ML18067A555
| ML18067A555 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 05/27/1997 |
| From: | Robert Schaaf NRC (Affiliation Not Assigned) |
| To: | Bordine T CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 9705290340 | |
| Download: ML18067A555 (5) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555--0001 Thomas. C. Berdine Manager, Licensing Palisades Plant 27780 Blue Star Memorial Highway Covert, Ml 49043 May 27' 1997
SUBJECT:
PALISADES PLANT - REQUEST FOR ADDITIONAL INFORMATION REGARDING CONSUMERS POWER COMPANY'S CABLE AMPACITY ADJUSTMENT METHODOLOGY
Dear Mr. Berdine:
The NRC staff held a teleconference with members of your staff and representatives of Sargent & Lundy (S&L) on April 10, 1997, to discuss the results of analyses performed to verify that cables in cable trays and conduits loaded in excess of the limits identified in the Palisades Final Safety Analysis Report (FSAR) do not exceed their qualified temperatures. This issue was initially identified on July 11, 1996, when Consumers Power Company determined that a number of cables did not meet the ampacity design basis stated in Section 8.5.2 of the Palisades FSAR. Specifically, power cables in overfilled cable trays (i.e., trays with greater than 30 percent physical fill) had not been analyzed or dispositioned to confirm that existing ampacity limits were acceptable.. Your report of this condition included a determination that all of the affected cables remained operable.
Your preliminary reviews of overfilled cable trays determined that approximately 2700 of 2900 power cables were routed in trays with greater than 30 percent fill. The most limiting conditions identified were cables routed through penetrations, where the potential for cable overheating is greatest. You analyzed overfilled cable tray sections to identify cables that exceeded their ampacity ratings using the IPCEA/ICEA method and made adjustments using the Harshe-Black ampacity methodology. The Harshe-Black methodology, described in the Institute of Electrical and Electronic Engineers (IEEE) paper entitled "Ampacity of Cables in Single Open-Top Cable Trays," by B. L.
Harshe and W. Z. Black, is a mathematical thermal model for predicting the operating temperatures for cables when there is load diversity (i.e., cable trays do not have all cables loaded simultaneously to their maximum allowable levels) in a single, horizontal, open-top cable tray. Based on the adjustments made using this methodology, you concluded that while certain analyzed cables exceeded the IPCEA/ICEA ampacity limits, the cable thermal limits were not exceeded and therefore, the FSAR design basis was met.
To assess your application of the Harshe-Black ampacity methodology, which has not previously been reviewed by the staff, to the overfilled cable raceways at P.* alisades, J
the staff requests your response to the enclosed questions.* In order to support
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I l 290060 ac IMP!
o 9705290340 970527 PDR ADOCK 05000255 P
- .1 T. contract assistance to the NRC staff in the conduct of this review, we request that you provide this information within 45 days from the date of this letter.
If you have any questions regarding this request, you may contact me at (301) 415-1312.
Docket No. 50-255
Enclosure:
As stated cc w /encl: See next page DISTRIBUTION:
Docket File PUBLIC PD# 3-1 Reading J. Roe OGC ACRS R. Jenkins B. Burgess, Riii Sin.cerely, ORIGINAL SIGNED BY Robert G. Schaaf, Project Manager Project Directorate 111-1 Division of Reactor Projects - 111/IV Office of Nuclear. Reactor Regulation DOCUMENT NAME: G:\\WPDOCS\\PALISADE\\AMPACITY.RAI To receive a copy of this document, indicate in the box C =Copy w/o attachment/enclosure E =Copy with attachment/enclosure N
= No copy OFFICE LA:PD31 BC:EELB 1f NAME CJamerson JCalvo *(VfC DATE
')"I zU97 5 I z.'f197
Mr. Thomas C. Bordine Consumers Power Company cc:
Mr. Thomas J. Palmisano Site Vice President Palisades Plant 27780 Blue Star Memorial Highway Covert, Michigan 49043 Mr. Robert A. Fenech, Sr Vice Pres Nuclear, Fossil, and Hydro Operations Consumers Energy Company 212 West Michigan Avenue Jackson, Michigan 49201 M. I. Miller, Esquire Sidley & Austin 54th Floor One First National Plaza Chicago, Illinois 60603 Mr. Thomas A. McNish Vice President & Secretary Consumers Energy Company 212 West* Michigan Avenue Jackson, Michigan 49201 Judd L. Bacon, Esquire Consumers Energy Company 212 West Michigan Avenue Jackson, Michigan 49201 Regional Administrator, Region Ill U.S. Nuclear Regulatory Commission 801 Warrenville Road' Lisle, Illinois 60532-4351 Jerry Sarno Township Supervisor Covert Township 36197 M-140 Highway Covert, Michigan 49043 Office of the Governor Room 1 - Capitol Building Lansing, Michigan 48913 Palisades Plant U.S. Nuclear Regulatory Commission Resident Inspector's Office Palisades Plant 27782 Blue Star Memorial Highway Covert, Michigan 49043 Drinking Water and Radiological Protection Division Michigan Department of Environmental Quality 3423 N. Martin Luther King Jr Blvd P. 0. Box 30630 CPH Mailroom Lansing, Michigan 48909-8130 Gerald Charnoff, Esquire Shaw, Pittman, Potts and Trowbridge 2300 N Street, N. W.
Washington DC 20037 Michigan Department of Attorney General Special Litigation Division 630 Law Building P.O. Box 30212 Lansing, Michigan 48909 April 1997
- 1..J,,..
REQUEST FOR ADDITIONAL INFORMATION CABLE AMPACITY ADJUSTMENT METHODOLOGY PALISADES NUCLEAR PLANT
- 1.
Please explain how the population of cables analyzed was selected. What assurances exist that all cables requiring adjustment in accordance with Final Safety Analysis Report (FSAR) Section 8.5.2 have been identified for analysis?
- 2.
Palisades FSAR Section 8.5.2 (pg. 8.5-2) states, in part, that:
Cables installed in ventilated trays, conduit or underground ducts are thermally sized in accordance with NEC or IPCEA/ICEA ampacity values (depending on cable physical size) of concentric stranded insulated cable for the conductor operating temperature of the insulation. Insulation type may be of thermosetting, rubber or plastic. Ampacities are adjusted based on actual field conditions when possible. These adjustments may include, but not be limited to, conductor operating temperature, ambient temperature, cable overall diameter, tray depth of fill, conduit percent fill, and fire-stops.
Insulated Power Cable Engineers Association/Insulated Cable Engineers Association (IPCEA/ICEA) or National Electrical Code (NEC) standards permit the modification of various design parameters for cables (typical design parameters are cited in the subject FSAR section). However, each parameter modification is adjusted in accordance with the IPCEA/ICEA or NEC procedure that reflects a well understood technical basis between the parameter and the allowable ampacity value. Please provide responses to the following qu~stions:
(a)
How are ampacity values adjusted consistent with *the FSAR design basis using the Harshe-Black ampacity methodology?
(bl What is the technical basis for using the Harshe-Black methodology versus the methodology specified by NEC or IPCEA/ICEA standards?
(c)
Is the Harshe-Black ampacity methodology more conservative in terms of ensuring that the applicable cables remain within their thermal limits than the approach taken by NEC or IPCEA/ICEA?
- 3.
The Harshe-Black ampacity methodology as detailed in the referenced IEEE
[Institute of Electrical and Electronic Engineers] paper, "Ampacity of Cables in Single, Open-Top Cable Trays," describes the following limitations to the applicable thermal model:
ENCLOSURE
a) b)
c)
- Since the model is one-dimensional and steady state, it should not be used where significant fill variation exists along the length of the tray or in situations where changes with respect to time exist.
The Uniform Model temperature assumes the individual power conductors are spread uniformly across the cable bundle. This model predicts the average temperature of the cable bundle in the tray, but it is not a good model for grouped power cables.
The maximum cable ampacity should still be restricted to 80 percent of the free-air ampacity as stated in the IPCEA/ICEA Standard.
For each of the points above confirm that the application of the Harshe-Black ampacity methodology has been implemented within the stated limitations or provide a technical justification for any deviations to the application of the subject model.
- 4.
You identified a number of cables that could exceed their derated ampacity limits and indicated that the cables should be considered operable as the calculated elevated temperatures could result in premature cable jacket aging, but not catastrophic failure. Please address the following questions:
a)
A number of cases involve cables in conduits, openings (cables in air),
sleeves, and ducts that did not meet the acceptance criteria. Given that the Harshe-Black ampacity methodplogy is based on cable trays, please explain how the subject methodology is applied for other electrical raceway types.
b)
It is not clear whether any of the identified cables have a rated temperature of 75 °C versus the 90 °C rating assumed in your analyses.
Given the elevated temperatures calculated, please estimate the remaining qualified life for the identified cables.
c)
Specify the schedule for final disposition of corrective action for cables that have been identified as not being in compliance with the ampacity design basis as stated in FSAR Section 8.5.2; and provide justification for continued operability of the affected cables, including consideration of the potential impact of cable failures on adjacent circuits.
- 5.
Please provide typical calculations for each raceway type (e.g., tray, conduit, duct, etc.) where the Harshe-Black ampacity methodology was utilized to adjust ampacity values in accordance with FSAR Section 8.5.2. The sample calculations should represent worst-case configurations in terms of uncertainty of calculated results using the Harshe-Black ampacity methodology.