CNL-20-081, Status Regarding the Improved Flood Mitigation System Project
| ML20274A368 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar, Sequoyah  |
| Issue date: | 09/30/2020 |
| From: | Jerrica Johnson Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| CNL-20-081 | |
| Download: ML20274A368 (4) | |
Text
Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-20-081 September 30, 2020 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 Watts Bar Nuclear Plant, Units 1 and 2 Facility Operating License Nos. NPF-90 and NPF-96 NRC Docket Nos. 50-390 and 50-391
Subject:
Status Regarding the Improved Flood Mitigation System Project
References:
- 1. TVA Letter to NRC, Status Regarding the Improved Flood Mitigation System Project, dated September 30, 2019 (ML19274B858)
- 2. TVA Letter to NRC, Request for Review and Approval of Topical Report TVA-NPG-AWA16, TVA Overall Basin Probable Maximum Precipitation and Local Intense Precipitation Analysis, Calculation CDQ0000002016000041, Revision 1, dated June 22, 2018 (ML18192A510)
- 3. NRC Letter to TVA, Final Safety Evaluation for Tennessee Valley Authority Topical Report TVA Overall Basin Probable Maximum Precipitation and Local Intense Precipitation Analysis Calculation CDQ0000002016000041, Rev. 1 (EPID L-2016-TOP-0011), dated March 18, 2019 (ML19010A212)
- 4. TVA Letter to NRC, Application to Revise Sequoyah Nuclear Plant Units 1 and 2 Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis, (TS-19-02), dated January 14, 2020 (ML20016A396)
- 5. TVA Letter to NRC, Supplement to Application to Revise Sequoyah Nuclear Plant Units 1 and 2 Updated Final Safety Analysis Report Regarding Changes to Hydrologic Analysis, (TS-19-02)
(EPID L-2020-LLA-0004), dated February 18, 2020 (ML20049H184)
By letter dated September 30, 2019, Tennessee Valley Authority (TVA) informed the Nuclear Regulatory Commission (NRC) of a change in the specified field implementation completion schedule to install improved flood mode mitigation systems (FMMS) at the Sequoyah Nuclear Plant (SQN), Units 1 and 2, and the Watts Bar Nuclear Plant (WBN),
Units 1 and 2 (Reference 1). The change in the implementation schedule was based on the ongoing TVA project to upgrade precipitation models and rerun hydraulic models to determine new probable maximum flood levels for both design basis and beyond-design-basis purposes.
U.S. Nuclear Regulatory Commission CNL-20-081 Page 2 September 30, 2020 TVA completed an updated precipitation calculation that includes updated data (storm and dew point), meteorological science, technology, weather radar, Geographic Information System (GIS) tools, and treatment of topography. The results reflected a potential precipitation volume/input decrease from the values reflected in the current licensing basis and reevaluated flood hazards for SQN and WBN. The revised updated precipitation calculation was submitted to NRC for review by letter dated June 22, 2018 (Reference 2).
NRC has completed the review of the revised updated precipitation calculation. The review and conclusions drawn from the review are documented in a Safety Evaluation that was provided by NRC by letter dated March 18, 2019 (Reference 3).
The revised precipitation data is being used as input into TVAs hydraulic models to determine the resulting flood levels at the SQN and WBN sites. The results from the hydraulic models used to establish resulting changes in flood levels at the SQN and WBN sites reflect decreases in analyzed flood levels at both sites. TVA will subsequently update its licensing basis for both SQN and WBN with the analyzed flood levels.
A License Amendment Request to incorporate the updated licensing basis for SQN was submitted by letter dated January 14, 2020 (Reference 4) and supplemented by letter dated February 18, 2020 (Reference 5).
Consequently, as described in Reference 1, TVA has concluded it is prudent to further defer the field implementation of FMMS until completion of the revised hydraulic modeling and the submittal of License Amendment Request associated with the update to the WBN licensing basis. This will allow TVA to demonstrate what appropriate margin, if any, should be designed into additional flood mitigating systems at SQN and WBN. Therefore, TVA is revising the Commitment 1 due date (Enclosure 1 of Reference 1) to implement an FMMS at SQN, Units 1 and 2, and WBN, Units 1 and 2, from September 30, 2020, to September 30, 2022.
The enclosure to this letter provides the one revised regulatory commitment contained in this letter. If additional information is needed regarding this update, please contact Russell Thompson at (423) 751-2567.
Respectfully, Jonathan T. Johnson Director, Nuclear Regulatory Affairs (Acting)
Enclosure cc: See Page 3
U.S. Nuclear Regulatory Commission CNL-20-081 Page 3 September 30, 2020 cc (Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Sequoyah Nuclear Plant NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRR Director - NRC Headquarters NRR Project Manager - Sequoyah Nuclear Plant NRR Project Manager - Watts Bar Nuclear Plant
E-1 CNL-20-081 ENCLOSURE COMMITMENT