05000369/LER-1981-058, Forwards LER 81-058/03L-0

Forwards LER 81-058/03L-0

ML20005A066
Person / Time
Site:	McGuire
Issue date:	05/18/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20005A067	List: 05000369/LER-1981-058, Forwards LER 81-058/03L-0 05000369/LER-1981-058-03, /03L-0:on 810418,while in Mode 3,lower Containment High Temp Alarm Was Received in Control Room Indicating That Units C & D Feeder Breakers Tripped.Caused by Incorrectly Adjusted Unit D Magnetic Overload Switch.Breaker Repla
References
NUDOCS 8106290324
Download: ML20005A066 (3)

LER-1981-058, Forwards LER 81-058/03L-0

Event date:
Report date:
3691981058R00 - NRC Website

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DUKE Powra COMPANY E

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May 18, 1981 f<' r a-O

^e ca 'ca Segase pe00wC? ion 373*'083 Mr, J. P. O'Reilly, Director U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303 Re: McGuire Nuclear Station Unit 1 Docket No. 50-369

Dear Mr. O'Reilly:

Please find attached Reportable Occurrence Report R0-369/81-58. This repgrt concerns the average lower containment air temperature exceeding 120 F.

This incident was considered to be of no significance with respect to the health and safety of the public, Very truly yours, d

1 William O. Parker, Jr.

RWO/djs Attachment ec: Director Mr. Bill 1.avalee Office of Management and Program Analysis Nuclear Safety Analysis Center U. S. Nucle'ar Regulatory Commission Post Office 3cx 10412 Washington, D.C.

20555 Palo Alto, California 94303 Ms. M. J. Graham La D

Resident Inspector-NRC Y$pF McGuire Nuclear Station p

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McCUIRE NUCLEAR STATION INCIDENT REPORT REPORT NUMBER: 81-58, REPORT DATE: May 7, 1981 OCCURRENCE DATE: April 18, 1981 FACILITY: McGuire Unit 1, Cornelius, N.C.

IDE!CIFICATION OF OCCURRENCE: The average lower containment air temperature exceeded 120"F.

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CONDITIONS PRIOR TO OCCURRENCE: Mode 3 Hot Standby DESCRIPTION OF OCCURRENCE: At 0305 hours0.00353 days <br />0.0847 hours <br />5.042989e-4 weeks <br />1.160525e-4 months <br /> on April 18, 1981, a lower containment high temperature alarm us received in the Control Room. The feeder breakers for containment ventilation (VL) air handling units (AHU's)

C and D had tripped (breakers deenergized). This was reportable pursuant 1

to Technical Specification 3.6.1.5 since the containment temperature exceeded 120 F.

APPARENT'CAUSE OF OCCURRENCE: The magnetic overload switch on VL AHU D breaker-(EMXD-2A) was found on April 11 to be adjusted incorrectly. This degraded the operation of the breaker and caused it to trip below its set-point. It could not be determined why VL AHU C breaker (EMXC-2A) tripped.

j ANALYSIS OF OCCURRENCE: A work request was written on April 8 to repair VL AHU D breaker.

It was tripping (breaker deenergizing) when the unit t

was operating in higt speed.

It was found that the current draw in high speed was approximately 110 amps (norttal). This was the same as the i

other VL AHU's (A,B, and C).

The belts and filters were in a good i

operating condition. On April 11, it was discovered that the magnetic overload (overcurrent) switch for VL AHU D breaker was depressed in the intermediate position between 2 and 3.

The switch was adjusted to the 1

j number 2 position. Also, when the switch is depressed, it cannot be 4

determined what the breaker trip setpoint will be.

VL AHU D operated satisfactorily and the' work request was signed off complete on April 15.

Another work request was written on April 16 to repair VL ANU D as it had begun tripping again on high speed. The breaker magnetic overload switch l

was adjusted to the number 4 position and the unit was returned to service; i

Atg305hoursonApril18,lowercontainmenttemperaturesincreaselabove 120 F because.VL AHU's C and D had tripped (breakers deenergized).

VL AHU C brasker (EMIC-2A) was reset and returned to service at 0339 hours0.00392 days <br />0.0942 hours <br />5.605159e-4 weeks <br />1.289895e-4 months <br />. The magnetic ovdeload switch on VL AHU D was adjusted to the number 6 position and the unit was operational a short while lacer.

At 1542 hours0.0178 days <br />0.428 hours <br />0.00255 weeks <br />5.86731e-4 months <br />, lower containment high temperature alarm was received in the Control Room. VL AHU's C and D had tripped again.

It was noticed that the breakers were hot. After the breakers cooled, they were reset and AHU's C and-D were returned to service. There have not been any more tripping problems with VL AHU C.

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May_18, 1981 Page 2 1

At approximately 2130 hours0.0247 days <br />0.592 hours <br />0.00352 weeks <br />8.10465e-4 months <br />, after VL AHU D had tripped several times, a fan was placed in front of the breaker cubicle to cool the breaker.

The breaker operated satisfactorily until April 23.

On April 23, the fuse contacts on VL AHU D breaker were cleaned and Tron clips were installed on them to ensure good electrical contact. The magnetic overload switch was adjusted to the number 3 position and the fan removed. The breaker tripped once when the unit was operated in high speed. The magnetic overload switch was set to position number 5 and the breaker tripped three tires on high speed. The fan was reinstalled and thus far the breaker has not tripped again.

VL AHU D breaker (EMXD-2A) was replaced on May 3, but the unit has not been operated because of preventative maintenance (changing a pulley, belts, checking the bearings, etc.).

The unit will be operated when the preventative maintenance is completed.

SAFETY ANALYSIS

VL AHU D would operate on low speed with no tripping problems and on high speed with a fan cooling its Orsaker. Thus, the health and safety of the public and safe plant operation were not affected.

Duringnormaloperation,TechnicalSpecificatgon3.6.1.5requiresthe containment temperature be kept less than 120 F or the reactor must be shut down (Kot Standby) within 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> if the normal temperature cannot be restored by then.

CORRECTIVE ACTION

VL AHU C breaker (EMXC-2A) was reset and AHU C returned r

to service. VL AHU D breaker (EMXD-2A) was replaced on May 3, 1981; the unit will be checked out when the preventative maintenance on it is finished.

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