ML18068A487
| ML18068A487 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 11/03/1998 |
| From: | Haskell N CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9811100212 | |
| Download: ML18068A487 (2) | |
Text
A CM~ Energy Co(;pany November 3, 1998 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Palisades Nuclear Plant
- Tel: 616 764 2276 27780 Blue Star Memorial Highway Fax: 616 764 2490 Covert, Ml 49043 Nathan L. Haslrall Director. Licensing DOCKET 50-255 - LICENSE DPR PALISADES PLANT ADDITIONAL INFORMATION REGARDING THE CABLE AMPACITY ADJUSTMENT METHODOLOGY USED FOR PALISADES PLANT While reviewing our cable ampacity evaluation for the Palisades Plant, NRC r~commended in a March 27, 1998, Request for Additional Information, that Consumers Energy modify the ampacity evaluation methodology. In our June 25, 1998 response, we indicated that we would make the modification and complete the evaluation. This letter reports completion of the evaluation and informs NRC of the results.
The March 27, 1998 recommendation was made by NRC to assure that the evaluation methodology would provide reasonable estimates of cable ampacity limits or cable operating temperatures in cases where there are a number of large cables grouped together and the cables are subjected to a range of diverse load conditions. In Item 2.2(b) of the March 27, 1998 letter, the NRC recommends:
A lower bound should be established on the thickness of the combined hot and warm zones in the diversity thermal model. This will (1) prevent excessive thinning" of the more heavily loaded cables, (2) more accurately reflect the presence of larger diameter cables in the hot group, and (3) ensure a conservative treatment of potential clustering effects. The combined thickness of the hot and warm zones should equal or exceed 80% of the diameter of the largest cable in these two groups. If the condition is not met -
by the nominal model formulation, then the width of the analyzed section may be adjusted (reduced) so as to increase the hot/warm zone thickness until the restriction is met provided that the overall heat load for each cable group is maintained at its correct value.
Consumers Energy's June 25, 1998 response stated that we agreed with the NRC's recommendation. We stated that although-our review indicated that adequate margin exists to accommodate any slight increases in cable tray temperatures which might occur due to this lower bound, we would continue our evaluation for every cable tray where a combined thickness of the hot and warm zones is less than 80% of the diameter of the largest cable in these two zones.
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During a te.Jeconf~rence call with Consumers Energy on October 22, 1998, we informed the NRC that of 367 open air cable trays potentially subject to this reevaluation, we had identified that 87 trays met the condition where the hot and warm zones did not exceed 80% of the diameter of the largest cable in these two zones. We indicated that the Palisades computer model had been revised to adjust the width of the tray to ensure the thickness of the hot and warm zones was equal to or greater than 80% of the diameter of the largest cable in these two zones. We stated that the 87 cable trays were then reevaluated using the revised computer model, and that the results indicate that the maximum calculated temperatures remain below the insulation temperature rating of the cables in the trays.
We also stated during the teleconference call that there are 34 trays that pass through fire stops. We indicated that these trays have also been reevaluated for the conditions described above. We stated that all reevaluations of these trays have been completed and, as with the open air trays, the calculated tray temperatures remain below the insulation temperature rating of the cables in the trays.
2 In summary, we have found that in some cases, depending on ampere load of the cables in the tray and the fill of cables in the tray, the maximum tray temperatures calculated as part of the reevaluation using the modified model, have risen slightly over temperatures calculated prior to the reevaluation. However, no calculated maximum tray temperatures have exceeded cable insulation temperature ratings.
During our October 22, 1998 teleconference call, the NRC indicated that receipt of written confirmation of our completion of the reevaluation yielding acceptable results would be needed to close this issue. This letter provides NRC that confirmation. In turn, Consumers requests that NRC provide, by return letter, their disposition of this issue.
To schedule inspection resources, NRC asked during the tel~conference call when the complete ampacity evaluation would be available for NRC Region Ill review. The evaluation will be available for NRC review after February 1, 1999, when Consumers will have completed final review of the evaluation which has been performed by our design engineering contractor.
SUMMARY
OF COMMITMENTS This letter contains no new commitments and no revisions to existing commitments.
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Nathan L. Haskell Director, Licensing CC Administrator, Region Ill, USNRC Project Manager, NRR, USNRC NRC Resident Inspector - Palisades