05000334/LER-2015-001
| Beaver Valley Power Station Unit Number 1 | |
| Event date: | 04-15-2015 |
|---|---|
| Report date: | 06-11-2015 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(C), 50.54(x) TS Deviation 10 CFR 50.73(a)(2)(iv)(B), System Actuation 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| Initial Reporting | |
| 3342015001R00 - NRC Website | |
Energy Industry Identification System (EllS) codes are identified in the text as [XX].
CONDITIONS PRIOR TO OCCURRENCE
Unit 1: Mode 1, 85% power with power reduction in progress 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
On April 15, 2015 at 0411 hours0.00476 days <br />0.114 hours <br />6.795635e-4 weeks <br />1.563855e-4 months <br /> EDT, Beaver Valley Power Station (BVPS) Unit 1 initiated a manual reactor trip from approximately 85 percent power due to the trip of one of the two running condensate [KA] pumps [P]. At 0405 hours0.00469 days <br />0.113 hours <br />6.696429e-4 weeks <br />1.541025e-4 months <br /> operators initiated an emergent power reduction following the identification of a degrading condition on the "A" condensate pump motor. At 0411 hours0.00476 days <br />0.114 hours <br />6.795635e-4 weeks <br />1.563855e-4 months <br />, a manual reactor trip was initiated when the "A" condensate pump tripped due to a motor [MO] overcurrent condition. All three auxiliary feedwater [BA] pumps [P] automatically started as designed, and were subsequently secured in accordance with station procedures. The response was as expected except for an undercompensated intermediate range instrument [JI] which prevented the source range instruments [JI] from automatically energizing. The source range instruments were manually energized by the operators. All control rods [AA] fully inserted into the core. The operators entered E-0 (Reactor Trip or Safety Injection) then transitioned to ES-0.1 (Reactor Trip Response) and stabilized the plant in Mode 3.
CAUSE OF EVENT
The cause of this event was a trip of one of the two running condensate pumps. Both condensate pumps must be running to maintain the appropriate suction pressure at the main feedwater [SJ] pumps [P] when the unit is greater than 70 percent power. Following the trip of one of the two running condensate pumps the reactor was manually tripped. The trip of the condensate pump was due to the failure of the inboard motor bearing caused by lack of oil lubrication.
The root cause evaluation determined that responses to technical questions were provided without the appropriate technical rigor or validation of assumptions regarding acceptable oil level for the pump motor.
This resulted in an incorrect change in the oil level sight glass configuration and continued operation of the motor with the oil level below the vendor recommended minimum level until bearing failure.
ANALYSIS OF EVENT
The plant risk associated with the BVPS Unit 1 manual reactor trip and auxiliary feedwater actuation system on April 15, 2015, due to the "A" Condensate Pump trip is considered to be very low. This is based on the change in average core damage frequency derived using the conditional core damage probability, and change in average large early release frequency derived using the conditional large early release probability for the event. Based on the above, the safety significance of the manual reactor trip and auxiliary feedwater actuation event on April 15, 2015, was very low.
The condensate system is not credited to mitigate the consequences of an accident described in the BVPS Updated Final Safety Analysis Report. The condensate system cannot compromise the availability of safety-related equipment.
This event was reported on 4/15/2015, at 0732 EDT, EN 50985, as an event or condition that results in the actuation of the Reactor Protection System (RPS) when the reactor is critical, 10 CFR 50.72(b)(2)(iv)(B) and specified system actuation, 10 CFR 50.72(b)(2)(iv)(A). This event is reportable pursuant to 10 CFR 50.73(a)(2)(iv)(A) as a condition that resulted in the manual actuation of the Reactor Protection System (RPS) 10 CFR 50.73(a)(2)(iv)(B)(1), and the automatic actuation of the auxiliary feedwater system 10 CFR 50.73(a)(2)(iv)(B)(6).
CORRECTIVE ACTIONS
1. Replacement of the condensate pump motor. (Complete) 2. Perform a review to ensure that all 4KV and single point vulnerability motors have the proper formal technical requirement for bearing reservoir oil level.
3. Evaluate training for the appropriate departments on the lessons learned from this event.
Completion of the above and other corrective actions are being tracked through the BVPS Corrective Action Program.
PREVIOUS SIMILAR EVENTS
A review of the previous three years has found that there were no similar events involving a reactor trip due to the failure of a large motor.
CR-2015-05256, 05262