United States Nuclear Regulatory Commission - Protecting People and the Environment


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.



*** END OF DOCUMENT ***



Page Last Reviewed/Updated Thursday, March 29, 2012