ML20212B398

Forwards Evaluations of Several Fire Barriers & Two Internal Penetration Seal Configurations That Provide Fire Resistance Less than 3 H for Review & Concurrence Per Generic Ltr 86-10.W/three Oversize Drawings

ML20212B398
Person / Time
Site:	Peach Bottom
Issue date:	12/10/1986
From:	Kowalski S PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Bernero R Office of Nuclear Reactor Regulation
Shared Package
ML20212B403	List: ML20212B398 ML20265B463 ML20265B467 ML20265B471
References
GL-86-10, NUDOCS 8612290236
Download: ML20212B398 (13)

Text

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PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. DOX 8699 PHILADELPHIA. PA.19101 DEC .101986 Docket Nos. 50-277 50-278 Mr. Robert M. Bernero, Director Division of Boiling Water Reactor Licensing U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Peach Bottom Atomic Power Station Appendix R Fire Barriers

Reference:

(1) Letter, J. W. Gallagher to D. G. Eisenhut, dated October 14, 1981 (2) Letter, V. S. Boyer to R. M. Bernero, dated January 17, 1986 (3) Generic Letter 86-10, dated April 24, 1986 Implementation of Fire Protection Requirements

Dear Mr. Bernero:

Philadelphia Electric Company, in Reference (1), stated that fire barriers would be provided to separate redundant safe shutdown methods in accordance with the requirements of Appendix R to 10FFR50 " Fire Protection Program for Operating Nuclear Power Plants,"Section III.G.2.

The penetration seal upgrade program to ensure the integrity of fire barriers was completed in January 1986 (Reference 2).

Several fire barriers and two internal penetration seal configurations were identified during the seal upgrade program that provide a fire resistance less than three hours. However, our hazard analyses have indicated that the installed barriers and seals or lack thereof do not jeopardize the ability of the barriers to provide acceptable separation of redundant safe shutdown equipment.

Nevertheless, per the provisions of the Reference 3 Generic Letter, we are submitting our evaluations for review and concurrence by the NRC Staff to assure their acceptability under the Appendix R Fire Protection requirements.

m 8612290236 861210 PDR ADOCK 05000277 PDR g f., ft p til

Enclosed for your review are analyses addressing the following:

1. The use of cement masonry unit construction rated at less than 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> for fire barriers in several areas of the plant including the barriers around the Battery Rooms and 4KV Switchgear Rooms. (Attachment I)

2. The acceptability of a small portion of a steel ventilation plenum to serve as a fire barrier between the Radwaste Building and Control Structure. (Attachment 1)

3. An evaluation supporting our internal conduit sealing program.

-(Attachment V)

4. The lack of 3-hour rated penetration seal installations within 4KV bus ducts. (Attachment V)

If you have any questions, please do not hesitate to call us.

Sincerely, i

S. J.'Kowalski Vice-President GJR/ pas /10248602 Attachment (1)

Copy to: T. P. Johnson, Resident Inspector NRC Document Control Desk i

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c ATTACHiENT I Docket Nos. 50-277 50-278 The following are fire barriers which have a fire resistance of less than three hours:

1. Turbine Building, elevation 135', Emergency Switchgear and Battery Rooms (twelve rooms). Walls between the Individual Emergency Switchgear and Battery Rooms, an access corridor, and two duct chases west of the rooms are constructed of two-hour fire resistant concrete block. The greatest coribustible loading in any of the Emergency Switchgear and Battery Rooms is 28,800 Btu /fts with a corresponding equivalent fire severity of 19 minutes. The two-hour rated walls are sufficient to withstand a fire of this duration. +

An automatic smoke detection system is provided in each rom.

In the event of a fire, the fire brigade will be dispatched to the area and utilize manual suppression consisting of portable extinguishers and hose reels to extinguish the fire.

An encapsulation type enclosure or a fireproof coating would be required to upgrade the walls to provide three-hour fire resistance. The cost to perform this Installation for 22 walls and considering the neber of penetrating items which would prevent a straightforward installation would be extremely high and would not significantly increase the existing fire protection. Therefore, for the reasons mentioned above, the underlying purpose of the rule, to ensure that redundant safe shutdown methods are protected from the effects of a fire, is achieved with the existing installation.

2. Radwaste Building, elevation 165', Remote Shutdown Panel Area. A.45" high, 69'-6" long, 1/8" thick steel angle is in place at the top of a three-hour rated barrier between the Remote Shutdown Panel Area and the Radwaste Centrifuge and Sanple Tank Area, Fire Areas 25 anc' 2 respectively Crefer to Attachment VII). The angle is part of a 10 gauge steel plate, fresh air ventilation plenun deck which provides a boundary between the two fire areas and spans the length and width above the Centrifuge and Sanple Tank Area (See Attachments II and III).

A 10 gauge steel plate wall extends frcm the top of the steel angle 12'-0" to the bottom of the Radwaste Building roof for 47'-10" of the 69'-6" length of the barrier. At the north end of the barrier a 21'-8" opening provides a fresh air intake.

A 10 gauge steel walk-in plenun encloses the opening in fire area 2 (described below). The largest fixed centustible loading of 54,775 Btu /fta with a corresponding equivalent fire severity of 41 minutes exists in the Renote Shutdown Panel Area. The fixed ccubustible loading in the Sample Tank and Centrifuge Area is 10,440 Btu /ft2 with a corresponding equivalent fire severity of 5 minutes. There are no fixed ccmbustibles located in the plenun above the fire areas.

A fire in the Sartple Tank Centrifuge Area will cause the plenun surface to heat up. Flames will not penetrate through the plenun. There is no safety related equipment in the plenun. A combustible free area is provided for 32 feet of the 69'-6"' length of the barrier and is carprised of two centrifuge roans, each with 3 foot thick concrete walls and ceilings adjacent to the barrier. The centrifuge roans are 22 feet wide with the metal plenun 4" above each room for their entire width. Thus, for the 32 feet which the centrifuge roans are adjacent to the barrier, the mininun distance between flame impingement and the adjacent fire area is 22 feet (See Attachment II). The increased surface temperature is not significant as it will be dissipated along the u1affected area above the centrifuge rooms. In addition to the centrifuge rooms, the barrier is spanned by a walk-in metal plenun on the rennte shutdown panel area side, 49 feet long beginning at the northern most end of fire area 2. The plenun will provide a " buffer" zone between the two areas Ilmiting heat transfer. As a result of this buffer zone, the metal angle at the top of the wall is exposed to both fire areas for only 20'-6" of the barrier beginning at the southern end of fire area 2.

There are no cable penetrations through either the steel angle or steel plate wall including the area where It is directly adjacent to both fire areas. In addition, there are no combustible materials (cabling) In the InTnediate vicinity of the angle. In the event of a fire, and the angle is heated to a terrperature in excess of acceptable limits, combustible material (cabling) is sufficiently far away from the angle on both sides of the barrier that it will not be Ignited. Flame and products of combustion will be prevented from passing through the barrier by the angle.

For reasons previously stated, the existing metal boundary will prevent the spread of fire fran one area to another.

Autanatic smoke detectors and line type heat detectors in all cable trays are provided in the Remote Shutdown Panel Area. A fire would be extinguished by the fire brigade utilizing fire hose and portable extinguishers. Protection of the metal plenun would entall the Installation of a fireproof coating over a surface area of 3,340 square feet which would be extremely costly. The fireproofing would not significantly increase the fire protection provided. Therefore, for the reasons mentioned above, the underlying purpose of the rule to ensure that redundant safe shutdown methods are protected from the effects of a fire is achieved.

3. Turbine Building, elevation 135', Access Corridor behind the Emergency Switchgear and Battery Roans. Two heating and venti 1ating duct chases serve as fire barriers between the corridor and the 13 KV switchgear area below, Fire Areas 2 and 50 respectively (refer to Attachments VIII and IX). The

duct chases are located in two, 4 KV Emergency Switchgear rooms and contain heating, ventilating, and air conditioning ducts.

The ducts which are located between the corridor and the duct chase walls contain fire dampers. A three-hour rated penetration seal closing the opening between the danpers and the chase.Is provided in the " floor" between the chase and the switchgear area below. (See Attachment IV). The fire dampers are either a single,11 hour1.273148e-4 days <br />0.00306 hours <br />1.818783e-5 weeks <br />4.1855e-6 months <br /> rated danper (one location), two li hour rated dampers in series (two locations) as described in the fire protection Nuclear Regulatory Conmission Safety Evaluation Report dated March 13, 1985 and an exemption request letter frcm J. S. Kemper to D. G. Eisenhut dated Septenter 17, 1984 respectively, or are qualified 3-hour fire dampers (two locations). There are no conbustibles in either duct chase. The largest fixed ccmbustible loading in any of the fire areas is 22,200 Btu /ft with a corresponding equivalent severity of 14 minutes. A fire in the switchgear area below will be prevented from passing into the corridor through the duct chase by the penetration seal at the floor. Flame and products of conbustion which have entered into the ductwork will be stopped by the fire dampers in the wall approximately 12 feet above the seal. Similarly, a fire in the corridor will be stopped at the wall by the dampers and then by the penetration seal at the floor. Automatic smoke detection systems are provided. A fire will be extinguished by the fire brigade utilizing available manual suppression, including fire hose and portable extinguishers before the rating of the fire barrier is exceeded. The cost to Install the dampers and penetration seal in the same plane would be high. The penetration seals could be installed at the walls, only after the ducts containing the in place fire dampers were temporarily renoved. Conduit and cable tray interferences along with the inability to install a temporary penetration seal dam while the ductwork is in place prevents seal Installation at the wall. The fire dampers were existing prior to upgrading fire barriers to meet Appendix R requirements. Cost to relocate the dampers would involve shutting down HVAC systems, cutting ductwork, Installing new dampers, and reconnecting the ducts. Such modifications will not significantly increase the provided fire protection.

Therefore, for the reasons mentioned above, the underlying purpose of the rule to ensure that redundant safe shutdown methods are protected frcm the effects of a fire is achieved.

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Seventeen normally energized 4KV bus ducts penetrate fire rated barriers on the 135' elevation as .shown on Attachnent VI. Three bus ducts identified in the sketch are l'4" X 3'0" while the remaining fourteen are l'4" X 2'2"._ The bus ducts are constructed of .0833" thick steel plate (Gage No. 14) and penetrate the walls at approximately 10'-6" above the floor. Each bus duct penetration is sealed with a smoke-tight porcelain through-bushing to seal off the movement of air or ionized gases through the bus duct.

Copper bus bars, wrapped in a flame retardant insulating-material, are contained in the bus ducts. There are no cont >ustible materials located within the bus duct. Therefore, a fire will not originate in the bus duct.

The particular rooms with bus duct penetrations and other pertinent Information concerning these rooms are listed below:

Room Name & Nuiber Cont >ust ibl e Fire Wall Loading Btu /sq. ft. Rating Unit 2 MG Set Rm 206 152,000 3 hr Emer Swgr Rm 217 24,000 2 hr Emer Swgr Rm 226 15,000 2 hr Emer Swgr Rm 227 25,000 2 hr Emer Swgr Rm 231 29,000 2 hr Emer Swgr Rm 261 9,000 2 hr Emer Swgr Rm 263 22,000 2 hr Emer Swgr Rm 265 15,000 2 hr Emer Swgr Rm 267 18,000 2 hr Emer Swgr Corridor 262 23,000 2 hr or 3 hr The cont >ustible materials in the switchgear rooms consist of cable insulation. The cabling in these rooms is IEEE-383 quallfled. The worst case fire postulated would be a cable spreading fire involving cable Insulation. A cable spreading insulation fire would be slow in flame propagation and heat l

developnent due to the inherent slow surface burning nature of the materials. Tests by Sandla Laboratories and post fire analysis conducted at Browns Ferry indicate a surface burning rate of 6 to 7 ft. per hour along cable trays. Temperatures in the room will not reach (1100oF) for at least 119,,.inutes into the fire development.

The Switchgear rooms and corridor are protected by an'early warning smoke detection system which alarms autcmatically in the control room. The conbination of the metal plate duct and porcelain barrier will combine to provide a degree of fire resistance necessary to contain a fire to the room of fire origin.

In addition, the early warning smoke detection system will alert station personnel of a fire and subsequent fire brigade efforts would be employed to bring the fire under control. Manual suppression located in the area consists of hose stations and portable fire extinguishers. Therefore, the likelihood of a fire penetrating the bus duct and adversely exposing equipment in adjacent areas is minimal.

The MG Set room is protected by a local application automatic preaction sprinkler system. The sprinkler system is actuated by an area smoke detection system. The local appilcation sprinkler system for the MG Set room is being extended in order to provide full room coverage. The conbustible materials in the MG Set room consist of lubricating oil contained within the MG Sets and cable insulation. A fire in this area would be detected and controlled by the preaction sprinkler system. The combination metal plate, porcelain barrier together with the early warning detection system, automatically actuated sprinkler system and fire brigade efforts would preclude the 1IkelIhood of a fire penetrating the bus duct and exposing equipment in adjacent areas. Therefore, for the reasons described above, the underlying purpose of Section III.M of Appendix R to provide penetration seals capable of withstanding a fire equivalent to the rating required of the fire barrier is achieved.

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