ML12061A360

10 CFR 50.46 Annual Report ECCS Evaluation Model Revisions

ML12061A360
Person / Time
Site:	Callaway
Issue date:	03/01/2012
From:	Maglio S A Ameren Missouri, Union Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ULNRC-05840
Download: ML12061A360 (10)

Text

WAmeren MISSOURI Callaway Plant ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

March 1, 2012 ULNRC-05840 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Ladies and Gentlemen:

10 CFR 50.46 DOCKET NUMBER 50-483 CALLA WAY PLANT UNIT 1 UNION ELECTRIC CO. FACILITY OPERATING LICENSE NPF-30 10 CFR 50.46 ANNUAL REPORT ECCS EVALUATION 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 6) ULNRC-05769 dated 3-1-11 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 2011 to March 2012. 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 6 provided annual10 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, MD 65251 AmerenMissouri.com ULNRC-05840 March 1, 2012 Page2 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.

Sincerely, (Vr-Scott A Maglio Regulatory Affairs Manager GGY/nls Attachments:

1) Changes to the Westinghouse ECCS Evaluation Model and PCT Penalty Assessments

2) ECCS Evaluation Model Margin Assessment for Callaway ULNRC-05840 March 1, 2012 Page3 cc: Mr. Elmo E. Collins, Jr. Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 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 0-8B 1 Washington, DC 20555-2738 ULNRC-05840 March 1, 2012 Page4 Index and send hardcopy to QA File A160.0761 Hardcopy:

Certrec Corporation 4150 International Plaza Suite 820 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 ULNRC Distribution:

A. C. Heflin F. M. Diya C. 0. Reasoner III L. H. Graessle S.M. Maglio T. B. Elwood R. Holmes-Bobo NSRB Secretary G. G. Yates Mr. Paul Parmenter, Director (SEMA) Mr. Thomas Mohr, Senior REP Planner (SEMA) Mr. Tom Masso, 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 1 to ULNRC-05840 ATTACHMENT ONE CHANGES TO THE WESTINGHOUSE ECCS EVALUATION MODEL AND PCT PENALTY ASSESSMENTS Attachment 1 to ULNRC-05840 TABLE OF CONTENTS 1. RADIATION HEAT TRANSFER LOGIC 2. MAXIMUM FUEL ROD TIME STEP LOGIC 3. GENERAL CODE MAINTENANCE 1

Attachment 1 to ULNRC-05840

1. RADIATION HEAT TRANSFER LOGIC Two errors were discovered in the calculation of the radiation heat transfer coefficient in the SBLOCTA computer code. First, existing diagnostics did not preclude non-physical negative or large (negative or positive) radiation heat transfer coefficients from being calculated.

These calculations occurred when the vapor temperature exceeded the cladding surface temperature or when the predicted temperature difference was less than 1 degree. Second, a temperature term incorrectly used degrees Fahrenheit instead ofRankine.

These errors have been corrected in the SBLOCTA code and represent a closely related group ofNon-Discretionary Changes in accordance with Section 4.1.2 ofWCAP-13451. A combination of SBLOCT A sensitivity calculations performed by Westinghouse and their engineering judgment have resulted in an estimated PCT impact of 0°F for existing Small Break LOCA analysis results. 2. MAXIMUM FUEL ROD TIME STEP LOGIC An error was discovered in the SBLOCT A code that allowed the fuel rod time step to exceed the specified maximum allowable time step. The time step logic has been corrected in the SBLOCT A code. This error represents a Non-Discretionary Change in accordance with Section 4.1.2 of WCAP-13451.

A combination ofSBLOCTA sensitivity calculations performed by Westinghouse and their engineering judgment have resulted in an estimated PCT impact of 0°F for existing Small Break LOCA analysis results. 3. 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 Large Break and Small Break LOCA analysis results and they represent Discretionary Changes that will be implemented on a forward-fit basis in accordance with Section 4.1.1 ofWCAP-13451.

Westinghouse has judged this issue to have an estimated PCT impact of 0°F on existing Large Break and Small Break LOCA analysis results. 2 Attachment 2 to ULNRC-05840 ATTACHMENT TWO ECCS EVALUATION MODEL MARGIN ASSESSMENT FOR CALLAWAY Attachment 2 to ULNRC-05840 A. B. C. LARGE BREAK LOCA ANALYSIS OF RECORD (AOR) PRIOR ECCS MODEL ASSESSMENTS CURRENT LOCA MODEL ASSESSMENTS

-March 2012 LICENSING BASIS PCT +MARGIN ALLOCATIONS ABSOLUTE MAGNITUDE OF MARGIN ALLOCATIONS SINCE LAST LBLOCA 30-DA Y REPORT 1 PCT = 1939°F Attachment 2 to ULNRC-05840 A. B. c. SMALL BREAK LOCA ANALYSIS OF RECORD (AOR) PRIOR ECCS MODEL ASSESSMENTS CURRENT ECCS MODEL ASSESSMENTS

-March 2012 LICENSING BASIS PCT +MARGIN ALLOCATIONS ABSOLUTE MAGNITUDE OF MARGIN ALLOCATIONS SINCE LAST SBLOCA 30-DA Y REPORT 2 PCT = 1043°F