ML19329A685
| ML19329A685 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 09/27/1976 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML19329A679 | List: |
| References | |
| RO-287-76-15, NUDOCS 8001090670 | |
| Download: ML19329A685 (1) | |
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Oconee Unit 3 Report No: 50-287/76-15 Report Date: September 27, 1976 Occurrence Date: September 11, 1976 Facility: Oconee Unit 3, Seneca, South Carolina Identification of Occurrence:
Incorrect " thermal power best" valve resulting from erroneous data input to Core Thermal Power Analysis Program Conditions Prior to Occurrence: Unit at 53% full power Description of Occurrence:
On September 11, 1976, it was discovered that on September 10, 1976, a data val,ue had been incorrectly input into the Core Thermal Power Analysis (CTPA) program on the Oconee Unit 3 computer.
As a result, for approximately 26 hours3.009259e-4 days <br />0.00722 hours <br />4.298942e-5 weeks <br />9.893e-6 months <br />, the " thermal power best" computer point, a determination of the reactor power calculated from primary and secondary system heat balances, indicated a power level of 44% full power rather than the correct value of 53% full power.
Upon discovery of this error the computer program was corrected and the power range out of core detectors which had previously been calibrated to the incor-rect reactor power calculation, were recalibrated to the corrected " thermal power best" value.
Apparent Cause of Occurrence:
This incident resulted from the incorrect storage of a data valus within the CTPA program. The technician involved, needing a computer location in which to store a numerical constant, placed the constant in a location occupied by a zero, thinking such to be an unused computer memory location.
The zero stored in that location.however, was normally used by the program for calcu-lation of Reactor Coolant pressure. Therefore, changing this data value resulted in an incorrect pressure calculation and in a 10% error in the " thermal power best" determination.
Analysis of Occurrence:
This incident resulted in the operation of the unit for a period of approxi-mately 26 hours3.009259e-4 days <br />0.00722 hours <br />4.298942e-5 weeks <br />9.893e-6 months <br /> during which the out-of-core detectors were indicating a power level approximately 10% below the actual power. During this time, however, no safety limits were exceeded because the unit was operating at a reduced power level in preparation for a refueling outage.
It is concluded therefore, that the health and safety of the public was not affected by this occurrence.
i Corrective Action:
It is felt that this occurrence is an isolated incident.
However, efforts are underway to evaluate the present controls for computer software and to imple-ment, as determined necessary, appropriate formal administrative policies.
8001090870
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