ML20151B755

Forwards Results of Evaluation of HVAC Sys,Per Insp Repts 50-295/87-34 & 50-304/87-35 Open Item.Hvac Sys Mod Implementation Schedule Will Be Transmitted During Wk of 880718

ML20151B755
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	07/15/1988
From:	Trzyna G COMMONWEALTH EDISON CO.
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8807210089
Download: ML20151B755 (13)

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) Commonwealth Edison One First National Plaza, Ch'cago, Illinois

$ C ~] Address Reply to: Post Omce Box 767 (f Chicago. Illinois 60690 0767 July 15, 1988 Director of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Station P1-137 Washington, DC. 20555

Subject:

Zion Nuclear Power Station Units 1 and 2 NRC Docket Nos. 50-295 and 50-304 Elre Protection - Auxiliary Building HVAC l

Reference:

April 8, 1988 letter from H.J. Miller to Cordell Reed Gentlemen:

The referenced letter which transmitted Inspection Report 50-295/87-034 and 50-304/87-035 indicated that the issue of the requirements of 10CFR 50, Appendix R and its applicability to the Auxiliary Building HVAC at Zion Station would be considered as an Open Item. A meeting during January, 1988 between NRR and CECO personnel confirmed that the fire protection criteria must be addressed for the Auxiliary Building HVAC.

Subsequent to that meeting, a study was commissioned by CECO to perform an engineering evaluation of the HVAC system. The results of this evaluation are contained in the Attachment to this letter. This evaluation was discussed at a meeting on June 28, 1988 with NRR and CECO personnel. This meeting resulted in the following understandings:

(1) Commonwealth Edison requested NRR to submit a SER to formally address the issue of Auxiliary l Building HVAC and fire protection. l (2) Commonwealth Edison acknowledged that an aggressive implementation schedule was appropriate to finalize the HVAC/ Fire Protection concerns, fD It 88o7210089 880715 PDR l O

ADOCK 05000295 '

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The implementation schedule will be transmitted durini; the week of July 18. Most of the modif:. cation work that is required to address the fire protection concerns will require extensive scaffolding on the floor which functions as the main entry to the Aux. Building. The impact of these modifications on the upcoming U2 refueling outage is uncertain at this time. Therefore, we are carefully scoping this work to be both responsive to NRC concerns and to minimize the effect on the forthcoming outage.

Please direct any questions that you may have on this issue to this office.

Very truly yours, G. E. Trzyna Nuclear Licensing Administrator

/kij cc: J.A. Norris-NRR NRC Resident Inspector-Zion 4928K

ATTACHMENT Zion Nuclear Power Station HVAC-Fire Protection Engineering Evaluation l

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Attachment, P433, EL3188-053 Page 2 l l

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ENGINEERING EVALUATION AUXILIARY BUILDING HVAC SYSTEM Descriotion The 642ft elevation of the Auxiliary Building, identified as Fire Zone 11.7-0, contains six exhaust fans, the associated ductvork, and support equipment. The exhaust fans are iccated inside the ductvork. The exhaust system consists of the exhaust fans, four booster fans, and charcoal filter banks. The Auxiliary Building ventilation system control panel, 0LP17, i s also located on this elevation.

Three of the exhaust fans are povered off of Unit 1 ESS buses (137, 138, and 139) and three are povered off of Unit 2 LCS buses (237, 238, and 239). The exhaust (75,000 cfm each) fans serve all areas of the Auxiliary and Fuel Buildings, except for specific locations (Control Room, Computer Rooms, Auxiliary Electric Equipment Rooms, Miscellaneous rooms) which are served by independent systems.

Figures 1 and 2 identif' the existing arrangement of HVAC-equipment and cables on the . 642ft and 617ft elevations. The figures should be referenced with respect to the discussion which follows on HVAC location and atrangement.

The filter banks, booster fans, and heating and ccoling coils are located in separate cubicles constructed of 12in thick reinforced concrete on the 642ft elevation. The exhaust fans and associated ductwork a'e located in the main open area of the 642ft elevation. The main open area is arranged in the form of an inverted Y. The stem of the Y-shaped open area is located along the vest side of this elevation, with the top, or arms, along the east side. A common corridor approximately 72 feet i n length connects the stem with the arms of t's Y-shaped open area.

The three Unit 1 exhaust fans are located side-by-side i n the southern arm of the Y-shaped open area along the east vall.

The three Unit 2 exhaust fans are located side-by-side in the northern arm of the Y-shaped open area along the east vall. The Unit 1 and Unit 2 exhaust fans inside their associated ductvork are separated by approximately 60 feet. Located in between the Unit 1 and Unit 2 exhaust fans and ductvork are ventilation plenum rocms, approximately 36 feet vide, constructed of 12in thick reinforced concrete. Thn plenum rooms prevent direct line-of-site ccntact between the Un.t 1 and Unit 2 exhaust fans and associated ductwork.

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Attachment, P433, EL3188-053 Page 3 An open stair and equipment access shaft connect the'642ft elevation with the 617ft elevation below. The main open area of the 617ft elevation is identified as Fire Zone 11.5-0. The stair and equipment access shafts are located in the corridor providing access to the northern and southern arms of the Y-shaped open area. Control panel OLP-17 for the HVAC system supply and exhaust dampers is located adjacent to the plenum room wall at the top of the shaft openings.

The Unit 1 exhaust fan power cables are routed towards the shaft openings and penetrate down to the 617ft elevation just south of the shafts. The Unit 2 power cables are also routed towards the shaft openings and penetrate down to the 617ft elevation just north of the shafts. The Unit 1 and Uait 2 power cables are separated by a minimum of approximately 24 feet in the vicinity of the shafts on the 642ft elevation, with this distance increasing to 60 feet at their respective exhaust fans.

The power feeds for the exhaust fans are routed in cable tray and conduit, running east-west in Fire Zone 11.5-0 on the 617ft elevation, prior to entering the Unit 's and U. nit 2 Outer power Cable Spreading Rooms. The cables for the Unit exhaust fans run near the ceiling of 617ft elevation just south of the stair and equipment shaft apenings. The power cioles for the Unit 2 exhaust fans also run near the cei)ing of the 617ft elevation and are routed just to the north of the shaft openings.

A minimum separation distance of 14 feet e,eparate the power feeds where they run on the Unit 1 (just south) and Unit 2 (just north) sides of the shaft openings.

Pire Protection Systems The main open area of the 642ft elevation is provided with three ionization smoke detectors which alarm in the continuously manned control roem. One detector is located directly over the supply f ans. on'. is located directly over the Unit 1 exhaust fans, and opc is located directly over the Unit 2 exhaust fans.

The charcor.. filter banks are protected by temperature sensing devices and manually-actuated deluge water spray systems. The main open area of the 617ft elevation is provided with 13 1 ioniza'. ion smoke detectors which alarm in the continuously manned j contrcl room.  !

l Portable extinguishers and manual hose stations are l available for use on both elevations.

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e Attachment, P433, EL3188-053 Page 4 Safe Shutdown Ecuioment The Auxiliary Building HVAC system has not been identified as a required system to demonstrate conformance with Appendix R criteria. ,However, the system is being analyzed as a support system to address concerns relative to maximum allowed operating temperatures for required safe shutdown equipment.

Given a fire that damages Auxiliary Building HVAC equipment or cable, the highest temperatures vould be reached on the 579ft The 579ft elevation is identified as having the elevation.

highest temperatures based ca the limited height of the elevation

(~10ft), the limited vo ir.ie for heat dissipation (~125,000ft3),

and the equipment requ ced 3

to operate for safe shutdown (one charging and one a',xiliary feedvater pump per unit). The Appendix R safe shutdown scenario for a fire of on one the 642ft charging or pump 617ft elevationr ,ould result in the use (with door open) and one auxiliary feedvater pump (with the most heat generated from the turbine-driven pump) per unit.

t Given a fire on the 642ft or 617ft elevations, a minimum of two 75,000cfm rated capacity exhaust fans vill be available with their inlets full open, no supply fans operating, and with the inlet and outlet dampers of one supply fan system full open. The Auxiliary Building is normally maintained at a negative pressure during operating conditions. The make up air under this scenario comes from leakage into the building via doorways and from the supply air svotem with the inlet and outlet dampers of one fan full open.

Fire Hazards Analysis A failure of the Auxiliary Building HVAC system due to a fire on the 642ft or 617ft elevations could result in operational difficulties but would not prevent safe shutdown of the plant.

Inside the Auxiliary Building, equipment and cable for the HVAC system are located only on the 642ft and 617ft elevations in Fire Zones 11.7-0 and 11.5-0, respectively. Cables for the required systems run from the 642ft to the 617ft elevations and penetrate into the Unit 1 and Unit 2 Outer Cable Spreading Rooms.

With the exception of the routing of power and control cables for ventilation system panel OLP17 (discussed in morc detail below),

adequate separation exists outside of the Auxilirry Building to demonstrate conformance with Appendix R criteria.

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Attachment, P433, EL3188-053 Page 5 A fire that involves either OLP17 ori the 642f t elevation or where they are routed in the its power and/or control cables Auxiliary Building, cable spreading rooms and control room, will fail open the supply and/or exhaust air dampers. This can result in operational difficulties with respect to exhausting air to the the exhaust fans. The exterior due to a loop recirculation at inlet dampers to two exhaust fans and the inlet and outlet dampers to one supply air fan system should be maintained in the full open position in order to ensure HVAC operability in the Auxiliary Building during this scenario. Manually positioning the dampers will be accomplished through use of the e.isting T locking pins for the supply and exhaust air inlet vortex dampers and field-mounted manual damper positioning restraints (with turnbuckles) for the outlet dampers. The existing FOPS which identify required operator actions will be updated to incorporate manual damper positioning.

The 642ft elevation of the Auxiliary Building, FiheZone 11.7-0, has a combustible loading of less than 40,000 Btu /ft2 for an equivalent fire severity of under 30 minutes. This combustible loading is confined to the charcoal filter banks located inside reinforced concrete cubicles, with the filter banks protected by a temperature sensor and a deluge water spray system. The main open area of this elevation, referred tc as the Y-shaped open area, is essentially void of fixed combustible materials. Ionization smoke detectors are located directly above each of the three supply and six exhaust fans.

The 617ft elevation of the Auxiliary Building, Fire Zone 11,5-0, has a combustible loading of less than 25,000 Stu/ft2 for an equivalent fire severity of less than 20 minutes. The majority of the combustible loading consists of protective clothing stored in open bins due east of the stair and equipment shaft openings, and cable insulation in trays also routed near the shaft openings. Ionization smoke detectors are provided at ceiling level in this zone; however, the potential exists for heat and hot gases to spread up to the 642ft elevation due to the lack of automatic suppression on the 617ft elevation.

The existing separation of exhaust fans on the 642ft 1

elevation is sufficient to meet the spatial separation criteria of Section III.G.2.b of Appeadix R. As previously identified, the exhaust fan units for Unit 1 are separated from the exhaust fan units for Unit 2 by a horizontal distance of approximately 60 feet, with reinforced concrete plenum rooms located in between exhaust In addition, an the Unit 1 and Unit 2 fan areas.

ionization smoke detector is provided directly over each group of supply and exhaust fans. The main open area of the 642ft elevation is essentially void of fixed combustibles. As such, 60 feet free of intervening combustibles separate the three Unit 1 exhaust fans from the three Unit 2 exhaust fans, i 4

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Attachment, P433, EL3188-053 Page 6 The minimum separation of exhaust fan power cables on the 642ft elevation is approximately 24 feet. This minimum distance occurs in the vicinity of thein riser penetrations through the immediate vicinity of the floor to the 617ft elevation the On the 617ft elevation, the stair and equipment shaft openings.

minimum separation between the Unit 1 and Unit 2 exhaust fan power cables is 14 feet.

In order to address the spatial separation concerns on the 617ft elevation, along with the potential for heat and hot gases to rise up to the 642 elevation from the 617ft elevation, the power cables for Unit 1 exhaust fans OA642ft and OB will be rerouted elevation down to directly f rom the fan housings on the 617ft elevation. This vill ensure that the rerouted power cables for the two Unit 1 exhaust fans vill be separated from the Unit 2 exhaust fan power cables by approximately 50 feet without intervening combustibles on the 642ft elevation. Exhaust fans OA and associated power cables vill also be and OB their '

approximately 30 feet away from the open shafts to the 617ft elevation below. The rerouted cables will be protected with one hour rated material on the 617ft elevation up to the point that they enter the Unit 1 Outer Cable Spreading Room. Figures 3 and 4 identify the locations for the proposed power feed reroutes and one hour protection.

The rerouting and one hour protection for the OA and OB exhaust fan power cables as described above provide reasonable assurance that a minimum of two exhaust fans will be available based on the locations of postulated fires on the 617ft or 642ft elevations of the Auxiliary Building. In order to ensure fan operability under loss of offsite power conditions, the existing FCPs for operator ac: ions vill be updated to incorporate manual fan start up from the associated essential switchgear rooms.

Each division of Unit 1 and Unit 2 switchgear are located in separate fire areas.

Conclusions Based on the previous analysis, the existing level of detection and suppression coverage on the 617ft and 642ft elevations of the Auxiliary Building meets the criteria of Appendix R Section III.G.2, as supplemented by the guidance of Generic Letters 83-33 and 86-10. The technical bases which justify the evaluation are summarized as follows: ,

(1) The Y-shaped open area of the 642ft elevation, which contains HVAC equipment and cables, is essentially void of fixed ccmbustible materials.

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Attachment, P433, EL3188-053 Page 7 (2) With two 75',000cfm rated capacity exhaust fans operating, the inlets to the exhaust fans full open, no supply fans operating, and fthe inlet and outlet dampers ull open, sufficient air is of one supply fan system entrained into the Auxiliary Building via doorways and the open supply ' air dampers to support long term hot and cold shutdown functions.

free of intervening (3) A minimum of 60ft of separation combustibles separates the Unit 1 and Unit 2 exhaust fans on the 642ft elevation. While 24ft free of intervening combustibles separates the power cables for the Unit 1 and Unit 2 exhaust fans on the 642ft elevation, this distance is in the vicinity of the shaft openings to the 617ft elevation below.

(4) The. power cables for Unit 1 exhaust fans 0A and OB will fan housings down to the be rerouted directly from the 617ft elevation and into the Unit 1 Outer Cable Spreading Room. The rerouted power cables will be protected with one hour rated material on the 617ft elevation. On the 642ft elevation, the rerouted Unit i exhaust fan power cables vill be a minimum of 50ft from the Unit 2 exhaust fan power cables, and 30 feet from the shaft openings to the 617ft elevation.

(5) Manual control capability of the position of the supply and exhaust dampers will be provided through the use of existing locking pins for the inlet dampers and installing manual damper positioning restraints in the vicinity of the dampers.

(6) The existing FOPS for operator actions given a fire vill be updated to incorporate manual damper positioning given loss of OLP17 and/or manual fan startup from the associated essential switchgear room (s) given loss of offsite power.

(7) The existing configuration and proposed modifications provide reasonable assurance that the Auxiliary Building HVI.; system vill support long term hot and cold shutdown functions given postulated fires in the Auxiliary Building.

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