This is a non-emergency eight hour notification in accordance with
10 CFR 50.72(b)(3)(iv)(A), for an automatic actuation of the 3A
Emergency Diesel Generator (
EDG).
On 11/18/15 at approximately 0326 [EST] a loss of power was experienced on the 3A 4KV Bus. The redundant 3B 4KV bus did not experience a loss of power. All systems operated as expected following the loss of power with the 3A EDG automatically sequencing onto the 3A 4KV bus and the load sequencer loading as designed. At the time of the actuation, Unit 3 was in a refueling outage in MODE 5. Investigation into the cause of the loss of power is in progress. There was no impact on Unit 4 operation during this time.
The NRC Resident Inspector has been informed.
- * * UPDATE AT 2100 EST ON 01/19/16 FROM JIM SPEICHER TO S. SANDIN * * *
The licensee is retracting the original notification of a valid actuation and has re-categorized this as a 60-day optional report based on the following:
This 60-day telephone notification is being made under the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of the 3A EDG. The 3A EDG start resulted from an unexpected actuation of the 3A load sequencer during setup activities for the 3A Engineered Safeguards Integrated Test (ESIT) loss of offsite power (LOOP) sequence.
On November 18, 2015, at approximately 0330 EST with Unit 3 in Mode 5 during a refueling outage, an unexpected LOOP occurred on the 3A 4160 V bus. At the time, an Instrument and Control (I&C) specialist was working in sequencer cabinet 3C23A verifying proper placement of flags in preparation for the installation of a local test switch that would be used to initiate the 3A ESIT LOOP signal. The 3A EDG started and functioned as designed. Initial troubleshooting determined that there were no actual plant conditions or parameters (e.g., undervoltage, degraded voltage, manual initiation) involved in the actuation.
The root cause investigation revealed that individuals working in the room near the open cabinet did not have their mobile phones in airplane mode as required and two computer tablets being used adjacent to the sequencer cabinet were not in airplane mode as required prior to entering the 3A sequencer room. The cause of the actuation was determined to be an unintended human interaction in the form of electromagnetic or radio frequency interference at the proximity of the 3C23A cabinet.
The licensee notified the NRC Resident Inspector.
Notified R2DO (McCoy).
