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EN Revision Imported Date : 10/6/2020 CONTROL ROOM BOUNDARY DOOR FAILURE On June 5, 2020, at 0320 (EDT) a loss of control room envelope (CRE) was declared inoperable due to failure of door 204-36-007. The door was repaired at 0322 (EDT), restoring the CRE to operable. The NRC Resident Inspector, state, and local authorities were notified.

• * * RETRACTION ON 07/09/2020 AT 1443 EDT FROM GERALD A. BAKER TO OSSY FONT * * *

The purpose of this call is to retract a report made on June 5, 2020, NRC Event Number EN54738. NRC Event Report number EN54738 describes a condition at Millstone Power Station Unit 2 (MPS2) in which a control room envelope boundary door was discovered to not be able to fully close due to the latching mechanism being stuck in the extended position. The condition was reported to the NRC pursuant to 10 CFR 50.72(b)(3)(v)(D) via an 8 hour prompt report as an event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. Upon further review, MPS2 determined that there was no loss of safety function. An engineering evaluation determined that even with the control room boundary door unable to be fully closed due to the latching mechanism being stuck in, the extended position, control room air in-leakage would not have been sufficient to prevent the control room emergency ventilation system from performing its safety function. Therefore, this condition is not reportable and NRC Event Number EN54738 is being retracted. The basis for this conclusion has been provided to the NRC Resident Inspector. Notified R1DO (Dimitriadis).

• * * UPDATE FROM MICHAEL GAGNON TO BRIAN P. SMITH AT 1444 EDT ON 10/01/2020 * * *

The purpose of this call is to provide an update to the retraction for a report made on June 5, 2020, NRC Event Number EN54738. The retraction being updated was made on 7/9/2020 at 1443 hours. NRC Event Report number EN54738 describes a condition at Millstone Power Station Unit 2 (MPS2) in which a control room envelope boundary door was discovered to not be able to fully close due to the latching mechanism being stuck in the extended position. The condition was reported to the NRC pursuant to 10 CFR 50.72(b)(3)(v)(D) via an 8 hour prompt report as an event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident (the Control Room Envelope). A subsequent engineering evaluation of the conditions that existed at the time, determined that the inability of the control room boundary door to fully close due to the latching mechanism being stuck in the extended position did not have an adverse impact upon the ability of the CRE to perform its safety function. The CRE remained operable throughout this event, and the ventilation system would have performed its safety function. Therefore, this condition is not reportable and NRC Event Number EN54738 is being retracted. The basis for this conclusion has been provided to the NRC Resident Inspector. Notified R1DO (Lally).