ML19317D790
| ML19317D790 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 03/30/1977 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML19317D781 | List: |
| References | |
| RO-269-77-07, RO-269-77-7, NUDOCS 7912100542 | |
| Download: ML19317D790 (2) | |
Text
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DUKE F0WER COMPANY OCONEE UNIT 1 9
Report No.: R0-269/77-7 Report Date: March 30, 1977 Occurrence Date: February 28, 1977 Facility: Oconee Unit 1, Seneca, South Carolina Identification of Occurrence: Reactor quadrant power tilt limit exceeded Conditions Prior to Occurrence: Unit at 100 percent full power Description of Occurrence:
On February 28, 1977 group 1 control rod 6 dropped into the core due to a failed stator. The unit ranback to 55 percent full power on the resulting asymmetric rod indication. An attempt was made to transfer control rod 6 in group 1 to the auxiliary power supply but the transfer could not be made.
All six fuses in the group 1 rod 6 power supply including two blown fuses were replaced but the transfer could not be made. The quadrant power tilt began increasing, therefore in anticipation of the requirements.of Oconee Technical Specification 3.5.2.4.c a controlled shutdown was initiated.
Approximately one hour after the rod drop, the reactor quadrant power tilt increased above the 9.44% Technical Specification limit. The power level was at approximately 20 percent full power at this time. The reactor was shutdown within another hour, and on March 5, 1977, after the unit was cooled down, the stator was replaced.
Apparent Cause of Occurrence:
This occurrence resulted from the drop of control rod 6 of group 1.
The control rod stator had failed, apparently due to control rod drive motor tube leakage.
Analysis cf Occurrence:
This occurrence resulted in the core quadrant tilt exceeding the limits specified in Technical Specification 3.5.2.4.c.
A reactor shutdown was in progress at this time in anticipation cf the technical specification requirements and was completed within the four hour period allowed by the specification. The limits on allowable quadrant tilt, in conjunction with the limits on power level, control rod group position, axial imbalance and xenon conditions, are specified to prevent the maximum linear heat rate from exceeding the LOCA limited values.
In this incident, although the indicated tilt exceeded the maximum allowable value, c linear heat r-te below the established limits was assured by the conservative values he other power peak inducing parameters and the gradual power decrease.
o The capability of the reactor protective system was not affected by this incident and therefore, it is concluded that the health and safety of the public was not affected.
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Corrective Action:
The control rod stator was replaced and verified to be functioning properly.