ML20043B028
| ML20043B028 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 05/17/1990 |
| From: | Walt T PORTLAND GENERAL ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9005240093 | |
| Download: ML20043B028 (6) | |
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- May 17,1990 Trojan Nuclear Plant Docket 50-344 License NPF-1 U.S. Nucletir Regulatory Commission Attn: Document Control Desk s
Washington DC 20555-
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Dear Sirs:
Room Cooling Support for ac and de Electrical Distribution Equipment Rooms q
1 The purpose of this letter is to inform the NRC of actions being taken by-Portland General Electric Company (PCE)-to assure the operability of
' Engineered Safety Features (ESF) electrical equipment under all Service Water. System (SWS) temperature conditions and train outages.
'l The actions being taken are necessary to assure that:
1.
ESF, electrical equipment room temperatures remain below acceptable' equipment-operating limits under all design basis heat loading and SWS temperature conditions.
i 2.
ESF electrical equipment remain operable during SWS train outages as l.
L allowed by the Trojan Technical Specifications.
l' The attachment to this letter provides a detailed explanation of (a) the-room cooling design for the ESF electrical distribution equipment in the l
Control Building, (b) the actions currently being implemented and D
justification for these actions, and (c) long-term corrective actions and schedules for implementation.
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PDC 121 S.W Salmon Street, Portland Oregon 97204
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Document Control Desk May 17, 1990 Page 2 This information is Provided in follow-up to telephone conversations between PGE, the NRC project manager for Trojan (Mr. Roby Bevan), and members of the NRC staff.
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Sincerely, l
T. D. Walt Acting Vice President Nuclear Attachment et Mr. John B. Martin Regional Administrator, Region V U.S. Nuclear Regulatory Commission Mr. David Stewart-Smith State of Oregon
' Department of' Energy Mr. R. C. Barr NRC Resident Inspector Trojan Nuclear Plant t
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I Trojan Nuclear Plant Document Control Desk Docket 50-344 May 17, 1990 i
License NPF-1 Attachment Page.1 of 4 ROOM COOLING SUPPORT FOR AC AND DC ELECTRICAL DISTRIBUTION EOUIPMENT ROOMS i
The Trojan Nuclear Plant was originally designed with the Control Building A-train electrical auxiliary equipment and the B-train electrical auxiliary and switchgear equipment in the same room. This room was provided with j
redundant Engineered Safety Features (ESP) train cooling capability, namely two A-train coolers (VE-145A & VE-145C) and two B-train coolers (VE-145B &
VE-145D), and a single non-ESF cooler (VE-145E). The A-train electrical 3
switchgear room in the Turbine Building was provided with a similar j
configuration of ESF A-train and B-train coolers.
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A three-hour fire wall was installed in 1982 between the A-train and B-train electrical auxiliary equipment in the control Building in order to meet train separation requirements for fire protection. Because this modification 1
affected the original room cooling design, the original non-ESF cooler (VE-145E) was replaced with a larger ESF cooler to provide safety-related cooling for the A-train electrical auxiliary room.
This left the four original room coolers (VE-145A, B, C, D) in the B-train electrical auxiliary and switchgear room. The wall separating these rooms was provided with two non-safety-related transfer fans (VC-157 & -158) and three ventilation openings (each with two dampers) to allow for air exchange between rooms in the_ event that cooler VE-145E became unavailable, due to equipment or service water train outages. The current design is depicted in Figure 1.
l During the process of reviewing room cooling calculations in February 1990 Portland General Electric Company (PCE) determined that the ESF electrical equipment room temperatures may not have remained below the Final Safety Analysis Report (FSAR) design basis of 104'F if some room coolers were out-of-service with design basis heat loads and summer design temperature conditions.
This condition existed because of an incorrect original design basis,.and was compounded by the three-hour fire wall installation in 1982.
Interim corrective action was taken to prepare special guidance, which specifies the acceptable combinations of Service Water System (SWS) trains, ESF electrical equipment room coolers, and SWS temperatures which assure operability of the electrical distribution systems, by assuring electrical equipment room temperatures will remain below the 104*F limit during design basis conditions. This condition was the subject of Licensee Event Report (LER)90-005 dated February 16, 1990.
Subsequent review of cooler out-of-service configurations by PGE, followed by discussions with the NRC staff, determined that the non-safety related transfer fans could not be relied upon to assure A-train electrical equipment operability in accordance with Technical Specification requirements, in the event of an A-train service water outage or the unavailability of cooler VE-145E.
It was determined that the two-hour action limit of Trojan Technical Specification 3.8.2.3, "D.C.
Distribution - Operating", should be invoked for the electrical equipment in the A-train electrical auxiliary room whenever A-train service water or cooler VE-145E is removed from service.
If efforts i
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Trojan Nuclear plant Document Control Desk Docket 50-344 May 17, 1990 Licenso NpF-1 Attachment page 2 of 4 t
to return the affected room cooler or service water train cannot be completed f
within the two-hour Technical Specification action limit (vs. the normal 72-hour limit applied to single-train outages of service water), a plant shutdown must be initiated.
Because service water train outages can occur during normal power operations, PGE has initiated interim measures to upgrade the existing alternative source of cooling to the A-train electrical auxiliary room. The purpose of these interim measures is to allow service water train outages of up to 72-hours for SWS temperatures up to the design maximum of 75'F, without declaring associated train electrical equipment out-of-service. These interim measures include the following:
1.
Train B Emergency Diesel Generator backed power will be provided to the non-safety-related transfer fans, VC-157 & -158.
Also, a seismic capability evaluation will be performed for these transfer fans and the associated wall dampers, with appropriate mounting modifications made as necessary.
The purpose of these modifications and design reviews is to provide assurance that the transfer fans will function at a high level of reliability under all design basis conditions.
2.
An elevated temperature capability evaluation will be performed for the ESF equipment in the electrical auxiliary and switchgear rooms.
Equipment function will be evaluated at temperatures up to 122*F for seven days with subsequent temperatures of 104*F for a duration of one year.
The purpose of this evaluation is to establish the capability of this equipment to perform its safety-related function at elevated temperatures beyond the original design basis of 104*F.
The 122*F temperature extreme for seven days is based on a reasonable estimate of the maximum time that room temperatures would be in an elevated condition following a design basis event and eventual deenergization of equipment not essential to long-term cooldown.
Once completed, this evaluation will be used to support continued electrical equipment operability during high SWS temperature conditions up to the 75*F maxinum design limit.
These interim measures provide adequate assurance that ESF electrical equipment will perform its safety function for all design basis accident conditions and under SWS temperatures up to the design limit.
The interim measures described above will be completed prior to allowing a VE-145E outage in excess of two hours during Modes 1-4 following the current refueling outage.
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Docket 50-344 May 17,1990 License WPF Attachment
-Page 3 of 4 a
f Permanent corrective actions will be' implemented to provide. redundant train k
cooling capability to.the A-train electrical auxiliary room. The selected approach will be implemented by the end of the 1994 refuelinr, outage.
This
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schedule is necessary to allow adequate time for review of dealgn alternatives,'and completion of detailed design. procurament, and installation.
efforts.-
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Trojan Nuclear Plant Document Control Desk i < ; - * ' Docket'50-344 May 17, 1990 License NPF-1 Attachment Page 4 of 4 Figure 1
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- VE-145A. C. & E ARE SAFETY GRADE ROOM COOLERS (TRAIN A) l
- VE-145B & D ' ARE SAFETY GRADE ROOM COOLERS (TRAIN B) l
- VC-146A 6-B ARE SAFETY GRADE EXHAUST FANS (TRAINS A & B)
- VC-157 & 158 ARE NON-SAFETY GRADE VENTILATION FANS.
t ELECTRICAL AUXILIARY AND SWITCHGEAR ROOMS CONTROL BUILDING 61' 65' EL.
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