Lpci Inoperability Due to Overvoltage Relay Actuation
On November 22, 2017, at 2043 (CST), Unit I MCC (Motor Control Center) 18/19-5 overvoltage relay target was found actuated and would not reset. MCC 18/19-5 was powered from the normal feed, Bus 19. Bus 19 voltages were verified to be normal. The overvoltage relay actuation would result in MCC 18/19-5 being de-energized in the event of a DBA LOCA (Design Basis Accident Loss of Coolant Accident) in which the 1/2 Emergency Diesel Generator fails to energize Bus 18, therefore rendering both divisions of the Low Pressure Cooling Injection (LPCI) mode of Residual Heat Removal (RHR) system inoperable. Technical Specification 3.5.1 Condition E was entered, requiring restoration of LPCI in 72 hours.
The overvoltage target was subsequently able to be reset at 2114 (CST), restoring the LPCI function of RHR. Technical Specification 3.5.1 Condition E was exited at that time.
This event is reportable under 10 CFR 50.72(b)(3)(v)(D) as an event or condition that could have prevented fulfillment of a safety function.
The licensee notified the NRC Resident Inspector.
* * RETRACTION FROM RONALD SNOOK TO STEVEN VITTO ON 01/11/18 AT 1913 EST * * *
The purpose of this notification today (01/11/18) is to retract the ENS Report made on November 23, 2017 at 0248 hours EST (ENS Report #53089).
Upon further review, it was determined that the Unit 1 MCC 18/19-5 overvoltage relay target that was found actuated and would initially not reset was caused only by intermittent degraded DC control power. During this event, MCC 18/19-5 remained powered from the normal feed Bus 19, and Bus 19 voltages were verified to be normal.
It was further determined from plant drawings that under this condition the degraded DC control power to the Unit 1 MCC 18/19-5 overvoltage relay has no impact to the Technical Specification 3.5.1 required capability to auto transfer power from the normal Bus 19 to the alternate Bus 18 should Bus 19 lose power such as during a DBA LOCA. This overvoltage relay was installed in the early 1990's only to support enhanced reliability of the power supply to the LPCI injection valves, and its actuation due to degraded DC control power would not impact the ability to auto transfer to alternate Bus 18. Therefore, both divisions of the Low Pressure Cooling Injection (LPCI) mode of Residual Heat Removal (RHR) system would have remained fully operable under the as-found relay condition, and Technical Specification 3.5.1 Condition E was not required to be entered.
On December 6, 2017, it was determined that a loose fuse clip terminal had caused the DC control power to the overvoltage relay to become degraded which in turn caused the relay target and its reset to become erratic. This fuse clip terminal was repaired on December 6, 2017. Based on the subsequent reviews of this event, the LPCI system was not required to be declared inoperable in accordance with Technical Specifications 3.5.1 during the period of the MCC 18/19-5 overvoltage relay actuation (i.e., 31 minutes on 11/22/17), and hence was not required to be reported under 10CFR 50.72(b)(3)(v)(D) as an event or condition that could have prevented fulfillment of a safety function.
Therefore, based on this information, ENS Report #53089 is being retracted.
The NRC Resident Inspector has been notified.
Residual Heat Removal Minimum Flow Valves OUt of Position Results in Loss of Safety Function and Condition Prohibited by Technical Specifications LER 17-001-00 for Cooper Regarding Residual Heat Removal Minimum Flow Valves Out of Position Results in Loss of Safety Function and Condition Prohibited by Technical Specifications
On February 5, 2017, during a quarterly sealed valve log audit, Residual Heat Removal (RHR) Valves RHR-V-58 and RHR-V-60 were discovered sealed closed. Normal configuration for these valves is sealed opened. Consequently, Operations declared RHR pumps A and C Inoperable at 0756 hours and entered Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.5.1 Condition A, LCO 184.108.40.206 Condition A, and LCO 220.127.116.11 Condition A.
Subsequently, the operating crew opened RHR-V-58 and RHR-V-60, independently verified the position of the valves and applied seals to the valves. As such, RHR pumps A and C were declared Operable at 1041 hours on February 5, 2017, and TS LCO 3.5.1 Condition A, LCO 18.104.22.168 Condition A, and LCO 22.214.171.124 Condition A were exited.
The root cause is Operations Department standards related to Operator Human Performance and Configuration Control are inadequate and do not meet industry expectations. Licensed and Non-Licensed Operators completed training focused on Standards and Expectations related to attention to detail and configuration control. To prevent recurrence, expectations will be established and institutionalized for Operations Leadership to reinforce consistent application of operator fundamentals and to identify and correct performance gaps for the operating crews.