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On August 18, 2014, with the Davis-Besse Nuclear Power Station operating in Mode 1 approximately 100 percent full power, a door to a mechanical penetration room could not be secured following normal usage.

This door is required to be latched closed to maintain the shield building negative pressure boundary except when open under administrative control. With the door unable to be latched closed, the Station Emergency Ventilation System could not perform its required safety function of maintaining a negative pressure in the affected area. The door was restored to the latched status in ten minutes. A similar failure to latch on August 20, 2014, was also experienced, and the door was re-latched in four minutes.

The cause of this event was a design flaw that could cause the latch fingers to stick, preventing the door from latching; and an infantile failure of the door closer. A vendor modified version of the latch was installed along with a new door closer to correct the problem.

This event is being reported pursuant to 10 CFR 50.73(a)(2)(v)(C) and (D) as an event that could have prevented fulfillment of the safety function of the Station Emergency Ventilation System.