ML20198J003

SER Accepting Licensee Response to GL 92-08,ampacity Derating Issues for Perry Nuclear Power Plant,Unit 1

ML20198J003
Person / Time
Site:	Perry
Issue date:	12/22/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20198J001	List: ML20198H996 ML20198J003
References
GL-92-08, GL-92-8, NUDOCS 9812300070
Download: ML20198J003 (6)

Text

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UNITED STATES

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NUCLEAR REGULATORY COMMISSION t

WASHINGTON, D.C. 20666 0001

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION GENERIC LETTER 92-08 AMPACITY DERATING ISSUES THE CLEVELAND ELECTRIC ILLUMINATING COMPANY PERRY NUCLEAR POWER PLANT. UNIT NO.1 DOCKET NO. 50-440 BACKGROUND By letters date April 16,1993, February 11,1994, December 15,1994, March 22,1995, June 28,1995, October 2,1996, and January 12,1998, The Cleveland Electric illuminating Company responded to Generic Letter 92-08, "Thermo-Lag 330-1 Fire Barriers," dated December 17,1992, in regard to Thermo-Lag 330-1 fire barriers installed at the Perry Nuclear Power Plant, Unit No.1 (PNPP). In addition, letters dated November 20,1995, June 28,1996, and October 28,1996, addressed Thermo-Lag ampacity derating issues.

The consideration of ampacity derating factors for Thermo-Lag fire barriers at PNPP is based on a similarity analysis.1 he licensee used the results from the Texas Utilities Electric Company (TUEC) ampacity derating tests in its evaluation of PNPP Thermo-Lag fire barriers. The specific Thermo-Lag ampacity derating value selected and applied to each configuration was determined by: (1) Reviewing the ampacity derating testing conducted by TUEC; (2) confirming by similarity analysis that the TUEC tested configurations bound instalbd Thermo-Lag configurations at PNPP; and (3) applying the comments discussed in the NRC " Safety Evaluation of Ampacity issues Related to Thermo-Lag Fire Barriers at Comanche Peak Steam Electric Station, Unit 2,"

dated June 14,1995.

The staffs evaluation of the ampacity derating methodology for PNPP follows.

EVALUATION j

After reviewing the licensee's submittals, the staff agrees with the licensee analyses and conclusions. The ampacity derating analysis questions, the licensee's response, and the staffs evaluation of the responses follow.

9812300070 981222 PDR ADOCK 05000440 P

PDR ENCLOSURE i

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) Amoacity Deratino Analysis Review Question 1 The licensee should confirm that all fire barrier construction for the subject configuration (s) are representative of the barrier construction used in the Comanche Peak Steam Electric Station (CPSES), Unit 2 ampacity derating tests.

Licensee Response in its submittal dated October 28,1996, the licensee stated that based on the comparison of the Thermo-Lag installations tested by TUEC to obtain the derating factors described in the referenced 1995 NRC Safety Evaluation and those installed at PNPP, the PNPP Thermo-Lag installations are bounded by the TUEC installations. The PNPP configurations are conservative, from an ampacity perspective, because the tested configurations have a slightly greater thickness of Thermo-Lag material than the PNPP configurations. The upgraded assemblies tested by TUEC presented a worst case when compared to the baseline installation applicable to the PNPP assemblies from an ampacity perspective.

Staff Resoonse The information provided by the licensee fully res Slves the staff's concems.

Question 2 The licensee should verify whether the installed Thermo-Lag fire barriers are single (one 1" thick) or double (two %" thick) layer systems. The Thermo-Lag fire barrier system tested at CPSES 2 was a single layer system.

I Licensee Resoonse i

in its submittal of October 28,1996, the licensee stated that at PNFP, the 1" thick preformed conduit sections of Thermo-Lag are single layer systems. These systems are used for 3-hour rated barriers. Only one conduit is protected by a 3-hour fire rated barrier at PNPP. However, this conduit contains only control power and position indication circuits for the inboard MSIV main pilot air control valves. The licensee confirmed that control cables are adequately sized at PNPP.

39ff Resoonse 4

The information provided by the licensee fully resolves the staff's concerns.

i Question 3

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The typical ampacity derating calculation for a conduit (1R33F01038) used an adjustment factor of 0.8 for 6 energized conductors per National Electric Ccie (NEC).

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t This conduit included 7 cables (at least 30 conductors). The NEC recommends adjustment factor of 0.6 which includes the effects of a load diversity of 50 percent. The licensee needs to provide justification for using 0.8 instead of 0.6. The staff believes that the adjustment factors shall be based on number of conductors in the conduit.

j Licensee Resoonse s

In its submittal of October 28,1996, the licensee stated that the following information is provided for Conduit 1R33F0103B, which contains seven cables.

l Type of Number of B/M Cable Class Circuit Cable in this Cables Number Number j

Conduit 7

l A

1 EKA-72 3/C#6 1M39F68 l

B 1

EKA-75 3/C#12 1E12F8B C

2 EKB-12 2/C#14 D

2 EKB-16 9/C#14 -

E 1

EKB-11 STP#16 l

4 A random sampling of cables supplying loads with operating duration less than 120 seconds (Types C and D) was selected for calculation of their ampacity margins. Their positive margins indicated that the cables supplying loads of short operating duration are adequately sized at PNPP, and therefore, were excluded from the calculation. In addition, instrumentation cables (Type E) were excluded from the calculation because they are not sized on the basis of ampacity. They carry low current in the milli-ampere range and the Thermo-Lag fire barriers have no impact on the ampacity of these cables.

i Therefore, the only cables included in the derating calculation for this conduit were j-Types A and B. The adjustment factor provided in NEC Table 310-19 Note 8 was applied. Load diversity was not credited in the PNPP Calculation MISC-009.

i From the table above, there is one Type A cable in this conduit, which is a three-l conductor #6 AWG cable. In addition, there is one Type B cable in this conduit which is

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a three-conductor #12 AWG cable. As stated above, the only cables included in the derating calculation for this conduit were Types A and B. Per NEC, the adjustment factor is 0.8 for 6 energized / current carrying conductors in conduit.

Staff Response 1

l The information provided by the licensee fully resolves the staff's concems.

Question 4 l

For cables installed in exposed or enclosed groups of conduits in air, the grouping j

factors given in Table IX of ICEA Standard P-46-426 shall be used when the spacing l

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} between conduit surfaces is not greater than the conduit diameter or less than 1/4 of the conduit diameter. The sample calculation did not use conduit grouping factor. Provide a discussion about conduit grouping factor at PNPP.

Licensee Resoonse in its submittal of October 28,1996, the licensee stated that the use of conduit grouping factor described in ICEA Standard P-46-426 applies to cables installed in exposed or i

enclosed groups of conduits in air. However, conduits are wrapped individually at PNPP.

Therefore, the use of the conduit grouping factor is not applicable to PNPP.

Staff Resoonse The information provided by the licensee fully resolves the staffs concems.

Question 5 j

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Provide conduit size and conduit fill for the sample calculation for conduit Number 1R33F0103B. Provide justification of cable ampacity if the conduit fill exceeds the value given in NEC tables.

l Licensee Response I

j in its submittal of October 28,1996, the licensee stated that Conduit Number 1R33F01038 is a 2.5" conduit. As stated in Section 3.03 of PNPP Calculation No.

MISC 5009 conduits, trays, and cables are instal!ed per PNPP Installation Standard i

Specification SP-2250, Electrical Work and Equipment. This installation specification l..

administratively controls the maximum conduit fill for conduits at PNPP to be 40%, in accordance with NEC requirements provided in Table 1 of NEC Chapter 9.

4 Staff Resoonse p

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The information provided by the licensee fully resolves the staffs concems.

I Question 6 i

The licensee needs to provide specific and complete examples of the ampacity derating calcubtions illustrating all aspects of those calculations in detail (baseline ampacity with source, cable characteristics, cable diameter, tray size and type, percent fill, fire barrier l

rating, etc.) for typical 1-hour tray (480 volt circuit) and typical air drops.

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l Ligpnsee Response In its submittal of October 28,1996, the licensee provided a typical ampacity derating calculation for a tray in Attachment 2 of the subject submittal.

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I The two cable bundle free air drop configurations tested by TUEC consisted of 12' long cable bundles. At PNPP, there are no air drop configurations similar to this configuration. However, there are raceway configurations where intersecting trays and/or conduits are not continuous (physically joined with fittings). Field walkdowns of Thermo-Lag installations were performed to determine the space between tray / tray and tray / conduit intersections. The space between tray / tray intersections is less than 16",

i and the space between tray / conduit intersections is less than 10". The cable (s) routed through these sections of the raceways are wrapped with Flex Blanket Thermo-Lag. The interfaces between raceways protected with Thermo Lag materials are not factors in determining the overall ampacity derating. This type of configuration variation occurs for a short part of the overall run of the Thermo-Lag protected raceways. As stated in the l

referenced 1995 NRC Safety Evaluation, the variations in construction for short i

t distances are not expected to impact the overall ampacity derating given the conservatism applied in the derating factors used. Therefore, no ampacity derating calculations were performed for these variations in construction.

Additionally, the ampacity of cables with the above configurations were derated based on j

their applicable raceways (i.e., tray or conduit) in addition to derating due to the presence l

of Thermo-Lag material. The nominal ampacity of a cable routed in a tray was derated based on the depth of cables in the tray and then derated again by 3.5% for the presence of Thermo-Lag material. The nominal ampacity of a cable routed in conduit i

was adjusted per NEC Table 310-19 Note 8 and further derated by 21% for the presence j

of Thermo-Lag material.

~ 'ff Response j

The information provided by the licensee fully resolves the staff's concems.

_ uestion 7 i

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The sample calculation used a load factor of 1.0 for resistive loads and 1.1 for other loads. This is acceptable provided the loads are not operating at an overload condition l

or at a service factor. Provide a discussion about the overload or the service factor of the load.

l Licensee Response i

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In its submittal of October 28,1996, the licensee stated that a PNPP long time j

overcurrent protection for motors is based on the fullload current rating of the motor. An j

additional step in assuring the adequacy of motor protection was accomplished during i

initial testing. Field measured motor currents in excess of the full load current ratings (overload) noted during testing were reported to engineering personnel in accordance l

with procedure gel-0049. The measured values were then evaluated to determine f

acceptability of the motor and motor protection.

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I At normal plant operating voltages, heater and motor load ampacities are typically below their nameplate values or have been evaluated by the above mentioned procedure. No overloads have been identified, therefore, the load factors identified are appropriate.

Staff Response The information provided by the licensee fully resolves the staffs concerns.

Question 8 Certain non-continuous loads (heaters, heat trace circuits) may operate for an extended period when called on to operate (during extreme cold weather, the heaters might i

operate at near continuous levels for extended periods). Provide a discussion of these circuits.

Licensee Resoonse in its submittal of October 28,1996, the licensee stated that ampacity derating calculations for heater circuits described in Calculation MISC-009 are based on continuously energized leads. Ampacity margins for the feeder circuits were calculated as continuous loads based on the heater nameplate rating with the exception of two heaters. For these two heaters, the subject calculation utilized the actual field test results. Therefore, the loads cited in this question were considered to be continuously energized, regardless of environmental changes, and have been conservatively derated by the licensee.

1 Staff Response The information provided by the licensee fully resolves the staffs concerns.

Acolication of Amoacity Deratino Methodolooy Using the Thermo-Lag ampacity derating factor (ADF) based upon industry tests, the licensee incorporated the applicable test data in PNPP cable ampacity design. The resulting ampacity derating value was then compared to the plant service loads to ensure that the actual operating conditions do not result in exceeding cable ratings. The licensee response to the staffs l

questions indicates that all of the PNPP Thermo-lag protected cable installations are applicable l

to its corresponding TUEC tested configuration.

CONCLUSIONS On the basis of its review, the staff concludes that no ampacity derating cencems as identified by GL 92-08 rema'in outstanding at the Perry Nuclear Power Plant.

Principal Contributor: Ronaldo Jenkins Date: December 22, 1998

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