ML18064A805
| ML18064A805 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 06/16/1995 |
| From: | Haas K CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9506280355 | |
| Download: ML18064A805 (2) | |
Text
consumers Power POWERING MICHIGAN'S PIUIGllE55 Palisades Nuclear Plant: 27780 Blue Star Memorial Highway, Covert, Ml 49043 June 16, 1995 U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT KurtM. Haas Plant Safety and Licensing Director NOTIFICATION OF SIGNIFICANT CHANGE TO EMERGENCY CORE COOLING CALCULATION Licensees are required to provide an emergency core cooling system (ECCS) designed so that its calculated core cooling performance following postulated loss-of-coolant accidents conforms to the criteria set forth in 10 CFR 50.46.
This ECCS cooling performance must be calculated in accordance with an acceptable evaluation model.
10 CFR 50.46 also sets forth the criteria for reporting changes or errors in the evaluation model, or in the application of the model.
Peak cladding temperature (PCT) is a result of the evaluation model and is used to define the magnitude of any change.
When the PCT changes by more than 50°F, it is considered a significant change and the nature of the change or error must be reported within 30 days, along with a schedule for reanalysis.
REANALYSIS FOR CYCLE 12 - PCT Reload batch "P" fuel is being loaded during the 1995 refueling outage for use during Cycle 12.
As a result of an enrichment distribution study, a new enrichment distribution that provided fuel cost savings was utilized for Cycle
- 12. This new Alternate Enrichment Scheme (AES) results in flatter power distributions in the fuel bundles.
The change in the power distribution causes fuel rods neighboring the peak rod to be at higher, more uniform temperatures.
The higher temperatures result in a reduction in radiant heat transfer from the peak rod to the neighboring rods.
The reduction in radiant heat transfer could result in an increase in PCT.
Therefore, a reanalysis of the Palisades large break LOCA was performed to support the AES used for the reload 'P' fuel assemblies.
260029 9506280355 950616 PDR ADOCK 05000255 p
For this reanalysis, an effort was made to identify conservatism in the analysis that went beyond 10 CFR 50 Appendix K, and Siemens Power Corporation approved methodology requirements.
Removing the excess conservatism from the input parameters and assumptions would allow a better understanding of the actual m*rgin available in the calculated PCT.
2 The calculated PCT changed from 2192°F to 2095°F.. The primary reason for the change in the PCT was a reduction in the conservatism used in calculating the stored energy for the End of Cycle (EOC} axial shape case.
The previous Siemens analysis, EMF-91-177. '.'Palisades Large Break LOCA/ECCS Analysis With*
Increased Radial Peaking and Reduced ECCS Flow,." used a Beginning of Cycle (BOC} stored energy and a conservative radiation heat transfer model for the EOC axial shape case.
The new analysis used the Middle of Cycle (MOC} stored energy and* reduced the amount of conservatism in the radiation heat transfer model fo~ the EOC axial power case.
The reduction in the conservatism in the
- radiation heat transfer model minimized the impact of the flatter power distribution associated with the AES.
Use of the MOC stored energy accounted for the majority of the reduction in the calculated PCT.
The changes made for the current analysis are consistent with 10CFR 50 Appendix K and Siemens Power Corporation's NRC approved methodology.
ADDITIONAL ACTIONS The peak clad temperature change as a result of the reanalysis is defined as a significant change by 10 CFR 50.46.
This change does not constitute a safety concern since the change is in the conservative direction, but is reportable since the change is greater than 50°F.
There is no need for additional reanalysis in response to this ~CT change since the change resulted from a reanalysis performed in co~pliance with 10 CFR 50 Appendix K and the NRC approved Siemens Power Corporation methodology.
The new ahalysis has been documented as Supplement 1 to EMF-91-177. This analysis supports operation for Cycle 12 and future cycles.
No furth~r action is required.
SUMMARY
OF COMMITMENTS This letter contains no new commitments and no reviSions to existing*
commitments.
I Kurt M. Haas Plant Safety and Licensing Director cc Administrator, Region III, USNRC Project Manager, NRR, USNRC Resident Inspector, Palisades, USNRC