Part 21 Report - 1998-331
ACCESSION #: 9804240161
GENERAL INFORMATION or OTHER EVENT NUMBER: 34119
LICENSEE: SIEMENS POWER CORP-NUCLEAR NOTIFICATION DATE: 04/22/98
DIVISION NOTIFICATION TIME: 12:40 (ET]
CITY: RICHLAND REGION: 4 EVENT DATE: 04/21/98
COUNTY: BENTON STATE: WA EVENT TIME: 12:00 [PDT]
LICENSE#: SNM-1227 AGREEMENT: Y LAST UPDATE DATE: 04/22/98
DOCKET:
NOTIFICATIONS
ELMO COLLINS, R4 RDO
NRC NOTIFIED BY: DON CURET JIM GAVULA, R3 RDO
HQ OPS OFFICER: DICK JOLLIFFE VERN HODGE NRR
EMERGENCY CLASS: NOT APPLICABLE
10 CFR SECTION:
CCCC 21.21 UNSPECIFIED PARAGRAPH
EVENT TEXT
10CFR PART 21 REPORT - NONCONSERVATIVE PREDICTION OF MONITORED CORE
MCPR -
SIEMENS POWER CORPORATION (SPC) PERSONNEL DETERMINED THAT ADDITIVE
CONSTANTS USED IN MINIMUM CRITICAL POWER RATIO (MCPR)
DETERMINATION FOR
SIEMENS ATRIUM-9B FUEL BY THE CORE MONITORING SYSTEM WERE FOUND TO
BE
NON-CONSERVATIVE (UP TO 7.6% BASED ON THE ORIGINAL ADDITIVE
CONSTANTS).
ALSO SPC PERSONNEL DETERMINED THAT THE UNCERTAINLY IN THE ADDITIVE
CONSTANT FOR THIS FUEL DESIGN WAS LARGER THAN PREVIOUSLY
ESTIMATED. THE
REVISED UNCERTAINTY HAS THE POTENTIAL TO AFFECT THE MCPR SAFETY
LIMIT.
SPC PERSONNEL NOTIFIED ALL SPC CUSTOMERS WITH ATRIUM-9B LEAD TEST
ASSEMBLIES OR RELOAD QUANTITIES OF THE FUEL OF THE POSSIBLE
NONCONSERVATIVE PREDICTION OF THE MONITORED MCPR AT CONDITIONS
WHERE A
SEVERELY UP-SKEWED AXIAL POWER SHAPE COULD OCCUR.
PLANTS AFFECTED ARE DRESDEN UNIT 3 (CYCLE 15), QUAD CITIES UNIT 2 (CYCLE
15) AND KUOSHENG UNITS 1 &: 2.
Form "FUEL CYCLE AND MATERIALS EVENT NOTIFICATION WORKSHEET" omitted.
NRC Operations Center
U.S. Nuclear Regulatory Commission
Washington, D. C.
Attachment to Siemens Power Corporation - Nuclear Division 10 CFR Part 21
Report (Fuel Cycle and Materials Event Notification Worksheet/NRC Form
361A) of April 21, 1998
10 CFR Part 21 Notifcation of Defect Relative to Non-Conservative
Prediction of Monitored Core MCPR.
Additive constants used in MCPR determination for Siemens
ATRIUM**[Trademark]-9B fuel by the core monitoring system were found to
be non-conservative. Also the uncertainty in the additive constant for
this fuel design was determined to be larger than previously estimated.
The revised uncertainty has the potential to affect the MCPR safety limit
However, an interim additive constant uncertainty larger than the value
calculated using new CHF data, had been used in safety limit
calculations. Because the monitored MCPR could be non-conservative (up
to 7.6%) based on the original additive constants, the MCPR safety limit
could have been exceeded during the limiting transient while operating
with less than 7.6% MCPR margin and with a severely up-skewed axial power
shape in the limiting MCPR assembly.
SPC took immediate steps to determine the potential safety impact on
plants operating with ATRIUM-9B fuel and completed an operability
assessment on February 26, 1998. The assessment addressed the potential
impact on both monitored MCPR and the MCPR operating limit. Where
necessary, the operability assessment identified conservative
compensatory actions to ensure that MCPR limits were adequate for ATRIUM-
9B fuel. For operation with a positive axial offset (up-skewed power
profile), restrictions on the Maximum Fraction of Limiting CPR (MFLCPR)
were determined which ensure that adequate MCPR margin exists to cover
the potential non-conservatism in ANFB. MFLCPR restrictions of up to 8%
were calculated for plants using ATRIUM-9B fuel. For operation when the
axial power offset is less than zero (down-skewed power profile), the
ANFB correlation is conservative and no limitation on MFLCPR is required.
All SPC customers with ATRIUM-9B lead test assemblies or reload
quantities of the fuel were notified of the possible non-conservative
prediction of the monitored MCPR at conditions where a severely up-skewed
axial power shape could occur.
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