ML18153A033

Provides Info Re Changes to ECCS Evaluation Models & Application in Existing Licensing Analyses

ML18153A033
Person / Time
Site:	Surry, North Anna
Issue date:	08/01/1996
From:	Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
96-390, NUDOCS 9608050263
Download: ML18153A033 (11)

Text

e e VIRGINIA ELECTRIC AND POWER COMPANY RICHM:OND, VIRGINIA 23261 August 1, 1996 United States Nuclear Regulatory Commission Serial No.96-390 Attention: Document Control Desk NL&OS/MAE Washington, D.C. 20555 Docket Nos. 50-338/339 50-280/281 License Nos. NPF-4/7 DPR-32/37 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA AND SURRY POWER STATIONS UNITS 1 AND 2 REPORT OF ECCS EVALUATION MODEL CHANGES AND 30-DAY REPORT OF ECCS EVALUATION MODEL CHANGES PER REQUIREMENTS OF 1 OCFRS0.46 Pursuant to 10CFR50.46(a)(3)(ii) Virginia Electric and Power Company is providing information concerning changes to the ECCS Evaluation Models and their application in existing licensing analyses. Information is also provided which quantifies the effect of these changes upon reported results for North Anna and Surry Power Stations, and demonstrates continued compliance with the acceptance criteria of 10CFR50.46.

Attachment 1 contains excerpted portions of Westinghouse reports describing the changes to the Westinghouse ECCS Evaluation Models which are applicable to North Anna and Surry.

Information regarding the effect of the ECCS Evaluation Model changes upon the reported LOCA analysis of record (AOR) results is provided for the North Anna and

.Surry Power Stations .in Attachments 2 and 3, respectively. To summarize the information in Attachments 2 and 3, the calculated PCT for the small and large break LOCA analyses for North Anna and Surry are given below. Results which represent significant changes, based on the criterion established in 10CFR50.46(a)(3)(i), are designated with an asterisk.

North Anna Units 1 and 2 - Small break: 1675°F (*)

North Anna Units 1 and 2 - Large break: 2053°F Surry,Units 1 and 2 - Small break: 1813°F (*)

Surry Units 1 and 2 - Large break: 2098°F We have evaluated these issues and the associated changes in the applicable licensing basis PCT results. These results demonstrate compliance with the requirements of 10CFR50.46(b). Although the North Anna and Surry small break LOCA changes described in Attachment 2 and 3 are significant, as defined in 10CFR50.46(a}(3)(i), the licensing basis PCT results have adequate margin. {\D o\

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10CFR50.46(a)(3)(ii) requires that the 30-day report include a proposed schedule for providing a reanalysis or that other action be taken as may* be needed to show compliance with 10CFR50.46 requirements. A reanalysis of the small break LOCA accident for Surry Units 1 and 2 is scheduled to be completed by the end of the fourth quarter 1996. However, a reanalysis of the small break LOCA accident for North Anna Units 1 and 2 is not scheduled at this time. A reanalysis of this accident was recently performed for North Anna and documented in our letter of November 29, 1995 (Serial No.95-608). Furthermore, the effect of the reported errors for the small break LOCA

. results in a net. benefit in PCT .margin .. As stated above, the licensing basis PCT results comply with the requirements of 10CFR50.46(b). No further action is required to demonstrate compliance with 10CFR50.46 requirements.

If you have further questions or require additional information, please contact us.

Very truly yours,

~P.o,J-~

James. P. O'Hanlon Senior Vice President - Nuclear cc: Regional Administrator U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, N.W.

Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station Mr. R. D. McWhorter NRC Senior Resident Inspector North Anna Power Station Attachments:

1) Westinghouse Report of ECCS Evaluation Model Changes - North Anna Units 1 and 2 and Surry Units 1 and 2

2) Effect of ECCS Evaluation Model Changes - North Anna Units 1 and 2

3) Effect of ECCS Evaluation Model Changes - Surry Units 1 and 2

e ATTACHMENT 1 WESTINGHOUSE REPORT OF ECCS EVALUATION MODEL CHANGES NORTH ANNA UNITS 1 AND 2 AND SURRY UNITS 1 AND 2

SBLOCTA FUEL ROD INmALIZATION

Background

An error was discovered in the SBLOCTA code related to adjustments which are 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 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 also had a small affect on the fuel rod initialization process, and can produce small affects during the transient.

Due to the small magnitude of affects, and the interaction between the two items, they are being evaluated as a single, closely related affect.

Affected Evaluation Models 1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMP Estimated Effects Representative plant calculations with the corrected model demonstrated that these revisions result in a predicted peak clad temperature increase on the order of +10 °P. This 10 °P penalty will therefore be assessed against all existing analyses of record with the above model.

e LOOP SEAL ELEVATION ERROR

Background

An error was discovered in raw plant geometric data that supports input to the Evaluation Model codes. The erroneous_ datum was a term associated with the relative elevation of tQe crossover leg.

Affected Evaluation Models 1985 Westinghouse Small Break LOCA Evaluation Model Using NOTRUMP 1981 Westinghouse Large Break LOCA Evaluation Model 1981 Westinghouse Large Break LOCA Evaluation Model Using BART 1981 Westinghouse Large Break LOCA Evaluation Model Using BASH Estimated Effects The erroneous elevation terms are estimated to have ~ negligible effect on Large Break LOCA Evaluation Model*

calculations. Representative sensitivity calculations with NOTRUMP have determined that a non-significant PCT effect is to be expected due to the influence of the erroneous elevation on the loop seal clearing process. PCT 'effects ranging from -44 °F to + 24 °F have been assigned to affected plants depending on the magnitude and direction of the error.

e ATTACHMENT 2 EFFECT OF ECCS EVALUATION MODEL CHANGES NORTH ANNA UNITS 1 AND 2

Effect of ECCS Evaluation Model Changes - North Anna The information provided herein is applicable to North Anna Power Station, Units 1 and 2. It is based upon reports from Westinghouse Electric Corporation for issues involving the ECCS evaluation models and plant-specific application of the models in the existing analyses. Peak cladding temperature (PCT) values and margin allocations represent issues for which permanent resolutions have been implemented.

The assessments for small break and large break LOCA are presented in Sections A and B, respectively.

Section A - Small Break LOCA Margin Utilization - North Anna Units 1 and 2 A. PCT for Analysis of Record 1704°F (1)

B. Prior PCT Assessments Allocated to AOR 0°F SBLOCA Augmented PCT for AOR 1704°F C. PCT Assessments for 10CFR50.46(a)(3)(i) Accumulation {1} 89°F

1. NOTRUMP Specific Enthalpy Error +20°F(2}

2. SALIBRARY Double Precision Errors -15°F(2)

3. Fuel Rod Initialization Error {2} {3} +10°F

4. Loop Seal Elevation Error {2} {3} -44°F SBLOCA Licensing Basis PCT (AOR PCT+ PCT Assessments) 1675°F Section B - Large Break LOCA Margin Utilization - North Anna Units 1 and 2 A. PCT for Analysis of Record 2013°F(1)

B. Prior PCT Assessments Allocated to AOR 40°F

1. LBLOCA/Seismic SG Tube Collapse +30°F(1)

2. BASH Accumulator Empty Flag +10°F(1)

LBLOCA Augmented PCT for AOR 2053°F C. PCT Assessments for 10CFR50.46(a}(3)(i) Accumulation LBLOCA Licensing Basis PCT (AOR PCT+ PCT Assessments) 2053°F Notes { } and References ( ) on the following page

e Effect of ECCS Evaluation Model Changes - North Anna Notes:

{1} The accumulation of changes (sum of absolute magnitudes) exceeds 50°F and is

, significant, as defined in 10CFR50.46(a)(3)(i).

{2} The current report is the initial quantification of effects for this issue.

{3} Refer to the Westinghouse Report of ECCS Evaluation Model Changes provided in Attachment 1. Westinghouse has determined that a 44°F benefit is applicable to North Anna.

References:

(1) Letter from J. P. O'Hanlon (VEPCO) to Document Control Desk (USN RC),

"Virginia Electric and Power Company, North Anna Power Station Units 1 and 2, 30-Day Report of ECCS Evaluation Model Changes Per Requirements of 10CFR50.46," Serial No.95-608, November 29, 1995.

(2) Letter from J. P. O'Hanlon (Va. Electric & Power Co.) to USNRC, "Virginia Electric and Power Company, North Anna and Surry Power Station Units 1 and 2, Report of ECCS Evaluation Model Changes and 30-Day Report of ECCS Evaluation Model Changes Per Requirements of 10CFR50.46," Serial No.96-111, March 14, 1996.

ATTACHMENT 3 EFFECT OF ECCS EVALUATION MODEL CHANGES SURRY UNITS 1 AND 2

e e Effect of Westinghouse ECCS Evaluation Model Changes - Surry The information provided herein is applicable to Surry Power Station, Units 1 and 2. It is based upon reports from Westinghouse Electric Corporation for issues involving the ECCS evaluation models and plant-specific application of the models in the existing analyses. Peak cladding temperature (PCT) values and margin allocations represent issues for which permanent resolutions have been implemented. The assessments for small break and large break LOCA are presented in Sections A and B, respectively.

Section A - Small Break LOCA Margin Utilization - Surry Units 1 and 2 A. PCT for Analysis of Record (AOR) 1852°F (1)

B. Prior PCT Assessments Allocated to AOR -5°F

1. Safety Injection in the Broken Loop (NOTRUMP) Q°F (2)

2. NOTRUMP Drift Flux Flow Regime Map Errors -13°F (2)

3. Vessel & SG Calculation Errors in LUCIFER -16°F (3)

4. SBLOCA Limiting Time in Life - Zirc/Water Oxidation +15°F (3)

5. NOTRUMP Boiling Heat Transfer Correlation Errors -6°F (4)

6. NOTRUMP Steam Line Isolation Logic Errors +18°F (4)

7. ZIRLQTM Cladding +15°F (5,6)

8. SBLOCTA Revisions and Axial Nodization Errors -38°F (7)

9. Automatic Containment Spray Actuation 0°F (7)

10. NOTRUMP Specific Enthalpy Error +20°F (8)

SBLOCA Augmented PCT for AOR 1847°F C. PCT Assessments for 10CFR50.46(a)(3)(i) Accumulation {1} 54°F

1. Fuel Rod Initialization Error {2} {3} +10°F

2. Loop Seal Elevation Error {2} {3} -44°F SBLOCA Licensing Basis PCT (AOR PCT+ PCT Assessments) 1813°F Section B - Large Break LOCA Margin Utilization - Surry Units 1 and 2 A. PCT for Analysis of Record (AOR) 2120°F (3)

B. Prior PCT Assessments Allocated to AOR (None) -16°F

1. ZI RLOTM Cladding -16°F LBLOCA Augmented PCT for AOR 2104°F C. PCT Assessments for 10CFR50.46(a)(3)(i) Accumulation 6°F

1. Vessel & SG Calculation Errors in LUCIFER -6°F(3)

2. LBLOCA Rod Internal Pressure Issues 0°F(3)

LBLOCA Licensing Basis PCT (AOR PCT+ PCT Assessments) 2098°F Notes { } and References ( ) on the following page

e Effect of Westinghouse ECCS Evaluation Model Changes - Surry Notes:

{1} The accumulation of _changes (sum of absolute magnitudes) exceeds 50°F and is significant, as defined in 10CFR50.46(a)(3)(i).

{2} The current report is the initial quantification of effects for this issue.

{3} Refer to the Report of Westinghouse ECCS Evaluation Model Changes provided in Attachment 1. -Westinghouse has determined that a 44°F benefit is applicable to Surry.

References:

(1) Letter from W. L. Stewart (Va. Electric & Power Co.) to NRC, "Surry Power Station Units 1 and 2 - Proposed Technical Specifications Changes - F11H Increase/Statistical DNBR Methodology," Serial No.91-374, July 8, 1991.

(2) Letter from W. L. Stewart (Va. Electric & Power Co.) to NRC, "Report of ECCS

- Evaluation Model Changes and 30-Day Report Per Requirements of 10CFR50.46-Surry Power Station Units 1 and 2, North Anna Power Station Units 1 and 2,"

Serial No. 93-1828, November 9, 1993.

(3) Letter from W. L. Stewart (VEPCO) to Document Control Desk (USN RC), "Virginia Electric and Power Company, Surry Power Station Units 1 and 2, 30-Day Report of ECCS Evaluation Model Changes Per Requirements of 10CFR50.46," Serial No.94-254, April 27, 1994.

(4) Letter from W. L. Stewart (VEPCO) to Document Control Desk (USNRC), "Virginia Electric and Power Company, Surry Power Station Units 1 and 2, 30-Day Report of ECCS Evaluation Model Changes Per Requirements of 10CFR50.46," Serial No. 94-254A, September 26, 1994.

(5) Letter from J. P. O'Hanlon (Va. Electric & Power Co.) to USNRC (Document Control Desk), "Virginia Electric and Power Company, Surry Power Station Units 1 and 2, Proposed Technical Specification Changes to Implement ZIRLO Fuel Cladding," Serial No.94-673, November 29, 1994.

(6) Letter from B.C. Buckley (USNRC) to J. P. O'Hanlon (Va. Electric & Power Co.),

"Surry Units 1 and 2 - Issuance of Amendments Re: Use of ZIRLO (TAC Nos.

M91003 and M91004)," July 27, 1995.