ML18153A603

Forwards Rept of ECCS Evaluation Changes & 30-day Rept of ECCS Evaluation Model Changes Per 10CFR50.46

ML18153A603
Person / Time
Site:	Surry, North Anna
Issue date:	03/14/1996
From:	Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
96-111, NUDOCS 9603190250
Download: ML18153A603 (15)

Text

e e VIRGINIA.

ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 March 14, 1996 United States Nuclear Regulatory Commission Attention:

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

VIRGINIA ELECTRIC AND POWER COMPANY Serial No. NAF/KFF/GDM Docket Nos. License Nos. 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 10CFR50.46 96-111 RO 50-338 50-339 50-280 50-281 NPF-4 NPF-7 DPR-32 DPR-37 Pursuant to 1 OCFR50.46(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 1 OCFR50.46.

Attachment 1 contains excerpted portions of the Westinghouse report describing the changes to the Westinghouse ECCS Evaluation Models which are applicable to Surry and North Anna and have been implemented during calendar year 1995. Information regarding the effect of the EGGS Evaluation Model changes upon the reported LOCA analysis of record results is provided for North Anna and Surry Power Stations in Attachments 2 and 3, respectively.

To summarize the information in Attachments 2 and 3, the calculated peak cladding temperature (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 1 OCFR50.46(a)(3)(i), are designated with an asterisk.

North Anna Units 1 and 2 -Small break: 1709° F North Anna Units 1 and 2 -Large break: 2053°F Surry Units 1 and 2 -Small break: 184 7° F (*) Surry Units 1 and 2 -Large break: 2098° F 9603190250 960314 PDR ADOCK 05000280 P

• PDR J e We have evaluated these issues and the associated changes in the applicable licensing basis PCT results. These results demonstrate compliance with the requirements of 1 OCFR50.46(b).

Although the Surry small break LOCA changes described in Attachment 3 are significant, as defined in 1 OCFR50.46(a)(3)(i), the licensing basis PCT results have adequate margin to the limit. 1 OCFR50.46(a)(3)(ii) specifically requests that the 30-day report include a proposed schedule for providing a reanalysis or taking other action as may be needed to show compliance with 1 OCFR50.46 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. No further action is required to demonstrate compliance with 1 OCFR50.46 requirements.

If you have further questions or require additional information, please contact us. Very truly yours, James P. O'Hanlon Senior Vice President

-Nuclear Attachments:

1) Westinghouse Report of ECCS Evaluation Model Changes for 1995 -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 e ATTACHMENT 1 WESTINGHOUSE REPORT OF ECCS EVALUATION MODEL CHANGES FOR 1995 NORTH ANNA UNITS 1 AND 2 AND SURRY UNITS 1 AND 2 e e NOTRUMP SPECIFIC ENTHALPY ERROR Background A typographical error was found in a line of coding in the NOTRUMP code. 'This line of coding was intended to model the calculation found in Equation L-127 of WCAP-10079-P-A.

Although the equation in the topical report is correct. the coding represented the last term as a partial derivative with respect to the fluid node mixture region total energy instead of the mixture region total mass. 'This correction is a Non-Discretionary Change in accordance with Section 4.1.2 of WCAP--13451.

Affected Evaluation Model 1985 Westinghouse Small Break LOCA Evaluation Model Using NOTRUMP Estimated Effect Representative plant calculations have led to an estimated effect of +20°F for this error correction.

e SALIBRARY DOUBLE PRECISION ERRORS Background During migration of the LOCA codes from the CRAY computer to UNIX-based platforms, programming errors were made in two library routines related to improper specification of double precision variables.

These errors were found and fixed during later code maintenance.

Affected Evaluation Models 1981 Westinghouse Large Break LOCA Evaluation Model Using BASH 1985 Westinghouse Small Break LOCA Evaluation Model Using NOTRUMP Estimated Effect Test cases with individual codes in the models demonstrated very small differences in only the SATAN . and NOTRUMP code results, with correspondingly minor effects on final peak clad temperature predictions.

Because the error only affects a very limited number of LBLOCA analyses which were performed on the UNIX platform prior to correcting the codes, the evaluation of effects for LBLOCA analyses were assessed on a plant-specific basis. For SBLOCA analyses performed on the UNIX platform, representative plant calculations resulted in an estimated generic impact of -15°F for affected analyses.

e MACBETH CORRELATION ERROR Background An error was found in the implementation of the Macbeth correlation for critical heat flux calculations.

Tilis error involved an incorrect determination of the boundary between the low flow and high flow regimes in that model leading to the possibility of using the incorrect regime correlation in some circumstances.

Tilis correction is a Non-Discretionary Change in accordance with Section 4.1.2 of WCAP-13451. Affected Evaluation Models 1975 Westinghouse Small Break LOCA Evaluation Model Using WFLASH 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 Effect Representative plant calculations have led to an estimated non-significant effect of +0°F for this correction in all of the LBLOCA and SBLOCA Evaluation Models. .

SPADES UPPER HEAD ENTIIALPY ERROR Background An error was discovered in the SPADES computer code in which the code incorrectly sets the initial NOTRUMP upper head enthalpy equal to the top core node enthalpy for Thot upper head plants. In the current NOTRUMP methodology, the upper head enthalpy is set equal to the hot leg enthalpy for Thot upper head plants. lbis was determined to be a Non-Discretionary change and corrected as described in section 4.1.3 of WCAP-13451.

Affected Evaluation Model 1985 Westinghouse Small Break LOC~ Evaluation Model Using NOTRUMP Estimated Effect The difference between the hot leg enthalpy and top core node enthalpy calculated using SP ADES is negligible.

Additionally, the primary side pressure and temperature conditions typically change during the process of generating a suitable steady state calculation by more than the initial differences introduced by this error. As such, this error is estimated to result in a net PCf effect of 0°F for all analyses.

e CORE BARREL STRUCTURAL METAL MODEL ERRORS Background Errors were discovered in the calculations of the effective equivalent diameter of the heat links connecting metal from the core barrel to fluid nodes in the BASH model. These calculations are performed with the BASHER input processor which is used to generate input decks for the BASH code. The effective equivalent diameter is a minor parameter in the entire strucrural metal heat transfer model. Affected Evaluation Model 1981 Westinghouse Large Break LOCA Evaluation Model Using BASH Estimated Effects Evaluation of the effect of the corrections determined that there was negligible effect on calculated peak cladding temperatures.

No penalty or benefit will be assessed to existing analyses.

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 (AOR) 1704°F B. Prior PCT Assessments Allocated to AOR 0°F SBLOCA Augmented PCT for AOR 1704°F C. PCT Assessments for 1 OCFR50.46(a)(3)(i)

Accumulation 35°F 1. NOTRUMP Specific Enthalpy Error {1} {2} +20°F 2. SALIBRARY Double Precision Errors {1} {2} -15°F SBLOCA Licensing Basis PCT (AOR PCT+ PCT Assessments) 1709°F Section B -Large Break LOCA Margin Utilization

-North Anna Units 1 and 2 A. PCT for Analysis of Record (AOR) B. Prior PCT Assessments Allocated to AOR 1 . LBLOCNSeismic SG Tube Collapse 2. BASH Accumulator Empty Flag LBLOCA Augmented PCT for AOR 2013°F 40°F +30°F +10°F 2053°F C. PCT Assessments for 1 OCFR50.46(a)(3)(i)

Accumulation 0° F LBLOCA Licensing Basis PCT (AOR PCT+ PCT Assessments) 2053° F (Notes { } and References ( ) on the following page.) (1) (1) (1) (1)

Notes: {1} The current report is the initial quantification of effects for this issue. {2} Refer to the Westinghouse Report of ECCS Evaluation Model Changes for 1995 provided in Attachment 1 .

Reference:

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

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) B. Prior PCT Assessments Allocated to AOR 1. Safety Injection in the Broken Loop (NOTRUMP)

2. NOTRUMP Drift Flux Flow Regime Map Errors 3. Vessel & SG Calculation Errors in LUCIFER 4. SBLOCA Limiting Time in Life -Zirc/Water Oxidation

5. NOTRUMP Boiling Heat Transfer Correlation Errors 6. NOTRUMP Steam Line Isolation Logic Errors 7. ZIRLOTM Cladding {1} SBLOCA Augmented PCT for AOR C. PCT Assessments for 1 OCFR50.46(a)(3)(i)

Accumulation

{2} 1 . SBLOCTA Revisions and Axial Nodization Errors 2. Automatic Containment Spray Actuation

3. NOTRUMP Specific Enthalpy Error {3} {4} SBLOCA Licensing Basis PCT (AOR PCT+ PCT Assessments)

Section B -Large Break LOCA Margin Utilization

-Surry Units 1 and 2 A. PCT for Analysis of Record (AOR) B. Prior PCT Assessments Allocated to AOR (None) 1. ZIRLOŽ Cladding {1} . LBLOCA Augmented PCT for AOR C. PCT Assessments for 1 OCFR50.46(a)(3)(i)

Accumulation

1. Vessel & SG Calculation Errors in LUCIFER 2. LBLOCA Rod Internal Pressure Issues LBLOCA Licensing Basis PCT (AOR PCT+ PCT Assessments) (Notes { } and References ( ) on the following page.) 1852°F (1) +13°F 0°F (2) -13°F (2) -16°F (3) +15°F (3) -6°F (4) +18°F (4) +15°F (5,6) 1865°F 58°F -38°F (7) 0°F (7) +20°F 1847°F 2120°F (3) -16°F -16°F 2104°F 6°F -6°F (3) 0°F (3) 2098°F Notes: {1} Virginia Electric and Power Company in Reference 5 requested changes to the Technical Specifications of Surry Power Station Units 1 and 2 to allow the use of ZIRLO as a fuel cladding material.

The supporting safety evaluation presented changes in the application of the ECCS Evaluation Models Small and Large Break LOCA. The proposed Technical Specification changes were reviewed and approved by the NRC in Reference

6. {2} The accumulation of changes (sum of absolute magnitudes) exceeds 50° F and is significant, as defined in 1 OCFR50.46(a)(3)(i).

{3}.. The current report is the initial quantification of effects for this issue. {4} Refer to the Report of Westinghouse ECCS Evaluation Model Changes for 1995 provided in Attachment 1 .

References:

(1) Letter from W. L. Stewart (Va. Electric & Power Co.) to NRC, "Surry Power Station Units 1 and 2 -Proposed Technical Specifications Changes -FDH 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 1 OCFR50.46-Surry Power Station Units 1 and 2, North Anna Power Station Units 1 and 2," Serial No. 93-182B, November 9, 1993. (3) 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 1 OCFR50.46," 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 1 OCFR50.46," 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.

e e *~ (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. (7) Letter from J. P. O'Hanlon (Va. Electric & Power Co.) to USNRC, "Virginia Electric and Power Company, North Anna Power Station Units 1 and 2, Surry Power Station Units 1 and 2, Report of ECCS Evaluation Model Changes Pursuant to Requirements of 1 OCFR50.46" Serial No.95-198, April 25, 1995.