05000281/LER-2013-002
| Surry Power Station, Unit 2 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2812013002R00 - NRC Website | |
1.0 DESCRIPTION OF THE EVENT At 21:00 on June 23, 2013, with both Unit 1 and Unit 2 operating at 100%, and while preparing for an emergency diesel generator maintenance package, an operator identified a discrepancy with the valve position on the Unit 2 Turbine Driven Auxiliary Feedwater Pump (TDAFWP) turbine trip throttle valve [EllS-BA-ISV]. The Unit 2 trip throttle valve stem position appeared to not be fully withdrawn from the valve body.
At 21:30 a troubleshooting plan was initiated and the diesel generator maintenance package was delayed. On June 24, 2013 at 01:15, the Unit 2 TDAFWP [EllS-BA-P] was taken out of service for troubleshooting and at 01:23 the Unit 2 trip throttle valve was determined not to be in the fully open position.
At 03:05 on June 24, 2013, the trip throttle valve was returned to open, the handwheel was secured in the open position, and the Unit 2 TDAFWP was returned to service. At 14:45, a test was conducted on the Unit 2 TDAFWP to determine whether vibrations from the pump caused the trip throttle valve to rotate. At 17:03, it was noted the trip throttle valve did not change position during the pump run and the device used to secure the handwheel was removed.
An apparent cause evaluation was initiated and interviews conducted to determine if the valve could have been repositioned by personnel working in the area. An operator noted the Unit 2 trip throttle valve to be in the open position during his rounds on June 18, 2013, at 20:09. A review of plant history noted the Unit 2 'B' Motor Driven Auxiliary Feedwater (MDAFW) pump operated between 13:47 and 14:09 on June 20, 2013, prior to finding the trip throttle valve partially closed on June 23. On July 3, 2013, the Unit 2 'B' MDAFW pump was run and the trip throttle valve was observed to rotate toward the closed direction due to the vibration from the MDAFW pump. A temporary modification was implemented to secure the trip throttle valve in the open position and the Unit 2 TDAFWP was returned to service at 19:35 on July 3, 2013.
Based on the most recent Unit 2 'B' MDAFW pump run and the initial installation of the device to secure the Unit 2 TDAFWP turbine trip throttle valve handwheel, the Unit 2 TDAFWP was determined to be inoperable from 14:09 on June 20, 2013 to 03:05 on June 24, 2013. The Unit 2 trip throttle valve was fully opened on June 24, 2013 and the Unit 2 TDAFWP was available, however, since the handwheel was not secured in the open position, vibrations from adjacent equipment could have had an effect on the position of the trip throttle valve. Therefore, until further evaluation, the Unit 2 TDAFWP was also considered inoperable from June 24 to July 3, 2013.
These timeframes exceed the Technical Specification 72-hour limiting condition of operation. Therefore, this report is being submitted, pursuant to 10 CFR 50.73(a)(2)(i)(B) for operation prohibited by Technical Specifications.