05000255/LER-2012-002
| Palisades Nuclear Plant | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown |
| 2552012002R00 - NRC Website | |
steam/water leak near a drain valve [V] of an atmospheric dump valve [PCV] from the "B" Steam Generator [SG]. The leak was discovered by an operator during a normal plant walkdown. The leak originated from a pin-hole size through-wall flaw in the socket weld on the inlet side of the drain valve. The drain valve is part of the ASME Section XI Class 2 piping system that provides steam to the turbine [TRB]. No structures, components, or systems were inoperable or contributed to the event at the time of discovery.
Due to the inoperable PCS loop, Technical Specification (TS) 3.4.4, Condition A, required the plant be placed in Mode 3 within six hours. The plant entered Mode 3 at 1621 hours0.0188 days <br />0.45 hours <br />0.00268 weeks <br />6.167905e-4 months <br /> on November 4, 2012. At 1224 hours0.0142 days <br />0.34 hours <br />0.00202 weeks <br />4.65732e-4 months <br /> on November 5, 2012, the plant entered Mode 5 to execute repairs. Repairs were completed and affected equipment was declared operable at 2149 hours0.0249 days <br />0.597 hours <br />0.00355 weeks <br />8.176945e-4 months <br /> on November 5, 2012.
CAUSE OF THE EVENT
During fabrication of the socket weld in 1986, the welder did not utilize proper welding techniques to create a quality weld for the shield metal arc welding process used at that time. Lack of a quality weld resulted in a through-wall flaw and subsequent leak.
CORRECTIVE ACTIONS TAKEN
The drain valve was replaced utilizing a gas tungsten arc welding process. An extent of condition review identified one additional weld that was fabricated by the same welder, in approximately the same time period. That weld was replaced in 2010 during a plant modification process.
ASSESSMENT OF SAFETY CONSEQUENCES
The through-wall flaw, and subsequent leakage, from the socket weld of the drain valve did not challenge radiological or nuclear safety. The minor steam/water leakage was from the secondary side steam system of the plant. Even though the un-isolable leak from the through-wall flaw necessitated a TS required plant shutdown due to a PCS loop being declared inoperable, the loop was available and used to cool down the PCS.
PREVIOUS SIMILAR EVENTS
None