ML14295A106

October 22, 2014, Meeting Slide for Hydrology License Amendment Requests for Watts Bar Nuclear Plant

ML14295A106
Person / Time
Site:	Watts Bar
Issue date:	10/22/2014
From:	Watts Bar Special Projects Branch
To:	Tennessee Valley Authority
Hon A
References
Download: ML14295A106 (36)

Text

Hydrology License Amendment Requests Watts Bar Nuclear Plant October 22, 2014 1

Hydrologic Calculation Flow Chart 2

Hydrologic Calculation Flow Chart 3

Tennessee River System Watts Bar Nuclear Plant Chattanooga Knoxville Wilson Dam Large and complex river system 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 W tt Bar Watts B Nottely Hiwassee Sequoyah Plant Apalachia Blue Ridge Elk River Chickamauga Nickajack Ocoee 1, 2, 3 Browns Ferry Plant Raccoon Mountain Tims Ford Guntersville D k Ri 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

Main Stem Profile 813 741 682.5 634.5 556 595 507.7 Summer Pool Elevations 414 359 300 NOT TO SCALE 6

Historical Timeline of PMF 1982 - 1997 Feb/March 2008 September 2014 TVA Dam Safety Bellefonte NOV & Hydrology model Watts Bar LAR Modification Program reconstitution project started supplement 1999 & 2001 July & Aug 2012 Watts Bar & Sequoyah WBN & SQN LAR UFSAR change submittal, respectively reflect PMF reevaluation, respectively 1997-1998 Dec 2009 PMF re-evaluated e e a uated HESCO for barriers installed TVA Dam Safety Mods 1979 & 1982 2004 2013-2014 Sequoyah & Watts Bar TVA Reservoir Dam Stabilityy Reports p

Hydrology Analysis Operation Study approved by NRC, completed respectively 7

Model Results WBN

(

(Feet)

)

Original Licensing PMF Elevation 738.1 1998 Calculation PMF Elevation 734.9 2012 LAR PMF Elevation 739.2 2014 LAR HEC-RAS PMF Elevation 738.9 p

2014 LAR Proposed Design g Basis PMF Elevation 739.2 8

Hydrologic Calculation Flow Chart 9

PMP Isohyets for 21,400 Square-Mile Event ((Downstream Placement))

10

PMP Isohyets for 7,980 Square-Mile Event Centered at Bulls Gap, p, TN 11

Seasonal Variations of Rainfall (PMP)

Antecedent Three-Day PMP (in inches) (in inches)

Dry Interval 7,980-sq.mi. 21,400-sq.mi. 7,980-sq.mi. 21,400-sq.mi.

before PMP Month Basin Basin Basin Basin (days)

March 5.97 6.18 3 17.05 16.18 April 5.92 5.92 3 16.91 15.51 May 5.84 5.63 3 16.69 14.74 June 5.73 5.19 3 16.35 13.59 July 4.20 3.57 2-1/2 15.98 12.46 August 4.20 3.62 2-1/2 15.98 12.63 September 4.46 4.12 2-1/2 17.00 14.40 Sources: March - Appendix G, CDQ000020080053 Other values calculated using ratios in HMR-41 Table 7-7 12

Rainfall/Runoff Relationship Development Unchanged from 2012 LAR Rainfall-runoff relationships contained in the API method were developed by the U.S. U S Weather Bureau (USWB) in the 1950s using procedures outlined in Kohler and Linsleys USWB Research Paper No. 34, Predicting the Runoff from Storm Rainfall, 1951.

The relationships were developed from storm and flood records which relate precipitation excess to:

- Basin rainfall

- The week of the year

- Location - API region

- A Antecedent d precipitation i i i iindex d (API) 13

API Background Unchanged from 2012 LAR The Antecedent Precipitation Index (API) method is currently used by TVA River Operations in forecasting and was used by TVA in previous analyses of the Tennessee River system for the TVA Nuclear Power Group.

The API method is currentlyy used byy TVA River Operations to accomplish their federally mandated, integrated operation of the TVA reservoir system which includes flood control responsibilities In CDQ000020080052, the API method was compared d to two industry d standard d d methods.h d 14

Computed API Prior to Main Storm The API for any day is equal to that of the 12 previous day multiplied by 0.9, plus any y rain on that day y

Adopted API prior to antecedent storm, varies API to demonstrate sensitivity 10 Pre ecipitation o or API in Inch hes Computed API prior to main storm, 3.65 inches 8

Computed APIs are same at this point; runoff in main 6 storm not sensitive to adopted p initial moisture conditions beginning of storm 4

2 3-day dry period main storm antecedent storm 1 2 3 4 5 6 7 8 9 10 11 Days 15

Loss Method Comparisons 16

Loss Method Comparisons 17

SRO Hydrograph Development Unchanged from 2012 LAR TVA FLDHYDRO computer code was used to develop surface runoff (SRO) hydrographs for all basins Code used verified unit hydrographs, distributed rainfall, initial API and API region as inputs FLDHYDRO output imported to Excel for processing Baseflow and initial soil moisture conditions were developed from long term TVA gage data 18

Inflow Hydrograph Routing 19

Hydrologic Calculation Flow Chart 20

Geometry Data Original cross sections were extracted from previous models and verified with new data data. Several data sources were used to develop new profiles of the river channels. These include:

Reservoir

- DTM/DEM Data

- Corps of Engineers Bathymetric Survey Tributaries b

- DTM/DEM Data

- Tennessee River Surveyy (TRS)

( ) Maps p

- USGS Topo Maps

- TVA Field Surveys

- FEMA Models 21

Geometry Data 22

HEC-RAS Steady-State Calibration 1973 Flood High g Water Marks 625 615 HEC-RAS 1973 Flood 605 Profile 595 Elevation in Feet above MSL L

585 1973 High-575 Water Marks 565 555 River Bottom 545 River Steady-state model calibrated Bottom Elevation 535 to observed high water marks 525 340 350 360 370 380 390 400 410 420 430 440 450 Tennessee River Mile 23

HEC-RAS Unsteady-State Calibration This process calibrates reaches not influenced by R

Reservoir i Operations O i off the h Dam D

24

HEC-RAS Unsteady-State Calibration Minor differences in headwater elevation using i Discharge Di h as downstream d boundary b d 25

Dam Rating Curves Unchanged from 2012 LAR Changes from FSAR to 2012 LAR Reduced d d maximum i openings i

Orifice discharge coefficients Submergence effects

- reference data for spillway free flow used

- model data for orifice flow available HESCO Concertainers Turbine discharge Rim Leaks 26

Watts Bar Rim Leaks Unchanged from 2012 LAR 27

Dam Rating Curves Changes from 2012 LAR to 2014 LAR Cases added as a result of dam stability calculations Cases added to reflect permanent dam modifications Not all cases were used to support 2014 LAR 28

Flood Operational Guides Unchanged from 2012 LAR Capture reasonable dam operations Simulate those operations in our model R

Review i and d concurrence ffrom Ri River SScheduling h d li (R (RvS)S) of the model dam simulation 29

Flood Operational Guide Curve to DRC Unchanged from 2012 LAR 780 Combined Operating Guide and 770 DRC to simulate how the dam operates during flood events 760 Gates Fully Open Headwatter Elevation (ft) 750 Top of Gates Recovery Mode 740 Recovery y

Mode Elbow 730 Recovery Mode Base Point DRC Curve - Spillway 720 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 Discharge (1000 cfs) 30

Unsteady Flow Rules

• Water surface elevations at appropriate headwater/tailwater sections are extracted at the beginning of each computational time step

• IInternal t lbboundary d average fl flows over th the nextt ti time step are computed as a function of these elevations as prescribed in the FOG & DRC calculations 31

Unsteady Flow Rules Checking Tool 32

Model Setup

• Combine the calibrated reservoirs into a composite HEC RAS model HEC-RAS

• Use of Inline/Lateral structures to connect each reservoir

• Geometry modifications necessary for the composite model are noted in the calculation 33

Assumptions Assumption FSAR 2012 LAR 2014 LAR Chickamauga Lock Current Lock Current Lock Current Lock Configuration Modeled as a Dallas Bay/Lick Included in the rating curve at Included in the unsteady Branch/North unsteady SOCH Chickamauga HEC-RAS model Chickamauga Cr model Dam W t Saddle West S ddl D Dam F Failure il T t l Failure Total F il T t l Failure Total F il T t l Failure Total F il (Lowered (L d to t 752 ffeet) t)

Modeled as a Discharge separated Discharge separated as a local in West Saddle Dam Routing rating curve at as a local in Yellow Yellow Creek Watts Bar Dam Creek The average Correction for Correction for tailwater rating submergence was Correction for submergence was Submergence curve used for performed for each performed for each event each event event HESCO Dam Modifications Not included Included Concertainers Evaluated for each Operational Allowances Not included Evaluated for each simulation simulation Rim Leaks at Fort Loudoun, Watts Bar, and Not included Included Included Nickajack 34

Assumptions Assumption FSAR 2012 LAR 2014 LAR Level pool Unsteady SOCH Melton Hill Reservoir Unsteady HEC-RAS model routing model Hiwassee River (mouth to Unsteady SOCH Lag routed Unsteady HEC-RAS model HRM 18.9) model Main Stem Unsteady Flow SOCH SOCH HEC-RAS Model Tributary Unsteady Flow TRBROUTE TRBROUTE HEC-RAS Model Evaluated for Evaluated for all Evaluated for all dams with Turbine Discharge main river dams dams with turbines turbines If operating deck was overtopped then the If operating deck was overtopped Operational Deck/Gate Not considered gates are assumed to then the gates are assumed to be operability be inoperable on the inoperable on the recession side recession side No failures Downstream Dams No failures assumed No failures assumed assumed Loss Method API API API Norris Subbasins 4 1 1 Melton Hill Subbasins 10 1 1 35

Hydrologic Calculation Flow Chart 36