Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 53467 | 22 June 2018 12:14:00 | At 0841 EDT on June 22, 2018, the Watts Bar Unit 2 reactor automatically tripped while operating at 95% power. All control and shutdown bank rods inserted properly in response to the automatic reactor trip. All safety systems including Auxiliary Feedwater actuated as designed. The plant is stable with decay heat removal through Auxiliary Feedwater and Steam Dump Systems. The reactor automatically tripped due to a main turbine trip. The turbine trip was caused by main generator electrical trip. An investigation is in progress. The automatic actuation of the Reactor Protection System (RPS) is being reported as a four hour report under 10 CFR 50.72 (b)(2)(iv)(B). The expected actuation of the Auxiliary Feedwater System (an engineered safety feature) is being reported as an eight hour report under 10 CFR 50.72 (b)(3)(iv)(A). The NRC Senior Resident Inspector has been notified for this event. The plant is currently stable at normal operating temperature and pressure. The grid is stable and the plant is in its normal shutdown electrical lineup. Unit 1 was unaffected by the Unit 2 trip. |
| ENS 51955 | 24 May 2016 17:48:00 | CPNPP (Comanche Peak Nuclear Power Plant) experienced an unplanned loss of the seismic monitoring instrument on May 24, 2016 at 1022 (CDT). The unplanned loss of the seismic monitor resulted in a loss of assessment capability for the HA1.1 (seismic event greater than operating basis earthquake) Alert emergency classification. The seismic monitor was restored to service on May 24, 2016 at 1043. This loss of assessment capability is reportable to the NRC within 8 hours of discovery in accordance with 10 CFR 50.72(b)(3)(xiii). The NRC Resident Inspector has been notified.
On May 24, 2016 at 1748 (EDT), Comanche Peak reported an unplanned loss of emergency assessment capability per 10 CFR 50.72(b)(3)(xiii) (EN# 51955). Specifically, Comanche Peak reported an unplanned loss of the seismic monitoring instrument. The unplanned loss of the seismic monitor would have resulted in a loss of assessment capability for the HA 1.1 (seismic event greater than operating basis earthquake) Alert emergency classification. The seismic monitor was restored to service on May 24, 2016 at 1043 (CDT). The engineering review determined that the alarms displayed on the seismic monitoring screen provides Operations awareness of the system status. Signals were still being received from the sensor and if there was an OBE (Operating Basis Earthquake) during the time the alarms were in, it would have displayed on the monitoring screen and on the Main Control Board by providing an OBE Exceedance alarm, maintaining emergency assessment capability. Therefore, Comanche Peak requests that the May 24, 2016, 10 CFR 50.72(b)(3)(xiii) reportable event for Units 1 & 2 be retracted. The licensee will notify the NRC Resident Inspector. Notified R4DO (Deese). |
| ENS 51751 | 23 February 2016 20:45:00 | At CPNPP (Comanche Peak Nuclear Power Plant), eyewash stations are located just outside of the Class 1E battery rooms. The battery room doors are normally open and if a MELB (Moderate Energy Line Break) occurred on the demineralized water line connected to the eyewash station, the water could potentially spray onto the Class 1E safety related batteries. If this occurred, an electrical short could potentially cause a loss of both the batteries and the associated battery chargers. This condition has been conservatively determined to be reportable per 10 CFR 50.72(b)(3)(ii)(B) as an unanalyzed condition. Currently, the demineralized water lines on the battery room eyewash stations for both Units 1 and 2 have been isolated, therefore, all safety related equipment is currently operable. Comanche Peak Engineering is performing a past operability review of this condition. The NRC Resident Inspector has been notified.
On February 23, 2016 at 2045 (EST), Comanche Peak reported an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B). Specifically, the reported condition involved eyewash stations that are located just outside of the Class 1E battery rooms. The battery room doors are normally open and if a Moderate Energy Line Break (MELB) occurred on the demineralized water line connected to the eyewash station, the water could potentially spray onto the Class 1E safety related batteries. If this occurred, an electrical short could have potentially caused a loss of both the batteries and the associated battery chargers. This condition was conservatively determined to be reportable per 10 CFR 50.72(b)(3)(ii)(B) as an unanalyzed condition. The demineralized water lines on the battery room eyewash stations for both Units 1 and 2 were isolated, and Comanche Peak Engineering initiated a past operability evaluation of this condition. The past operability evaluation has been completed and shows that there are no operability concerns regarding a MELB impact on the Class 1E batteries, DC bus or Class 1E battery chargers. Therefore, Comanche Peak requests that the February 23, 2016, 10 CFR 50.72(b)(3)(ii)(B) reportable event for Units 1 & 2 be retracted. The NRC Resident Inspector has been notified. Notified the R4DO (Whitten). |
| ENS 50835 | 19 February 2015 20:18:00 | During Main Steam Safety Valve testing conducted prior to refueling outages, normally closed watertight doors are opened in support of the testing. If a postulated one square foot non-mechanistic crack were to occur within the Break Exclusion Area during the test, safety related equipment located just outside of these doors could be adversely affected. With these watertight doors open, compliance with the Comanche Peak licensing basis may not be assured. This condition has been conservatively determined to be reportable as an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B). Currently, the watertight doors on both Units 1 and 2 are closed, therefore, all safety related equipment is currently operable. Comanche Peak Engineering is performing a review of the original Comanche Peak licensing basis regarding the non-mechanistic crack event to determine what equipment impacts are required to be assessed. The NRC Resident Inspector has been notified. |