05000369/LER-1981-170, Forwards LER 81-170/03L-0.Detailed Event Analysis Encl

Forwards LER 81-170/03L-0.Detailed Event Analysis Encl

ML20033B444
Person / Time
Site:	McGuire
Issue date:	11/24/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20033B445	List: 05000369/LER-1981-170, Forwards LER 81-170/03L-0.Detailed Event Analysis Encl 05000369/LER-1981-170-03, /03L-0:on 811025,temp Indication for Reactor Coolant Pump 1C Motor Upper Thrust Bearing Exceeded Limit. Apparently Caused by Corrosion on Screw Connections Where Thermocouple Cable Attaches in Terminal Cabinet
References
NUDOCS 8112010418
Download: ML20033B444 (2)

LER-1981-170, Forwards LER 81-170/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
3691981170R00 - NRC Website

text

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NOV3 01981* b Re: McGuire Nuclear Station Unit 1 D, W.A $in Docket No. 50-369 b

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Dear Mr. O'Reilly:

Please find attached Reportable Occurrence Report R0-369/81-170. This report concerns T.S. 3.4.1.1, "All reactor coolant loops shall be in operation." This incident was considered to be of no significance with respect to the health and safety of the public.

Very truly yours, 0 /

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L William O. Parker, Jr.

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cc: Director Records Center Office of Management & Program Analysis Institute of Nuclear Power Operations U. S. Nuclear Regulatory Commission 1820 Water Place Washington, D. C. 20555 Atlanta, Georgia 30339 Mr. Paul Bemis Senior Resident Inspector-NRC McGuire Nuclear Station l

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McGUIRE NUCLEAR STATION REPORTABLE OCCURRENCE REPORT NUMBER: 81-170 REPORT DATE: November 24, 1981 OCCURRENCE DATE: October 25, 1981 FACILITY: McGuire Unit 1; Cornelius, North Carolina IDENTIFICATION OF OCCURRENCE: Reactor Coolant (NC) Pump IC was tripped due to an indication of high upper thrust bearing temperature.

CONDITIONS PRIOR TO OCCURRENCE: Mode 1, approximately 285 Mwe, conducting low power testing.

DESCRIPTION OF OCCURRENCE: At 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> on October 25, the computer alarm (180 F) for NC pump 1C motor upper thrust bearing temperature was received.

The computer point indicated that the temperature was 182 F but was decreasing and finally stabilized at 175 F.

At 1305 the temperature reading had in-creased to 180 F but the pump vibration and all other parameters were satis-factory. Control room operators, however, increased the level in S/G IC in preparation for tripping NC pump 1C.

At 1317, NC pump IC was tripped because the temperature indication began increasing again and finally reached a maxi-mum el 250 F.

The operators began reducing reactor power per Procedure

" loss of NC Flow."

This incident was reportable pursuant to Technical Specifica-tion 3.4.1.1.

APPARENT CAUSE OF OCCURRENCE: The NC pump 1C motor upper thrust bearing high temperature indication.as probably due to corrosion on the screw connections where the thermocouple cable attaches inside Analog Remote Terminal Cabinet No. 2.

ANALYSIS OF OCCURRENCE: Prior to the incident, all of the other NC pump 1C operating parameters (seal flows, vibration, temperatures) were in their normal bands which indicated that the problem was probably an erroneous thermo-couple reading. However, since procedure requires that the NC pumns be tripped if any motor bearing temperature exceeds 195 F, NC pump 1C was tripped at 1317. The thermocouple cable leads and screw connections in Analog Remote Terminal Cabinet No. 2 were removed and cleaned. NC pump 1C was restarted and the upper thrust bearing temperature returned to its normal operating band.

SAFETY ANALYSIS

Even though all other pump parameters indicated that the high bearing temperature was probably erroneous, the operating procedure requires that the pump be tripped to ensure pump safety. The other three pumps were capable of providing sufficient flow to cool the reactor satisfactorily while pump 1C was shut down. Thus, safe plant operation and the health and safety of the public were not affected by this incident.

CORRECTIVE ACTION

NC pump 1C was tripped per procedure when its upper thrust bearing temperature exceeded 195 F.

A Work Request was writti to trouble-shoot and repair the false tanperature indication. The thermocouple cable connections in Analog Remote Terminal Cabinet No. 2 were cleaned and retightened.