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| Entered date | Event description | |
|---|---|---|
| ENS 49807 | 7 February 2014 16:31:00 | 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 telephone notification is being made pursuant to the reporting requirements of 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of the Palo Verde Nuclear Generating Station Unit 2 'A' train Main Steam and Feedwater Isolation System (MSFIS) logic. On December 11, 2013, at approximately 2011, Mountain Standard Time, Unit 2 was shut down in Mode 4 with Reactor Coolant System (RCS) temperature at approximately 425 degrees Fahrenheit and 1900 pounds per square inch absolute. While starting up the plant following completion of repairs to the 1A reactor coolant pump, an invalid actuation of the 'A' train MSFIS fast close logic occurred due to a random electrical failure in the 'A' train MSFIS logic cabinet. This resulted in the closure of all four Main Steam Isolation Valves and the two 'A' train Economizer Feed Water Isolation Valves. No other engineered safety feature actuations occurred and none were required. The invalid actuation was initiated by a ground fault in a 30-volt direct current power supply in the 'A' train MSFIS Logic cabinet. Repairs were completed on December 12, 2013. This was a complete actuation of 'A' train MSFIS equipment and all the affected equipment responded as designed. RCS temperature and pressure were maintained stable using atmospheric dump valves. Feed water to the steam generators was being provided by Auxiliary Feed Water and was not affected by the event. The NRC Resident Inspector has been notified. |
| ENS 54832 | 12 August 2020 11:24:00 | On August 11, 2020, at approximately 1432 MST, a licensed operator's test results were confirmed positive for use of a controlled substance following a random Fitness For Duty screening test. The individual's unescorted access has been terminated in accordance with station procedures. The NRC Resident Inspector has been notified. |
| ENS 55521 | 14 October 2021 14:30:00 | On October 13, 2021, at 1420 MST, a Non-Licensed Supervisor's test results were confirmed positive for use of a controlled substance following a random Fitness For Duty test which resulted in determination that the individual violated the station's FFD Policy. The Non-Licensed Supervisor's unescorted access has been terminated in accordance with station procedures. The NRC Senior Resident Inspector has been notified. |