During flooding walkdowns being performed on August 22, 2012, with the unit at 100 percent power, South
Texas Project Unit 2 discovered the potential for water intrusion into the 10' Elevation Electrical Auxiliary Building (EAB) via a 2-inch underground conduit that was found to be missing its flood seal. It has been determined that the missing flood seal compromised the external flood design controls for the EAB. If flooding of the 10 [foot] EAB were to occur as a result of the missing flood seal, the operability of the Train A Engineered Safety Features (
ESF) switchgear and the
ESF Sequencers for all three Standby Diesel Generators could have been affected. Additionally, the Qualified Display Parameter System process cabinets (which control
Auxiliary Feedwater flow and
Steam Generator PORVs) and the Auxiliary Shutdown Panel are also located on the 10' Elevation.
Repairs have been made and the 2-inch conduit is sealed.
The event is being reported under 10 CFR 50.72(b)(3)(ii)(B) for Unit 2 being in an unanalyzed condition that significantly degraded plant safety, and under 10 CFR 50.72(b)(3)(v) as an event or condition that could have prevented the fulfillment of a safety function.
The NRC Resident Inspector has been notified.
- * * RETRACTION FROM JAMES MORRIS TO JOHN KNOKE AT 1658 EDT ON 09/20/12 * * *
The purpose of this call is to retract the notification made on 09/05/2012, Event Number 48277. Further analysis indicates that water intrusion resulting from the missing 2-inch conduit seal would not have been sufficient to affect the operability of the equipment located on the 10-foot elevation of the Unit 2 Electrical Auxiliary Building. It has been determined that the maximum water depth would not have exceeded 2 inches in depth and all safety related equipment on the 10-foot elevation is greater than 2 inches above the floor, therefore there would be no impact to any safety-related equipment. Accordingly, this event notification is being retracted.
The licensee will notify the NRC Resident Inspector. Notified the R4DO (
Geoffrey Miller).
