ML19317F448

RO 270/76-02:on 760174,Group 8,Rod 1 Was Misaligned.Caused by Blown Fuse.Personnel Cautioned.No Adverse Effects on Health & Safety

ML19317F448
Person / Time
Site:	Oconee
Issue date:	02/05/1976
From:	DUKE POWER CO.
To:
Shared Package
ML19317F443	List: ML19317F442 ML19317F448
References
RO-270-76-02, RO-270-76-2, NUDOCS 8001140684
Download: ML19317F448 (2)

Text

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wQ b DUKE POWER COMPANY OCONEE UNIT 2 Report No._: R0-270/76-2 Report Date_: February 5, 1976 Occurrence Date_: January 24, 1976 Facility:

Oconee Unit 2, Seneca, South Carolina Operation with Group 8, Rod 1 misaligned Identification of Occurrence _:

Reactor power escalated from 60% to 80%

Conditions Prior to Occurrence: full power Description of Occurrence:

On January 24, 1976, an investigation was commenced at 0900 for an asymetric condition which appeared to exist on rod 1 of Group 8 Axial Power Shaping The investigation led to the conclusion that the rod had an Rods (APSR's). This conclusion was based upon erratic position Indication (PI) tube. In addition, the Group 8 erratic behavior on several previous occasions. 0, 25, 50, 75, rods were driven to one of the reference switches located at or 100 percent withdrawn to verify the actual position of the questionable rod. In this instance, the nearest reference position was at 0% withdrawn,This and, when the Group 8 rods reached this position, rod 1 did a the problem was actually a faulty PI tube.

1105 hours0.0128 days <br />0.307 hours <br />0.00183 weeks <br />4.204525e-4 months <br /> to 80 percent full Reactor power was increased from 60 percent atAt 1235, further investigation revea power on rod at 1143 hours0.0132 days <br />0.318 hours <br />0.00189 weeks <br />4.349115e-4 months <br />.Thus, 1 Group 8. the reactor had operated above 60 percent full power for about 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> with a Group 8 control rod misaligned.

Designation of Apparent Cause of Occurrence:

The apparent cause of this occurrence was a blown fuse in rod 1 Group 8 phase BB.

This caused the rod to drive either in or out at approximately Thus, when the one-half of the speed of the remaining rods in the group.

rods were driven to.0% withdrawn, they all reached the referenc? position at the same time; however, if any of the other reference positions Whenhad been a fuse is used, it would have been apparent that rod 1 was misaligned.

blown on any of the other seven regulating or safety groups, it will trip when attempting to drive it.

8001140dh

i Report No. R0-270/76-2 February 5, 1976 Page 2 Analysis of Occurrence:

The Group 8 This incident resulted in one rod of Group 8 being misaligned.ly to aid rods are not a part of the Reactor Protective System and serve onNo reduction in shutdo in controlling the core power distribution. rred as or in the ability to bring the reactor to a shutdown condition occu a result of this incident. 6%

the maximum reactor quadrant tilt experienced was +5.9 In this incident, at 20% full power.

This did not affect station operationi since operation f 3.19% with with a quadrant tilt greater than the error adjusted lim t o indication of a misaligned control The rod is permitted maximum observed up to 60%

quadrant tilt full power by Technical Specification 3.5.2.4.b. his was recorded after escalation above 60% full power was +3.17%, and tThese value decreased to +1.38% at 80% full power. Additionally, the axial power acceptable Technical Specification limits. It is, therefore, imbalance was maintained within acceptable limits. ffected by concluded that the health and safety of the public was not a this incident.

Corrective Action: l to This incident has been thoroughly discussed with the instrument In personne addition, make them aware of situations which can exist with Group 8 rods. d t Operations personnel will obtain anshould This evaluation help inanytime recognizing an ifindicated a qua r tilt in excess of 1.5% is observed.

control rod has become misaligned.

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