ML19317D822
| ML19317D822 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 04/05/1977 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML19317D817 | List: |
| References | |
| RO-269-77-11, NUDOCS 7912100557 | |
| Download: ML19317D822 (2) | |
Text
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e DUKE POWER COMPANY OCONEE UNIT 1 EP Report No.:
RO-269/77-ll Report Date: April 5, 1977 Occurrence Date:
March 22, 1977 Facility:
Oconee Unit 1, Seneca, South Carolina Identification of Occurrence:
Primary-to-secondary system leakage in "1B" once-through steam generator Conditions Prior to Occurrence: Unit at 100 percent full power Description of Occurrence:
On March 22, 1977, a high radiation alarm was received on condenser steam air ejector monitor, RIA-40, indicating a possible primary-to-secondary system leak.
Procedures to control and monitor secondary activity were promptly initiated.
Analysis of a steam line sample confirmed that primary-to-secondary leakage was occurring in the "1B" once-through steam generator (OTSG). Within 2h hours after the high radiation alarm, a reactor shutdown was commenced.
Within five hours, reactor shutdown was completed.
The reactor coolant system was cooled and drained within 2 days and an internal inspection cf the "1B" OTSG was initiated.
Apparent Cause of Occurrence:
This occurrence resulted from a weld crack on the plug used to isolate tube 25 of row 77 in a previous outage.
The weld had been inspected and approved at that time, and pressure and hydro tests had confirmed the integrity of the weld.
The reason for the weld failure ha: not been determined.
Eddy current examination of 100 other tubes revealed no other tube leaks.
However, eddy current signal distortions were found on tubes 3, 5, 8, 22, and 29 of row 77.
Therefore, as a precautionary measure, these five tubes were plugged.
Analysis of Occurrence:
The weld leak developed on the top plug of tube 25 in row 77.
A portion of this tube had been removed during an early March outage for steam generator tube repair.
At that time, both ends of the tube had been closed by plugging.
The we'.ds were inspected, approved, and tested.
Primary-to-secondary system leakage, resulting from the weld leak, was approxi-mately 0.2 gallons per minute and was detected by installed radiation monitoring equipment. The leakage did net exceed the operational limits of Oconee Technical Specification 3.1.6.1.
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- t The calculated gaseous activity released to the environment via the air ejectors was 1.494 curies.
This amount is considered insignificant in comparison to the station's annual release limit.
Secondary side activity l
was closely monitored to assure control of radioactive material.
It is considered that this incident did not affect the health and safety of the public.
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Corrective Action:
The weld failure on tube 25 of row 77 was repaired and inspected.
Five other tubes with qaestionable eddy current signals, tubes 3, 5, 8, 22, and 29 in row 77, were plugged utilizing a stabilizer rod.
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