ML18036B332
| ML18036B332 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 06/23/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18036B331 | List: |
| References | |
| NUDOCS 9306280163 | |
| Download: ML18036B332 (4) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSlON WASHINGTON, D.C. 20555-0001 ENCLOSURE
.SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO DERATING FACTORS FOR CABLE TRAY COV RS TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT. UNIT 2 DOCKET NO. 50-260
- 1. 0 INTRODUCTION During the NRC staff's review of the Tennessee Valley Authority's (TVA or licensee) cable ampacity evaluation program plan for the Browns Ferry Nuclear Plant (BFN), the staff became aware that TVA was not using a derating factor for cable.tray covers less than 10 feet long.
TVA only applied a
25 percent derating for tray covers over 10 feet 'long.
When the staff requested a copy of the licensee's technical basis and evaluation on this
- issue, TVA responded that this position was based on engineering judgment.
Whereupon, the staff then requested TVA to either conduct a test to demonstrate the derating factor or reduce the tray cover lengths to 6 feet.
This request was documented in Section 3. 11.3.1 of NUREG-1232, Volume 3, Supplement 2 (SSER-2),
dated January 1991, wherein the staff requested TVA to establish derating factors
(-including a technical basis) for cable tray covers between 6 and 10 feet long, and to take any necessary corrective actions, before the end of the first refueling outage following restart.
By letter dated December 29,
- 1992, TVA provided a response to the staff's concern expressed in SSER-2.
In an enclosure to this letter, the licensee indicated that TVA Electrical Design Standard DS-E12.6.3, Revision 2, was i'ssued to incorporate derating factors for cable tray covers over 6 feet long for BFN.
2.0 EVALUATION 2.1 R~VA 2 The licensee stated that Table 8.0-5 in Attachment A of TVA Electrical Design Standard DS-E12.6.3, Revision 2, "Auxiliary and Control Power Cable Sizing, Up to 15000 Volts" provides derating factors for cables in trays with covers and/or bottoms longer than 6 feet and for trays with multiple covers and/or bottoms with combined length exceeding 6 feet and spaced less than 10 feet apart.
The licensee further indicated that this design standard is based upon calculation EEB-CSTF-0001, R2, "Methodology Used as Basis for Cable Ampacities Shown in TVA Electrical Design Standard DS-E12.6.3."
TVA stated that q30b280aibCK 050002b0 p
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Section 4. 11 of calculation EEB-CSTF-0001, R2, addresses cable ampacity factors for tray covers and/or tray bottoms.
In its December 29, 1992 letter, TVA indicated that the 25 percent cable ampacity der ating factor used for sheet metal top tray covers was based on data from "Ampacity of Cable in Covered Tray," Gary Engmann, IEEE Transactions on Power Apparatus and Systems, Volume PAS-103, No. 2, February
- 1984, Paper
'No. 83, SM 305-0.
TVA also stated that the cable tray segments affected by Revision 2 of Design Standard DS-E12.6.3 have been evaluated and properly
- derated, and no physical modifications were required.
2.2 Staff Evaluation Based on a review of the TVA Electrical Design Standard DS-E12.6.3, Revision 2, the staff finds that the licensee has properly applied ampacity derating factors for trays with covers and/or bottoms longer than 6 feet, and for trays having multiple covers and/or bottoms whose combined length exceeds 6 feet and which are spaced less than 10 feet apart.
The multiplying factors used for BFN, Unit 2 are as follows:
Descri tion Multi 1 in Factor Sheet metal bottom Sheet metal top Sheet metal top and bottom 0.890 0.750 0.660 The staff did not review the licensee's evaluations of,cable tray segments affected by Revision 2 of Design Standard DS-E12.6.3.
However, the staff accepts TVA's statement that no physical'odifications were required based on Revision 2 of Design Standard DS-E12.6.3, with the understanding that the Unit 2 cables in tray segments affected by DS-E12.6.3, Revision 2, were derated appropriately.
Based on this review, the staff finds its concern regarding the derating factors for cable tray covers between 6 and 10 feet long, has been resolved.
- However, TVA should retain records of its the evaluation of cable tray segments affected by Revision 2 of Design Standard DS-E12.6.3 for possible future NRC audit or inspection.
3.0
SUMMARY
AND CONCLUSION The staff reviewed TVA's December 29, 1992 response regarding the establish-ment of derating factors (including a technical basis) for cable tray covers between six and ten feet long, and taking any necessary corrective actions,,
before the end of the first refueling outage following Unit 2 restart.
The staff concludes that TVA's response is acceptable and hence, the staff's concern regarding derating factors for cable tray covers between 6 and 10 feet long is considered resolved.
Principal Contributor:
A. N. Pal Date:
June 23, 1993
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