ML20006A877

LER 89-028-00:on 891204,self-initiated Technical Audit Team Personnel Identified Gap Around Control Room Ventilation Air Handling Unit Access Door.Caused by Possible Const/ Installation Deficiency.Door Sys modified.W/900122 Ltr

ML20006A877
Person / Time
Site:	McGuire
Issue date:	01/21/1990
From:	Mcconnell T, Sipe A DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-028-01, LER-89-28-1, NUDOCS 9001300406
Download: ML20006A877 (8)

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i Duke 1%uvr Cornpany (704) 815-4000

• %fcGuire Nuclear Station P O Bat 488 Cornelius, N C 28031-9488 DUKEPOWER January 22, 1990 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555

Subject:

McGuire Nuclear Station Units 1 and 2 Docket No. 50-369 Licensee Event Report 369/89-28 Gentlemen:

Pursuant to 10 CFR 50.73 Sections (a)(1) and (d), attached is Licensee Event Report 369/89-28 concerning the Control Room Ventilation System being inoperable due to a gap around the control room air handling unit access door. This report is being submitted in accordance with 10 CFR 50.73(a)(2)(v)'and-(a)(2)(i).. This.

event is considered to be of no significance with-respect to'the health and safety of the public.

Very truly yours, L

T.L. McConnell DVE/ADJ/cb1 Attachment xc: Mr. S.D. Ebneter American Nuclear Insurers Administrator, Region Il c/o Dottie Sherman, ANI Library U.S. Nuclear Regulatory Commission The Exchange, Suit 245 101 Marietta St., NW, Suite 2900 270 Farmington Avenue Atlanta, GA 30323 Farmington, CT '06032 INPO Records Center Mr. Darl Hood-Suite 1500 U.S. Nuclear Regulatory Commission _

1100 Circle 75 Parkway Office of Nuclear Reactor' Regulation Atlanta, GA 30339 Washington,-D.C. 20555 M&M Nuclear Consultants Mr. P.K. Van Doorn 1221 Avenue of the Americas NRC Resident Inspector New York, NY 10020 McGuire Nuclear-Station 9001300406 900121 PDR ALOCKOSOOg9 ff%?

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On December 4, 1989, Self Initiated Technical Audit (SITA) Team personnel were performing a visual evaluation of Control Room Ventilation (VC) system components and identified a gap around the VC Air Handling Unit (AHU) access door. On l

December 5, 1989, SITA Team personnel documented their concern that the gap around the access door could allow an additional inleakage of unfiltered air into the Control Room (CR). This leakage could have resulted in the radiation dose to CR personnel exceeding that assumed by the design basis analysis. On December 22, 1989, Design Engineering personnel performed a Past Operability Determination that concluded that, although the CR portion of the VC system was technically inoperable, the inleakage of unfiltered air and radiation dose to the CR personnel would have been reduced by factors which are not considered in the design basis analysis. This event is assigned a cause of Possible Construction / Installation Deficiency because the access door does not fit sufficiently flush around the perimeter to maintain seal contact. A contributing cause of Management Deficiency is assigned because of the lack of direction in the ventilation system preventative maintenance programs to verify that access doors are sealed. The access door closure system will be modified to provide better sealing. The preventative maintenance program will be enhanced to include verification that access doors seal properly. Unit 1 and Unit 2 were in Mode 1 (Power Operation) at 100 percent power when this event was discovered.

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0l0 0l2 0F 0 l6 nxf ame. Mm.a o u. a mM wec r sasemm j EVALUATION:

Background

There are two independent trains of the Control Area Ventilation (VC) system ,

[EIIS:VI) which are designed to maintain the habitable environment in the Control  !

Room (CR) [EIIS:NA), Control Room Area, and Switchgear Rooms during normal and accident conditions. Based on these criteria, the system is designed as an. .

Engineered Safety Features (ESF) system with high efficiency particulate (HEPA) and carbon filtration in the outside air intakes and with equipment redundancies for use as conditions require.

The CR is designed to be maintained at a positive pressure during an accident to prevent entry of contaminants. Each CR VC system train consists of one 100 percent capacity Air Handling Unit (AHU) [EIIS:AHU], one 100 percent capacity CR pressurization fan [EIIS: FAN] and one filter [EIIS:FLT] assembly. Each filter assembly consists of a pre-filter, a HEPA filter, a carbon absorber [EIIS: ABS], ,

controls, ductwork [EIIS: DUCT), and isolation dampers [EIIS:DMP). The filter assembly components are mounted on a common steel channel [EIIS:CHA] base. Both CR  ;

ventilation system trains are interconnected through a common plenum located . i between the AHUs and the pressurization filter assemblies.

Technical Specification (TS) 3/4.7.6 addresses the requirement where two independent VC systems shall be operable in all modes. In Mode 1 (Power Operation), Mode 2 (Startup), Mode 3 (Hot Standby), and Mode 4 (Hot Shutdown), the TS requires that with one train of the VC system inoperable,.the inoperable' train must be restored to operable status within seven days or be -in at least Hot Standby within the next six hours, and in Cold Shutdown within the next thirty hours. In Modes 5 (Cold Shutdown), and Mode 6 (Refueling) the TS requires the following: d,

a. With one VC system train inoperable, restore the inoperabie train to -

operable status within 7 days or initiate and maintain operation of.the remaining operable VC system train in the recirculation mode; and-

b. With both VC system trains inoperable or with the operable VC-system train, required to be in the recirculation mode by Action a., not capable of being powered by an operable emergency power source, suspend all' operations involving core alterations or positive reactivity changes.

TS 3/4.7.6 applies to both Unit 1 and Unit 2 because the VC system is shared by both units. Also, TS 3/4.7.6 includes requirements that two independent VC trains shall be demonstrated operable at least once each 18 months by verifying a system flow rate of 2000 CFM +/-10 percent and a CR positive pressure of >/=0.125 inches water gauge, relative to outside atmosphere.

Description of Event On December 4, 1989, at approximately 1430, Self Initiated Technical Audit (SITA)

Team personnel identified gaps between the sealing surfaces of the.VC system CR AHU common plenum and the plenum access door (EIIS:DR]. The SITA team was examining _ '

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the components of the VC system as part of their audit evaluation. The gaps were '

located at the top right hinge side and lower left latch side of the access door.

On December 5,1989, SITA Team personnel originated Problem Investigation Report serial number 0-M89-0312 documenting the concern that gaps around the plenum. access door could allow inleakage of unfiltered air into the CR. At.approximately 1125, Work Request number 89121 was originated to place duct tape around the perimeter of the plenum access door. Mechanical Maintenance personnel taped around the plenum access door and performed a smoke test verification by approximately 1400.

On December 14, 1889, at approximately 1210, Performance personnel verified'the effect that the gap around the access door had on the ability to pressurize the CR.

Performance personnel used test procedure PT/0/A/4450/08C, Control Area Ventilation Performance Test. At 1210, the CR pressure stabilized at 0.15 inch water gauge >

(W.G.) with the access door sealed with tape. At 1220, the CR pressure stabilized at 0.17 inch W.G. with the taped removed from around the access door. At 1225, the CR pressure again stabilized at 0.15 inch W.G. after the access door was resealed with tape. The acceptance criteria for CR pressurization is greater than or equal to 0.125 inch W.G. relative to outside atmosphere. Although the sealed access door reduced the CR pressure, it was still above the minimum acceptance criteria.

On December 22, 1989, Design Engineering (DE) personnel completed a Past Operability Determination. DE personnel determined that, although the VC system was technically inoperable, the inleakage of unfiltered air and radiation dose to the CR personnel would have been reduced by factors, as defined in the Safety Analysis section of this report, which are not considered in the design basis analysis.

Conclusion This event is assigned a cause of Possible Construction / Installation Deficiency because the access door does not fit sufficiently flush around the perimeter to maintain a good seal ccatact. The door is slightly bowed outward. This bow is ,

transverse from the upper right hinge side to the lower left latch side. It is possible that the access door was bowed from the time it was manufactured. Also, the bow could have occurred from stresses that were induced during manufacture.

The door appears to be well built based on the manufacturer drawing detail, Duke Power Vendor Manual Drawing number MCM 1211.00-0712, Revision 2. The door is approximately 30 inches wide, 60 inches high, and 2 inches thick. The main door member is formed from 11 gauge (0.12 inch no'minal) galvanized steel. This member is formed to a two inch deep dish. A 0.75 inch wide lip is formed at a right angle-to the dish which provides the door sealing surfaces. A 22 gauge (0.03-inch nominal) galvanized steel outer door skin is crimped over the 0.75 wide lip of the main member. The door is reinforced with full thickness plywood core sections across the width at the three sets of hinges and latches locations. It seems highly unlikely that this door could have been deformed by normal use. Also there is no indication of service abuse to the door or to the AHU plenum frame.

A contributing cause of Management Deficiency is assigned because of the lack of direction in the ventilation system preventative maintenance program to verify the NXC 701 3eeA 'U.S. CPoi 1964 520 5s9.00070 WEM

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0l 0 0l4 OF 0l6 iExt a, ., ,k w ==c i amaw sin sealing of access doors. Step 11.7 of Mechanical Maintenance procedure l MP/0/A/7450/03, Fans And Air Handling Units Preventive Maintenance, states " Ensure all doors, panels, and openings to units are closed prior to leaving job." There is a corresponding sign-off on Enclosure 13.2. This step does not address the need to verify that these doors, panels, or openings are sealed. Investigations revealed that this step was added to the procedure only for verification of door or panel closure, since this process had been omitted on occasion in the past.- The need was not perceived to verify adequate sealing of these types of doors, panels, or openings.

A review of the Operating Experience Program (OEP) Data Base for the previous twelve months revealed no events involving Safety Function Impairment that was attributed to a Possible Construction / Installation Deficiency or a Management Deficiency because of the lack of direction. Therefore, this event is not  !

recurring.

As a result of other events involving various ventilation systems' identified in  ;

LERs 369/89-01, 369/89-02, 369/89-15, 369/89-17, 369/89-18, 369/89-21, 369/89-26, l 369/89-27, 369/89-30, and 369/89-31, the problem with operability of the I ventilation systems in general is considered to be recurring.

This event is not Nuclear Reliability Data System (NPRDS) reportable.

There were no personnel injuries, radiation overexposures, or uncontrolled releases of radioactive material as a result of this event. -l~

CORRECTIVE ACTIONS:

Immediate: The perimeter of the access door was sealed with duct tape.

Subsequent: Project Services personnel have initiated Work Request number 890177 which will provide additional closure latches and a new seal. 5 Planned: 1) Project Services personnel will initiate a request for additional door modification if the new latches and new seal fail to solve the problem. ,

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2) Maintenance Engineering Services personnel will revise procedure MP/0/A/7450/03, Fans and Air Handling Units Preventive Maintenance, to include direction to verify that access doors are sealed on ventilation system as necessary.

SAFETY ANALYSIS:

The design requirements of the VC system are to supply filtered air at a controlled temperature and humidity to the CR and to pressurize the CR to prevent inleakage of unfiltered air. The VC system helps ensure that radiation doses to CR personnel are ALARA and remain below Code of Federal Regulation, Title 10, Part 50 (10CFR50),

Appendix A, Criteria 19 (GDC-19) limits.

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0 l6 texm m . . ,wucr., m mim During a recent visual inspection as a result of a VC system SITA audit, the plenum personnel access door at the inlet to CR AHU-1&2 was found to not fit flush against  ;

the AHU plenum casing. This prevents the door from making contact with the plenum. '

This allows unfiltered air from the Control Room Area to leak into the AHU plenum at an estimated maximum rate of 155 cubic feet per minute (cfm). This source of leakage was promptly corrected.

The design basis analysis of the radiation dose to Control Room personnel assumes an inleakage of 10 cfm to account for doors being opened for personnel access.

Using the very conservative assumptions employed for design basis analysis, with the additional 155 cfm inleakage, the system would not maintain the CR environment in conformance with GDC-19 criteria. The system was thus inoperable according to I design basis analysis. l The consequences of an accident with the VC system operation with 155 cfm inleakage would have been reduced by the following factors, as identified in the Past Operability Determination, which are not considered in the design basis analysis: i 1

1) Dilution of any air leaking into the CR by this path by the Auxiliary i Building Ventilation (VA) system [EIId:VF].

2) Operation of the VA exhaust filters to remove radioactive iodine and particulates from the air leaving the Auxiliary Building [EIIS:NE]. This substantially reduces the radiation dose contribution from assumed Emergency Core Cooling System leakage.

3) Lower iodine releases in realistic accidents than those assumed in the ,

design basis accident due to the following factors: )

i A) The iodine removal capability of the containment spray system (EIIS:BE) is greater than that assumed in the design basis calculation af ter recirculation of sump water begins.

B) The release fraction of iodine and cesium iodide from the fuel into .

the gap is significantly lower than assumed in the design basis l accident. '

C) The realistic partition factor for iodine is lower than assumed in i the design basis accident.

4) The CR radiation dose calculation assumes operation of only one train of annulus ventilation along with failure of one train of the VC system.

This double failure assumption adds conservatism.

5) The presence of an area radiation monitor (EHF 12) (EIIS:IL] in the CR would alert the operators if there were contaminated air being drawn into }

the CR. The re fo re , the operators would use the respirators that are available to CR personnel. This would reduce radiation dose during periods when contaminated air is being drawn into the CR.

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6) The average dispersion factor assumed for inleakage is conservetive and is assumed to exist for the entire 30 day accident period.

Consideration of these factors would reduce the radiation dose to the CR personnel {

and its consequence.

l This event did not af fect the health and safety of the public.

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