At 1420 [EST] on November 24, 2018, operators discovered that a door was blocked open creating a breach of the auxiliary building
secondary containment enclosure (
ABSCE) boundary that exceeded the allowed
ABSCE breach margin [of three minutes]. As a result, Unit 1 entered Technical Specification Limiting Condition of Operation (LCO) 3.7.12 Condition B for two trains of
Auxiliary Building Gas Treatment System (
ABGTS) inoperable due to an inoperable
ABSCE boundary in MODE 1, 2, 3, or 4, and both Units entered Condition E for one required
ABGTS train inoperable with fuel stored in the spent fuel pool.
In MODES 1, 2, 3, and 4, the analysis of the loss of coolant accident (LOCA) assumes that radioactive materials leaked from the Emergency Core Cooling System are filtered and absorbed by the ABGTS. For the fuel handling accident, the analysis assumes that the ABSCE boundary is capable of being established to ensure releases from the auxiliary and containment buildings are consistent with the dose consequence analysis.
The event is reportable in accordance with 10 CFR 50.72(b)(3)(v) as an event or condition that could have prevented fulfillment of the safety function of structures or systems that are needed to: (C) control the release of radioactive material and (D) mitigate the consequences of an accident.
No actual LOCA or fuel handling accident occurred while both trains of ABGTS were inoperable. The condition had no impact on the health and safety of the public.
The NRC Resident Inspector has been notified.
This situation occurred because of maintenance activities. A breeching permit had been initiated however, the required personnel to ensure the door could be closed within the required three minutes were not assigned. The door was closed approximately 15 minutes after the situation was noticed.
