ST-HL-AE-5514, Fowards Annual Rept of ECCS Model Revs During 1996

Fowards Annual Rept of ECCS Model Revs During 1996

ML20132B805
Person / Time
Site:	South Texas
Issue date:	12/11/1996
From:	Leazar D HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-5514, NUDOCS 9612170403
Download: ML20132B805 (7)

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t l The Light c o mp a ny South Tesas Project Dectric Enerating Station M. Box 289 Wadsworth, Texas m83 llouston Lighting & Power December 11, 1996 ST-HL-AE-5514 File Nos.: G03.I1 G03.17 M33.02 10CFR50.46 l U. S. Nuclear Regulatory Commission i Attention: Document Control Desk Washington, DC 20555 South Texas Project i Units 1 & 2 l Docket Nos. STN 50-498, STN 50-499 10CFR50.46 Annual Report of Emercency Core Cooling System Model Revisions l

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References:

1) Correspondence from D. A. Leazar to NRC Document Control Desk, i "10CFR50.46 Annual Report of ECC System Model Revisions," dated

December 6,1995 (ST-HL-AE-5247) l

2) WCAP 13451, " Westinghouse Methodology for Implementation of 10 CFR 50.46 Reporting," October 1992 l

3) WCAP 10054 Addendum 2 Revision 1," Addendum to the Westinghouse Small Break ECCS Evaluation Model Using the NOTRUMP Code: Safety Injection Into the Broken Loop and COSI Condensation Model," 1995 l

Pursuant to 10CFR50.46(a)(3)(ii), the South Texas Project submits this annual report I

concerning revisions to the accepted Emergency Core Cooling System evaluation model for South Texas Project Units 1 and 2. No changes were made to the Large Break Loss of Coolant I

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Accident evaluation model during 1996. However, the following revisions have been made to j the Small Break Loss of Coolant Accident evaluation model results:

Previous Small Break Loss of Coolant Accident Peak Cladding Temperature (from Reference 1) 2158 F

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Correction of Typographical Error in NOTRUMP Code + 20 F Correction of SBLOCTA Code Error + 10 F Reduction of the Small Break Loss of Coolant Accident axial offset input from 20% to 13% -30 F New Peak Cladding Temperature 2158 F Project Manager on Behalf of the Participants in the South Texas Project i

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[ n n t- 9612170403 O ADOCK961211 PDR 05000498 P PDR

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Ifouston Lighting & Power Company South Texas Project Electric Generating Station ST-HL-AE-5514 File Nos.: G03.11 G03.17 M33.02 1 Page 2

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The new Peak Cladding Temperature remains below the 10CFR50.46 limit of 2200 F.

t l Consequently, a reanalysis will not be performed.

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Of the changes made in 1996, only the correction of the typographical error in the NOTRUMP code and the SBLOCTA code error correction are' changes to the Small Break Loss of Coolant Accident evaluation model. The 30 F credit assigned to the reduction in the Small Break Loss of Coolant Accident axial offset input from 20% to 13% is not a change to the evaluation model l as defined in WCAP 13451 (Reference 2). The reduction in the Small Break Loss of Coolant-Accident axial offset input is a change in a plant specific input as defined in Item 11 on Page 10 ,

of WCAP 13451. For the South Texas Project, the Large Break Loss of Coolant Accident analysis assumes an axial offset of 13%. The South Texas Project core designs ensure that this limit is not exceeded. The change in the axial offset assumption for the Small Break Loss of Coolant Accident analysis results in assumptions consistent with the Large Break Loss of Coolant  ;

Accident analysis and core design.

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In 1993, Westinghouse identified a 150 F Peak Cladding Temperature benefit for the Small Break Loss of Coolant Accident analysis associated with the COSI improved condensation model. As

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stated in reference 1, the South Texas Project took the conservative position of not taking credit - 1 l for the 150 *F benefit'until NRC approval of the model. Based on limitations identified in the 1 l

Safety Evaluation Report for WCAP 10054 Addendum 2 Revision 1 (Reference 3), the 150 F benefit does not apply to the South Texas Project.

If there are any questions regarding this matter, please contact either Mr. P. L. Walker at (512) 972-8392 or me at (512) 972-7795.

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D. A. Leazar )

Director, '

Nuclear Fuel and Analysis PLW/esh I Attachments: 1. Changes to the Accepted Emergency Core Cooling System Models

, Since the Last 10CFR50.46 Annual Report '

2. Current Large Break and Small Break Loss of Coolant Accident Emergency Core Cooling System Evaluation Model Peak Cladding Temperatures i

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I Houston Lighting & Power Company ST-HL-AE-5514 South Texas Project Electric Generating Station File No.: G03.11 G03.17 M33.02 Page 3 Leonard J. Callan Rufus S. Scott Regional Administrator, Region IV Associate General Counsel U. S. Nuclear Regulatory Commission Houston Lighting & Power Company 611 Ryan Plaza Drive, Suite 400 P. O. Box 61%7 Arlington, TX 76011-8064 Houstort, TX 77208 Thomas W. Alexion Institute of Nuclear Power Project Manager, Mail Code 13H3 Operations - Records Center U. S. Nuclear Regulatory Commission 700 Galleria Parkway Washington, DC 20555-0001 Atlanta, GA 30339-5957 David P. Loveless Dr. Bertram Wolfe Sr. Resident L.spector 15453 Via Vaquero c/o U. S. Nuclear Regulatory Comm. Monte Sereno, CA 95030 P. O. Box 910 Bay City, TX 77404-0910 Richard A. Ratliff Bureau of Radiation Control l J. R. Newman, Esquire Texas Department of Health Morgan, Lewis & Bockius 1100 West 49th Street l 1800 M Street, N.W. Austin, TX 78756-3189 Washington, DC 20036-5869 i J. R. Egan, Esquire M. T. Hardt/W. C. Gunst Egan & Associates, P.C.

City Public Service 2300 N Street, N.W. -

P. O. Box 1771 Washington, D.C. 20037 San Antonio, TX 78296 J. C. Lanier/M. B. Lee U. S. Nuclear Regulatory Commission City of Austin Attention: Document Control Desk '

Electric Utility Department Washington, D.C. 20555-0001 721 Barton Springs Road Austin, TX 78704 Central Power and Light Company J. W. Beck A'ITN: G. E. Vaughn/C. A. Johnson Little Harbor Consultants, Inc.

P. O. Box 289, Mail Code

N5012 44 Nichols Road Wadsworth, TX 77483 Cohassett, MA 02025-1166 l

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! CHANGES TO THE ACCEPTED EMERGENCY CORE COOLING SYSTEM MODELS SINCE THE LAST 10CFR50.46 ANNUAL REPORT l

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CHANGES TO THE ACCEPTED EMERGENCY CORE COOLING SYSTEM MODELS SINCE THE LAST 10CFR50.46 ANNUAL REPORT ,

Since the last 10CFR50.46 annual report (Reference 1), Westinghouse has notified the South ,

l Texas Project of severalitems impacting the results of the Small Break Loss of Coolant Accident l evaluation model. The items impacting the Small Break Loss of Coolant Accident evaluation model results are described below.

l 1) NOTRUMP Specific Energy Error

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Westinghouse discovered a coding error in the NOTRUMP computer code. Westinghouse

corrected the error as a Non-Discretionary Change in- accordance with Section 4.1.2 of WCAP-13451. Correction of the error resulted in a calculated base Peak Cladding Temperature increase of 20 F. This item is a change to the Small Break Loss of Coolant Accident evaluation i model. i 1

2) . SBLOCTA Code Fuel Rod Initialization Error An error was discovered in the SBLOCTA code related to adjustments made as part of the fuel rod initialization process which is used to obtain agreement between the SBLOCTA model and the fuel data supplied from the fuel thermal-hydraulic design calculations at full power, steady state conditions. Specifically, an adjustment to the power, which is made to compensate for E

. adjustments to the assumed pellet diameter, was incorrect, Additionally, updates were made to the fuel rod clad creep and strain model to correct logic errors that could occur in certain transient conditions. These model revisions had a small effect on the fuel rod initialization i process, and could produce small effects during the transient. Due to the small magnitude of the effects, and the interaction between the two items, they were evaluated as a single, closely related effect, in accordance with WCAP 13451. Correction of the error resulted in a calculated base Peak Cladding Temperature increase of 10 F. This item is a change to the Small Break Loss of Coolant Accident evaluation model.

3) Reduction of the Small Break Loss of Coolant Accident Axial Offset Input l Westinghouse reviewed the inputs to the Small Break Loss of Coolant Accident analysis to i

determine if any excessive margin existed. Westinghouse determined that the axial offset input used in the Small Break Loss of Coolant Accident analysis was overly conservative. For the South Texas Project, axial offset is limited by the Large Break Loss of Coolant Accident value of +13%. This parameter is checked for each fuel cycle as part of the reload 10CFR50.59 l, evaluation. The Small Break Loss of Coolant Accident analysis axial offset input was reduced from +20% to +13% for consistency with the South Texas Project core design. We;tinghouse l performed an evaluation and determined that this reduction in the axial offset input from 20%

to 13% results in at least a 30 F reduction in the calculated Small Break Loss of Coolant Accident Peak Cladding Temperature.

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t ATTACHMENT 2 l CURRENT LARGE BREAK AND SMALL BREAK LOSS OF COOLANT ACCIDENT EMERGENCY CORE COOLING SYSTEM EVALUATION MODEL PEAK CLADDING TEMPERATURES 1

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. 1 Attachment 2 ST-HL-AE-5514 Page 1 of 1 i

CURRENT LARGE BREAK AND SMALL BREAK LOSS OF COOL ANT ACCIDENT EMERGENCY CORE COOLING SYSTEM EVALUATION MODEL PEAK CLADDING TEMPERATURES l

The current Emergency Core Cooling System evaluation model Peak Cladding Temperatures are summarized below.

Large Break Loss of Cooline Accident Previous Peak Cladding Temperature Result 2159 F LUCIFER Error Benefit 0F 2159 F Small Break Loss of Cooline Accident Previous Peak Cladding Temperature Result 2158 F Correction of Typographical Error in NOTRUMP Code + 20 F Correction of SBLOCTA Code Error + 10 F Reduction of the Small Break Loss of Coolant Accident

' Axial Offset Input from 20% to 13% -30 F l

2158 F l I

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