ML051120164

Emergency Core Cooling System (ECCS) Evaluation Model Changes - Annual Notification and Reporting for 2004

ML051120164
Person / Time
Site:	Watts Bar
Issue date:	04/19/2005
From:	Pace P Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML051120164 (15)

Text

Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 APR 1 9 2005 10 CFR 50.46 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Gentlemen:

In the Matter of the

)

Docket No. 50-390 Tennessee Valley Authority

)

WATTS BAR NUCLEAR PLANT (WBN) UNIT I - EMERGENCY CORE COOLING SYSTEM (ECCS) EVALUATION MODEL CHANGES - ANNUAL NOTIFICATION AND REPORTING FOR 2004

Reference:

1. TVA letter to NRC dated April 19, 2004, "WBN Unit 1 - Emergency Core Cooling System (ECCS) Evaluation Model Changes - 30 Day Report and Revised Annual Notification and Reporting for 2003" This letter provides information that fulfils the annual reporting requirements of 10 CFR 50.46. The enclosed information addresses changes or errors in the WBN ECCS evaluation model that affect the calculation of peak cladding temperature (PCT). WBN's ECCS evaluation model is contractually maintained by Westinghouse Electric Corporation and the last 10 CFR 50.46 report for WBN was submitted in a letter dated April 19, 2004. The changes to the model that have been made since that time are described in Enclosure 1 and are based on information provided by Westinghouse in a letter dated April 6, 2005.

A DC)

U.S. Nuclear Regulatory Commission Page 2 APR 19 2005 The PCT margin allocations resulting from the changes listed in Enclosure 1 are summarized in Enclosure 2. The PCT change since the submittal of the 2003 report (referenced above) is listed below:

LOCA PCT Summary for Best Estimate Large Break 2003 Report 2004 Report Change in PCT I Composite 17850F 17900F 50F Reflood 1 17630F 17680F 50F Reflood 2 17850F 17900F 5OF LOCA PCT Summary for Small Break 11 850F 11850F 00F There are no regulatory commitments in this letter. Should there be questions regarding the information provided in this letter, please call me at (423) 365-1824.

P. L. Pace Manager, Site Licensing and Industry Affairs Enclosures

1.

Description of Changes which affect WBN's Emergency Core Cooling System Evaluation Model(s) and its Calculation of Peak Cladding Temperature

2.

Summary of Peak Cladding Temperature Margin Allocations Resulting from Changes to the Emergency Core Cooling System Evaluation Model cc: See Page 3

U.S. Nuclear Regulatory Commission Page 3 APR 19 2005 Enclosures cc (Enclosures):

NRC Resident Inspector Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381 Mr. D. V. Pickett, Project Manager U.S. Nuclear Regulatory Commission MS 08G9 One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738 U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303

ENCLOSURE 1 DESCRIPTION OF CHANGES WHICH AFFECT WBN'S EMERGENCY CORE COOLING SYSTEM EVALUATION MODEL(S) AND ITS CALCULATION OF PEAK CLADDING TEMPERATURE REVISED BLOWDOWN HEATUP UNCERTAINTY DISTRIBUTION

Background:

Correction of modeling inconsistencies and input errors in the LOFT input decks have resulted in a change in the predicted peak cladding temperature transients. Revised analyses of the LOFT and ORNL tests were performed using the current version of WCOBRA/TRAC. As a result of this re-analysis, revised blowdown heatup heat transfer coefficients were developed and the revised cumulative distribution function (CDF) was programmed into a new version of HOTSPOT. The revised CDF was previously reported to the NRC in LTR-NRC-04-1 1. The overall code uncertainty for blowdown was also recalculated and programmed into a new version of MONTECF. The overall code uncertainty for reflood was not affected. These corrections were determined to be Non-Discretionary changes in accordance with Section 4.1.2 of WCAP-1 3451.

Affected Evaluation Models:

1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model.

1999 Westinghouse Best Estimate Large Break LOCA Evaluation Model, Application to PWRs with Upper Plenum Injection.

2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM.

Estimated Effect:

An estimate of the PCT effect of the revised blowdown heatup CDF was performed for the 1996 and 1999 Evaluation Models by calculating the impact on the reference transient for representative 2-, 3-and 4-loop plants. The estimates bound all of the 95th percentile HOTSPOT results.

Estimates of the effect of the revised overall code uncertainty for blowdown were made on a plant-specific basis by repeating the MONTECF analysis, for those plants that track the blowdown period.

The revised blowdown heatup heat transfer multipliers have been and will be used for all analyses based on the 2004 ASTRUM Evaluation Model.

Therefore, no PCT assessments are necessary for those plants.

E1-1

2.

GENERAL CODE MAINTENANCE (NOTRUMP)

Background:

Various changes in code input and output format have been made to enhance usability and help preclude errors in analyses. This includes both input changes (e.g., more relevant input variables defined and more common input values used as defaults) and input diagnostics designed to preclude unreasonable values from being used, as well as various changes to code output which have no effect on calculated results. In addition, various updates were made to eliminate inactive coding, improve active coding, and enhance commenting, both for enhanced usability and to facilitate code debugging when necessary. These changes represent Discretionary Changes that will be implemented on a forward-fit basis in accordance with Section 4.1.1 of WCAP-13451.

Affected Evaluation Models:

1981 Westinghouse Large Break LOCA Evaluation Model with BASH.

1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMP.

Estimated Effect:

The nature of these changes leads to an estimated PCT impact of 00 F.

3.

IMPLEMENTATION OF ASTRUM CAPABILITY IN HOTSPOT

Background:

The HOTSPOT code was modified to be compatible with the Automated Statistical Treatment of Uncertainty Methodology (ASTRUM, described in WCAP-1 6009-P-A). An option is used to trigger the ASTRUM HOTSPOT technique (single iteration mode) or the Monte Carlo mode used in the previous Best Estimate Large Break LOCA evaluation models. These changes were considered to be Discretionary changes in accordance with Section 4.1.1 of WCAP-13451.

Affected Evaluation Models:

1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model.

1999 Westinghouse Best Estimate Large Break LOCA Evaluation Model, Application to PWRs with Upper Plenum Injection.

E1-2

Estimated Effect:

None of these changes affect the results of design basis analyses performed with these evaluation models. Therefore, the estimated effect is zero.

4.

GENERAL CODE MAINTENANCE (WC/T)

Background:

A number of coding changes were made as part of normal code maintenance. Examples include correction of debug plots not used in design analyses, and improved consistency between the HOTSPOT nominal PCT (not used in the uncertainty analysis) and WCOBRA/TRAC PCT. All of these changes are considered to be Discretionary changes in accordance with Section 4.1.1 of WCAP-13451.

Affected Evaluation Models:

1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model.

1999 Westinghouse Best Estimate Large Break LOCA Evaluation Model, Application to PWRs with Upper Plenum Injection.

2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM.

Estimated Effect:

None of these changes affect the results of design basis analyses.

Therefore, the estimated effect is zero.

5.

IMPROVED AUTOMATION OF END OF BLOWDOWN TIME

Background:

Heat transfer multipliers are considered in the uncertainty methodology as a function of the time period in the transient. The blowdown cooling heat transfer multipliers are applied during the time period following turnaround of the blowdown heatup through the end of blowdown. For simplicity, the end of blowdown was originally defined as the time when the system pressure dropped below 40 psia. In cases where the pressure did not drop below 40 psia, the analyst would manually redefine the end of blowdown E1-3

based on the time of minimum system pressure. The automated selection of the end of blowdown time was improved by replacing the 40 psia criterion with a selection based on the time at which the system pressure stops decreasing. All of these changes are considered to be Discretionary changes in accordance with Section 4.1.1 of WCAP-13451.

Affected Evaluation Models:

1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 1999 Westinghouse Best Estimate Large Break LOCA Evaluation Model, Application to PWRs with Upper Plenum Injection 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect:

The correct end of blowdown time was selected in all prior analyses.

Therefore, the estimated effect is zero.

E1-4

ENCLOSURE 2

SUMMARY

OF PEAK CLADDING TEMPERATURE MARGIN ALLOCATIONS RESULTING FROM CHANGES TO THE EMERGENCY CORE COOLING SYSTEM EVALUATION MODEL E2-1

- PCI' Sheets Our ref: WAT-D-1 1334 April 6, 2005 W*estinglhouse LOCA Peak Clad Temperature Summary for Best Estimate Large Break Plant Name:

Watts Bar Unit I Utility Name:

Tennessee Valley Authority Revision Date:

414105 Composite Analvsis Information EM:

WCOBRA/TRAC Analysis Date:

8/1198 Limiting Break Size: Guillotine FQ:

2.5 Fdll:

1.65 Fuel:

Vantage +

SGTP (%):

10 Notes:

Mixed Core -Vantage + I Performance + / RFA-2 Clad Temp (0F)

Ref.

Notes LICENSING BASIS Analysis-Of-Record PCT 1892 1,2 MARGIN ALLOCATIONS (Delta PCI')

A. PRIOR PERMANENT ECCS MODEL ASSESSMENTS I VesselCbannelDXError 4

3 2. MONTECFDecaylleatUnccrtaintyError 4

6 3. Input Error Resulting in Incornplete Solution Matrix 0

7 4. Tavg BiasError 8

7 B. PLANNED PLANT CHANGE EVALUATIONS I. Accumulator Line/Pressurizer Surge Line Data Evaluation

-131 4

2. Increased Accurnulator Temperature Range Evaluation 4

5 3. 1.4% Uprate Evaluation 12 5

4. Increased Stroke Timc forthe ECCS Valves 0

9 C. 2004 PERMANENT ECCS MODEL ASSESSMENTS I

Revised Blowdown Heatup Uncertainty Distribution 5

8 D. TEMPORARY ECCS MODEL ISSUES*

I. None 0

E. OTHER I. None 0

LICENSING BASIS PCT + MARGIN ALLOCATIONS PCa =

1790 It is recomnmended that these temporary PCT allocations which address current LOCA model issues not be considered with respect to 10 CFR 50A6 reporting requirements.

References:

I. WCAP-14839, Rev. 1. "Best Estirate Analysis of the Large Break Loss of Coolant Accident for the Watts Bar Nuclear Plant," August 1998.

2. WAT-D-10499. "Tennessee Valey AuthorityWatts Bar Nuclear Plant Units Iand 2, 10 CFR 50.46 Annual Notification and Reporting for 1997," February27. 1998.

3. WAT-D-10618,"Tcnnessec Valley Authority, Watts Bar Nuclear Plant Units I and 2. 10 CFR 50A6 Annual Notification and Reporting for 1998." March 5, 1999.

4. WAT.D-10725,"Tennessee Valley Authority, Watts Bar Nuclear Plant Unit 1, 10 CFR 50A6 Annual Notification and Reporting for 1999," February 23,2000.

A BNFL Group company

- PCTr Sheets Our ref: WAT-D-1 1334 April 6,2005 Westinghouse LO CA Peak Clad Temperature Summary for Best Estimate Large Break Plant Naame:

Watts Bar Unit 1 Utility N'ame:

Tennessee Valley Authority Re,%,ion Date:

4/4105 Composite 5

WAT-D-10840, Tennessee Valley Authority, Watts Bar Nuclear Plant Unit.Final Dcliverables for.4% Uprate Program," August 31.2000.

6. WAT-D-10904. '10 CFR 50.46 Annual Notification and Reporting for 2000," February 2001.

7. WAT-D-11225, "10 CFR 5046 Annual Notiication and Reporting for 2003," March 2004.

8. WAT-D-11334, "10 CFR 50.46 Annual Notification and Reporting for 2004," March 2005.

9 WAT-D-11285, "Evaluation of Proposed Changes to die Stroke Time for the ECCS Valvcs," Novcmber 2004.

Notes:

None A BNFL Group company

- PCT Sheets Our ref: WAT-D-11334 April 6,2005 Westinghoiiue LO CA Peak Clad Temperature Sunmiary for Best Estimate Large Break Plant Name:

Watts Bar Unit 1 Utility Name:

Tennessee Valley Authority Reiision Date:

4/4/05 Reflood 1 Analvsis Infor7nation EMN:

WCOBRA/TRAC Analysis Date:

8/1/98 Limiting Brenk Size: Guillotine FQ:

2.5 Fdll:

1.65 Fuel:

Vantage+

SGTP (%):

10 Notes:

Mixed Core - Vantage + I Performance + / RFA-2 Clad Temp (°F)

Ref.

Notes LICENSING BASIS Analysis-Of-Record PCT 1656 1,2 MARGIN ALLOCATIONS (Delta PCT)

A. PRIOR PERMANENT ECCS MODEL ASSESSMENTS I. Vessel Channel DXError 56 3

2. M IONTECF DeayHeat UncertaintyError 4

5 3. Input Error Resulting in Incomplete Solution Matrix 60 6

4.Tavg Bias Error 8

6 B. PLANNED PLANT CHANGE EVALUATIONS I. Accumnulator Line/Pressurizer Surge Line Data Evaluation

-37 4

2. IncreasedAccunsulatorTenperatureRangeEvaluation 4

4 3.1.4% Uprate Evaluation 12 4

4. IncreasedStrokeTimefortlieECCS Valves 0

8 C. 2004 PERMANMENT ECCS MODEL ASSESSMENTS 1. Revised Blowdown lleatup Uncertainty Distribution 5

7 D. TEMI PORARY ECCS MODEL ISSUES*

I. None 0

E. OTIIER I. None 0

LICENSING BASIS PCT + MARGIN ALLOCATIONS PCT =

1768 It is recommended that these temporary PCT allocations which address current LOCA nrodel issues not be considered with respect to 10 CFR 50.46 reporting requirements.

Retcrences:

I WCAP-14839, Rev. 1, flest Estimate Analysis of the Large Break Loss of Coolant Accident for the.atts Bar Nuclear Plant," August 1998.

2. WAT-D-10499, "Tennessee Valey Authorityl attsBar Nuclear Plant UnitS I and 2,10 CFR50.46 Annual Notirication and Reporting for 1997." February 27. 1998.

3. WAT-D-10618."Tennessee Valley Authority. lWattsBar NuclcarPlant Units 1 and 2, 10 CFR 50A6 Annual Notirication and Reporting for 1998." March 5. 1999.

4. WAT-D-10840,"Tennessee Valley Authority,.WattsBar NuclearPlant Unit l.Final Deliverables for 1A% Uprate Program." August 31.2000.

A BNFL Group company

- PCT Sheets Our ref: WAT-D-1 1334 April 6, 2005 Westingliouse LOCA Peak Clad Tcmperaturc Summary for Best Estimate Large Break Plant Name:

Watts Bar Unit I Utility Name:

Tennessee Valley Authority Revision Date:

4 /4/05 Reflood 1 5

WAT-D-10904, "10 CFR 50.46 Annual Notification and Reporting for 2000." February 2001.

6 WAT-D-11225, "10 CFR 50.46 Annual Notification and Reporting for 2003." March 2004.

7 W.'AT-D-11334, "10 CFR 50.46 Annua Notification and Reporting for 2004," March 2005.

8 WAT-D-11285. "Evaluation of Proposed Clanges to the Stroke Time for the ECCS Valves," Noventer 2004.

Notes:

None A BNFL Group company

- PCT Sheets Our ref: WAT-D-1 1334 April 6,2005 Westinghouse LO CA Peak Clad Temperature Sununary for Best Estimate Large Break Plant Name:

Watts Bar Unit I Utility Name:

Tennessee Valley Authority Revision Date:

4 /4105 Reflood 2 Analvsiv Infonnation ENM:

WCOBRAtlRAC Analysis Date:

8/1/98 Limiting Break Size: Guillotine FQ:

2.5 Fdll:

1.65 Fuel:

Vantage +

SGTP (%):

10 Notes:

Mixed Core - Vantage + / Performance + / RFA-2 Clad Temp ('IF)

Ref.

Notes LICENSING BASIS Analysis-Of-Record PCT 1892 1,2 MARGIN ALLOCATIONS (Delta PCT)

A. PRIOR PE RMANENT ECCS MODEL ASSESSNIENTS I. Vessel ChannelDXError

-4 3

2. IO.NTECF Decay Heat UncertaintyError 4

6 3. Input Error Resulting in Incomplete Solution Matrix 0

7 4. Tavg Bias Error 8

7 B. PLANNED PLANT CHANGE EVALUATIONS I. Accumulator Line/Pressurizer Surge Line Data Evaluation

-131 4

2. Increased Accumulator Temperature Range Evaluation 4

5 3. 1.4% Uprate Evaluation 12 5

4. Increased Stroke Time for the ECCS Valves 0

9 C. 2004 PERNMANENT ECCS MODEL ASSESSMENTS I.RevisedBlowdownileatupUncertaintyDistribution 5

8 D. TEMPORARY ECCS MODEL ISSUES*

I. None 0

E. OTHER

1. None 0

LICENSING BASIS PCT + MARGIN ALLOCATIONS PCT =

1790 It is recommended that these tenporary PCT allocations which address current LOCA rnodel issues not be considered with respect to 10 CFR 50.46 reporting requirements.

References:

I. WCAP-14839, Rev. 1. 'Best Estirnte Analysis of the Large Break Loss of Coolant Accident for the Watts Bar Nuclear Plant," August 1998.

2. NVAT-D-10499. "Tennessce Valley Authority WVatts Bar Nuclear Plant Units 1 and 2. 10 CFR 50.46 Annual Notification and Reporting for 1997," February 27, 1998.

3. WAT-D-10618,"Tennessce Valley Authority, WattsBar Nuclear PlantUnits land 2,10 CFR50A6 Annual Notirication and Reporting for 1998." Marcl 5,1999.

4. WAT-D-10725,"Tennessee Valley Authority, Watts Bar Nuclear Plant Unit 1, 10 CFR 50A6 Annual Notification and Reporting for 1999," February 23, 2000.

A BNFL Group company

- PCT Sheets Our ref: WAT-D-1 1334 April 6, 2005 Westinghouse LOCA Peak Clad Temperature Sununary ror Best Estimate Largc Break Plant Namc:

Watts Bar Unit 1 Utility Name:

Tennessee Valley Authority Rcvision Date:

4/4/05 Reflood 2 5 WAT-D-10840. Tennessec Vallcy Authority,WattsBar Nuclear PlantUnit l,Final Delivcrables for.4% Uprate Program'" August 31,2000.

6.WAT-D-10904. "10 CFR 50.46 Annual Notirication and Reporting for 2000," February 2001.

7.WAT-D-1 1225, '10 CFR 50.46 Annual Notification and Reporting for 2003,' Mlard 2004.

8.WAT-D-1 1334. "10 CFR 50.46 Annual Notification and Reporting forr 2004. lard 2005.

9. WAT-D-11285, "Evaluation of Proposed Ciangesto the Stroke Tine for the ECCS Valves,' Novenbr 2004.

Notes:

None A BNFL Group company

- PCT Sheets Our ref: W'AT-D-1 1334 April 6,2005 Westinghouse LO CA Peak Clad Temperature Summary for Small Break Plant Name:

Watts Bar Unit I Utility Name:

Tennessee Valley Authority Revision Date:

4 /4/05 Annlvsis Information EM:

NOTRUMP Analysis Date:

1111/96 Limiting Break Size: 4 inch FQ:

2.5 Fdll:

1.65 Fuel:

Vantage+

SGTP(%):

10 Notes:

Mixed Core - Vantage + / Performance + / RFA-2 Clad Tenmp (°;)

Ref.

Notes LICENSING BASIS Analysis-Of-Record PCT MARGIN ALLOCATIONS (Delta PCT)

A. PRIOR PERNIANENT ECCS MODEL ASSESSMENTS 1. NOTRUMP Mixture Level Tracking /RegionDepletion Errors 2. NOTRUMP BubbleRise/DrifFlxux Modcl Inconsistency Corrections B. PLANNE-D PLANT CHANGE EVALUATIONS I

Annular Blankets 2. Increased Stroke Time for the ECCS Valves C. 2004 PERNIANENT ECCS MODEL ASSESSMENTS I

None D. TEMPORARY ECCS MODEL ISSUES*

I None E. OTIIER I. Tavg Uncertainty of 6 IF 1126 1,2 13 4

35 5

10 3

0 6

0 0

LICENSING BASIS PCT + MARGIN ALLOCATIONS PCT =

1185 It is recomnmended that these temporary PCT allocations which address current LOCA modcl issues not be considered with respect to 10 CFR 50.46 reporting requirements.

References:

I.WVAT-D-10337, "Tennessee Valey AuthorityWatts Bar NuclearPlant. Final SafetyEvaluation to Support Technical Specification Changes," March 5, 1997.

2. WAT-D-10356, "Tennessee Valley Authority. Watts Bar Nuclear Plant Units I & 2. Final Report and Safety Evaluation for the 10% SGTP Program," June 2. 1997.

3. WAT-D-10618, "Tennessee Valle AuthorityWatts Bar Nuclear Plant Unit 1,10 CFR 50.46 Annual Notification and Reporting for 1998," March 5. 1999.

4. WAT-D-10S10, "Tennesscc Valley Authority, WattsBarNuclearPlant Unit 1,10 CFR 50.46 Appcndix K (BARTIBASII/NOTRUMP) Evaluation Model Mid-Year Notification and Reporting for 2000." June 30,2000.

5. VAT-D-I 1195. "10 CFR 50.46 Mid-Year Notification and Reporting for 2003." Novcnber 2003.

6. WAT-D-1 1285, "Evaluation of Proposed Changes to the Stroke Time for the ECCS Valves," November 2004.

Notes:

None A BNFL Group company