Control Room Emergency Ventilation Ac System Inoperable
On October 9, 2018 at 2002 CDT the Control Room Emergency Ventilation Air Condition (CREV AC) system was in the process of being returned to service following maintenance. During the return to service, the end bell on the CREV AC Condenser developed a significant leak requiring isolation. No work was performed on the CREV AC Condenser during the work window.
The CREV AC system maintains a habitable control room environment and ensures the operability of components in the control room emergency zone during accident conditions.
This notification is being made in accordance with 10CFR50.72(b)(3)(v)(D), "Event or Condition That Could Have Prevented Fulfillment of a Safety Function " because the CREV system is a single train system required to mitigate the consequences of an accident.
Control Room Emergency Ventilation System Inoperable
At 0113 EDT on September 11, 2018, it was discovered both trains of CREVS (control room emergency ventilation system) were simultaneously inoperable; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v).
There was no impact on the health and safety of the public or plant personnel.
The NRC Resident Inspector has been notified.
The door to the main control room habitability zone from the turbine building was left open and unattended for about a minute, breaking the pressure boundary in the room, resulting in an alarm. The door was closed, clearing the alarm and the CREVS was considered operable.
Nine Mile Point Nuclear Station, Unit 1 - Report of Full Compliance with Phase 1 and Phase 2 of June 6, 2013 Commission Order Modifying Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe ...
Invalid Actuation of a General Containment Isolation Signal Affecting More than One System
This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid actuation of a general containment isolation signal affecting more than one system.
On August 16, 2018, at approximately 1736 CDT, Browns Ferry Nuclear Plant (BFN), Unit 2 experienced an unexpected loss of the 2B Reactor Protection System (RPS). This resulted in Primary Containment Isolation System (PCIS) groups 2, 3, 6, and 8 isolations, and initiation of Standby Gas Treatment Trains A, B, and C and Control Room Emergency Ventilation System Train A. All affected safety systems responded as expected with the exception of the Unit 1 Refuel Zone Supply Fan Outboard Isolation Damper, 1-FCO-64-5, that failed to indicate closed position.
Plant conditions which initiate PCIS Group 2 actuations are Reactor Vessel Low Water Level (Level 3) or High Drywell Pressure. The PCIS Group 3 actuations are initiated by Reactor Vessel Low Water Level (Level 3) or Reactor Water Cleanup Area High Temperature. The PCIS Group 6 actuations are initiated by Reactor Vessel Low Water Level (Level 3), High Drywell Pressure, or Reactor Building Ventilation Exhaust High Radiation (Reactor Zone or Refuel Zone). The PCIS Group 8 actuations are initiated by Low Reactor Vessel Water Level (Level 3) or High Drywell Pressure. At the time of the event, these conditions did not exist; therefore, the actuation of the PCIS was invalid.
The cause of the RPS MG (Motor Generator) Set trip was a failed (shorted) operating coil associated with the 480 VAC motor starter inside the control box.
There were no safety consequences or impact to the health and safety of the public as a result of this event.
This event was entered into the Corrective Action Program as Condition Reports 1440047 and 1440050.
The NRC Resident Inspector has been notified of this event."