05000334/LER-2013-001
| Beaver Valley Power Station Unit Number 1 | |
| Event date: | 9-30-2013 |
|---|---|
| Report date: | 11-27-2013 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(i)(C), 50.54(x) TS Deviation 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3342013001R00 - NRC Website | |
Energy Industry Identification System (EllS) codes are identified in the text as [XX].
CONDITIONS PRIOR TO OCCURRENCE
Unit 1: Mode 3, Planned shutdown for a refueling outage.
There were no systems, structures, or components (SSCs) that were inoperable at the start of the event that contributed to the event.
DESCRIPTION OF EVENT
At approximately 0228 hours0.00264 days <br />0.0633 hours <br />3.769841e-4 weeks <br />8.6754e-5 months <br /> on September 30, 2013, during a planned shutdown of Beaver Valley Power Station (BVPS) Unit 1 for a refueling outage (1R22), the "B" motor driven Auxiliary Feedwater (AFVV) pump [BA] was manually started, while in Mode 3, due to lowering levels in the steam generators [SG]. The condensate pump recirculation flow control valve (FCV] had opened resulting in a reduction of the condensate flow to the steam generators and a decrease in the steam generator levels. The operators recognized that adequate feedwater flow was not available using the normal flow path of the condensate pump [P] through the bypass feedwater regulating valves (FCV] to the steam generators. In response to the lowering steam generator levels, the operators manually started the "B" motor driven AFW pump to restore the steam generator water levels. Following the start of the AFW pump, the steam generator levels were returned to their normal operating control band.
The lowest observed steam generator narrow range level from the plant computer data was 44.5 percent narrow range level (NRL), and occurred in the "C" steam generator. This was well above the AFW actuation setpoint of 19.6 percent (NRL). The heat sink capability was maintained at all times. The AFW System responded as expected. Steam generator blowdown and sample system isolations resulted from the start of the B motor driven AFW Pump, as designed.
Subsequent investigation revealed that the condensate flow control valve setpoint was out of calibration for single pump operation. Testing determined that the flow control valve did not respond as expected to the inputted flow signals. Additionally, the air pressure regulator to the pneumatic controller was found to be leaking air and was replaced.
CAUSE OF EVENT
The apparent cause of the steam generator level transient was the condensate pump recirculation flow controller being out of calibration. This caused the condensate recirculation flow control valve to open when it was not intended, diverting condensate flow away from the steam generators. Due to the dynamics of the system at the time of the event, a single condensate pump was unable to provide sufficient flow to the steam generators due to the loss of discharge pressure associated with the flow control valve opening.
ANALYSIS OF EVENT
The safety significance associated with the manual start of the "B" train AFW pump that occurred at BVPS Unit 1 on September 30, 2013 is considered to be very low. This is based on the successful start of the pump to restore the steam generator levels back to their normal control operating band and providing the necessary risk-significant heat removal functions to prevent or mitigate core damage and large early releases. All risk significant SSCs functioned as designed in response to the manual start of the AFW pump. The unit was safely shutdown for 1R22 and in Mode 3 at the time of the event. Full shutdown defense-in-depth was available for the decay heat removal and RCS inventory functions, as well as the remaining key shutdown defense-in-depth safety functions. This event is being reported under 10 CFR 50.73(a)(2)(iv) as a condition that resulted in the valid manual start of a system listed in (a)(2)(iv)(B)(6) - Auxiliary Feedwater.
CORRECTIVE ACTIONS
The controller for the condensate flow control valve was repaired and functionally checked during the 1R22 refueling outage. The control scheme of these components is unique to the Unit 1 Condensate System, therefore, this condition does not apply to Unit 2.
PREVIOUS SIMILAR EVENTS
A review found no prior BVPS Unit 1 and one Unit 2 event (listed below) within the previous three years involving the actuation of a safety system.
BVPS Unit 2 LER 2012-001-00 "Automatic Actuation of Standby Service Water Pump during Emergency Diesel Generator Test" CR 2013-15253