Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 54560 | 4 March 2020 02:07:00 | At 2050 MST on March 3, 2020, Unit 2 reactor automatically tripped on Low Steam Generator (SG) Number 1 level signal from the Reactor Protection System. The low SG level occurred as the result of a trip of both Main Feedwater Pumps, which tripped during restoration of power to the Main Feedwater Pump Lube oil control panel. Auxiliary Feedwater (AFAS-1 and AFAS-2) actuated due to low SG levels in both SG post reactor trip as designed. This event is being reported as a reactor protection system and a specified system actuation in accordance with the reporting criteria of 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A). Following the reactor trip, all (control element assemblies) CEAs inserted fully into the core. All systems operated as expected. No emergency plan classification was required per the Emergency Plan. Safety related busses remained powered during the event from offsite power and the offsite power grid is stable. Unit 2 is stable and in Mode 3. Steam Generators are being fed via the class 1E powered motor driven auxiliary feedwater pump. The NRC Senior Resident Inspector has been informed. Units 1 and 3 were unaffected by the trip and remain at 100 percent power.
The event reported on March 4, 2020 (EN 54560) also included actuations of the Emergency Diesel Generators in response to the AFAS-1 and AFAS-2 actuations. The Class 4.16kV buses remained energized from off-site power. The NRC Senior Resident Inspector has been informed. Notified R4DO (Drake). |
| ENS 52229 | 9 September 2016 03:59:00 | The following event description is based on information currently available. If through subsequent reviews of this event additional information is identified that is pertinent to this event or alters the information being provided at this time a follow-up notification will be made via the ENS or under the reporting requirements of 10 CFR 50.73. This event is being reported pursuant to 10 CFR 50.72(b)(3)(xiii) for a loss of emergency assessment capability at the Palo Verde Nuclear Generating Station (PVNGS). On September 8, 2016 at 1856 (MST), seismic monitoring (SM) system computer AJSMNXYQI0001**INSTRU was determined to be non-functional due to a power spike which caused a temporary loss of power to the seismic instrumentation and resulted in a locked in the Control Room alarm. At 2305, I&C technicians re-booted the computer and verified the SM system was functioning. On September 8, 2016, at approximately 2353, further review of this equipment failure and the related impact to the capability of the SM system determined that this was a reportable loss of emergency assessment capability during the period between 1856 and 2305. This specific SM functions to provide indication that the Operational Basis Earthquake threshold has been exceeded following a seismic event and is used in the PVNGS Emergency Plan to perform classification for emergency action level HA1.1, Natural or Destructive Phenomena affecting Vital Areas. As a compensatory measure, PVNGS procedures for seismic event evaluation provide alternative methods for HA1.1 event classification with the SM out of service. Maintenance to correct the condition has been completed. The NRC Resident Inspector has been informed of this condition. |
| ENS 51041 | 5 May 2015 00:48:00 | The following event description is based on information currently available. If through subsequent reviews of this event additional information is identified that is pertinent to this event or alters the information being provided at this time a follow-up notification will be made via the ENS or under the reporting requirements of 10CFR50.73. This event is being reported pursuant to 10 CFR 50.72(b)(3)(xiii) for a loss of emergency assessment capability at the Palo Verde Nuclear Generating Station (PVNGS). On May 4, 2015 at 0320, seismic monitoring (SM) system force balance accelerometer R0006 was determined to be non-functional due to an emergent equipment failure. On May 4,2015, at approximately 1600, further review of this equipment failure and the related impact to the capability of the SM system determined that this was a reportable loss of emergency assessment capability. This specific accelerometer functions to provide indication that the Operational Basis Earthquake threshold has been exceeded following a seismic event and is used in the PVNGS Emergency Plan to perform classification for emergency action level HA1.1, Natural or Destructive Phenomena affecting Vital Areas. As a compensatory measure, PVNGS procedures for seismic event evaluation provide alternative methods for HA1.1 event classification with accelerometer R0006 out of service. Maintenance to correct the condition is in-progress. The NRC Resident Inspector has been informed of this condition. |