ML19317F342

LER 78-003/03L-0:on 780301,during Performance Test,Control Rod Group 5 Experienced Momentary Loss of Power.Cause Undetermined.Mod to Increase Rod Control Power Source Reliability Planned for All Units

ML19317F342
Person / Time
Site:	Oconee
Issue date:	04/04/1978
From:	Ken Wilson DUKE POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19317F336	List: ML19317F335 ML19317F342
References
LER-78-003-03L-01, LER-78-3-3L-1, NUDOCS 8001100715
Download: ML19317F342 (2)

Text

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DUKE POWER O'MPANY 0CONCE UNIT 2 -

Repo rt - Numbe r: R0-270/78-3.  !

Report Date: April 4,1978 Occurrence Date: March 1, 1978 Facility: Oconee Unit 2, Seneca, South Carolina .

Identification of Occurrence: Control Rod Group Overlap Limits Exceeded Conditions Prior to Occurrence: 100 percent Full Power Description of Occurrence:

On March 1,1978, at 0119, during the performance of PT/0/A/0600/15 (Control Rod Drive Movement Performance Test) a momentary loss of power to Control Rod Group 5 was experienced. The power loss caused the stators to de-energize and allowed the rods to drop. When power was re-established, stators were re-energized and the rods were latched at different heights. The required Control Rod Group Overlap of 25 5 percent was not maintained (Technical Specification 3.5.2.5b). The con-trol operator drove the rod group into the core to realign the rods. The maximum imbalance experienced was -14 at 27 percent full power, which was the minimum power reached during realignment. Acceptable overlap was re-established within 1.) hours.

Apparent Cause of Occurrence:

An immediate investigation was undertaken into the cauce of the incident. All fuses and power supplies were examined and found to be properly functioning and no evidence was found to indicate any failures. No apparent cause could be de-termined.

' Analysis of Occurrence:

During the performance test, . the Rod Control Drive and the ICS Control and Gen-erator Master Systems were in manual operation. The maximum power imbalance was -14 which occurred at 27 percent reactor power which is within Technical Specification limits. The rod overlap of 2515 percent was not maintained when the rods . dropped but was re-established within the 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> limit imposed by Tech-nical~ Specifications (T.S. 3.5.2.5b).

The health and safety of the general public were not af fected by this incident.

, Corrective Action:

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, A modification to improve CRD gate drive circuitry is planned for all units to

' increase'the reliability of the control rod drive power supplies and to pre-vent instances'of. power supply failure. ,

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