ML19274E685

LER 79-026/03L-0 on 790318:during Reactor Startup,Discovered Absolute Position Indication for Rod 8 Was Inoperable.Caused by Sticking Reed Switch.Variable Ac Frequency,Applied to Reed Switch Circuit,Eliminated Sticking

ML19274E685
Person / Time
Site:	Crystal River
Issue date:	04/05/1979
From:	Cooper J FLORIDA POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19274E683	List: ML19274E682 ML19274E685
References
LER-79-026-03L, LER-79-26-3L, NUDOCS 7904170171
Download: ML19274E685 (2)

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EVENT QESCRIPTLCN AND #RC9ASLE COreSECuENCES h oi: I At 1921, durine a reactor startun. It was discovered that the absolute  !

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"a". No effect upon public health and safety. Rod position was verified y

, , , 9 through relative rod position indication. Operability was restored in one I ae, l hour following maintenance. This is the seventh occurrence reported. I a,4 i Peference LER's (77-71, 112, 125) and 08-49, 62. 68). 80

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,,. [ The cause of this event can be attributed to a sticking reed switch. The  ;

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SUPPLEMENTARY INFORMATION Report No.: 50-302/79-026/03L-0 Facility: Crystal River Unit #3 Report Date: 5 April 1979 Occurrence Date: 18 March 1979 Identification of Occurrence:

Absolute rod position indication inoperable contrary to Technical Specification 3.1.3.3.

Conditions Prior to Occurrence:

Mode 2 operation (reactor critical)

Description of Occurrence:

At 1921, during a reactor startup, following criticality, absolute rod position indication for rod 8, group 6, tas inoperable. Entered action statement "a". Reactor maintained in a stable condition. Verified nuclear overpower trip set-point at 5%. Verified rod 8, group 6 position through relative rod position indication. Operability was restored at 2020 following maintenance.

Designation of Apparent Cause:

The cause of this event can be attributed to a stuck reed switch. Magnetization, eminating from spurious magnetic fields generated during control rod operation,causes the reed switch to stick.

Analysis of Occurrence:

There was no hazard to the plant or general public as rod position was verified through relative rod position indication.

Corrective Action:

The application of a variable AC frequency to the reed switch circuit eliminates the magnetic field. This maintenance action restored operability. No further corrective action required.

Failure Data:

This is the seventh occurrence reported. Reference LER's (77-71, 112, 125) and (78-49, 62, 68).

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