ML20237J508
| ML20237J508 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 08/12/1987 |
| From: | Sailer W GILBERT/COMMONWEALTH, INC. (FORMERLY GILBERT ASSOCIAT |
| To: | Murley T Office of Nuclear Reactor Regulation |
| References | |
| REF-PT21-87-150-000 PT21-87-150, PT21-87-150-000, NUDOCS 8708180204 | |
| Download: ML20237J508 (3) | |
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,c tilbert / Com monwealth engineers and consultants 721.riERT / COMMONWEALTH. INC., P.O. Box 1498. Reading. PA 19603/Tel. 215 Tl5-2600/ Cable Gilasoc/ Telex 836431
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August 12,1987 W F.SalLER Vice Pn sident & General Manager Quality Assurance Division United States Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, DC 20555 Attm Dr. T. E. Murley, Director Re: Reportable Event
. Control Room Normal and Emergency Ventilation System Det / Dr..Murley:
This documents a report by telephone under the provisions of 10CFR21 on August 7,1987, at approximately 5:15 P.M. to Mr. Kevin Wally.
Individual Who Reported Mr. W. F. Sailer, Vice President and General Manager, Quality assurance Division, Gilbert / Commonwealth, Inc.
Facility /Comoonent/ Activity involved Design of the control room ventilation system at the Virgil C. Summer Nuclear Station, owned and operated by the South Carolina Electric and Gas Company (SCE&G).
Firm Supplyinst the Basic Component Gilbert / Commonwealth, Inc., performed the control room ventilation system design.
Nature of the Failure to Comoly/ Safety Hazard Created The design of the control room ventilation system is not in compliance with system requirements identified in the FSAR, and with the single failure criteria.
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The control room ventilation system consists of two redundant trains of fans, cooling coils and filters. Each train has a dedicated outside air duct for the pressurization function. Each outside air auct is equipped with two butterfly valves in series, and assigned to the same safety channel as their related ventilation train.
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Cilb:rt/Cimm nwe lth enamemommaems Dr. T. E. Murley usunicowawauc.no 8 ma noenom amne mmameca.ca=ncoem Unitcd States Nuclear Regulatory Commission August 12,1987 Page2 The failure modes of the butterfly valves have a significant impact on the capability of the ventilation system to meet the single failure criterion The valves fall closed on loss of instrument air or electrical power. The valves are interlocked with their respective fans such that the valves must be open for the fan to start and run.
The air supply to the valves includes check valves and air accumulator tanks to assure valve operability should the instrument air be lost. However, the check valves, isolation valve, and regulator are not classified as safety related, and the selection and sizing of the check valves and air tanks is not adequate.
The consequences of losing air to these valve operators would be an actuation of the interlocks with the fans and a loss of both ventilation trains with no remote mitigating features available to the operator. Loss of the redundant ventilation trains would eventually result in unacceptable environmental conditions for the safety related equipment cooled by these systems and/or unacceptable dcse to the operator due to a icss of filtering and pressurization.
Also, since the controls of the valves are the same actuation channel as their related fans and share ae same control cabinets and wiring, a single failure within one train can be postulated which results in opening of the valve without the related fan operating. The single failure with the air supply system available would increase the outleakage of the control room, resulting in a positive pressure less than the normal 1/8". While this single failure would be acceptable if the air supply system is available (based upon a previous analysis which is bounding), it is not acceptable when coupled with the inadequate air supply.
The above conditions indleate that single failure in conjunction with a loss of the instrument air system can result in loss of the control room ventilation function.
Date Information was Obtained The Reporting Officer, W. F. Sailer, was informed on August 7,1987, of the deportability of this item.
Number and Location of Components The noncompliance described above is unique to Gilbert / Commonwealth's design of the V. C. Summer control room ventilation system.
Corrective Action SCE&G described a noncompliance in the Control Room Ventilation System by telephone to the NRC Region 11 Office (Mr. II. C. Dance and others) on July 30,1987. A Justification for Continued Operation was discussed and approved l
that day. SCE&G has kept Region Il fully informed of corrective actions aeing implemented while the JCO is in effect. They have committed to make a permanent modification to the air supply and control system for the outside air intake dampers as soon as practical, and no later than the next refueling outage.
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~ cilbert/cammraw cith enon =.adwa.un.na Dr. T. E. Murley stumcouvawuta ac.co so, wm a..ame m man u nsaac.m.ca-ocn.* me United States Nuclear Regulatory Commission August 12,1987 Page 3 If you require any further information, please call me at (215) 775-2009.
Very truly yours, W. F. Saller -
Vice President and General Manager Quality Assurance Division WFS:mak.
cc:
T. E. Murley - NRC (2)
E. W. Merschoff - Vendor Inspection Branch - NRC Document Management Branch - NRC R. B, Clary - SCE&G C. D. Williams W. K. Burkhart 1