ML13210A404

Meeting Slide for 7/30-31/2013 Meeting Re. Hydrology License Amendment Requests

ML13210A404
Person / Time
Site:	Watts Bar, Sequoyah
Issue date:	07/30/2013
From:	Tennessee Valley Authority
To:	Andrew Hon Plant Licensing Branch II
Hon A
References
Download: ML13210A404 (37)

Text

Hydrology License Amendment Requests Watts Bar and Sequoyah Nuclear Plants July 3031, 2013 1

Background

In Feb 2008, NRC inspection of the quality assurance processes and procedures for the hydrology and hydraulics model, Simulated Open Channel Hydraulics (SOCH), for the Bellefonte Combined License Application (COLA) resulted in violations regarding:

- SOCH software was not in compliance with the procedure for software validation and verification

- Design inputs for the hydrology model were not documented in accordance with procedure

- Computer input files were not controlled in accordance with the procedure 2

Background

TVA utilized results from an updated hydrology calculation (circa 1998) for Bellefonte COLA

- Primary subject of the Feb 2008 inspection This calculation was used as the basis for UFSAR Section 2.4 revisions

- Watts Bar initiated UFSAR changes in 1998

- Sequoyah initiated UFSAR changes in 2002 This calculation was updated for Tennessee River dam safety improvements (modifications). All other inputs remained the same.

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Historical Timeline of PMF 1999 & 2001 Watts Bar & Sequoyah UFSAR change 1972 reflect PMF reevaluation, Browns Ferry 1982 - 1997 respectively Dec 2009 Hydrology Analysis TVA Dam Safety HESCO Modification Program Feb/March 2008 barriers installed Approved by NRC Bellefonte NOV &

Hydrology model reconstitution project started June & Aug 1979 & 1982 Sequoyah & Watts Bar 1997-1998 2012 PMF re-evaluated 2004 Completion of WBN Hydrology Analysis for TVA Reservoir & SQN analysis, approved by NRC, TVA Dam Safety Mods Operation Study respectively respectively completed 4

Tennessee River System Overview Bristol Projects (2) Nolichucky Holston River French Broad Clinch River River Little Tennessee Boone South Holston Ft. Patrick Henry Watauga Thorpe (N)

John Sevier Wilbur Doakes Creek Douglas Nantahala (N)

Cherokee Fontana Cheoah (T)

Calderwood (T) Santeetlah (T)

Norris Ft. Loudoun Chilhowee (T) Hiwassee River Melton Hill Chatuge Tellico Watts Bar Plant Watts Bar Nottely Hiwassee Sequoyah Plant Apalachia Blue Ridge Elk River Chickamauga Nickajack Ocoee 1, 2, 3 Browns Ferry Plant Raccoon Mountain Tims Ford Guntersville Duck River Cumberland River Normandy Wheeler Bear Creek Projects (4)

Wilson Green River Tennessee-Tombigbee Waterway Pickwick Barkley (C) Note:

Ohio River (C) U.S. Army Corps of Engineers Dams Beech River Projects (8)

(N) Nantahala Power & Light Company Kentucky (subsidiary of Duke Energy)

(T) Brookfield Smokey Mountain Hydro Power (Formerly Tapoco)

Mississippi River 5

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Hydrologic Calculation Flow Chart 6

Updated Analysis TVA initiated project in March 2008 to

- Validate and verify legacy hydrology software

- Verify or regenerate all model inputs Original model assumptions kept the same unless discrepancies found

- Dam discharge rating curves

- Reservoir Operations 7

Model Results WBN SQN LAR Proposed PMF 739.2 722.0 Elevation Original Licensing PMF 738.1 722.6 Elevation 1998 Calculation PMF 734.9 719.6 Elevation 8

SOCH Segment 1 9

SOCH Segment 2 10

Probable Maximum Flood Potential Seismic Dam Failures

• Reevaluation of the controlling dam combinations from the original analysis (plus addition of an assumed seismic failure of Tellico dam)

- Norris Dam Failure for Load Case OBE + 1/2 PMF

- Fontana Dam Failure for Load Case OBE + 1/2 PMF

- Cherokee and Douglas for Load Case OBE + 1/2 PMF

- Fontana, Hiwassee, Apalachia, and Blue Ridge Dam Failures for Load Case OBE + 1/2 PMF

- Norris, Cherokee and Douglas Failures for Load Case SSE + 25 year flood

• PMF elevations have enveloped the calculated Potential Dam Failure elevations in previous analyses; Potential Dam Failure analyses have determined warning times in previous analyses 11

Unit Hydrographs Unit Hydrographs excluding Wheeler (used for WBN & SQN)

- 33 directly validated

- 14 indirectly validated Unit Hydrographs above Wheeler Dam (used for BLN model 2009)

- 39 directly validated

- 23 indirectly validated Norris was previously divided into four gaged subareas and lagrouted to Norris Dam in early 1970s. The combined area was validated as a single subbasin in 2009.

Melton Hill was previously divided into 10 subbasins with synthetic unit hydrographs. It was replaced by a single unit hydrograph in 1984.

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Unit Hydrographs Revisions All revisions administrative or technical for Browns Ferry Nuclear only CDQ000020080059 Guntersville UH (49 & 50) Revision 2 CDQ000020080060 Nickajack UH (47A & 47B) Revision 3 CDQ000020080061 Chickamauga UH (38, 39, 40, 41, 43) Revision 2 CDQ000020080062 Little Pigeon UH (7) Revision 2 CDQ000020080064 Chickamauga Local UH (44B & 45) Revision 3 CDQ000020080070 Little Tennessee above Chilhowee UH (1923) Revision 2 13

Inflow Hydrograph Routing HEC Products used for Dam Failure Outflows Blue Ridge Dam HECRAS Cherokee Dam HECHMS Chilhowee Dam HECRAS Douglas Dam HECHMS Fontana Dam HECHMS Hiwassee Dam HECRAS Norris Dam HECHMS 14

Computational Time Step Use of different model configurations and time steps in the SOCH model can produce reasonable, but different, results.

Downstream impact (BLN & BFN) is greater than upstream impact (SQN & WBN).

Model configuration revised (for BLN & BFN) to allow for an increased time step.

Test simulation with revised model configuration with longer time steps results in the same elevation at WBN and a slightly lower elevation at SQN.

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Revised Configuration Segment 1 (for WBN and SQN)

- No revisions. Limited to 5 second time step due to Fort LoudounTellico Canal.

Segment 2 (for WBN and SQN)

- No revisions. Limited to 5 second time step due to Lick Branch.

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Revisions to Calculations Resulting from Time Step Issue CDQ000020080059 Guntersville UH (49 & 50) Revision 2 due to timestep issue CDQ000020080060 Nickajack UH (47A & 47B) Revision 4 due to timestep issue CDQ000020080064 Chickamauga Local UH (44B & 45) Revision 3 due to timestep issue CDQ000020080039 Chickamauga Calibration Revision 3 CDQ000020080040 Nickajack Calibration Revision 3 CDQ000020080041 Guntersville Calibration Revision 3 Others evaluated, but not changed for WBN and SQN time step:

- CDQ000020080054, CDQ000020080080, CDQ000020080081, CDQ000020080082 17

Geometry Revisions In general, the two main types of changes to geometry are:

- Extension of crosssections because of overtopping during simulations

- Addition or removal of interpolated crosssections for model stability Additional types of changes include:

- Addition of slots in channel bottoms for stability

- Adjustment of Mannings n for stability

- Addition of a channel geometry crosssection in place of a failed dam

- Revision of storage calculation for drain down analysis 18

Revisions to Geometry Differing from those used by PNNL Calculation Geometry Affected Modification CDQ80 Appendices E & F, CDQ82 Extended crosssection to higher Appendix A 15 crosssections elevation.

CDQ80 Fort Loudoun - Tellico Canal 1 foot slot added for stability CDQ80 Appendix B Fort Loudoun - Tellico Canal 14 foot slot added for stability.

Interpolated section between TRM CDQ82 Appendix A 0.3 and 33.6 in Tellico Reservoir Crosssection removed Extended crosssection to higher CDQ80 Appendix A 5 crosssections elevation CDQ80 Appendix A CRM 23.1 Copied crosssection from Lower Clinch Extended crosssection to higher CDQ80 Appendix B 5 crosssections elevation CDQ54 Appendices A, B, H, K, and M Extended crosssection to higher 7 crosssections CDQ80 Appendix B elevation Extended crosssection to higher CDQ82 Appendix A - Fontana Failure 38 crosssections elevation Mannings n value changed for stability CDQ54 RM 2.86 and consistency CDQ54 Appendices E - H and M RM 2.62 Interpolated crosssection removed 19

Revisions to Geometry Differing from those used by PNNL Calculation Geometry Affected Modification Crosssections between TRM 480.5 CDQ54 and 471.0 Removal of interpolated crosssections Mannings n value changed for stability RM 2.86 CDQ80 and consistency CDQ80 RM 2.62 Interpolated crosssection removed Crosssections between TRM 480.5 CDQ80 and 471.0 Removal of interpolated crosssections Mannings n value changed for stability CDQ82 RM 2.86 and consistency Crosssections between TRM 480.5 CDQ82 and 471.0 Removal of interpolated crosssections Extended crosssection to higher CDQ82 30 Crosssections elevation.

Extended crosssection to higher CDQ54 Appendices E, F, and G 5 crosssections elevation.

Extended crosssection to higher CDQ54 Appendices H and M 3 crosssections elevation.

Crosssection revised to include storage CDQ81 3 crosssections available at Lick Branch and North Chickamauga Creek 20

Dam Rating Curve Differences Changes from FSAR to LAR Assumed maximum openings Orifice discharge coefficients Submergence effects

- reference data for spillway free flow used

- model data for orifice flow available HESCO Concertainers Turbine discharge Rim Leaks 21

HESCO Concertainers Cherokee

- North Embankment

- South Embankment

- Three Saddle Dams Fort Loudoun Dam

- South Embankment

- Marina Saddle Dam Tellico Dam

- Saddle Dams 2 and 3

- Right Bank Saddle Dam

- Main Dam Works Watts Bar Dam

- East Embankment 22

Dam Rating Curve Revisions Fort Loudoun Dam Rating Curve - CDQ00002008009 Revision 3 (6/12) - added rim leaks Tellico Dam Rating Curve - CDQ000020080018 -

Revision 2 (7/10) - corrected saddle dam elevation and HESCO barrier elevations Melton Hill Dam Rating Curve - CDQ000020080013 -

Revision 2 (1/10) - corrected turbine shutoff time Watts Bar Dam Rating Curve - CDQ000020080020 -

Revision 3 (12/11) corrected overflow length in East Embankment failure, corrected barrier elevations Revision 4 (6/12) - added rim leaks 23

Dam Rating Curve Revisions Chickamauga Dam Rating Curve - CDQ000020080006

- Revision 2 (6/11) added case for south embankment failure for drain down analysis Nickajack Dam Rating Curve - CDQ000020080014 -

Revision 2 (6/12) - added rim leaks Guntersville Dam Rating Curve - CDQ000020080011

- Revision 3 (6/11) - added case for BFN, no impact to WBN/SQN 24

Lock Gate Failure Flow over the lock gates is accounted for in the dam rating curves Stability of the lock gates evaluated for PMF loading

- Hydrostatic load of the PMF was compared to the design impact load of the lock gate

- Design margin ratios developed for each dam

- No catastrophic failure during a PMF event

- Operability of the gates during and after the event was not considered

• Assumed unavailable during and after the event 25

Fort Loudoun Rim Leak A rim leak was identified at Fort Loudoun Lowest elevation of the rim leak was elevation 835.15 feet PMF elevation is 835.63 feet Impact to PMF is negligible 26

Fort Loudoun Rim Leak 27

Nickajack Rim Leak A rim leak was identified at Nickajack 2,500 feet northeast of the Dam.

Lowest elevation of the rim leak was elevation 654.54 feet PMF elevation is 667.41 feet Impact to PMF is negligible given that Nickajack is a significant distance downstream of Watts Bar and Sequoyah nuclear plants Nickajack is not failed during the analysis of Watts Bar and Sequoyah nuclear plants 28

Nickajack Rim Leak Q max = 2,533cfs 29

Watts Bar Rim Leaks 30

Watts Bar Rim Leak Routing Seven Rim Leaks were identified

- 4 east of the dam

- 3 west of the dam Discharge of rim leaks 16 are combined with Watts Bar Dam discharge for Segment 1 simulations Rim leak 7 was removed at TRM 538.40 for Segment 1 simulations 31

Watts Bar Rim Leak Routing Segment 2 simulations separated the rim leak discharge from the main dam discharge West rim leaks were added as a concentrated local at Yellow Creek at TRM 526.82 without attenuation.

East rim leaks were added as a concentrated local at Watts Creek at TRM 528 without attenuation 32

Watts Bar West Saddle Dam Total failure postulated for West Saddle Dam (consistent with previous model assumption)

Discharge of West Saddle Dam combined with Watts Bar Dam discharge for Segment 1 simulations Segment 2 simulations separated the West Saddle Dam discharge and added it as a concentrated local at Yellow Creek at TRM 526.82 without attenuation.

- Yellow Creek is the natural drainage path

- HECRAS study model for Yellow Creek determined negligible attenuation effect on flow from the West Saddle Dam to the mouth of Yellow Creek.

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Watts Bar West Saddle Dam 34

Dallas Bay Routing Dallas Bay, Lick Branch, and North Chickamauga Creek geometry

- Take advantage of storage in the reaches

- Account for the submergence effects of the rim leak on the Chickamauga Dam tailwater Use SOCH to develop an elevation/discharge relationship at the rim leak Only valid when no failures are postulated at Chickamauga Dam 35

Dallas Bay / Lick Branch Rim Leak 36

Assumptions Assumption FSAR LAR Chickamauga Lock Configuration Current Lock Current Lock Modeled as a rating curve at Dallas Bay/Lick Branch/North Chickamauga Cr Included in the unsteady SOCH model Chickamauga Dam West Saddle Dam Failure Total Failure Total Failure Modeled as a rating curve at Discharge separated as a local in West Saddle Dam Routing Watts Bar Dam Yellow Creek The average tailwater rating Correction for submergence was Correction for Submergence curve used for each event performed for each event HESCO Concertainers Not included Included for PMF simulations Operational Allowances Not included Evaluated for each simulation Rim Leaks at Fort Loudoun, Watts Bar, and Not included Included Nickajack Melton Hill Reservoir Level pool routing Unsteady SOCH model Hiwassee River (mouth to HRM 18.9) Lag routed Unsteady SOCH model Turbine Discharge Evaluated for main river dams Evaluated for all dams with turbines If operating deck was overtopped then Operational Deck/Gate operability Not considered the gates are assumed to be inoperable on the recession side Downstream Dams No failures assumed No failures assumed Loss Method API API Norris Subbasins 4 1 Melton Hill Subbasins 10 1 37