ML20239A211

Part 21 & Deficiency Rept Re Design of Control Room Essential (CRE) HVAC Sys.Initially Reported on 870713. Backdraft Dampers Added to Unit 1 CRE HVAC Units & Will Be Added to Unit 2 Commensurate W/Const Schedule

ML20239A211
Person / Time
Site:	Vogtle
Issue date:	09/14/1987
From:	Rice P GEORGIA POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
REF-PT21-87, REF-PT21-87-166-000 GN-1396, PT21-87-166, PT21-87-166-000, NUDOCS 8709170177
Download: ML20239A211 (4)

Text

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. Georgia Ftwer Company.

Post Office Box 282 Waynesboro, Georgia 30030 Telephone 404 554 9961, Extension 3413 404 724 8114, Extension 3413 m

r.o.me. Georgia Power Vice President vogtie project September 14, 1987 """"*'"*"*""

United States Nuclear Regulatory Commission File: X7BG03-M139 Document Control Desk Log: GN-1396 Washington, D. C. 20555

Reference:

Vogtle Electric Generating Plant - Unit 2; 50-425 Control Room Essential HVAC Letter GN-1391, dated August 12, 1987 l' In previous correspondence, Georgia Power Company notified the NRC of a potentially reportable condition associated with the design of the Control Room Essential HVAC System. Georgia Power Company has' completed its deportability evaluation and has. determined that a reportable condition as defined by the . reporting requirements of 10CFR Parts 21 and 50.55(e) does_ e&ist. Based upon NRC guidance in NUREG-0302, Revision 1, and other NRC correspondence, Georgia Power requirements Company is reportinge).

of 10CFR50.55 (this Acondition summary pursuant to the reporting of our evaluation is attached. This condition has been reported for Unit 1 in LER 50-424/1987-044.

The broadness review to determine if this or a similar situation exists on other systems is not yet complete. If any other systems are found with this condition, then a supplemental report will be submitted providing this information.

This correspondence contains no proprietary information and may l

be placed in the NRC Public Document Room.

, ,h.h / n P. D. Rice CWH/PDR/wkl xc: USNRC - Region 11 Suite 2900 101 Marietta Street, NW Atlanta, GA 30323 H. G. Baker D. R. Altman L. T. Gucwa .

J. P. O'Reilly J. A. Bailey C. W. Hayes l R. E. Conway G. Bockhold R. W. McManus l R. H. Pinson C. E. Belflower Sr. Resident (NRC) l E. D. Groover J. F. D'Amico C. C. Garrett (OPC) i C. T. Moore D. Feig (GANE) J. E. Joiner (TSLA) J G. A. McCarley NORMS j (g

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EVALUATION OF A POTENTIALLY REPORTABLE CONDITION' CONTROL ROOM ESSENTIAL HVAC j ..

/ i Initial Report: On July 13, 1987, Mr. R. E. Folker, Project Quality Assurance Engineer, notified Mr. E. F. Christnot of the ' USNRC Region 11 and Mr. H. H. Livermore, Senior Resident inspector, of a potentially reportable condition associated with the Control ,.

Room Essential HVAC System. In subsequent correspondence with 1' the NRC, Georgia Power Company indicated that a final report on. >

this_ issue would be submitted by September 15, 1987.

Background Information: The control building control room essential (CRE) HVAC system consists of two redundant and physically separated 100 percent capacity HVAC units ' for each . side of the control room, I' or four for the combined - Unit 1 and Unit 2 control room. Each I

of the two redundant HVAC' units belongs to a different safety train. However, portions of the outside air ' intake ductwork 'and the control room supply and return ductwork are common to each of the HVAC units. This system is . shown ' schematically in ~ FSAR Figure 9.4.1-2.

To protect against high airborne radioactivity inside the control room, following receipt of a safety injection signal or a control room outside air intake high radiation signal, the control room HVAC is automatically transferred from the normal units to the CRE units in the emergency mode of operation. The associated dampers for the essential units are automatically opened and the The essential unitst normal units are automatically isolated.

are designed to be capable of:

1) removing the sensible and latent heat loads from the contr61 room,

2) recirculating the air within the control room. through engineered -

l safety feature filters to provide continuous purification I

capability, and l

3) pressurizing the control room to 1/8 inch water gauge (w.g. ) ,

pressure relative to the adjacent areas to minimize unfiltered g inleakage (Technical Specification 3/4.7.6).

On July 2, 1987, Plant Engineering identified a design problem related to the adequacy- of the- CRE HVAC system analysis for operatior in the emergency mode. Either loss of power to an operating train of' CRE HVAC, or a . failure of the emergency , fan, while operating in the emergency mode, could change the ' amount of outside air available to pressurize the control room. This is because the dampers fail in the "as-is"' position, and there were no back-draft dampers installed. This failure . mode allows additional flow paths through the common ductwork and failed unit's ductwork potentially reducing the amount of outside air brought

, in through the operating unit. The effect of reducing the outside, l air flow would be to potentially reduce the control room pressure' .,..

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I below the design (1/8 inch w.g. positive)' value. There is also a flowpath which could increase the amount of outside air available to pressurize the control room. Bechtel WestMn Power Corporation is the architect / engineer for this system. },

Engineering Evaluation: An accurate analysis of the volume of 1 air which would be transmitted by the various flowpaths through the failed HVAC ductwork would be difficult to perform without test data. However, in lieu of a test, GPC decided to develop hardware modifications to eliminate the potential for changes in the amount of outside air available to pre:suMz,e Ve control room. Accordingly, no analytical conclusion can, be drawn regarding the effect on outside air flow resulting from the failure of en operating CRE HVAC train. ]

The root cause of this condition was determined to be the f ailure to perform an adequate failure modes and effects analysis (FMEA) of operation in the emergency mcde.

L Insufficient data exists to perform a calculation . to determine )

if a reduction in outside air makeup flow would dave ,occured. l Consequently, the ' effect of this potential reduction of control room pressurization on the amount of air inleakage to the control room and increased dose to the operators in the event of an accident cannot be adequately determined. Therefore, this condition is I considered repcrtable under 10CFR50.55(e) and 10CFR21.

Broadness Review: An inadequate FMEA on this system for its emergency mode of operation prevented this condition from being

( detected during design. A review of all other safety-related HVAC FEMA's will be conducted to determine if the same or a similar situation exists. This review is currently scheduled to be complete by the end of 1987. If this review finds any other systems with l

this condition, then a supplemental report will be submitted.

1 Evaluation of Quality Assurance Program Breakdown- At present, I the reported condition is isolated to one safety-related HVAC system. Therefore, it is not currently indicative of a significant breakdown in . , the Bechtel Quality Assurance Progra. If the broadness review discussed above finds any other defects, then another evaluation for a breakdown in the Quality Assurance Program will be conducted.

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Conclusion:

Base'd on the results of the above analysis,. it cannot l

be determined if the required 1/8 inch w.g positive , pressure could have been maintained in - the control room after a' CRE HVAC train failure. The pressure differential limit is a technical specification requirement, and is used in the design basis'1 for meeting General Design Criteria 19 contained in Appendix'A to 10CFR50. Therefore, GPC has concluded that a reportable condition I

as defined by the criteria of 10CFR50.55(e) and 10CFR21 does exist.

Based on the guidance in NUREG-0302, Revision 1, 'concedning duplicate reporting of an event, Georgia Power is reporting this event per the criteria of 10CFR50.55(e).

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k,,o i Corrective Action: To correct this condition, backdraft dampers have been added to the Unit 1 CRE HVAC units as described in LER 50-424/1987-044 and will be added to the Unit 2 outside_ air makeup branch and control room return air branch of each of the control building control room essential HVAC units. This work will be completed commensurate with the Unit 2 construction schedule.

Figure I below provides an illustration of the corrective action which will be.taken on Unit 2 to resolve this concern.

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