Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 51551 | 19 November 2015 00:56:00 | Unit 3 experienced Loss of Offsite Power due to lockout on Unit 3 Startup transformer. The 3B EDG auto started and loaded on the 3B 4KV Bus. The 3A Sequencer was out of service and prevented the 3A EDG from auto starting and supplying 3A 4KV busses. With only 3B 4KV bus powered from an EDG and no offsite power to Unit 3, Unit 3 entered an Unusual Event. Core cooling was restored with 3B RHR pump at 2343 EST. At 2350 EST, 3A 4KV Bus was manually loaded onto 3A EDG and conditions for Unusual Event were terminated. Additionally this is a non-emergency eight hour notification in accordance with 10CFR50.72(b)(3)(iv)(A), for a valid automatic actuation of the 3B Emergency Diesel Generator. While core cooling was lost, the core experienced a 3 degree heat up. Spent fuel pit cooling has also been restored. The cause of the transformer lockout is under investigation. Unit 4 was unaffected and continues to operate at 100% power. The licensee has notified state and local authorities about this event. The licensee has also notified the NRC Resident Inspector. |
| ENS 51515 | 5 November 2015 00:49:00 | This is a non-emergency, information only notification to the NRCOC. Plant conditions are as follows: Unit 3 is de-fueled and Unit 4 is in Mode 1 (At 100 percent power). The Unit 3 Startup transformer is INOPERABLE due to preplanned maintenance. The 3B Emergency Diesel Generator (EDG) became INOPERABLE due to loss of all 480V vital AC load centers on Unit 3. With Unit 4 in Mode 1, Technical Specification (TS) 3.8.1.1.c requires a 4-hour report to the NRC due to inoperability of 1 of 3 required EDGs onsite, concurrent with inoperability of a required Startup transformer. This report is for informational purposes only and is not required by 10CFR50.72/73. Spent Fuel Pool Cooling at Unit 3 remains available via 3B SFP Cooling Pump which is powered from Unit 4. The loss of the Unit 3 480V AC load centers is still under investigation. TS 3.8.1.1.c requires Unit 4 to exit the TS action statement in 2 hours or shutdown. To exit this TS, no two battery chargers may be powered from the same motor control center. The 480V vital AC load centers for Unit 3 must be restored since Unit 4 requires at least one train from Unit 3 480V AC load centers. The licensee is in the process of performing those actions. The licensee notified the NRC Resident Inspector. |
| ENS 50789 | 5 February 2015 18:34:00 | At approximately 1130 EST on 2/5/15, the site discovered degradation of the technical support center ventilation air handling unit. Compensatory measures were established during the period that the ventilation system was non-functional. The TSC ventilation system was subsequently restored to functional status. The TSC ventilation system was restored at approximately 1834 EST on 2/5/15. The issue was a failure of the automatic TSC air recirculation function due to a tripped circuit breaker. The licensee has notified the NRC Resident Inspector. |
| ENS 50714 | 2 January 2015 16:45:00 | At 0925 (EST) on 1/2/2015, Engineering personnel identified a gas void in each of two Unit 4 cold leg High Head Safety Injection (HHSI) discharge lines which exceeded procedural gas accumulation acceptance criteria. This condition rendered the cold leg HHSI flow path inoperable and required entry into Technical Specification 3.0.3. The voids were vented and Technical Specification (TS) 3.0.3 was exited at 1032. The testing for gas voids conducted on 1/2/2015 was a follow-up to a gas void found in one Unit 4 HHSI line on 12/26/2014. On 12/26/14, TS 3.0.3 was entered at 1020 and exited at 1048 after the gas void was vented. After further review, the 12/26/2014 event was also reportable in accordance with 10 CFR 50.72(b)(3)(v)(D). Engineering evaluation will be performed for both events to determine the specific impact of the gas voids on HHSI system function. Cause evaluation is being conducted to determine the source of the gas and any needed corrective actions. Unit 3 was verified to not have this voiding issue. The licensee notified the NRC Resident Inspector.
On 1/2/2015 at 1645 (EST), Event Notification 50714 reported to the NRCOC (Nuclear Regulatory Commission Operations Center) gas voids detected on 12/26/2014 and 1/2/2015 in Unit 4 cold leg High Head Safety Injection (HHSI) piping which exceeded procedural gas accumulation acceptance criteria. Subsequent analysis has determined that if a HHSI pump started with the measured gas voids present, the resulting system conditions would not have impacted the integrity of the Unit 4 HHSI discharge flow path to the reactor coolant system (RCS) and therefore its safety related function would not be impaired. The Unit 4 HHSI system discharge flow path to the RCS had been operable with the voids present, Technical Specification (TS) requirements were met, and entry into TS 3.0.3 was not required. The HHSI system remained capable of fulfilling the safety function to mitigate the consequences of an accident on Unit 4. Therefore, the immediate notification to the NRCOC on 1/2/2015 at 1645 in accordance with 10 CFR 50.72(b)(3)(v)(D) is hereby retracted. The NRC Resident Inspector has been informed. Notified R2DO (Shaeffer). |
| ENS 50645 | 30 November 2014 17:26:00 | This is an non-emergency event notification to the NRCOC (NRC Operations Center) in accordance with 10 CFR 50.72(b)(3)(iv)(A) due to preplanned manual actuation of Reactor Protection System and auto-initiation of AFW due to beginning of cycle operating conditions, IAW 4-GOP-103 (General Operating Procedure). On 11/30/14 at 1354 EST, Unit 4 reactor power was reduced to approximately 23% and manually tripped as a pre-planned evolution to facilitate repairs to an unidentified steam leak on Unit 4 High Pressure Turbine. All systems and components operated as designed. Unit 4 is currently stable in Mode 3, AFW has been secured. The licensee has notified the NRC Resident Inspector |