ML19317D920
| ML19317D920 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 10/18/1974 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML19317D912 | List: |
| References | |
| NUDOCS 7912100602 | |
| Download: ML19317D920 (2) | |
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DUKE POWER COMPANY OCONEE UUlT 1 i
Report No.: A0-269/74-14 gg l
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Report Date:_ October 18, 1974 i
Occurrence Datti October 5, 1974 Facility: Oconee Unit 1, Seneca, South Carolina Identification of Occurrence:
Failure of Pre'ssure Switch IPS-364 Conditions Prior to occurrence: Unit at 75 Percent of Full Power Description of Occurrence:
At 1350 October 5, 1974, a 4 spm reactor coolant leak was detected on Oconee Unit 1.
A reactor shutdown commenced i==ediately after discovery. During the shutdown, at 1441, the Channel A Engineered Safeguards (ES) and Reactor Protective Systems (RPS) tripped indicating low reactor coolant system The reactor was subcritical by 1547, however, personnel entry to pressure.
the Reactor Building was not possible until 0600 October 6, 1974.
Pressure Switch IPS-364, interlock for valve ILP-2, was found leaking and was Channel A ES pressure transmitter 1PT-21P was found to be damaged isolated.
due to steam frca 1PS-364.
Designation of Apparent Cause of Occurrence:
The reactor coolant leakage from pressure switch IPS-364 was the result of a defective diaphragm. This was the first failure of this type of valve at Oconee. The valve is proof tested to 4500 psi.
The failure of pressure transmitter IPT-21P was due to electronic component failure induced by heat from the steam being impinged on it.
Analysis of Occurrence:
Pressure switch IPS-364 creates an electrical interlock to the operation of valve ILP-2, decay heat removal from the reactor coolant system, whichThis prevents opening with reactor coolant pressur2 greater than 410 psi.
inadvertent overpressurization of the low pressure-injection will prevent The failure of the pressure switch resulted in the proper action of piping.
preventing the opening of valve ILP-2.
Valve lL?-l serves as a redundant isolation valve to prevent overpressurization of the low pressure injcetion system.
This valve is interlocked using a pressure signal from the intagrated control system which prevents operation with reactor coolant pressure in excess of 200 psi.. Valve ILP-1 was not affected by this incident.
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.I Pressure transmitter IPT-21P supplies pressura information to Channel A ES.
Die failure of thia transmitter gave a " sero" pressure indication to ES Channel A and resulted in a channel trip.
The pressure switch failed in a \\
conservative manner by giving a channel trip.
The maximum level of contamination in the Reactor Building was 2.1 x 10' pCi/ml of 1311.
Personnel radiation exposure was minimized during this incident. All entries into the Reactor Building were controlled by health physics personnel.
No activity was released to the environment.
It is concluded that the health and safety of the public was not affected.
Corrective Action:
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Pressure switch IPS-364 was isolated and removed.
The piping was capped because a spare pressure switch was not in stock. The breakers for valve ILP-2 and redundant valve ILP-1 were red tagged to prevent inadvertent I
actuation.
Pressure transmitter 1PT-21P was replaced with a new transmitter and was 3
properly calibrated.
1 Failure Data:
Pressure switch IPT-364 is a Custom Component, Type 6045GX4 (200-400 psi range, 4500 psi proof pressure, 35 psi deadband).
Pressure transmitter 1PT-21P is a Motorola Type 56 PH.
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