Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 55032 | 11 December 2020 17:38:00 | On October 13, 2020, at approximately 02:25 (MST), an automatic start of the Unit 1 'A' Train EDG and SP systems occurred following the restoration of power to the 'A' Train 4160 Volt Class Bus. The station was conducting a surveillance test during a Unit 1 refueling outage to verify the proper responses of the EDG and the Engineered Safety Features Actuation Systems to simulated design basis events. During the test, technicians installed a jumper across incorrect relay points that caused the running Unit 1 'A' Train EDG to trip, resulting in a loss of power to the 'A' Train 4160 Volt Class Bus. Following restoration of normal offsite power to the 'A' Train 4160 Volt Class Bus, the Loss of Power Actuation signal was reset, however, EDG start relay logic was not reset at the EDG Local Panel. This resulted in the Unit 1 'A' Train EDG and SP system actuations with the EDG running unloaded. The system actuations did not occur as a result of valid plant conditions or parameters and are therefore invalid. The Unit 1 'A' Train EDG and SP system actuations were complete and the systems started and functioned successfully. The event was attributed to a human performance error and entered into the corrective action program. There was no adverse impact to public health and safety nor to plant employees. The NRC Resident Inspectors have been informed. |
| ENS 53968 | 1 April 2019 06:40:00 | At 2006 (MST), on 3/31/2019, the Palo Verde Nuclear Generating Station Unit 1 Shift Manager was informed that leakage was measured from the Train A Emergency Core Cooling System (ECCS) piping at approximately 100 ml/minute through a High Pressure Safety Injection (HPSI) A drain valve. This value exceeds the assumed 3000 ml/hour ECCS leakage for a large break loss of coolant accident analysis. At 0230 (MST) on April 1, 2019, the valve was flushed and the leakage reduced to 10 ml/minute (600 ml/hour) and was no longer above the limit of the safety analysis. This condition is being reported as an unanalyzed condition per 10 CFR 50.72(b)3)(ii)(B) and a condition that could have prevented the fulfillment of a safety function to the control the release of radioactive material per 10 CFR 50.72(b)(3)(v)(C). This event did not result in an abnormal release of radioactive material. Notification received by Caty Nolan and emailed to HOO.HOC@NRC.GOV The NRC asked a followup question: Why was the criterion for Control of Radioactive Material selected? per the PVNGS Unit 1 Shift Manager, this criterion was selected due to the potential of exceeding offsite dose projections, post recirculation, following a Design Basis Accident. The resident inspector has been notified.
An engineering evaluation concluded that the as-found ECCS leakage would not have degraded the performance of the Pump Room Exhaust Air Cleanup system; therefore, it remained operable. The evaluation also concluded that the as-found leakage was within the analysis margins for HPSI pump hydraulic performance and containment flood level following a Large Break Loss of Coolant Accident; therefore, the ECCS also remained operable. Based on the above information, the condition identified on March 31, 2019, was an unanalyzed condition per 10 CFR 50.72(b)(3)(ii)(B), but did not prevent the fulfillment of the safety function of the structures or systems that are needed to control the release of radioactive material per 10 CFR 50.72(b)(3)(v)(C). The NRC resident inspectors have been informed. Notified R4DO (Proulx). |
| ENS 48920 | 13 April 2013 18:21:00 | At 1109 CDT on 4/13/13, R-20, Service Water System Effluent Line (Auxiliary Building Service Water Header) was declared non-functional due to low SW (Service Water) sampling flow. R-20 is used for Emergency Action Level (EAL) classifications of an unplanned release of liquid radioactivity to the environment that exceeds the requirements of the Offsite Dose Calculation Manual for an Unusual Event and an Alert, and is therefore, being conservatively reported under 10 CFR 50.72(b)(3)(xiii) as a loss of emergency assessment capability. The licensee will notify the NRC Resident Inspector. |
| ENS 48397 | 10 October 2012 18:34:00 | On October 10, 2012, at 1633 (CDT), Kewaunee Power Station staff identified (in response to concerns raised by the NRC Resident Inspector) that the Containment and Auxiliary Building SPING (Special Particulate Iodine Noble Gas) units could likely not have been relied upon to determine Emergency Classifications based on the Kewaunee Emergency Action (EAL) Level Matrix. This was due to these SPINGs having been nonfunctional during the period from 2/28/2011 at 0150 (CDT) until 3/30/2011 at 1845 (CDT). Alternate radiation monitoring capability remained available to provide indication of radiation levels in the Auxiliary Building and Containment vent stacks; however, they would not have been sufficient to identify the upper two emergency action levels. Alternate means (e.g., grab samples) could also have been used to make the appropriate declarations. However, use of the alternate means could potentially impair the plant's ability to declare an emergency in a timely manner. These SPING units had been returned to service on 3/30/2011 and were subsequently available for EAL classifications. However, the ramification of this condition was not fully recognized until today. This condition is being conservatively reported in accordance with 10CFR50.72(b)(3)(xiii) as an event that results in a major loss of emergency assessment capability. The NRC Resident Inspector has been notified. |