ML20080T385

Provides Response to Request for Addl Info Re Ampacity Derating at Plant Due to thermo-lag,per GL 92-08. Calculations Encls

ML20080T385
Person / Time
Site:	Wolf Creek
Issue date:	03/10/1995
From:	Rhodes F WOLF CREEK NUCLEAR OPERATING CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20080T388	List: ML20080T385 ML20080T498 ML20080T503 ML20080T513 ML20080T522
References
ET-95-0013, ET-95-13, GL-92-08, GL-92-8, NUDOCS 9503130293
Download: ML20080T385 (2)

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W$LFCREEK NUCLEAR OPERAllNG CORPORATION March 10, 1995 Forrest T. Rhodes Vice President Engineering ET 95-0013 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk b Mail Station P1-137 Washington, D. C. 20555

Reference:

1) Letter dated September 23, 1994, from R. P. Zimmerman, NRR, to N. S. Carns, WCNOC, Follow-up to the Rcquest for Additional Information Regarding Generic Letter 92-08

2) Letter dated December 22, 1994, from M. S. Carns, WCNOC, to the NRC, Response to the NRC's Follow-up to the Request for Additional Information (RAI) Regarding Generic Letter 92-08

Subject:

Docket No. 50-482: Reply to Requetit for Additional Information Regarding Ampacity Derating at Wolf Creek Due To Therno-Lag Gentlemen:

On January 20, 1995, Mr. Jim Stone, NRC Project Manager, and Mr. Ronaldo Jenkins, NRR Electrical Engineering Branch, initiated a phone call with Wolf Creek Nuclear Operating Corporation (WCNOC) to discuss WCNOC's response (Reference 2) to the NRC's . Follow-up to the Request for Additional Information (RAI) Regarding Generic Letter 92-08 (Reference 1). The purpose of the call was to to request additional information about the portion of Reference 2 concerning ampacn.y derating at Wolf Creek Generating Station (WCGS). Mr. Stone also requested that we provide a written response. This letter is WCNOC's response to those requests.

Mr. Jenkins' request for additional information was based on Section IV of Reference 2. In Section IV WCNOC indicated that ampacity derating at WCGS is

[ based on heat transfer calculations that were performed by WCNOC using TSI-supplied heat transfer coefficient values for Thermo-Lag 330-1, not on actual WCGS test results, and that these calculations indicate that WCGS has adequate ampacity margins. The letter further states that we do not intend to evaluate ampacity deratings on fire barrier configurations that enclose a raceway for six inches or less in length.

Mr. Jenkins requested we provide additional information concerning our methodology and calculations used for ampacity derating. He indicated that only a few plants stated, in response to Reference 1, that they had adequate ampacity margins. He indicated that the NRC would like to assess our methodology to help determine a generic resolution to the ampacity derating issue. Mr. Jenkins asked that we address: 1) how WCGS cable installation configurations compare to the standard configurations described in the draf t IEEE-848, " Procedure For The Determination of The Ampacity Derating of Fire Protected Cables," 2) what WCGS typical cable 9503130293 950310 .O. Box 411/ Burhngton, KS 66839 / Pt.one: '316) 364-8831 0 PDR ADOCK 05000482 P PDR An Equal Opportunity Employer M/F/HC/ VET \\

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L installation configurations are, and 3) how WCNOC ampacity derating calculations were developed. Mr. Jenkins also requested that we provide a typical calculation reflecting WCGS cable installation design, and WCNOC's basis for not evaluating Thermo-Lag barriers of six inches or less in length, p In' response to Mr. Jenkins' requests, WCNOC has enclosed with this letter the four calculations used at WCGS to determine ampacity derating requirements and ampacity

[ margins. These are: 1) Calculation F-10A, Revision 0, " Power Cables with Fire Protection Wrapping -

Temperature Calculations for Determining Derating

' Requirements," 2) Calculation'. XX-E-008, Revision -0, *Ampacity Deratings for f

Conduits with Thermo-Lag 330-1 Fire Wrapping," 3) Calculation XX-E-10, Revision 0,.

• Ampacity Margin of Conduits with Thermo-Lag 330-1 Fire Wrapping," and 4)

Calculation XX-E-011, Revision 0, "Ampacity Margin of Cable Trays with Thermo-Lag l-330-1 Fire Wrapping." These calculations contain discussions of the assumptions and methodologies used in the calculations. Please note that Calculation F-10A has been superseded by Calculation XX-E-008. Calculation F-10A has been included with the enclosures because it is identified in the other calculations as a reference calculation.

WCNOC has excluded from ampacity calculations conduits utilizing six inches or less of fire barrier material because of the heat dissipation characteristics of these installations. WCNOC calculations assume heat transfer on an infinite length of conduit with capped ends to prevent forced convection. The natural convection inside a conduit with six inches or less of fire barrier material, combined with the thermal mass of the cable within the conduit, will dissipate the heat from this short length of conduit such that there would be a minimal rise in temperature. Consequently, the temperature pr a1.n# for a six-inch section of fire-wrapped conduit is insignificant.

WCNOC Design Engineering personnel have discusbud the contents of the draft IEEE-848 with individuals in the industry who are knowledgeable of its contents.

Based on these discussions, our Design EnJ i neering personnel have concluded that WCGS does not contain any non-standard cable installation configurations.

If you should have any questions regarding this response, please contact me at (116) 364-8831, extension 4002, or Mr. Richard D. Flannigan at extension 4500.

Very truly yours,

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j /w Forrest T. Rhodes FTR/jad Enclosures cc: L. J. Callan (NRC), w/e D. F. Kirsch (NRC), w/o J. F. Ringwald (NRC), w/o J. C. Stone (NRC), w/e b

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