ML20138Q947
| ML20138Q947 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 10/31/1985 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML20138Q927 | List: |
| References | |
| NUDOCS 8511180346 | |
| Download: ML20138Q947 (8) | |
Text
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4 Analysis of Electray Hanger Rods In Unit 2 Auxiliary Feedwater Pump Room At i
McGuire Nuclear Station i
Prepared by - Design Engineering / Fire Protection Group Duke Power Company i
October 31, 1985 l
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I 8511180346 851104 PDR ADOCK 05000369 O
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i 1.0 Area Description The area under consideration is the southeast corner of the Unit 2 Motor Driven Auxiliary Feedwater Pump Room on the 716+0 ft. elevation of the Auxiliary Building. The bounding walls are constructed of reinforced concrete. The ceiling height is approximately 16 feet. The l
area under consideration is a small portion of a large room, therefore build up of a significant hot layer is not anticipated.
(See Attachment A for a sketch of the area). Automatic sprinklers, portable fire extinguishers and small hose stations are available for fire suppression. Smoke detectors are provided for early warning.
2.0 Problem Statement The problem is to determine if electray hanger rods will lose their support strengh due to elongation and possible subsequent failure of the rods due to the temperature developed as result of the fire below the rods.
In the area is one electray which contains power and control cables for certain motor operated valves. These valves may be required during certain shutdown operations. A one-hour fire resistive barrier wrap is installed on the electray to prevent an exposure fire from damaging the cables in the electray. The exposing cable trays are not wrapped. The postulated fire scenarios of concern are a fire in either of the two cable trays above the electray or floor level fires involving transient combustibles.
3.0 Combustible Loading The presence of combustibles in the area is limited due to the presence of two large CCW pipes. Combustible material present, is cable insulation material in the two cable trays noted in Attachment B.
Transient combustibles were considered, however station directives and housekeeping requirements limit the likelihood of accumulated transient combustibles.
The total loading in the two (2) cable trays shown on Attachment A is 871 lbs. of cable insulation and the average tray loading is 6.60 lbs/ft2 of tray surface area.
(SeeAttachmentsC1andC2forcable insulationcalculations). Enclosed combustibles such as cabling in conduit and in wrapped electray have not been considered in this analysis.
4.0 Analysis 1
The analysis for this area was conducted identical to that noted in the report developed by Professional Loss Control Inc. (PLC) pertaining to the Mechanical Pipe Chase. The same values were utilized regarding hanger rod strength, loading, yield strength and maximum temperature to reach yield point under loaded conditions.
The first scenario examined considered a cable fire in cable trays 1 or 2 approximately 5 feet above the electray.
From information derived in the PLC report:
- Har.ger rod working stress of 503 psi or 0.5 ksi
- Hanger rod yield point at 1597 F
- Surface controlled burning rate of 0.1 (1b/ min)/ft2
- Heat release rate of 16.67 (BTU /sec)/ft2
- Equivalent point source - Tray 1 or 2: 8 fte h=8fte x 16.67 (BTU /sec)/fte = 133.36 BTU /sec H = 3 ft. (Distance to ceiling above fuel source at which point electray support is attached)
This yeilds a maximum temperature at the ceiling of:
=300(Kh)2/3 AT 5/3 H
g,1 Substituting in the values a T = 300 (133.36 BW/sec %
= 1255*
(3)5/3 T = 1330" (ambient =75')
The second scenario examined is a floor level fire involving transient combustibles below the electray at the 724 ft. elevation. The electray supports are a minimum of 8 ft above the floor.
Substituting known values in the following equation aT = 300 (Kh) 2/3 5/3 H
andsolvingforh 1522'=300(6)U (8)5/3 h=2069 BTU /sec Using a heat release rate of 290(BTU /sec)/ft2 (Reference #6inthePLC report), this is equivalent to a 3 ft diameter flammable liquid pool fire, or 14 fte of compartmented cartons stacked 15 ft. high. With housekeeping requirements and automatic suppression capability, such is not considered a credible event.
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5.0 Conclusion 1)
Cable exposure creates a ceiling temperature around the electray supports of approximately 1330 F.
This worst case exposure is less than the failure temperature of the supports. Therefore, the fire endurance of the electray supports is assured in the event of a cable fire. Automatic sprinkler actuation provides an additional margin of safety, 2)
The size of a floor level transient fire capable of failing the electray supports at the 724 ft elevation is 2069 BTU /sec. This is equivalent to a flammable liquid pool fire of 3 ft diameter or 14 ft2 of compartmented cartons stacked 15 ft high.
This transient fire exposure, because of housekeeping reuqirements and station directives, is not a credible event. Automatic sprinkler actuation also provides an additional margin of safety.
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Cable Information Auxiliary Feedwater Pump Room (Unit 2) 1.
24", 26', max fill 97 cables 2.
24", 40', max fill 93 cables Most typical cables are:
3XJ12G1 - 3 conductor 12 Ga.
60 mil PVC 12XJ12G1 - 12 conductor 80 mil PVC 4 SPA 16G.3-4shieldedpair(ie)8 conductors Each conductor 30 mil EPR,15 mil Hypalon, Cables have PVC jackets 30 mil EPR = 10 lb/1000 LF 15 mil Hypalon = 6 lb/1000 LF 15 mil PVC = 6 lb/1000 LF Each conductor of shielded pairs 15 mil PVC & 20 mil Hypalon, 30 mil PVC jacket Suggest that cables be considered equally distributed among the trays.
Attachment B
Cable Insulation Calculations A
B C
(AB)+C No. of Jacket Insulation Conductors Conductor Insulation (PCV)
Total EPR Hypalon 3
10 lbs 6 lbs 4 x 6 lbs 72 lbs 1000 LF 1000 LF 1000 LF 1000 LF 12 10 lbs 6 lbs 5.3 x 6 lbs 224 lbs 1000 LF 1000 LF 1000 LF 1000 LF PVC Hypalon 8
6 lbs 1.3 x 6 lbs 2 x 6 lbs 122.4 lbs 1000 LF 1000 LF 1000 LF 1000 LF TOTAL 418.4 lbs 1000 LF Cables are considered to be equally distributed among trays:
418.4lbs+3 cables (type)=139.5lbs 1000 LF 1000 LF - cable
= 0.1395 lbs ft-cable Attachment C1
CableInsulationCalculations(Cont'd)
Tray 1:
(26ft.)(97 cables)0.1395lbs
= 351.82 lbs.
ft-cable Tray 2:
(40ft.)(93 cables)0.1395lbs
= 518.94 lbs, ft-cable TOTAL 870.76 lbs.
f Area of Trays Tray 1: (2ft.)(26ft.)= 52 ft. 2 Tray 2: (2ft.)(40ft.)= 80 ft. 2 TOTAL 132 ft.2 cable tray surface area Average Tray Loading = 870.76 lbs 132 ft
, 6.60 lbs 2
ft Attachment C2 I
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