05000302/LER-1979-085-03, /03L-0:on 790915,while in Mode 1,control Rod Partially Dropped.Cause Unknown.Rod Withdrawn to Group Average Position.No Further Corrective Action Deemed Necessary

/03L-0:on 790915,while in Mode 1,control Rod Partially Dropped.Cause Unknown.Rod Withdrawn to Group Average Position.No Further Corrective Action Deemed Necessary

ML19253B609
Person / Time
Site:	Crystal River
Issue date:	10/08/1979
From:	Cooper J FLORIDA POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19253B608	List: 05000302/LER-1979-085, Forwards LER 79-085/03L-0 05000302/LER-1979-085-03, /03L-0:on 790915,while in Mode 1,control Rod Partially Dropped.Cause Unknown.Rod Withdrawn to Group Average Position.No Further Corrective Action Deemed Necessary
References
LER-79-085-03L, LER-79-85-3L, NUDOCS 7910160488
Download: ML19253B609 (2)

LER-1979-085, /03L-0:on 790915,while in Mode 1,control Rod Partially Dropped.Cause Unknown.Rod Withdrawn to Group Average Position.No Further Corrective Action Deemed Necessary

Event date:
Report date:
3021979085R03 - NRC Website

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This created an event contrary to Technig g cal Specification 3.1.3.1.

Redundancy NA.

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SUPPLEMENTARY INFORMATION Report No.:

50-302/79-085/03L-0 Facility:

Crystal River Unit #3 Report Date:

8 October 1979 Occurrence Date:

15 September 1979 Identification of Occurrence:

Control rod 07-07 greater than 6.5% (indicated position) away from group average position.

Conditions Prior to Occurrence:

Mode 1 power operation (72%)

Description of 0 warra.ce:

At 1620 it was reported that rod 07-07 had dropped from 41%

withdrawn to 18% withdrawn.

This event resulted in a step drop in reactor power of 3%.

Reactor power was reduced to 60%.

Rod 07-07 was transferred to the auxiliary power supply and withdrawn to 25% by absolute position indication.

Rod 07-07 position was verified at 25% on zone reference lamps.

The rod was withdrawn to its average group position and power was returned to its normal supply.

Designation of Apparent Cause:

The cause of this event is unknown.

Troubleshooting of the control rod power supply revealed no immediate cause of this event.

Analysis of Occurrence:

No effect upon the plant or general public.

Corrective Action

No corrective action deemed necessary.

Failure Data:

This is the fifth occurrence of this type reported.

Reference LER's 77-34, 43, 47, and 135.

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