United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #: 9809240167


NRC Operations Center
U. S. Nuclear Regulatory Commission
Washington, D. C.

Attachment to Siemens Power Corporation - Nuclear Division 10 CFR 21 Report (Fuel Cycle and Materials Event Notification Worksheet/NRC Form 361A) of September 17, 1998 10 CFR Part 21 Notification of Defect Relative to MCPR Operating Limits as Impacted by Gap Conductance of Co-Resident BWR Fuel For BWR reactors where SPC provides reload fuel, postulated transient events are analyzed each cycle to establish MCPR operating limits. During transition cycles, SPC establishes limits for SPC fuel and also for co-resident fuel manufactured by other fuel vendors. Transient analyses are required to address co-resident fuel as well as SPC fuel because previous co-resident fuel transient analyses and limits may no longer be valid due to changes in core neuronic characteristics. Inputs to the transient analyses include the fuel pellet to cladding gap heat transfer coefficient for both SPC fuel and co-resident fuel. The gap heat transfer coefficient is calculated using the RODEX2 computer code.

An SPC internal licensing methodology review was performed and concerns were identified relative to the values for several fuel rod characteristics used in the RODEX2 analyses to calculate gap conductance values for input to the transient analyses for co-resident fuel. An evaluation of these concerns determined there exists reportable defects. The defects were a consequence of modeling the co-resident fuel with cold-worked cladding - typical of SPC cladding - instead of annealed cladding as it should have been. The gap conductance behavior of the co-resident fuel affected the core wide neutronic behavior through void reactivity feedback during certain transients and, consequently, the calculation of the transient delta CPR for the limiting SPC fuel.

The defects are non-conservative MCPR operating limits previously provided to ComEd for LaSalle Unit 2 Cycle 8 and Quad Cities Unit 2 Cycle 15. The previously calculated and reported operating limit for LaSalle will be revised before the reactor starts up (anticipated startup in March 1999). The previously calculated and reported operating limits for Quad Cities Unit 2 Cycle 15 were determined at the limiting EOC exposure conditions. Corrected analyses have been performed which demonstrate that the current operating limits are bounding from BOC to a cycle exposure of 8 Gwd/MTU. The Quad Cities Unit 2 operating limits will be revised before the cycle reaches 8 Gwd/MTU.


FUEL CYCLE FACILITY EVENT NUMBER: 34791
FACILITY: SIEMENS POWER CORPORATION NOTIFICATION DATE: 09/17/98
NOTIFICATION TIME: 18:31 [ET]
RXTYPE: URANIUM FUEL FABRICATION
COMMENTS: LEU CONVERSION (UF6 to UO2) EVENT DATE: 09/17/98
FABRICATION & SCRAP RECOVERY EVENT TIME: 12:00(PDT]
COMMERICAL LWR FUEL LAST UPDATE DATE: 09/17/98
CITY: RICHLAND REGION: 4
COUNTY: BENTON STATE: WA NOTIFICATIONS
LICENSE#: SNM-1227 AGREEMENT: Y MONTE PHILLIPS RDO
DOCKET: 07001257 VERN HODGE NRR
NRC NOTIFIED BY: HARVEY CURAT
HQ OPS OFFICER: DICK JOLLIFFE
EMERGENCY CLASS: NOT APPLICABLE
10 CFR SECTION: CCCC 21.21 UNSPECIFIED PARAGRAPH


EVENT TEXT

- 10CFR PART 21 REPORT - DEFECT RELATED TO MCPR OPERATING LIMITS -

FOR BWR REACTORS WHERE SIEMENS POWER CORPORATION (SPC) PROVIDES RELOAD FUEL, POSTULATED TRANSIENT EVENTS ARE ANALYZED EACH FUEL CYCLE TO ESTABLISH MINIMUM CRITICAL POWER RATIO (MCPR) OPERATING LIMITS. DURING TRANSITION CYCLES, SPC ESTABLISHES LIMITS FOR SPC FUEL AND ALSO FOR CO-RESIDENT FUEL MANUFACTURED BY OTHER FUEL VENDORS. TRANSIENT ANALYSES ARE REQUIRED TO ADDRESS CO-RESIDENT FUEL AS WELL AS SPC FUEL BECAUSE PREVIOUS CO-RESIDENT FUEL TRANSIENT ANALYSES AND LIMITS MAY NO LONGER BE VALID DUE TO CHANGES IN CORE NEUTRONIC CHARACTERISTICS. INPUTS TO THE TRANSIENT ANALYSES INCLUDE THE FUEL PELLET TO CLADDING GAP HEAT TRANSFER COEFFICIENT FOR BOTH SPC FUEL AND CO-RESIDENT FUEL. THE GAP HEAT TRANSFER COEFFICIENT IS CALCULATED USING THE RODEX2 COMPUTER CODE.

AN SPC INTERNAL LICENSING METHODOLOGY REVIEW WAS PERFORMED AND CONCERNS WERE IDENTIFIED RELATIVE TO THE VALUES FOR SEVERAL FUEL ROD CHARACTERISTICS USED IN THE RODEX2 ANALYSES TO CALCULATE GAP CONDUCTANCE VALUES FOR INPUT TO THE TRANSIENT ANALYSES FOR CO-RESIDENT FUEL. AN EVALUATION OF THESE CONCERNS DETERMINED THAT REPORTABLE DEFECTS EXIST. THE DEFECTS WERE A CONSEQUENCE OF MODELING THE CO-RESIDENT FUEL WITH COLD-WORKED CLADDING, TYPICAL OF SPC CLADDING, INSTEAD OF ANNEALED CLADDING, AS IT SHOULD HAVE BEEN. THE GAP CONDUCTANCE BEHAVIOR OF THE CO-RESIDENT FUEL AFFECTED THE CORE WIDE NEUTRONIC BEHAVIOR THROUGH VOID REACTIVITY FEEDBACK DURING CERTAIN TRANSIENTS AND, CONSEQUENTLY, THE CALCULATION OF THE TRANSIENT DIFFERENTIAL CRITICAL POWER RATIO FOR THE LIMITING SPC FUEL.

THE DEFECTS ARE NON-CONSERVATIVE MCPR OPERATING LIMITS PREVIOUSLY PROVIDED TO COMMONWEALTH EDISON FOR LASALLE UNIT 2 CYCLE 8 AND QUAD CITIES UNIT 2 CYCLE 15. THE PREVIOUSLY CALCULATED AND REPORTED OPERATING LIMIT FOR LASALLE WILL BE REVISED BEFORE THE REACTOR STARTS UP (ANTICIPATED STARTUP IN MARCH, 1999). THE PREVIOUSLY CALCULATED AND REPORTED OPERATING LIMITS FOR QUAD CITIES UNIT 2 CYCLE 15 WERE DETERMINED AT THE LIMITING END-OF-CYCLE EXPOSURE CONDITIONS. CORRECTIVE ANALYSES HAVE BEEN PERFORMED WHICH DEMONSTRATE THAT THE CURRENT OPERATING LIMITS ARE BOUNDING FROM BEGINNING-OF-CYCLE TO A CYCLE EXPOSURE OF 8 GWd/MTU. THE QUAD CITIES UNIT 2 OPERATING LIMITS WILL BE REVISED BEFORE THE CYCLE REACHES 8 Gwd/MTU.

SPC EVALUATED THIS ISSUE UNDER SPC CONDITION REPORT #6565, DATED 03/02/98, AND PREVIOUSLY INFORMED THE NRC OF THIS ISSUE VIA SPC INTERIM REPORT #98-004, DATED 07/22/98.


Attachment "FUEL CYCLE AND MATERIALS EVENT NOTIFICATION WORKSHEET"


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