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| Entered date | Event description | |
|---|---|---|
| ENS 53456 | 12 June 2018 22:11:00 | On June 12, 2018, at 1500 CDT, a Reactor Coolant System (RCS) Pressure Boundary leak was identified during a Mode 3, hot shutdown walkdown on a High Pressure Injection Line (HPI) to Reactor Coolant Pump (P32C) drain line weld near MU-1066A HPI Line Drain Valve and MU-1066B HPI Line Drain Valve. The 3/4 inch drain line containing drain valves MU-1066A and MU-1066B on the 'C' HPI header (CCA-5 pipe class) has a through-wall defect on the pipe stub or welds between the sockolet and valve MU-1066A. The leak location is in the ASME Class I RCS Pressure Boundary. The hot shutdown walkdown was being performed as part of a planned outage to investigate excessive Reactor Building Sump inleakage. Total unidentified RCS leakage prior to the investigation was determined to be at 0.165 gpm. After the initial investigation of the leakage, the following Tech Specs (TS) were determined be applicable: TS 3.4.5 - RCS Loops Mode 3, TS 3.4.13 - RCS Leakage, TS 3.5.2 - ECCS. Unit 1 is currently in Mode 3 and in progress of an RCS cooldown to comply with Tech Spec requirements. The licensee notified the NRC Resident Inspector. |
| ENS 54073 | 20 May 2019 00:02:00 | On May 19, 2019, at 1809 CDT, the Safety Parameter Display System (SPDS) was lost to both Arkansas Nuclear One Units 1 and 2 due to the SPDS Inverter (2Y-26) failure. The SPDS Inverter is the power supply to both units' SPDS. The Unit 2 Control Room dispatched operators in response to a smoke alarm received from the 2Y-26 Inverter room. Upon arrival, smoke was reported emanating from 2Y-26. There was no report of fire at any time. Field operators de-energized 2Y-26 and the smoke ceased. The loss of SPDS also caused the Power Operating Limits (POL) function of the Unit 2 Core Operating Limits Supervisory System (COLSS) to be lost, so Unit 2 reduced power to 91 (percent) in accordance with Technical Specifications. Both units are at power and stable. The NRC Resident has been notified. This is reportable per 10 CFR 50.72(b)(3)(xiii). |
| ENS 53404 | 16 May 2018 22:19:00 | At 1750 CDT, the Arkansas Nuclear One, Unit 1 (ANO-1) reactor tripped due to the trip of the 'B' Main Feedwater Pump. Unit 1 was at 10 percent power with escalation of power in progress with one Main Feedwater Pump in service. Investigation is in progress as to the cause of the Main Feedwater Pump trip. The Main Feedwater Pump trip resulted in RPS (reactor protection system) actuation on loss of both Main Feedwater Pumps and resulted in Emergency Feedwater (EFW) actuation. All Control Rods inserted into the core properly and the reactor was verified shutdown. EFW experienced a half-trip on the 'A' train of Emergency Feedwater Initiation and Control (EFIC) at time of system actuation, but was successfully actuated manually immediately upon discovery. Train 'B' EFIC actuated in Automatic as designed. The half-trip of the 'A' train of EFIC is currently believed to be associated with EFIC Channel 'C'; however, investigation is underway to verify this. Currently, ANO-1 has been stabilized and is being maintained in Mode 3 with Auxiliary Feedwater in service. Heat removal is via Turbine Bypass valves to the Condenser. No radiological releases have occurred due to this event. There was no effect on Arkansas Nuclear One, Unit 2. The licensee notified the NRC Resident Inspector and the State of Arkansas. |
| ENS 51340 | 24 August 2015 11:36:00 | This notification is being made in accordance with 10 CFR 50 72(b)(3)(xiii) as an event that will result in a major loss of emergency assessment capability, offsite response capability, or offsite communications capability (e.g. a significant portion of control room indication, Emergency Notification System or offsite notification system.) The emergency preparedness plan requires seismic monitoring instruments to diagnose an earthquake for emergency actions levels (EAL) HU6 (Natural or destructive phenomena affecting protected area) and HA6 (Natural or destructive phenomena affecting vital areas). At 1020 CDT on August 24, 2015 the Semi-Annual Seismic System Functional Test commenced. While this test is in progress, seismic alarm capability is not available for EAL declaration purposes. ANO procedures provide compensatory measures of using offsite sources to obtain seismic data. It should be noted that seismic data will still remain capable of being recorded, only alarm capability is lost. The licensee notified the NRC Resident Inspector. |