ML19317F093
| ML19317F093 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 12/26/1974 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML19317F092 | List: |
| References | |
| NUDOCS 8001080783 | |
| Download: ML19317F093 (2) | |
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"s DUKE POWER COMPANY OCONEE UNIT 3
' Report No.: AO-287/74-11
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Report Date: December 26, 1974 4
Occurrence Date:
December 10, 1974 Facility: 0conee Unit 3, Seneca, South Carolina Identification of Occurrence:
Failure to monitor reactor quadrant power tilt j '
Conditions Prior to Occurrence:
Unit at 40 percent full power i
Description of Occurrence:
On' December 10, 1974, Oconee Unit 3, 40 percent. power physics testing was being performed. The dropped rod test, which was in progress, had induced
.some quadrant power tilt. A computer failure, shortly after 1600, caused j
the test to be aborted; the loss of computer procedure was initiated.
This procedure provides for hand calculation of certain reactor parameters.. The control rods were returned to their normal position and quadrant power tilt wa's observed to decrease.
At 1800, the quadrant power tilt was computed using OP/0/1103/19, Power Imbalance and Quadrant Power Tilt Calculation Using the Backup Incore Detector System. The results achieved appeared inconsistent with previous computer calculated tilt, and at 1845 it was determined that some of the backup incore detectors had not been calibrated.
The power range detectors were used and a quadrant power tilt calculation was complete by 1930. Although an attempt was made to monitor quadrant tilt within the required m.inimum frequency of two hours, 315 hours0.00365 days <br />0.0875 hours <br />5.208333e-4 weeks <br />1.198575e-4 months <br /> elapsed between accurate quadrant power tilt measurements.
Designatien of Apparent Cause of Occurrence:
Quadrant power tilt is normally calculated by the computer using the power range channels. When the computer failed, the operator incorrectly used the procedure which utilizes the backup incore detector system. This pro-cedure is intended for use when one power range channel is inoperable, and the computer is also inoperable.
The operator should have used the power range channels to manually calculate quadrant power tilt.
Analysis of Cccurrence:
The Oconee Nuclear Station. Technical Specification 3.5.4 requires that the.
incore detector system be operable if the reactor is above 80 percent full Power. Oconee Unit 3 had been in power escalation testing at 40 percent full. power and had act.fet achieved 80 percent full power. Thus, all of the c
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