ML20212N864

Special Rept:On 860709,invalid Failure of Diesel Generator 2A Occurred Due to Fire Detection Lockout.Caused by High Temp in Diesel Generator Room.Small Ventilation Blower in Room Repaired

ML20212N864
Person / Time
Site:	Mcguire
Issue date:	08/08/1986
From:	Tucker H DUKE POWER CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 8609020007
Download: ML20212N864 (5)

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Duxn POWER GoxnuT P.O. HOx G3180 CHARLOTTE, N.C. 28242 HALB. TUCKER TELEPHONE vion rassionwr EM) MMU ww.s. ram enonection August 8, 1986 cc cn Dr. J. Nelson Grace, Regional Administrator >

U.S. Nuclear Regulatory Commission Region II @

101 Marietta St. NW, Suite 2900 CD Atlanta, Georgia 30323 y

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Subject:

McGuire Nuclear Station, Unit 2 --

Docket No. 50-370 cc Technical Specification 4.8.1.1.3/6.9.2 Diesel Generator Failure Special Report

Dear Dr. Grace:

Please find attached a Special Report submitted pursuant to Technical Specification 6.9.2 in fulfillment of the diesel generator failure reporting provisions of Technical Specification 4.8.1.1.3. This report concerns an invalid failure of diesel generator 2A which occurred while performing an operability test on July 9, 1986. The event was considered to be of no significance with respect to the health and safety of the public.

Very truly yours,

$8/E / W Hal B. Tucker PBN/23/jgm Attachment xc: INPO Records Center Suite 1500 1100 Circle 75 Parkway Atlanta, GA 30339 Docunent Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Mr. W.T. Orders NRC Resident Inspector McGuire Nuclear Station 8609020007 860808 %I PDR .ADOCK 05000370 S PDR p:P

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DUKE POWER COMPANY McGUIRE NUCLEAR STATION TECHkICAL SPECIFICATION 4.8.1.1.3/6.9.2 DIESEL GENERATOR FAILURE SPECIAL REPORT REPORT DATE: August 8, 1986 FACILITY: McGuire, Unit 2 IDENTIFICATION: Diesel Generator 2A Invalid Failure Due to Fire Detection Lockout -

INTRODUCTION:

On July 9, 1986, at approximately 1450, while performing an operability test on Diesel Generator (D/G) 2A, the D/G tripped (invalid failure) due to a fire detec-tion lockout actuation associated with the.D/G. Investigation determined that no fire existed, but the temperature around the fire detection heat sensors, which are located on the ceiling of the D/G room, was approximately 120 degrees F. Unit 2 was in Mode 1, Power Operation, at 100% power at the time of the incident.

The actuation of the fire detection heat sensor was a valid actuation caused by the high temperature in the D/G room. The high temperature in the D/G room was partially due to the small ventilation blower in the D/G room being inoperable since May 6, 1986. A contributing Cause was that the outside temperature was averaging near 100 degrees F during the day.

At 2115, the Emergency Stop Reset pushbutton was reset and D/G 2A restarted. The D/G was shut down at 2230 af ter successfully completing the operability test, and '

l subsequently declared operable at 2350. The small ventilation blower in the D/G

,' 2A room will be repaired.

D/G 2B was operable and available during the period in which D/G 2A'was inopera-ble. Also, after the trip on D/G 2A, the D/G would have been capable of an i

emergency start af ter the emergency stop reset pushbutton was reset. There were no personnel injuries, radiation overexposures or releases of radioactive material as a result of this incident, and the health and safety of the public were unaf-facted.

i f EVALUATION:

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! Background l Each unit at McGuire Nuclear Station has two independent diesel generators. These D/Gs are used to provide standby alternating current (AC) power to the equipment i

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. i 2-required to safely shut down the reactor in the event of a loss of normal power.

The D/Gs also supply power to the safeguards equipment as required during a major accident coincident with a loss of normal power (blackout).

The purpose of the Fire Detection (EFA) system is to monitor unattended areas of the station for smoke or fire and to alert plant personnel of the existence and location of a fira. The EFA system has smoke and heat sensors in the D/G room and if they detect a fire, a detection system relay is energized which energizes relays in the D/G control cabinet. These relays shut down the D/G and its oil-related auxiliaries if an emergency start relay is not energized.

- Each D/G at McGuire is housed in a separate room in the auxiliary building, and each room has its own ventilation system. During normal plant operation (the D/G not running), a small blower (3,000 cubic feet per minute) and a heating unit maintains proper room temperature. When the D/G starts, the blower is deenergized and two large fans (28,500 cubic feet per minute each) are energized.

Description of Event D/G 2A was declared inoperable at 0620 on July 9,1986 to allow installation of oil mister brackets for the starting air distributor. At 1420, after completion of the work, D/G 2A was started (start attempt 418) to perform an operability test. At approximately 1450, D/G 2A tripped due to a fire detection relay being energized (fire detection lockout actuation). This actuation not only trips the D/G (manual starts only) but also shuts down all D/G oil systems. After verifying no fire existed, start attempt 418 was declared as an invalid failure and the Emergency Stop Reset (ESR) pushbutton reset (which started the D/G oil systems and enabled the D/G to be restarted).

l Investigation of the fire detection heat sensor actuation determined the temper-

! ature near the detectors was approximately 120 degrees F (a thermocouple near the j heat sensors and a temperature gauge for the thermocouple near'the D/G local control panel were temporarily installed. The thermocouple and gauge would allow monitoring of the temperature at the heat sensors). The heat sensors are designed l to actuate at 135 degrees F and have an accuracy of approximately + 6 degrees F.

l The temperature readings were taken after the D/G room had time to cool down from I when the D/G was running. Therefore, the actuation was probably due to high temperature.

At 2115, D/G 2A was started (start attempt 419) to perform an operability test, and shut down at 2230 after successfully completing the operability test (start attempt 419 was logged as a valid success). D/G 2A was declared operable at 2350.

l A work request had previously been written on May 6,1986 to renair the small j ventilation blower in D/G 2A room (the work request was written due to the ven-l tilation blower tripping after running less than one minute). This work request

is currently on schedule to be performed.

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i conclusion D/G 2A was inoperable from 0620 to 2350 or. July 9,1986, a total of approximately 17 1/2 hours. Investigation of the cause of the fire detection lockout determinel

.that the heat sensors were working properly. The failure during start attempt 418 was not valid; therefore, the test frequency of the Unit 2 D/Gs was not increased.

The actuation of the fire detection heat sensor was a valid actuation caused by the high temperature in the D/G room. The high temperature was partially due to the small ventilation blower in the D/G roon being inoperable. A contributing cause was the outside temperature averaging near 100 degrees F during the day.

A review of past incidents indicates there has been one incident (non reportable) involving fire detection lockouts of the D/Gs. This previous incident' occurred t

while the D/G was not running and was caused by a component failure and a personnel error. Therefore, this incident is not considered recurring. This incident is not reportable to the Nuclear Plant Reliability Data System (NPRDS).

CORRECTIVE ACTIONS:-

The small ventilation blower in D/G 2A room will be repaired. This work is currently being performed and should be completed by August 31, 1986.

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SAFETY ANALYSIS:

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Technical Specification 3/4.8.1 requires that when either an offsite AC electrical power source or D/G is inoperable, the operability of the remaining power sources i be demonstrated within I hour and at least once per 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> thereafter. Three j operability runs were performed on D/G 2B (while D/G 2A was inoperable) starting

at 0615, on July 9.

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The operability of the AC and direct current (DC) power sources and associated

distribution systems during plant operation ensures that there is sufficient power

available to supply the safety-related equipment required for

(1) the safe i shutdown of the facility, and (2) the mitigation and control of accident con-ditions within the facility. Also, the definition of operability does not make reference to emergency powar. This allows the train without emergency power (i.e.

D/G not available) to be considered operable if it has normal power and the j redundant train has emergency power and is operable.

When one D/G is inoperable, there are requirements to verity that all required i' systems, subsystems, trains, components, and devices that depend on the remaining operable D/G as a source of emergency power be operable. This provides assurance that a loss-of-offsita power event will not result in a complete loss of safety function of critical systems during the period that one of the D/Gs is inoperable.

All of these requirements were met.

f D/G 2B was operabia and available during the period in which D/G 2A was inoper-l -able. Also, after the trip on D/G 2A, the D/G would have been capable of an i

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, e emergency start after the Emergency Stop Reset (ESR) pushbutton, located on the D/G local control panel, was reset.

i There were no personnel injuries, radiation overexposures, or releases of radio-

active material as a result of this incident. The health and safety of the public were not affected by this incident.

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