ULNRC-05769, 10 CFR 50.46 Annual Report, ECCS Evaluation Model Revisions

10 CFR 50.46 Annual Report, ECCS Evaluation Model Revisions

ML110610352
Person / Time
Site:	Callaway
Issue date:	03/01/2011
From:	Maglio S Ameren Missouri, Union Electric Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
ULNRC-05769
Download: ML110610352 (11)

Text

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WAmeren Callaway Plant MISSOURI March 1, 2011 ULNRC-05769 u.s. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 10 CFR 50.46 Ladies and Gentlemen:

DOCKET NUMBER 50-483 CALLAWAY PLANT UNION ELECTRIC COMPANY 10 CFR 50.46 ANNUAL REPORT ECCS EVALUA TION MODEL REVISIONS

References:

1) ULNRC-05260 dated 3-9-06

2) ULNRC-05378 dated 3-7-07

3) ULNRC-05475 dated 3-4-08

4) ULNRC-05600 dated 3-4-09

5) ULNRC-05683 dated 3-1-10 Ameren Missouri hereby submits the annual report required per 10 CFR 50.46(a)(3) for Callaway Plant. Attachment 1 to this letter describes changes to the Westinghouse ECCS Large Break and Small Break Loss of Coolant Accident (LOCA) Evaluation Models which have been implemented for Callaway during the time period from March 2010 to March 2011. Attachment 2 provides an ECCS Evaluation Model Margin Assessment which accounts for all peak cladding temperature (PCT) changes resulting from the resolution of prior issues as they apply to Callaway. No new PCT penalties are included in these attachments. References 1 through 5 provided annual 10 CFR 50.46 reports that were issued after the LOCA analyses were revised to reflect the installation of the replacement steam generators in 2005.

The PCT values determined in the Large Break and Small Break: LOCA analyses of record, when combined with all PCT margin allocations, remain below the 2200°F regulatory limit. As such, no reanalysis is planned by Ameren Missouri.

PO Box 620 Fulton, MO 65251 AmerenMissouri.com

ULNRC-05769 March 1, 2011 Page 2 This letter does not contain any new commitments. If you have any questions on this report, please contact Mr. Tom Elwood at (314) 225-1905.

Very truly yours, I1torf2 Scott Maglio Regulatory airs Manager GGY/nls Enclosure

ULNRC-05769 March 1, 2011 Page 3 cc: Mr. Elmo E. Collins, Jr.

Regional Administrator U.S. Nuclear Regulatory Commission Region IV 612 E. Lamar Blvd., Suite 400 Arlington, TX 76011-4125 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. Mohan C. Thadani (2 copies)

Senior Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 0-8G 14 Washington, DC 20555-2738 Mr. James Polickoski Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 0-8B lA Washington, DC 20555-2738

ULNRC-05769 March 1, 2011 Page 4 Index and send hardcopy to QA File A160.0761 Hardcopy:

Certrec Corporation 4200 South Hulen, Suite 630 Fort Worth, TX 76109 (Certrec receives ALL attachments as long as they are non-safeguards and may be publicly disclosed.)

Electronic distribution for the following can be made via Responses and Reports ULNRe Distribution:

A. C. Heflin F. M. Diya C. O. Reasoner III L. S. Sandbothe S. M. Maglio T. B. Elwood S. L. Gallagher T. L. Woodward (NSRB)

G. G. Yates Mr. Paul Parmenter, Director (SEMA)

Mr. Thomas Mohr, Senior REP Planner (SEMA)

Mr. John Campbell, REP Planner (SEMA)

Ms. Diane M. Hooper (WCNOC)

Mr. Tim Hope (Luminant Power)

Mr. Ron Barnes (APS)

Mr. Tom Baldwin (PG&E)

Mr. Wayne Harrison (STPNOC)

Ms. Linda Conklin (SCE)

Mr. John O'Neill (Pillsbury Winthrop Shaw Pittman LLP)

Mr. Dru Buntin (DNR)

ATTACHMENT ONE CHANGES TO THE WESTINGHOUSE ECCS EVALUATION MODEL AND PCT PENALTV ASSESSMENTS TABLE OF CONTENTS

1. URANIA-GADOLINIA PELLET THERMAL CONDUCTIVITY CALCULATION

2. PELLET CRACK AND DISH VOLUME CALCULATION

3. TREATMENT OF VESSEL AVERAGE TEMPERATURE UNCERTAINTY

4. GENERAL CODE MAINTENANCE

5. CONSIDERATION OF SAFETY INJECTION PUMP HEAT 1

Attachment 1

1. URANIA-GADOLINIA PELLET THERMAL CONDUCTIVITY CALCULATION Two errors were discovered in the pellet thermal conductivity calculation for urania-gadolinia pellets in the SBLOCTA code. First, the calculation did not include the terms required to adjust for pellet densities other than 95% of the theoretical density. Second, the conversion from Fahrenheit to Rankine temperatures used an addend of 459 instead of 459.67. These errors have been corrected and evaluated for impact on existing Small Break LOCA analysis results. These changes represent a closely-related group of Non-Discretionary Changes in accordance with Section 4.1.2 ofWCAP-13451.

SBLOCTA sensitivity calculations performed by Westinghouse have resulted in an estimated PCT impact of O°F for existing Small Break LOCA analysis results.

2. PELLET CRACK AND DISH VOLUME CALCULATION Two errors were discovered in the calculation of the normalized pellet crack and dish volumes in the SBLOCTA code. First, an incorrect operator was used to select between two tables of normalized volume vs. linear heat generation rate. Second, the normalized volume corresponding to a linear heat generation rate of 18 kW/ft was incorrectly programmed in one of the tables as 1.58 instead of 1.59.

These errors have been corrected in the SBLOCTA code and will be corrected (where applicable) in future versions of the BASH and LOCBART codes. These changes represent a closely-related group of Non-Discretionary Changes in accordance with Section 4.1.2 ofWCAP-13451.

Based on a combination ofSBLOCTA sensitivity calculations and engineering judgment, Westinghouse has estimated a PCT impact of O°F for existing Large and Small Break LOCA analysis results.

3. TREATMENT OF VESSEL AVERAGE TEMPERATURE UNCERTAINTY Historically, the overall vessel average temperature uncertainty calculated by Westinghouse considered only negatively-valued instrument uncertainties corresponding to the indicated temperature being lower than the actual temperature. This uncertainty was then applied as a "+/-" uncertainty in some LOCA analyses, rather than using specific positive "+" and negative "-" uncertainties. This discrepancy has been evaluated for impact on existing Small Break LOCA analysis results, and its resolution represents a Non-Discretionary Change in accordance with Section 4.1.2 ofWCAP-13451.

Westinghouse has judged this issue to have a negligible impact on existing Small Break LOCA analysis results, leading to an estimated PCT impact of O°F.

4. GENERAL CODE MAINTENANCE Various changes have been made to enhance the usability of the codes and to help preclude errors in analyses. This includes items such as modifying input variable definitions, units, and defaults; improving the input diagnostic checks; enhancing the code output; optimizing active coding; and eliminating inactive coding. These changes have been evaluated for impact on existing Small Break 2

Attachment I LOCA analysis results and they represent Discretionary Changes that will be implemented on a forward-fit basis in accordance with Section 4.1.1 of WCAP-13451.

Westinghouse has judged this issue to have an estimated PCT impact of O°F on existing Small Break LOCA analysis results.

5. CONSIDERATION OF SAFETY INJECTION PUMP HEAT Westinghouse letter SCP-IO-21, "TB-09-4, Rev. I - Impact of Auxiliary Pump Heat on Westinghouse and Combustion Engineering Analyses/Methodologies," dated April 13,2010, provided a Westinghouse Technical Bulletin documenting an evaluation of the addition of auxiliary feedwater (AFW) pump heat on various non-LOCA transients. Ameren Missouri subsequently requested that Westinghouse also address the impact of Safety Injection (SI) pump heat addition on Callaway's Appendix K Small Break LOCA (SBLOCA) and Appendix K Large Break LOCA (LBLOCA) analyses of record.

The effect of SI pump heat was considered for the Callaway Appendix K SBLOCA and Appendix K LBLOCA analyses. Westinghouse determined that the inclusion of SI pump heat will produce a negligible effect on the results of the Large Break and Small Break LOCA analyses, leading to an estimated PCT impact ofOoP for 10 CPR 50.46 reporting purposes.

3 ATTACHMENT TWO ECCS EVALUATION MODEL MARGIN ASSESSMENT FOR CALLAWAY LARGE BREAK LOCA A. ANAL YSIS OF RECORD (AOR) PCT = 1939°F B. PRIOR ECCS MODEL ASSESSMENTS C. CURRENT LOCA MODEL ASSESSMENTS -

March 2011 LICENSING BASIS PCT + MARGIN ALLOCATIONS ABSOLUTE MAGNITUDE OF MARGIN ALLOCATIONS SINCE LAST LBLOCA 30-DAY REPORT 1

SMALL BREAK LOCA A. ANAL YSIS OF RECORD (AOR) PCT = 1043°F B. PRIOR ECCS MODEL ASSESSMENTS C. CURRENT ECCS MODEL ASSESSMENTS -

March 2011 LICENSING BASIS PCT + MARGIN ALLOCATIONS ABSOLUTE MAGNITUDE OF MARGIN ALLOCATIONS SINCE LAST SBLOCA 30-DA Y REPORT 2