ML14191A044
| ML14191A044 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry, Watts Bar, Sequoyah  |
| Issue date: | 07/10/2014 |
| From: | Tennessee Valley Authority |
| To: | Plant Licensing Branch II |
| Hon A DORL/LPL2-2 301-415-8480 | |
| References | |
| Download: ML14191A044 (12) | |
Text
Tennessee Valley Authority Browns Ferry - Sequoyah - Watts Bar Near-Term Task Force Recommendation 2.1 Flooding Hazard Reevaluation Report Status Update July 10, 2014
2 TVA Nuclear Power Group Agenda
Introductions
Overview of Extension Requests Joe Shea Flooding Hazard Reevaluation Report Update Kevin Dutton
SQN/WBN HRR Project Status
BFN Project Status
September and December 2014 Update Format Multiple Dam Failure due to a Single Seismic Event Penny Selman TVA / ISG Dam Stability Differences Penny Selman
3 TVA Nuclear Power Group Overview of Flood Hazard Extensions SQN and WBN prioritized due date of March 12, 2013 TVA requested extension to March 12, 2015 Additional time required to complete evaluation of 17 upstream dams and 1 downstream dam in order to fully assess the flood hazard for the SQN and WBN sites Extension granted by NRC July 1, 2013 BFN prioritized due date of March 12, 2014 TVA requested extension to March 12, 2015 Addition time required to complete the evaluation of the 18 dams noted in the SQN/WBN extension request (all upstream of BFN) and 3 additional upstream dams and 1 downstream dam in order to fully assess the flood hazard for the BFN site Extension granted by NRC May 9, 2014
4 TVA Nuclear Power Group SQN/WBN and BFN MAIN TASK STATUS UPDATE SQN/WBN HRR Project Work continues on Sunny Day Dam Failure, PMF and Seismic Stability Analysis Tasks Work has started on Uncertainty Simulation Task Schedule on-track to complete and submit HRR by March 12, 2015 BFN HRR Project Credited SQN/WBN project work for Modeling Code Migration and Critical Storm Selection Tasks Work in-progress for Local Intense Precipitation Analysis, and the PMF and Seismic Stability Evaluation Tasks Schedule on-track to complete and submit HRR by March 12, 2015
5 TVA Nuclear Power Group SQN/WBN MAIN TASK STATUS UPDATE June 30, 2014 (updates shown in bold type)
TASK START FINISH STATUS 1a Main River Modeling Code Migration (SOCH to HEC-RAS)
Nov 2012 Complete 1b Tributary River Modeling Code Migration (SOCH to HEC-RAS)
Nov 2013 Complete 2
Confirm critical storm PMP selection Jan 2013 Complete 3
Perform local intense precipitation analysis for SQN/WBN May 2013 Complete 4a Sunny Day Dam Failure - WBH - east embankment failure Feb 2013 Complete 4b Sunny Day Dam Failure - Tributary Dams March 2013 Nov 2014 In-progress 5
Perform PMF simulations - 2 storms - all dams stable Feb 2013 March 2013* In-progress*
6 Evaluate Stability of 18 dams under PMF conditions March 2014 Complete 7
Perform PMF simulations using results of stability analysis April 2014 Dec 2014 In-progress 8
Develop dam specific seismic hazards April 2013 Complete 9
Evaluate seismic stability of 18 dams March 2014 Complete 10 Perform simulations using results of seismic stability analysis April 2014 Dec 2014 In-progress 11 Perform simulations to quantify uncertainties June 2014 Dec 2014 In-progress 12 Prepare HRRs with results and interim actions, as required Jan 2015 March 2015 Not Started
- Task completed but indicated as in-progress to allow for revisiting the breach modeling techniques in light of the dam stability ISG.
6 TVA Nuclear Power Group BFN MAIN TASK STATUS UPDATE June 30, 2014 (updates shown in bold type)
TASK START FINISH STATUS 1a Main River Modeling Code Migration (SOCH to HEC-RAS)
Completed in SQN/WBN Project 1b Tributary River Modeling Code Migration (SOCH to HEC-RAS)
Completed in SQN/WBN Project 2
Confirm critical storm PMP selection Completed in SQN/WBN Project 3
Perform local intense precipitation analysis for BFN Aug 2013 July 2014 In-progress 4
Sunny Day Dam Failure - 3 Upstream Dams Nov 2014 Dec 2015 Not Started 5
Perform PMF simulations - 2 storms - all dams stable Nov 2014 Jan 2015 Not Started 6
Evaluate Stability of 4 dams under PMF conditions Oct 2013 Sep 2014 In-progress 7
Perform PMF simulations using results of stability analysis Nov 2014 Jan 2015 Not Started 8
Develop dam specific seismic hazards Oct 2013 Complete 9
Evaluate seismic stability of 4 dams Oct 2013 Sep 2014 In-progress 10 Perform simulations using results of seismic stability analysis Nov 2014 Jan 2015 Not Started 11 Perform simulations to quantify uncertainties Nov 2014 Jan 2015 Not Started 12 Prepare HRRs with results and interim actions, as required Jan 2015 Mar 2015 Not Started
7 TVA Nuclear Power Group September and December 2014 Quarterly Updates Continue with current quarterly update format, adding BFN HRR project status, for the September and December 2014 updates.
Continue reporting status and progress of remaining tasks as they are scheduled to start and finish.
8 TVA Nuclear Power Group Methodology for Evaluating the Potential for Multiple Dam Failures Due to Seismic Events Revision to Multiple Dam Failures due to Seismic Events Methodology In June 27, 2013 public meeting, TVA communicated its intent to use a probabilistic risk based screening assessment for evaluation the potential for site flooding due to multiple dam failures due to seismic events Due to schedule concerns, TVA will now follow JLD-ISG-2013-01 Section 5.5 guidance TVA is continuing to develop the probabilistic risk based approach for evaluating the potential for site flooding due to multiple dam failures due to a seismic event
9 TVA Nuclear Power Group Highlights of TVA vs ISG Dam Stability Differences JLD-ISG-2013-01, Section 4.2.2 Overtopping, Staff Position Onsite or offsite temporary structures can continue to be credited in the Recommendation 2.1 flood hazard reevaluation if such credit has been evaluated and accepted by the NRC staff prior to the request for information letter (NRC, 2012). No other temporary structures or measures (including mitigation or compensatory measures) should be credited in the flood hazard reevaluation. Temporary structures or measures not credited in the hazard reevaluation may be proposed as interim actions and discussed in the appropriate section(s) of the hazard reevaluation response as described in the request for information letter (NRC, 2012)
TVA is performing analysis assuming permanent structures on Cherokee, Fort Loudoun, Tellico, and Watts Bar Dams are in place TVA has committed to have the temporary structures on Cherokee, parts of Fort Loudoun, Tellico, and Watts Bar Dams permanently replaced by October 2015 TVA revised the commitment to complete permanent replacement of the temporary structures on Fort Loudoun Dam by February 2017
10 TVA Nuclear Power Group Highlights of TVA vs ISG Dam Stability Differences JLD-ISG-2013-01, Section 4.2.8 Waterborne Debris, Staff Position Licensees should consider regional and/or local conditions before the final debris weight is selected. On navigable waterways, for example, the potential for impact from watercraft and barges should be considered in addition to that from trees, logs, and common manmade objects.
TVA will perform gate operability sensitivity analysis which would account for any loss of degraded function to spillways, gates, or outlet works due to barge impacts
11 TVA Nuclear Power Group Highlights of TVA vs ISG Dam Stability Differences JLD-ISG-2013-01, Section 5.2.3 Spillways, Gates, Outlet Works, and Other Appurtenances, Staff Position Seismic evaluation of dams should include consideration of whether a seismic event could lead to dam failure and subsequent uncontrolled release of the reservoir due to loss of degraded function of spillways, gates, outlet works, and other appurtenances.
As discussed in April 29, 2013 public meeting, TVA is performing global stability evaluations of 22 potentially critical dams utilizing the TVA dam safety analysis criteria which does not include evaluation of spillway, gates, outlet works, and other appurtenances TVA intends to perform hydrologic uncertainty evaluations with one or more gates inoperable to determine if loss of degraded function of spillways, gates, or other outlet works could lead to dam failure
12 TVA Nuclear Power Group Questions/Discussion