ML12097A312

3/29/2012 Meeting Slides - Pre-Submittal Meeting Regarding Watts Bar Unit 1 Hydrology Licensing Basis Change

ML12097A312
Person / Time
Site:	Watts Bar
Issue date:	03/29/2012
From:	Tennessee Valley Authority
To:	Lyon C Watts Bar Special Projects Branch
Lyon, Fred
Shared Package
ML12097A293	List: ML12097A306 ML12097A312
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TAC ME8200
Download: ML12097A312 (29)

Text

Tennessee VaUey Authority Pre-Submittal Meeting Watts Bar (WBN) Unit 1 Hydrology Licensing Basis Change March 29, 201 ,2

M Agenda Introductions/Op-e-ning Statements NRC Description of WBN Unit 1 Hydrology License Amendment Request and Schedule TVA Break Open Discussion ALL Public Comment Period ALL Adjourn

1V4; Background WBN Unit 2 sub.mitted FSAR"amendment in January 2010

• WBN Unit 1 License Amendment Request has been prepared based on latest approved calculations and conformance to WBN Unit 2

- Original analysis: PMF elevation 738.1'

- 1998 analysis results: PMF elevation: 734.9'

- 2009 analysis results:. P,M Fel'evation 738.8'

M Hydrology Liceqse Amendment Re

• License Amendment Request describes technical changes to WBN Unit 1 UFSAR Sections 2.4, , -"

2.4.1 , 2.4.2, 2.4.3, 2.4.4, 2.4.11 , and '.'2 .4.14

- Hydrological, Engineering (UFSAR Section 2.4)

• Conforming changes based on detailed "Ghang'e s to other UFSAR 2.4.x sections

- Increased PM F elevation from 734.9' to 738.8'

- Updated results for coincident wind wave activity resulting in wind waves of up to 2.2'

- Updated wind wave run up values for the Diesel Generator Builat critical wall of the Intake Pumping Structure, and walls of the Auxiliary, Control and Shield Buildings

- Updated estimated probable minimum flow past the site 2,000 cfs to 3,200 cfs

]\141 Hydrology License Amendment Re

- Hydrological Description (UFSAR Section 2.4.1)

• Updated-the descriptions of the dams and their associated reservoirs, with updated detention areas and capacities

• Updated figures showing the current reservoir seasonal operating guides I

W41 Hydrology License Amendment ReulH"J?

- Floods (UFSAR: Section 2.4.~2)

• Updated historical flood information used to calibrate the hydrologic models used for the hydrologic analysis

• Updated discussion of impact of increased -PMF and co.incident wind wave activity on Design Basi,s Flood (DBF) elevations for the Diesel Generator Building, Intake Pumping Structure, and Auxiliary, Control and Shield Buildings

IVAI Hydrology License Amendment Re

- PMF (UFSAR S'ection 2.4.3)

• Updated inputs and models for determining PMF, resulting in increase in PMF from elevation 734.9' to 738. 8'

- Updated discussion of the inputs for determining Probable Maximum Precipitation (PMP) using the more recent Hydrometeorological IReport No. 56

- Controlling PMP event changed from a postulated 7,980 square-mile storm to a postulated 21 ,400 square-mile storm

- Updated antecedent precipitation index (API) from a median API, as determined from past records, to an 11-year period of historical rainfall records (1997-2007) at the start of the antecedent storm

- Updated the runoff and stream course model, which is the TVA Simulated Open Channel Hydraulics (SOCH) model for flood routing calculations for the Tennessee River and selected tributaries

1\'4 Hydrology License Amendment R PMF (UFSAR Section 2:4.-3) (cont'd)

• Updated i.np'uts and models for determining PMF (cont'd)

- Updated the runoff and stream course model, which is the TVA Simulated Open Channel Hydraulics (SOCH) model for flood routing calculations for the Tennessee River and selected tributaries

>> Updated the Melton Hill routing to adopt unsteady flow for better refinement for dam seismic failure cases

>> Updated model for main river reservoirs, Tellico, and Melton Hill using unsteady flow techniques and calibrated using profiles computed from the U.S. Army Corps of Engineers (USACE)

River Analysis System (HEC-RAS) software

>> Updated Fort Loudoun-Tellico complex unsteady flow model, and updated verification of the model using May 2003 flood data, instead of March 1973 flood data

!YAl Hydrology License Amendment R

- PMF (UFSAR: S'ection 2.4.3)* (co.nt'd)

• Updated inputs and models for determinin.g PMF (cont'd)

- Updated the runoff and stream course model (cont'd)

>> Updated the French Broad River and Holston River models, including Douglas Dam and Cherokee Dam, and updated verification at two gauged points each using the March 1973 flood and at one point each using the May 2003 flood. Models are also verified by replicating the FEMA published 1DO-year and 500-year flood profiles

>> Updated the Little Tennessee River model, including Tellico Dam, Tellico Reservoir, and Chilhowee Dam

>> Updated the Watts Bar reservoir model, including Clinch River up to Melton Hill Dam

>> Added junction ~t..,. Tennessee River mile 601.1 to Tellico Dam at Little Tennessee River mile 0.3 in the model

Hydrology License Amendment Re PMF (UFSAR 'Section 2.4.3) (c.ont'd)

• Updated inputs and models for determi:niil9 PMF (cont'd)

- Updated the runoff and stream course model (cont'd)

>> Updated the Chickamauga reservoir model, including a junction with the Dallas Bay arm and the Hiwassee River arm, and updated verification using both March 1973 and May 2003 flood data

>> Updated the overall model from use of the TVA standard-step backwater program or USACE HEC-2 software for river hydraulics, to the use of steady-state profiles computed using the USACE HEC-RAS software, using March 1973 and May 2003 flood data for verification

Hydrology License Amendment

- PMF (UFSAR Secti'on 2-..4*.3) (cont'd)

• Updated inputs and models for determining PM.F (cont'd)

- Updated the runoff and stream course model (cont'd)

>> Updated the inputs to the overall model to include turbine discharges in the analysis (main river and tributaries) until head differentials are too small or the respective powerhouse is flooded, and to assume that all gates remain operable without failure

>> Updated median initial reservoir elevations used at the start of the storm sequence as inputs to the model to reflect changes to the reservoir operating guidelines

>> Updated the inputs to the overall model to include increased height of embank-ments using sand baskets to prevent earth embankment overtopping at Fort Loudoun, Cherokee, Tel and Watts Bar

Ml Hydrology Licen~e Amendment Re PMF (UFSAR.*S*ection 2.4.3) (cont'd)

• Updated inputs and models for determining PMF (cont'd)

- Updated the controlling PMF discharge of 1 ,288,000 cfs from a 7,980 square-mile storm centered at Bulls Gap to a PMF discharge of 1 ,065,000 cfs from a 21 ,400 square-mile storm in March with a downstream storm pattern

- Updated the analysis to assume that the West Saddle Dike at Watts Bar Dam is overtopped and breached with the discharge input at the mouth of Yellow Creek, and to assume that Chickamauga Dam is overtopped but not postulated to fail

- Updated the concrete section analysis to evaluate all of the upstream dams instead of just those whose headwater/tailwater comparison were greater than 20%

M Hydrology License Amendment Re PMF (UFSAR Section 2.4.3) (cont'd)

• Updated inputs and models for determining PMF (cont'd)

- Updated the discussion of the Watts Bar Dam spillway gates, as already described in the Watts Bar Unit 2 FSAR

- Added commitment to update the Watts Bar Unit 2 FSAR to include discussions of the impact of waterborne objects on dams already included in the Watts Bar Unit 1 UFSAR

- Added commitment to update the Watts Bar Unit 2 FSAR to include discussions concerning possible failure of the Fort Loudoun, Watts Bar and Chickamauga lock gates already included in the Watts Bar Unit 1 tJFSAR

- Deleted discussion of the potential for embankment breaching and analysis results since no breach is assumed except for failure of the Watts Bar West Saddle Dike previously described 1

Hvdrology License Amendment

- PMF (UFSAR Seqtion*-2.4.3) (cont'd)

• Updated the results of the PMF eval,uation, describing the increase in PMF from elevation 734.9' to 738.8'

• Updated the wind wave and runup elevations (as well as fetch lengths to determine those levels) for safety-related structures, with wind speed kept the same, but fetch lengths changed due to the updated PMF level which therefore increases the wind wave height and runup level

1\'41 Hydrology License Amendment R

- Potential Dam, Failures (UFSAR .Section 2.4.4)

• Updated the analysis of potential se'ismically induced dam fai,lu:res by considering five controlling dam permutations

- Failure of Norris and Tellico Dams for Load Case OBE + 112 PMF

- Failure of Fontana and Tellico Dams for Load Case OBE + 1h PMF

- Failure of Fontana, Tellico, Hiwassee, Apalachia, and Blue Ridge Dams for Load Case OBE + Y2 PMF

- Failure of Cherokee, Douglas, and Tellico Dams for Load Case aBE

+ Y2 PMF

- Failure of Norris, Cherokee, Douglas, and Tellico Dams for Load Case SSE + 25 year flood

1V4' Hydrology License Amendment Re

- Potential Dam*,Failures (UF'S A'R Section 2.4.4)

(cont'd)

• PMF (UFSAR Section 2.4.3) elevations continue to envelope the calculated Potential Dam Failure elevations, the peak water surface elevation at WBN is produced by the controlling combination of failure of Norris, Cherokee, Douglas, and Tellico Dams for Load Case SSE + 25 year flood at elevation 731 .17'

• Updated the analysis to include partial fail-Ure of Fontana Dam postul.ated at a higher elevation dl:J,e 'to modifications of the dam and ad.ditional analysis utilizing finite element analysis

Hvdrology License Amendmen

- Potential Dam Failur.e.s (UFSAR Section 2.4 (cont'd)

• Updated the analysis to include failure ot Tellico Dam for seismic events

• Updated the analysis to use outflow from .Norris, Cherokee Douglas, and Fontana Dams based on USACE Hydrologic Modeling System (HEC-,HMS) software model using a revised dam failure rating curve for Fontana Dam for partia failure at a high.e r elevation, with results validated by comparing results with TVA's TRB'R'OUTE computer code

• Updated the analysis to**develop the outflow hydrogra the case of dams which are postulated to fail com (Hiwassee, Apalachia and Blue Ridge) using Hl:u...' :*

Ml Hydrology License Amendment Re

- Potential Dam* Fai'lures (UF'S AR Section 2.4.4)

(cont'd)

• Analyzed the complete failure of Tellico Dam using the TVA SOCH model

• Updated the analysis to determine failure time and initial reservoir elevations for each dam from a pre-failure TRBROUTE analysis

• Used HEC-HMS to develop the post failure outflow hydrographs based on the previously determined dam failure rating curves I

• Validated the outflow. h.y drographs by comparing the HEC-HMS results with those generated by simulatio using TRBROUTE

lV41 Hydrology License Amendment R

- UFSAR Sections 2.4.5 through 2.4.10, 2.4.12, and 2.4.13

• Included editorial changes only

• Change"d the name of the TVA Water Management Organization to TVA River Operations (RO) to reflect the current organization name

Hvdrology License Amendment -

- Low Water Considerations (UFSAR Section 2.4.11)

• Updated the, probable minimum water level at WBN Unit 1

- Water level at the WBN site upon loss of downstream dam from headwaters at elevation 682.5' begins to drop in 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> and reaches elevation 666.0' ft in 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br />

- Updated the routing model cross-sectional data using new bathymetr~ and recalibration of the models, resulting in ne results

- Required minimum elevation of 666.0' is reached at a later time than original analysis (27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> instead of 22 ho II

~

1\14

--~

Hydrology License Amendment Re~....~

- Low Water Consid'erations (U FSAR Section 2.4.11) (cont'd)

• Updated:the minimum flow requirement at the essential raw cooling water (ERCW) intake r

- Updated flow required to maintain an elevation of 665.9' producing a 5.9 ft depth at the ERCW intake channel from 2,000 cfs to 3,200 cuffs

- Updated historical low water records for WBN Unit 1 at the ERCW intake to include analysis of additional years of record

- Added estimated low flow for the period (1903 - 2010) on the basin above' WBN with the 15 day, "30 day, 50 day and 100 day sustained row flow as 2,907 cfs, 3,158 cfs, 3,473 cfs" an:

4,012 cfs, respectively

1\14, Hydrology License Amendment R

- Flooding Protecti"on RequIrements (UFSAR Section 2.4.,1"4)

• Updated Design Basis Flood (DBF) elev,ations at various, plant locations that would result~for the controlling PMF

- PMF (still reservoir) increased from 734.9' to 738.8'

- DBF runup on 4:1 sloped surfaces increased from 736.9' to 741.2'

- DBF Runup on critical vertical wall of the Intake Pumping Structure increased from 736.9' to 741.0'

- DBF surge level within flooded str~ctures increased from 735.4' to 739.3' .

drology License Amendmen

- Flooding ProtectioOcHequirements (UFSAR Section 2.4.14) (cont'd)

• Updated the flood protection warning plan to reflect revised analysis

- Updated the initial median reservoir levels based on flood operational guides that have been revised, updated dam rating curves at some dams, and updated the SOCH model 0 1 the Tennessee River to meet current quality assurance standards

- For rainfall floods, forecasted levels for issuing Stage I and Stage II warnings are changed to reflect the updated hydrological basis for the warning plan

!VAl Hydrology License Amendment Re

- FI90ding Protection Requirements (UFSAR Section 2.4.14) (cont'd)

• Updated the flood protection warning plan to reflect the revised' analysis (cont'd)

- For seismically induced dam failures and coincident storm conditions, three postulated combinations of seismically induced dam failures are considered

- Updates to the TVA flood forecast system are included to reflect current processes, gage network and forecast procedures

- The forecast procedure is based upon--an analysis of nine of the 17 hypothetical:-:storms up to PMP magnitude judge controlling

~ Hydrology License Amendment R-~

- Flooding Prote,c tio"n Requirements (UFSAR Section 2.4. t'4) (cont'd)

• Updated the flood protection warning plan to reflect the revised analysis (cont'd)

- 27 hours3.125e-4 days <br />0.0075 hours <br />4.464286e-5 weeks <br />1.02735e-5 months <br /> is allowed for preparation of the plant for operation in the flood mode, with an additional 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> for communication and forecasting computations to translate rain on the ground to river elevations at the plant

- 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> of Stage I preparation and an additional 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> for Stage n,i* preparation that is not concurrent with the Stage I activity is required

- Stage I target river elevations are revised to reflect the revis' hydrologic analysis, and no changes to flood protection preparation timing is required

drology License Amendment ~

elusions

- The revised DBF elevation at the WBN:' 'Unit 1. site is determined to not impact any safety-related systems, structures, or components required to be avajlable during' a plant flood

- No physical change to the systems, structures, or components is necessary to ensure that they remain adequately protected from the effects of external floods

- The warning time for WBN shows that there is sufficient time available in both rainfall and seismically induced dam failure floods safe plant shutdown

-The updated low water level analysis. demonstrates that there is sufficient flow to support operations of WBN Unit 1

Hydrology License Amendment act on Plant Safety

- Flood protection of safety-related systems, structures, or compon during external flooding events is assured; however, options to obtain additional margin between the calculated DBF elevation and the limiting elevations of safety-related systems, structures, or components required during a plant flood are being evaluated

- Most limiting component is Thermal Barrier Booster Pump motors, with procedures in place to provide temporary flood barrier protection during Stage I flood preparations resulting in 1.2' of: margin

- The next limiting components are not discussed in License , I Amendment Request, but include the following: .'

• Essential Raw Cooling Water Flow Control Valves, with 0.7' margin to valve centerline and additional margin to air operators and electrical components

• Spent Fuel Pool Cooling Pumps with 0.9' of margin

• Intake Pumping Station with 0.5' of margin

1\'AI Hydrology License Amendment R Status of License Am.endment R'equest preparations

- Submittal and UFSAR change pages have been prepared and reviewed by licensing and technical subject matter experts within TVA

- Plant Operations Review Committee (PORC) and Site Vice-President approvals have been obtained

- Nuclear Safety Review Board (NSRB) review is underway, with answers to comments from NSRB members being prepared

• Schedules

- Submittal of License Amendment Request dependent on NSRB review completion, estimated by April 16, 20,1 2

drology License Amendme

,~.sting Issues Potentially Affecting Review

- Potential Watts Bar ,Reservoir overflow ateas recently discover l

• Estimated impact on PMF of an additional 0.2'

• TVA Problem Evaluation Report (PER) 499217 tracks resolution of this issue

• TVA will update the License Amendment Request within 30 days of approval of th affected calculations if necessary

- Order EA-12-049 related to Fukushima Oai-ichi nuclear power plant

• Continued operation does not pose an imminent risk to public health and safety

• Final Interim Staff Guidance scheduled to be issued by the NRC by August 201

• Submit overall integrated plan to the Commission by February 28, 2013

• Complete full implementation no later than two (2) refueling cycles after subm of the overall integrated plan or December 31 , 2016, whichever comes first

- Chickamauga Lock Modifications

• Estimated completion beyond 2016