05000369/LER-1981-005-03, /03L-0:on 810202,power Supply to Both Excore Range Monitors Was Interrupted.Caused by Maint Personnel Cutting Off Power to Investigate Steam Generator Status Lights & lo-lo Level Alarms.Personnel Instructed

/03L-0:on 810202,power Supply to Both Excore Range Monitors Was Interrupted.Caused by Maint Personnel Cutting Off Power to Investigate Steam Generator Status Lights & lo-lo Level Alarms.Personnel Instructed

ML20008E907
Person / Time
Site:	McGuire
Issue date:	03/04/1981
From:	Ouellette R DUKE POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20008E890	List: 05000369/LER-1981-005, Forwards LER 81-005/03L-0 05000369/LER-1981-005-03, /03L-0:on 810202,power Supply to Both Excore Range Monitors Was Interrupted.Caused by Maint Personnel Cutting Off Power to Investigate Steam Generator Status Lights & lo-lo Level Alarms.Personnel Instructed
References
LER-81-005-03L, LER-81-5-3L, NUDOCS 8103100494
Download: ML20008E907 (2)

LER-1981-005, /03L-0:on 810202,power Supply to Both Excore Range Monitors Was Interrupted.Caused by Maint Personnel Cutting Off Power to Investigate Steam Generator Status Lights & lo-lo Level Alarms.Personnel Instructed

Event date:
Report date:
3691981005R03 - NRC Website

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MCGUIRE NUCLEAR STATION ISCIDENT REPORT Report Number:

369/81-05 Report Date: February 11, 1981 Occurrence Date: February 2, 1981 Facility: McGuire Unit 1, Cornelius, North Carolina Identification of Occurrence: Both source range monitors (Excore Instrumentation) were inoperable for 30 seconds.

Conditions Prior to Occurrence:

Initial Fuel Loading, Mode 6 Description of Occurrence:

On February 2, 1981 at 0802 hours0.00928 days <br />0.223 hours <br />0.00133 weeks <br />3.05161e-4 months <br />, the source range monitors' power supplies were interrupted causing the indicating lights associated with the monitors to go of f for approximately 30 seconds and then come back on.

This happened while I&E personnel were perforning maintenance work on steam generators 10-10 level alarms. The 30 second power interruption of these monitors caused a degraded mode of operation and was therefore reportable pursuant to Technical Specification 3.9.2.

Anparent Cause of Occurrence:

ISE personnel were investigating why the status lights on the steam generator A, B, and C lo-lo level alarms were actuated. As a troubleshooting technique, they attempted to completely isolate all input sigrsls that might have actuated the status lights in the Control Room.

Since these signals could be coming from either Train A or B, both ' INPUT ERROR IFHIBIT' switches on the Solid State Protective System (SSPS) panel were inadvertently placed in the ' INHIBIT' position causing power interruption to the source range monitors.

Analysis of Occurrence:

The 30 second power interruption on the source range monitors occurred while there was maintenance work going on at the fuel transfer tube; the air pump that runs the conveyor was being replaced. Since there was no fuel movement at the time the incident occurred, there was no significant effect as to the safety and health of the public.

Corrective Action

Power to the source range monitors were restored after 30 seconds of interrup-tion when I&E personnel placed the ' INPUT ERROR INHIBIT' switch back in the

' NORMAL' position.

I&E personnel were instructed not to perform maintenance work on testing on both trains of the SSPS cabinets at the same time even in Mode 6.

IP/0/A/3010/05, SSPS Safeguard Test, prohibits testing of both trains at the same t ime.