ML19317F103
| ML19317F103 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 11/14/1974 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML19317F097 | List: |
| References | |
| NUDOCS 8001080791 | |
| Download: ML19317F103 (2) | |
Text
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N DUKE POWER COMPANY OCONEE UNIT 3 Report No.: A0-287/74-7 Report Date:
November 14, 1974 Occurrence Date:
November 2, 1974 Facility: Oconee Unit 3, Seneca, South Carolina Identification of Occurrence:
Reactor coolant pressure transmitter out of calibration Conditions Prior to Occurrence:
Unit in cold shutdown Description of Occurrence:
On November 2, 1974, the calibration of the reactor coolant pre..ure trans-mitters for Oconee Unit 3 was checked.
The Channel A pressure cransmitter, RC3A-PT1,was found to be out of calibration by +3.2 percent.
The full scale error measured as a result of transmitter drift was +25.6 psi.
The pressure transmitters for Channels B, C, and D were within the required 2 percent limit.
These trans ters provide reactor coolant pressure information to the Reactor Pro ective System.
Analysis of Occurrence:
The Reactor Protective System (RPS) high and low pressure trips are actuated by signals from these pressure transmitters.
The RPS logic produces a trip when two out of four channels trip.
Due to the redundancy present in the RPS, the calibration of one pressure transmitter did not affect the safe operation of the unit.
The high pressure trip setpoint for the Channel A detector drifted in a conservative direction and would have produced a trip at an actual pressure of 2323.4 psi rather than 2349 psi, the high pressure trip setpoint.
The low pressure trip would have occurred at an actual pressure of 1780.4 psi baaed upon the setting of 1806 psi which had been set to allow for instrument drift.
It can be shown that this low pressure trip setting would result in operation within the core protection safety limits and a conservative margin to departure from nucleate boiling (DNB) was maintained even for this out of calibration transmitter.
It is concluded that the health and safety of the public was not affected.
Corrective Action:
The pressure transmitter was recalibrated to the required specifications.
To prevent similar occurrences, a check of these transmitters will be performed on a monthly basis until a sequence of tests can be performed to 8001080 ] /
's determine the cause of the instrument. drift.
Identical transmitters, cali-brated to the same specifications, will be subjected to a similar temperature environment over a period of time to determine the resulting instrument drif t.
Failure Data:
The RPS pressure transmitter is a Motorola Type 56PH ID No. 1224-0301.
Similar occurrences are discussed in Reports A0-269/74-8 dated May 17, 1974 and A0-269/74-18 dated November 13, 1974.
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