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A worker failed to physically challenge the latch on the inboard reactor enclosure airlock door when traversing from the refuel floor into the reactor enclosure. The next worker to use the airlock opened the outboard door causing the inboard door to open due to differential pressure across the door. The outboard door was closed in less than 10 seconds. This event resulted in a brief inoperability of reactor enclosure secondary containment integrity.

The event was caused by a degraded airlock door self-closing feature on the inboard airlock door. A contributing cause was a worker failure to verify that the inboard airlock door was latched fully closed. The worker failed to properly use the self-check fundamental. The airlock doors were immediately closed to restore reactor enclosure secondary containment integrity and the degraded door self-closing feature was repaired. The worker was coached regarding use of the self-check fundamental. The lessons learned were communicated to the site.

Workers simultaneously opened both doors of a reactor enclosure personnel airlock when transporting material through the airlock. One worker opened the outboard airlock door before the inboard airlock door was properly closed and latched. Both doors were closed in less than 10 seconds. This event resulted in a brief inoperability of reactor enclosure secondary containment integrity. The event was caused by the workers' failure to verify the inboard airlock door was latched fully closed prior to opening the outboard airlock door.

The workers failed to properly use the self-check fundamental. The airlock doors were closed to restore reactor enclosure secondary containment integrity. The workers were coached regarding use of the self-check fundamental. The lessons learned were communicated to the site.

Two workers simultaneously opened both doors of a reactor enclosure personnel airlock when entering the airlock. One worker opened the inboard airlock door and the other worker opened the outboard airlock door. Both doors were closed in less than 10 seconds. This event resulted in a brief inoperability of reactor enclosure secondary containment integrity.

This event was not prevented by the design of the reactor enclosure airlocks. The affected airlock doors were closed to restore reactor enclosure secondary containment integrity.

Both airlock doors were opened simultaneously when moving equipment through a reactor enclosure airlock causing an unplanned inoperability of reactor enclosure secondary containment integrity.

This event was caused by a non-functional airlock door open indicating light not providing the correct door status. The non- functional door open indicating light magnetic switch has been replaced. A review was conducted and no other non-functional door open indicating lights were identified.

A periodic routine test of the airlock door open indicating lights will be implemented to identify non-functional door open indicating lights.

The Unit 2 Division 2 redundant reactivity control system was determined to be inoperable due to instrument signal drift on a reactor pressure vessel pressure channel. T An investigation determined that the channel was inoperable for a time longer than permitted by the Technical Specifications. T The apparent cause of the unplanned inoperability of the affected channel was a premature failure of the reactor pressure analog trip module (ATM) card.

The ATM card failure was most likely due to a failure of the U1- amplifier sub-component on the card. T The degraded card was replaced, calibrated and tested successfully. T The Daily Surveillance Log/OPCONS 1,2,3 RRCS channel check has been revised to ensure unacceptable RRCS channel signal drift will be identified and evaluated as required.

An automatic actuation of the Unit 2 reactor protection system occurred due to an actuation of the turbine control valve fast closure logic. The actuation occurred during restoration from Maintenance on a main turbine control valve. The "Al" channel of turbine control valve fast closure logic was placed in the trip condition during the maintenance. The "Eil" channel tripped when the electrohydraulic control relayed emergency trip supply oil supply was restored to the control valve. The root cause of the event was a void in the electrohydraulic control relayed emergency trip supply oil supply line that resulted in a perturbation of the oil supply pressure at the adjacent control valve. A procedure will be developed and implemented to provide specific restoration steps for turbine control, stop, and combined intermediate valves.

NRC FORM 368 (10-2010) LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION

Over a period of approximately one month, the OB Main Control Room (MCR) Heating, Ventilating and Air Conditioning (HVAC) system experienced four failures. Troubleshooting was completed for each of the failures and for three of the failures the cause was determined to be an intermittent dropout or chattering of the Loss of Offsite Power (LOOP) start relay for two fans (0B-V116 MCR Supply and OB-V121 MCR Return Fans). The fourth failure was due to a contactor in the Motor Control Center (MCC) for the OB-V116 MCR Supply Fan. On 11/29/16 the second failure occurred on the LOOP start relay for the OB-V116 MCR Supply fan. The investigation identified a manufacturing defect of the Agastat/Tyco ETR Relays in the lot of relays used for the recent preventative maintenance (PM) relay replacements. The relays were determined to be unreliable since the initial PM replacement on 10/19/16 until 12/5/16, when the quality issue was identified and relays from a different lot were installed. The B train of MCR HVAC was determined to be inoperable due to the relay issue for a period of 47 days, which is greater than the allowable Limiting Condition for Operation (LCO) action window of 7 days (per TS 3.7.2.a.1) for an inoperable Control Room Emergency Fresh Air System (CREFAS) train.

Therefore, this was a condition prohibited by Technical Specifications (TS).