ML021070404

Emergency Core Cooling System (ECCS) Evaluation Model Changes, Annual Notification & Reporting for 2001

ML021070404
Person / Time
Site:	Watts Bar
Issue date:	04/03/2002
From:	Pace P Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML021070404 (6)

Text

Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 APR 0 3 2002 U.S. Nuclear Regulatory Commission 10 CFR 50.46(a) (3) (ii)

ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:

In the Matter of Docket Nos. 50-390 Tennessee Valley Authority WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 - EMERGENCY CORE COOLING SYSTEM (ECCS) EVALUATION MODEL CHANGES - ANNUAL NOTIFICATION AND REPORTING FOR 2001

Reference:

(1) Westinghouse Electric Company letter to TVA (WAT-D-10999),

March 1, 2002, "Watts Bar Nuclear Plant Units 1 and 2, 10 CFR 50.46 Annual Notification and Reporting for 2001."

The purpose of this letter is to provide NRC with the WBN Unit 1 10 CFR 50.46 Annual Notification and Report for 2001. The report notifies NRC of changes or errors discovered in the WBN ECCS evaluation models for peak cladding temperature (PCT) in accordance with 10 CFR 50.46. As detailed in Reference 1, there have been no non-zero PCT changes since TVA's last report (Revised Annual Notification Report for 2000), dated September 7, 2001. As also discussed in Reference 1, the Evaluation Model changes and errors (except plant specific errors in the application of the model) will be reported to the NRC via Westinghouse letter.

Accordingly, only the WBN specific errors are discussed in this report (Enclosure 1). The PCT margin allocations for this report are summarized in Enclosure 2.

b.

Prnted on recycled paper

U.S. Nuclear Regulatory Commission Page 2 APR 0 3 2002 If you should have any questions concerning this matter, please contact me at (423) 365-1824.

Si rely Manager, Licensing and Industry Affairs Enclosure cc (Enclosures):

NRC Resident Inspector Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381 Mr. L. Mark Padovan, Senior 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

1. WBN SPECIFIC - Large Break LOCA Vessel Geometry Input Errors

Background

Several minor geometric errors associated with metal heat slabs and channel volumes in the vessel portion of the WCOBRA/TRAC model of the BELOCA analyses were identified. A list of errors follows:

"* Small error leading to:

Too much lower plenum channel volume (judged conservative)

Too little metal heat slab in the lower plenum

"* Under-specification of vessel wall metal mass in the active core elevation

"* Some lower plenum metal heat slabs being apportioned too thick

"* Hot leg nozzle channel volume several percent off (negligible)

"* Over-specification of lower plenum radial keys metal heat slab volume In the aggregate, the heat slab errors are judged conservative since the net over-specification of metal heat slab will tend to promote lower plenum boiling during reflood.

Estimated Effect Engineering judgment was applied to asses the errors taking into account their relative magnitude and level of importance. The net impact of these vessel geometric errors is judged to be 0°F.

E1-I

ENCLOSURE 2

SUMMARY

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

Westinghouse LOCA Peak Clad Temperature Summary For Best Estimate Large Break Plant Name: Watts Bar Unit 1 Utility Name: Tennessee Valley Authority Revision Date: 2/12/02 Analysis Information EM: WCOBRA/TRAC Analysis Date: 08/98 Limiting Break Size: Guillotine FQ: 2.5 FdH: 1.65 Fuel: Vantage + SGTP 10om 0): pos e Notes: Mixed Core - Vantage + / Performance +

Clad Temp (IF) Ref. Notes LICENSING BASIS 1892 1,2 Analysis-Of-Record PCT MARGIN ALLOCATIONS (Delta PCT)

A. PRIOR PERMANENT ECCS MODEL ASSESSMENTS I Vessel Channel DX Error -4 3 2 . MONTECF Decay Heat Uncertainty Error 4 6 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 C. 2001 PERMANENT ECCS MODEL ASSESSMENTS I. None 0 D. TEMPORARY ECCS MODEL ISSUES*

1. None 0 E. OTHER I. None 0 LICENSING BASIS PCT + MARGIN ALLOCATIONS PCT = 1777

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

References:

I WCAP-l4839, Rev. 1, "Best Estimate Analysis of the Large Break Loss of Coolant Accident for the Watts Bar Nuclear Plant,"

August 1998.

2 WAT-D-10499, "Tennessee Valley Authority Watts Bar Nuclear Plant Units I and 2, 10 CFR 50.46 Annual Notification and Reporting for 1997," February 27, 1998.

3 WAT-D-10618,"Tennessee Valley Authority, Watts Bar Nuclear Plant Units I and 2, 10 CFR 50.46 Annual Notification and Reporting for 1998," March 5, 1999.

4 WAT-D- 10725,"Tennessee Valley Authority, Watts Bar Nuclear Plant Unit I, 10 CFR 50.46 Annual Notification and Reporting for 1999," February 23, 2000.

5 WAT-D-10840, "Tennessee Valley Authority, Watts Bar Nuclear Plant Unit I, Final Deliverables for 1.4% Uprate Program,"

August 31, 2000.

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

Notes:

None Friday, February 22, 2002 Page I of 4

Westinghouse LOCA Peak Clad Temperature Summary For Small Break Plant Name: Watts Bar Unit 1 Utility Name: Tennessee Valley Authority Revision Date: 2/12/02 Analysis Information EM: NOTRUMP Analysis Date: 11/96 Limiting Break Size: 4 inch FQ: 2.5 FdH: 1.65 Fuel: Vantage + SGTP (%): 10 Notes: Mixed Core - Vantage + / Performance +

Clad Temp (IF) Ref. Notes LICENSING BASIS 1126 1,2 Analysis-Of-Record PCT MARGIN ALLOCATIONS (Delta PCT)

A. PRIOR PERMANENT ECCS MODEL ASSESSMENTS I . NOTRUMP Mixture Level Tracking / Region Depletion Errors 13 4 B. PLANNED PLANT CHANGE EVALUATIONS I Annular Blankets 10 3 C. 2001 PERMANENT ECCS MODEL ASSESSMENTS I. None 0 D. TEMPORARY ECCS MODEL ISSUES*

1. None 0 E. OTHER I Tavg Uncertainty of 6 *F I 2 . Temporary SI Leakage to PRT 120 5 (a)

LICENSING BASIS PCT + MARGIN ALLOCATIONS PCT = 1270

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

References:

1. WAT-D-10337, "Tennessee Valley Authority, Watts Bar Nuclear Plant, Final Safety Evaluation 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 Valley Authority, Watts Bar Nuclear Plant Unit 1, 10 CFR 50.46 Annual Notification and Reporting for 1998," March 5, 1999.

4 . WAT-D-10810, "Tennessee Valley Authority, Watts Bar Nuclear Plant Unit 1, 10 CFR 50.46 Appendix K (BART/BASHINOTRUMP) Evaluation Model Mid-Year Notification and Reporting for 2000," June 30, 2000.

5 . WAT-D-10942, "Tennessee Valley Authority, Watts Bar Nuclear Plant Unit 1, Evaluation of Temporary SI Leakage to PRT,"

August 8, 2001.

Notes:

(a) PCT assessment for reduced St flow due to SI leakage to PRT is applicable until the end of Cycle 4.

Friday, February 22, 2002 Page 4 of`4