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At 0905 EDT, it was discovered both trains of Auxiliary Building Gas Treatment System (ABGTS) were simultaneously INOPERABLE due to the auxiliary building secondary containment enclosure (ABSCE) being 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. ABSCE and ABGTS were returned to operable.

• * * RETRACTION ON 10/14/2021 AT 0756 EDT FROM TRACY SUDOKO TO THOMAS HERRITY * * *

This is a retraction of the 8-hour Immediate notification (EN55421) made to the NRC by Sequoyah Nuclear Plant on August 20, 2021. Sequoyah is retracting this event notification based on the following: Regulatory Guidance in NUREG-1022, Revision 3, 'Event Reporting Guidelines 10 CFR 50.72 and 50.73', Sections 2.8 'Retraction and Cancellation of Event Reporting', and 4.2.3 'ENS Notification Retraction'. On August 20, 2021 personnel found door A-118 open. This door is part of the ABSCE. During the initial investigation, it was found that other personnel had the door open using Precaution A of 0-TI-SXX-000-016.0 which allows material access through ABSCE doors if the door is closed within three minutes. It was found that A-118 door had been open for greater than three minutes. With this door open the ABSCE was beyond its capability for ABGTS fan to maintain the required pressure during an Aux. Building Isolation. Thus, the site declared the ABSCE and both Trains of ABGTS inoperable per LCO 3.7.12 Conditions A, B and E. With the ABSCE being a single train system, this caused a condition that "could have prevented the fulfillment of the safety function" which requires an Immediate Notification to the NRC within eight hours under 10 CFR 50.72 (b)(3)(v)(C) and 10 CFR 50.72 (b)(3)(v)(D). This Immediate Notification was reported on August 20, 2021 at 1600 EDT. It was later determined that at 'Time of Discovery', although Door A-118 was open, it was not obstructed, the door was open by normal means, was capable of being closed and was now attended. The time requirement per 0-TI-SXX-000-016.0 for closure of an open ABSCE door is within three minutes of notification. Although the individual found holding the door was unaware of the requirement of 0-TI-SXX-000-016.0 to close the door, communications were established and the Main Control Room (MCR), upon discovery of the 'Open Door', could have directed closure starting at the Time of Discovery if required. Since the MCR was aware the door was open, had communications established with personnel at the door, the door was capable of closure and not restricted, the three minute closure requirement of 0-TI-SXX-000-016.0 was met. Subsequently, the door was closed within approximately two minutes of notification to close. The closure of the door with these procedural measures met confirmed the integrity of the ABSCE and therefore Operability of ABGTS. Based on the above critical thinking, entry into LCO 3.7.12 Condition A, B, and E was retracted on August 22, 2021 at 2044 EDT. With the LCO conditions retracted and the above determination that at the Time of Discovery safety function was maintained, the Immediate Notification per 10 CFR 50.72 (b)(3)(v)(C) and 10 CFR 50.72 (b)(3)(v)(D) was not required. The issue of Past Operability remains for instances in time that the door did not have appropriate compensatory measures in place. Any further notification required for this event will be submitted as a Licensee Event Report. Notified R2DO (Miller)