Install a The system will be installed in the Hardened Structure and operable, SQN:

Hardened including having required training and procedures in place, and December 2016 Enhanced powered by the FLEX 3.0 MWe diesels.

Flood Mode 0

An RCS Make-up Pump and controls will be installed in the RCS Makeup Hardened Structure.

WBN:

system Piping will be routed to the plant to allow the system to be December 2016 placed in service with minimal manual staging activities.

A water supply from the clean water source will be available for enhancing RCS make-up capacity.

Maintenance and testing will be developed in accordance with NEI 12-06.

TVA will provide periodic written updates regarding progress of the project by the last day of March, June, September and December of each year until the project is completed, beginning with the first written progress report to be filed by June 30, 2013.

Current Licensing Basis TVA is making the commitments discussed in this Enclosure to improve protection against external flood hazards going forward. TVA considers that the current licensing basis approach to external flood hazards represents sufficient bases for supporting a finding that the design and operation of SQN Units 1 and 2 and WBN Unit 1, and proposed design and operation of WBN Unit 2, provide adequate protection against design basis floods. The current licensing basis for SQN Units 1 and 2 and WBN Unit 1, and the proposed licensing basis for WBN Unit 2, are described in the SQN UFSAR, WBN Unit 1 UFSAR, and the WBN Unit 2 FSAR, respectively, as supplemented by the improvements described in TVA's letter dated June 13, 2012. TVA has proposed changes to the SQN and WBN Unit 1 UFSAR design basis flood levels to reflect updated flood hazard analyses (Reference 8 and 9). These proposed changes are currently pending NRC approval. TVA made conforming proposed changes to the Watts Bar 2 FSAR by letter dated August 23, 2012 (Reference 12).

REFERENCES:

1. Siva P. Lingam, NRC, to NRC Document Control Desk, "Summary of July 7, 2010, Public Meeting with TVA Regarding Status of Hydrology Issues Including the Flooding Effects on the TVA Operating Nuclear Plants," dated August 26, 2010 (Accession No. ML101930181).

2. Carl F. Lyon, NRC, to NRC Document Control Desk, "Summary of March 29, 2012, Pre-application Meeting with Tennessee Valley Authority on Changing the Licensing Basis for Hydrologic Engineering," dated April 11, 2012 (Accession No. ML101930181).

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3. Carl F. Lyon, NRC, to NRC Document Control Desk, "Summary of May 31, 2012, Senior Management Meeting with Tennessee Valley Authority on the Licensing Basis for Flooding/Hydrology," dated June 6, 2012 (Accession No. ML12157A457).

4. Scott M. Shaeffer, NRC, to Joseph Shea, TVA, "Public Meeting Summary - Flood Mode Operation Improvement Strategy for Watts Bar/Sequoyah - Docket Nos. 50-390, 50-327, 50-328," dated December 17, 2012 (Accession No. ML12352A208).

5. Andrew Hon, NRC, to NRC Document Control Desk, "Summary of December 13, 2012, Management Meeting with Tennessee Valley Authority on the Status of Hydrology," dated January 11, 2013 (Accession No. ML1301OA1 37).

6. TVA to NRC Document Control Desk, "Re-submittal of Attachments for Responses to Hydrology Action Items," dated March 21, 2011 (Accession No. ML110831044).

7. TVA to NRC Document Control Desk, "Commitments Related to Updated Hydrologic Analysis Results for Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Unit 1," dated June 13, 2012 (Accession No. ML12171A053).

8. TVA to NRC Document Control Desk, "Application to Revise Watts Bar Nuclear Plant Unit 1 Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis, TAC No. ME8200 (WBN-UFSAR-12-01)," dated July 19, 2012 (Accession No. ML12236A167).

9. TVA to NRC Document Control Desk, "Application to Revise Sequoyah Nuclear Plant Units 1 and 2 Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis, (SQN-TS-12-02)," dated August 10, 2012 (Accession No. ML122260684).

10. TVA to NRC Document Control Desk, "Impact of Potential Breaches of HESCO Modular Flood Barriers and Earthen Embankments on the Updated Hydrologic Analysis Results for Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Unit 1," dated October 30, 2012 (Accession No. ML12307A227).

11. TVA to NRC Document Control Desk, "Potential for Breaches of HESCO Modular Flood Barriers and Earthen Embankments Affecting the Updated Hydrologic Analysis Results for Sequoyah Nuclear Plant, Units 1 and 2, and Watts Bar Nuclear Plant, Unit 1," dated January 18, 2013 (Accession No. ML13025A262).

12. TVA to NRC Document Control Desk, "Watts Bar Nuclear Plant (WBN) - Unit 2 -

Final Safety Analysis Report (FSAR), Amendment 109," dated August 23, 2012 (Accession No. ML12244A018).

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ENCLOSURE 2 List of Commitments

1. TVA will implement an improved flood mitigation system at SQN Units 1 and 2 and WBN Units 1 and 2 by December 31, 2016. TVA will meet the project milestones depicted in the table in Enclosure 1.

2. TVA will provide periodic written updates regarding progress of the project by the last day of March, June, September and December of each year until the project is completed, beginning with the first written progress report to be filed by June 30, 2013.

3. TVA will submit an updated strategy for FLEX equipment storage at WBN Units 1 and 2 on or before June 30, 2013.

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