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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 56347 | 25 December 2022 11:37:00 | 10 CFR 50.73(a)(1), Submit an LER | 60-DAY Optional Telephonic Notification of Invalid Actuation of Emergency Diesel Generator (EDG) | The following information was provided by the licensee via email: This 60-day optional telephone notification is being made in lieu of an LER (Licensee Event Report) submittal as allowed by 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B). At approximately 0637 EST on December 25, 2022, the 2B EDG inadvertently started and ran unloaded without a valid undervoltage or safety injection actuation signal. It was determined that this condition was caused by the failure of the emergency start button due to age-related degradation. The button is normally held depressed (closed) by the glass enclosure in standby. To start the EDG using the Emergency Start Button, the button is released (open) when the glass enclosure is broken, which sends a start signal to the EDG. During troubleshooting, the resistance across the button contacts was measured at zero volts DC, indicating the button had failed to an open state causing the EDG to start. The button fell apart when the glass enclosure was removed. The actuation was not initiated in response to actual plant conditions, it was not an intentional manual initiation, and there were no parameters satisfying the requirements for initiation of the emergency diesel generator. The NRC Resident Inspector has been notified. | Emergency Diesel Generator | |
| ENS 44708 | 16 November 2008 23:27:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Actuation of an Emergency Diesel Generator | This notification of a system actuation is provided in accordance with 10 CFR 50.73(a)(2)(iv)(A). The Licensee is providing a telephone notification to the NRC Operations Center in accordance with 10 CFR 50.73(a)(1) instead of submitting a written Licensee Event Report, as the system actuation was invalid and was not the result of an actuation of the reactor protection system when the reactor was critical. The event involved the invalid actuation of 'Emergency AC electrical power systems, including: emergency diesel generators' as discussed in 10 CFR 50.73(a)(2)(iv)(B). At 1827 on November 16, 2008, with Calvert Cliffs Unit 2 operating at approximately 100% power, the Train A (2A) Emergency Diesel Generator (EDG) automatically started from the standby condition. The automatic start was caused by a degraded switch in the start circuit for the EDG. The 2A EDG successfully started and functioned properly, but did not automatically connect to the associated bus ('21' 4KV Bus) because no bus undervoltage signal was present. The 2A EDG start is considered to be invalid, as the start signal was not generated in response to actual plant conditions or parameters satisfying the requirements for initiation of the EDG start. The start was also not the result of an intentional manual action. The 2A EDG was removed from service and the Station Blackout diesel generator was aligned to '21' 4KV Bus. Following replacement of the degraded switch, the 2A EDG was tested and returned to Service at 2030 on November 17, 2008. The 2B EDG remained operable during this event. The licensee notified the NRC Resident Inspector. The degraded switch was in the EDG room and had degraded resulting in high resistance i.e. simulated an open circuit, which started the diesel. | Reactor Protection System Emergency Diesel Generator |