PY-CEI-NRR-2105, Responds to NRC 960905 RAI Re Thermo-Lag Ampacity Derating Issues

Responds to NRC 960905 RAI Re Thermo-Lag Ampacity Derating Issues

ML20134E787
Person / Time
Site:	Perry
Issue date:	10/28/1996
From:	Myers L CENTERIOR ENERGY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20134E790	List: ML20134E799 PY-CEI-NRR-2105, Responds to NRC 960905 RAI Re Thermo-Lag Ampacity Derating Issues
References
PY-CEI-NRR-2105, NUDOCS 9611040105
Download: ML20134E787 (8)

Text

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. CENTE.R.CO.R.

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PERRY NUCLEAR POWER PLANT Mail Address:

P.O. BOX 97 10 CENTER ROAD PERRY, OHIO M 81 PERRY, OHIO 44081 (216) 259 3737 i

October 28,1996 PY-CEI/NRR-2105L United States Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Perry Nuclear Power Plant Docket No. 50-440 Response to the Request for Additional Information - Thermo-Lag Ampacity Derating Issues, Perry Nuclear Power Plant Unit No.1 Ladies and Gentlemen:

In a letter dated June 28,1996, information mgarding the ampacity derating issue at the Perry Nuclear Power Plant (PNPP), Unit No.1, was submitted to the Nuclear Regulatory Commission l

(NRC). In a request for additional information dated September 5,19%, the NRC staff stated that an initial review of the response had been performed, and additional information was needed to complete the review. Attachments 1 and 2 to this letter pmvide the response to the request for additionalinformation.

If you have questions or require additional information, please contact Mr. James D. Kloosterman, Manager - Regulatory Affairs, at (216) 280-5833.

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Very truly yours, l

sO U Lew W. Myers Vice President - Nuclear KMN:sc l

Attachments cc:

NRC Project Manager NRC Resident inspector NRC RegionIII 9611040105 961028 PDR ADOCK 05000440 P

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Attachment I PY-CEI/NRR 2105L t

Page 1 of 7 BACKGROUND As described in Reference 2, the NRC staff mquested that additional information be pmvided l

with respect to the ampacity derating issues for circuits pmtected by %enno-Lag 330-1 fire barriers at the Perry Nuclear Power Plant (PNPP). Responses to the request for additional information are pmvided below.

NRC Ouestion 2.1 Confinn that all fire barrier construction for the subject configuration (s) are representative of the barrier constmetion used in the Comanche Peak Steam Electric Station (CPSES), Unit 2, ampacity den mts.

l PNPP Response to Ouestion 2.1 As stated in Reference 3, the following characteristics could affect the ampacity derating factor l

when comparing the %ermo-Lag barriers at PNPP to the configurations tested by Texas Utilities Electric Company (TUEC):

1. Configuration of the Raceway Pmtected (e.g., tray, conduit, boxes, airdmps)

2. Raceway Material (e.g., steel, aluminum) l~

3. Raceway Size j

4.

Barrier Material (i.e., nermo-Lag 330-1, 330-660 blanket)

5. Dickness of the Banier

6. Joint Assembly (e.g., prebuttered, dry fit) l

7. Stress Skin Application (i.e.,inside oroutside barrier)

De %ermo-Lag installations tested by TUEC to obtain the ampacity derating factors used in the PNPP ampacity derating calculations are described in References 4 and 5. De tested configurations are described below:

'ES'ED 'IRAYS - One 4-inch x 4-inch steel tray was tested. De barrier material consisted of a Thenno-Lag 330-1 preformed panel with a baseline thickness of 1/2";

+.125", -0". De joints wem prebuttered. De upgrade applied Stiess Skin over all seams, with 5" overlap on either side of the joints. An additional layer of appmximately 3/16" thick tmwel grade material was added for the 5" overlap. A coating of Ecrmo-Lag 350 Topcoat material was applied over upgraded areas.

TES'ED CONDUITS - nree conduits were tested: a 3/4" steel conduit, a 2" steel I

conduit, and a 5" steel conduit. The baseline barrier material for all sizes consisted of Thenno-Lag 330-1, preformed, half round sections with a thickness of 1/2"; +.125".-0".

De joints were prebuttered. De upgrade for the 3/4" and 2" conduits applied a preformed overlay section with a thickness of 1/4"; +.125", -0". Rese preformed l

sections were applied over the baseline with joints prebuttered. No additional preformed i

overlay section upgrade material was applied over the 5" conduit. A coating of %ermo-l Lag 350 Topcoat material was applied over the upgraded areas.

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'IES'IED AIR DROPS - Two types of air drops were tested: small air drops (single cane outside of a condult) and large air drops (several canes bundled into one barrier). De barrier material consisted of a %ermo-Lag 330-660 blanket. nree layen were applied, with a 2"- 4" ovedap at the seams. The overlap areas were plebuttered with Hermo-l Lag 330-660 Trowel Grade material.

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Rese configurations involved a reinforcement of the baseline application with additional stress l

sidn and/or Bermo-Lag thickness to achieve the additional stmetuml strength and thennal

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l resistance needed to survive the 1-hour fire test. Derefoie, fmm an ampacity pempective, these upgraded assemNies presented a worse case when compared to the baseline installations.

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A review of the plant design documents, inanHasion instructions, and vendor documentation has I

l been completed to determine the general installation techniques and details used for installation of

. the fine rated Bermo-lag barries at PNPP. A walkdown of several installations was done to verify the overall applicability of this information. %e examination ofintemal assembly details

- was limited to those areas where the material has been removed. Derefore, the infonnation on the baniers reflects the typical construction of the majority of the installations at PNPP. De installations at PNPP are comparable to the baseline installations described in References 4 and 5 without the upgrades.

PNPP TRAYS - De cable trays at PNPP are protected using Denno-Lag 330-1 prefabricated panels. The pints are plebuttered, with %ermo-Lag 330-1 trowel grade applied to the pints prior to assembly. De baseline fire barrier panel thickness is specified on plant design drawings (Reference 6). De 1-hour barrien installed at PNPP have a thickness of 1/2"; +.125", -0". His infonnation is also applicable to junction box assemNies.

PNPP CONDUITS - Prefonned conduit sections are used for raceways where ampacity derating is a concem. Stress skin is inside preformed assemNies. %e phits are prebuttered, with %ermo-Lag 330-1 tmwel grade applied to pints prior to assembly.

he completed conduit assemNy for the 1-hour barriers installed at PNPP have a j

thickness of 1/2"; +.125",-0" De 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> barrier installed at PNPP has a thickness of 1"; +.25", -0".

PNPP AIR DROPS - he PNPP design uses two layers of the %crmo-Lag 330-660 conformaNe blanket, surmunding the cables with a 2" overlap at the seams. Denno-

]

t Lag 330-1 tmwel grade is applied to gaps and pints. Dere is no overcoat required for j

l small air drops; however, the large drops between tmys have a coating of trowel grade material. For some applications, the cables are grouped in a layer of nermo-Lag 330-l.

70 conformable blanket over stress skin. The assembly is protected with a 0.5"; +.125",

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-0" layer of Denno-Lag 330-1 trowel grade material over another layer of stress sidn.

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Ris is equivalent to the thickness and material type used for the pitfonned panels 3

protecting the tray.

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%c following taNe pmvides a comparison of the TUEC tested installations and the installed 1

PNPP installations, i

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PY-CEl/NRR-2105L Page 3 of 7 COMPARISON OF PNPP AND TUEC THERMO-LAG CONFIGURATIONS CONFIGURATION OF THE COMANCHE PEAK PERRY RACEWAY AND BARRIER TESTED CONFIGURATION CONFIGURATION TRAY j

l Raceway Material Steel Steel l

t Raceway Size 24' wide; 4" high 6* 30" wide; 3" & 5"high Barrier Material TherrroLag 3301 preformed panois Thermo-Lag 3301 pseformed panels J

Baseline Thickness of Material 1/2"; +.125,"-0" 1/2"; +.125,* -0*

J Additional Thickness of Upgrade Trowel grade / Stress Skin At Joints None Joint Assembly Prebuttered Prebuttered Stress Skin Application inside Barrier inside Barrier Top Coat Thermo-La0 350 None CONDUlT Raceway Material Steel Steel i

Raceway Size 3/4" & 2" 3/4". 2" t

Barrier Material Thermo-La0 330-1 preformed sections Thermo-Lag 330-1 preformed sections i

Baseline Thickness of Material 1/2"; +.125,* 0*

1/2"; +.125,* -0" l

Additional Thickness of Upgrade 1/4*; +.125,* -0*

None i

Joint Assembly Probuttered Probuttered i

l Stress Skin Application inside Barrier inside Barrier

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Top Coat Thermo-tag 350 None 1

CONDUIT l

Raceway Material Steel Steel Raceway Size 5*

2" - 4*

Barrier Material Thermo-Lag 330-1 preformed sections Thermo-Lag 330-1 pretormed sections Baseline Thickness of Material 1/2"; +.125,* -0" 1/2"; +.125,"-0" Addinonal Upgrade Trowel Grade / Stress Skin (Bends Only)

None Joint Assembly Probuttered Prebuttered Stress Skin Application inside Barrier inside Barrier Top Coat Thermo-tag 350 None AIR DROP I

Raceway Material None None Barrier Material Thermo-Lag 330-660 blanket Thermo-Lag 33 mig 0 blanket

)

l Baseline Material Application 2 Layers 2 Layers l

Additional Upgrade 1 Layer None Joint Assembly Probuttered Probuttered Stress Skin Application N/A N/A l

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Based on the comparison of the Lenno-Lag installations tested by TUEC to obtain the derating factors described in Reference 5 and those installed at PNPP, the PNPP Thermo-Lag installations l

are bounded by the TUEC installations for ampacity derating concems, The PNPP l

configurations are conservative, from an ampacity perspective, because the tested configurations have a slightly greater thickness of Thermo-Lag material than the PNPP configurations.

Therefore, the use of the TUEC ampacity derating factors at PNPP is justified. We upgraded assemblies tested by TUEC presented a worst case when compared to the baseline installation applicable to the PNPP assemblies from an amg acity perspective.

NRC Ouestion 2.2 Confinn whether the installed Bermo-Lag fist barriers are single (one 1" thick) or double (two 1/2" thick) layer systems. We Denno-Lag fire barrier system tested at CPSES 2 was a single layer system.

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PY-CEI/NRR-2105L Page 4 of 7 If a double layer system is used at PNPP then the scaling methodology used on the TU test results is invalid and may prove to be non-conservative for application. If the above case proves true, CEI should provide additional justification for the extrapolation of the single layer test results to a double layer system or pmvide an altemative basis for ampacity derating detennination and analysis of the installed Thermo-Lag configuration.

PNPP Response to Ouestion 2.2, t

At PNPP, the 1" thick prefonned conduit sections of henno-Lag are single layer systems.

Rese are used for 3-hour rated barriers. As stated in Reference 3, only one conduit is pmtected by a 3-hour fire rated barrier at PNPP. However, this conduit contains only contml power and l

position indication circuits for the inboard MSIV main pilot air control valves. As described in l of Reference 3, control cables are adequately sized at PNPP.

l NRC Ouestion 23 I

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De typical ampacity derating calculation for a conduit (IR33F0103B) used an adjustment factor l

of 0.8 for 6 energized conductors per National Electric Code (NEC). This conduit included 7 l

cables (at least 30 corxiuctors). De NEC recommends adjustment factor of 0.6 which includes the effects of a load diversity of 50 percent. Provide justification for using 0.8 instead of 0.6.

PNPP Response to Ouestion 23 of Reference 3 pmvided the following information for conduit number l

1R33F0103B, which cornains seven cables.

Type of Cablein Number of B/M Circuit Cable Class this Conduit Cables Number Number A

1 EKA-72 3/C #6 1M39F6B B

1 EKA-75 3/C #12 1E12F8B C

2 EKB-12 2/C #14 D

2 EKB-16 9/C #14 E

1 EKC-11 STP #16 As stated in Reference 3, a random sampling of cables supplying loads with operating duration less than 120 seconds (types C aIxl D) was selected for calculation of their ampacity margins.

Beir positive margins indicated that the cables supplying loads of short operating duration are adequately sized at PNPP, and therefore, were excluded fmm the calculation. In addition, instmmentation cables (type E) were excluded from the calculation because they are not sized on the basis of ampacity. Rey carry low current in the milli-amp range and the %ermo-Lag fire l

barriers have no impact on the ampacity of these cables. Herefore, the only cables included in the derating calculation for this conduit were types A and B. The adjustment factor provided in NEC Table 310-19 Note 8 was applied. Load diversity was not credited as part of the Reference 7 calculation.

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PY-CEl/NRR-2105L Page 5 of 7 r

1 Fmm the table above, there is one type A cable in this conduit, which is a three-conductor #6 I

AWO cable. In addition, there is one type B cable in this conduit, which is a thme-conductor #12 AWG cable. As stated above, the only cables included in the derating calculation for this conduit l

were types A and B. Per National Electric Code (NEC), the adjustment factor is 0.8 for 6 i

energized / current carrying conductors in conduit.

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NRC Ouestion 2.4 For cables installed in exposed or enclosed groups of conduits in air, the grouping factors given l

in Table IX of ICEA Standard P-46-426 shall be used when the spacing between conduit surfaces l

is not greater than the conduit diameter or less than 1/4 of the conduit diameter. The sample l

calculation did not use conduit gmuping factor. Pmvide a discussion about conduit grouping factor at PNPP.

L PNPP Response to Ouestion 2.4 l

The use of the conduit grouping factor described in ICEA Standard P-46-426 applies to cables l

installed in exposed or enclosed groups of conduits in air. However, conduits am wrapped l

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

NRC Ouestion 2.5 Pmvide conduit size and conduit fill for the sample calculation for conduit number 1R33F0103B.

Pmvide justification of cable ampacity if the conduit fill exceeds the value given in NEC tables.

PNPP Response to Ouestion 2.5 Conduit number 1R33F0103B is a 2.5" conduit. As stated in Section 3.03 of Reference 7, conduits, trays, and cables are installed per Installation Standard Specification SP-2250, Electrical Wodc and Equipment (Refemnce 8). 'Ihis installation specification administratively controls the maximum conduit fill for conduits at PNPP to be 40%, in accordance with National Electric Code (NEC) requirements pmvided in Table 1 of NEC Chapter 9.

NRC Ouestion 2.6 Pmvide specific and complete examples of the ampacity derating calculations illustrating all i

aspects of those calculations in detail (baseline ampacity with source, cable characteristics, cable diameter, tray size and type, percent fill, fire barrier rating, etc.) for typical 1-hour tray (480 volt l

circuit) and typical air drops.

PNPP Resoonse to Ouestion 2.6 A typical ampacity derating calculation for a tray is provided as Attachment 2.

The two cable bundle free air dmp configurations tested by TUEC consisted of 12' long cable bundles (Reference 4). At PNPP, there am no air drop configurations similar to this. However, a

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PY-CEI/NRR 2105L Page 6 of 7 i

there are raceway configurations where intersecting trays and/or conduits are not continuous (physicallyjoined with fittings). Field walkdowns of Benno-Lag installations were perfonned to I

detennine the space between tray / tray and tray / conduit intersections. De space between j

tray / tray intersections is less than 16", and the space between tray / conduit intersections is less than 10". De cable (s) routed thmugh these sections of the raceways are wrapped with Flex

[

Blanket Denno-Lag (Reference 6 detail"H"). The interfaces between raceways protected with

%ermo-Lag materials are not factors in determining the overall ampacity derating. His type of f

l configuration variation occurs for a short part of the overall run of the Dermo-Lag pmtected i

raceways. As stated in the NRC staff Safety Evaluation (Reference 5), the variations in j

construction for short distances are not expected to impact the overall ampacity derating given l

the conservatism applied in the derating factors used. Derefore, no ampacity derating j

calculations were perfonned for these variations in construction.

1 Additionally, the ampacity of cables with the above configurations were derated based on their applicable raceways (i.e., tray or conduit) in addition to derating due to the presence of Bermo-Lag. 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 31.5% for the presence of nermo-Lag material. De j

nominal ampacity of a cable routed in conduit was adjusted per NEC Table 310-19 Note 8 and funher derated by 21% for the presence of Dermo-Lag material.

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NRC Ouestion 2.7 1

l De sample calculation used a load factor of 1.0 for resistive loads and 1.1 for other loads. His l

is acceptable provided the loads are not operating at an overload condition or at a service factor.

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

PNPP Response to Question 2.7

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At PNPP, long time overcurrent pmtection for motors is based on the full load current rating of the motor. An additional step in assuring the adequacy of motor protection was accomplished l

during initial testing. Field measured motor currents in excess of the full load cunent ratings l

(overload) noted during testing were reponed to engineering (Reference 10). De measured values were evaluated to detennine acceptability of the motor and motor protection.

At normal plant operating voltages, heater and motor load ampacities are typically below their nameplate values or have been evaluated by engineering (Reference 10). No overloads have been identified, therefore, the load factors identified are appropriate.

NBC ouestion 2.8 Cenain 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 operate at near continuous levels for extended periods). Provide a discussion of these circuits.

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l Attaciunent i PY-CEl/NRR 2105L Page 7 of 7 PNPP Response to Ouestion 2.8 l

i Ampacity derating calculations for heater circuits described in calculation MISC-0009 (Reference 7) are based on continuously energized loads. Ampacity margins for the feeder l

circuits were calculated as continuous loads based on the heater nameplate rating with the l

exception of two heaters. For these two heaters, the calculation utilized the actual field test l

msults (Reference 7). Therefore, the loads referenced in this question were considered to be l

continuously energized, regardless of envimnmental changes, and have been conservatively derated.

REFERENCES l

1.

NRC Genetic Letter (GL) 92-08, Thermo-Lag 330-1 Fire Barriers.

2. NRC Letter to D. Shelton (Centerior) dated 09/05S6, Request for Additional Infonnation 'Ihenno-Lag Related Ampacity Derating issues, Perry Nuclear Power Plant, Unit No.1 (PY-NRR/CEl-0832L).

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3. Letter fmm D. Shelton (Centerior) to NRC dated 06/28S6, Response to the Follow-up to the Request for Additional Information Regartling Generic letter 92-08,"Thermo-Lag i

330-1 Fire Barriers"- Ampacity Derating, Chemical Composition, and Radiant Energy l

Heat Shield (PY-CEl/NRR-2067L).

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4.

Omega Point Laboratories Report No.12340-94583,95165-95168,95246, Ampacity j

Derating of Fire Pmtected Cables, dated 03/19S3.

5. NRC Letter to Texas Utilities Electric Company dated 0&l4SS, Safety Evaluation of i

i Ampacity issues Related to Thermo-Lag Fire Barriers at Comanche Peak Steam Electric j

Station, Unit 2 (TAC No. M85999).

6. Perry Nuclear Power Plant (PNPP) Design Drawing D-201-146, Sheet 3-4.

7. PNPP Calculation Number MISC-0009, Revision 0.

8. PNPP Installation Standard Specification SP-2250, Electrical Work and Equipment.

9. National Electric Code (NEC) NFPA 70,1996.

10. PNPP Procedure gel-0049.

I1. Insulated Cable Engineers Association (ICEA)(IPCEA) Standard P-54-440 (NEMA WC 51),1986, Ampacities of Cables in Open-Top Cable Trays.

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