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This report is submitted pursuant to the 30 day Special Report requirement of 10 CFR 50.46(a)(3)(ii). The guidance provided in NURGEG 1022, Revision 3, allows the reporting under 10 CFR 50.73 and 10 CFR 50.46 to be combined.

On November 25, 2014, AREVA NP Inc. notified Entergy Operations, Inc. of a deficiency in the Arkansas Nuclear One, Unit 1 (ANO-1) Emergency Core Cooling System evaluation model. When the deficiency is accounted for, the Large Break Loss-of-Coolant Accident Peak Clad Temperature was estimated to exceed 2200°F and the absolute value of the deficiency is greater than the requirement of 10 CFR 50.46(a)(3)(ii).

Exceeding 2200°F resulted in ANO-1 making an 8-hour NRC notification on November 25, 2014. See Event Notification EN 50641. The purpose of this report is to provide the information required by 10 CFR 50.46(a)(3)(ii).

On March 19, 2016, two block-out penetrations separating the Arkansas Nuclear One, Unit 1 (ANO-1) Turbine Building from the Auxiliary Building were determined to be non-functional. The penetrations are located in the floor of Turbine Building elevation 354 ft. Below the penetrations is the Auxiliary Building, housing safety related equipment.

On March 17, 2016, it was identified that two penetration seals did not match approved fire penetration or approved flood seal details. Further investigation, completed on March 19, 2016, revealed that the two block-out penetrations were not grouted and represented a previously unknown vulnerability in a credited external flood barrier.

The apparent cause of this event was less than adequate project management control for the size and scope of the External Flood Mitigation Project associated with post Fukushima Dai-ichi resolutions and requirements set forth by the NRC.

Mitigating strategies and extent of condition reviews have been implemented for the identified conditions. Permanent repair of the deficient flood barriers is complete minus cure time. Actions to correct programmatic aspects of this condition are in progress.

On August 24, September 11, and September 15, 2016, during performance of an extent of condition evaluation related to the protection of Technical Specification (TS) equipment from external flood hazards, Arkansas Nuclear One, Unit 1 (ANO-1), identified non-conforming plant design conditions such that specific ANO-1 TS equipment was considered to not be adequately protected from tornado missiles. These are legacy design issues.

On August 24, 2016, at 0945, September 11, 2016, at 1504, and September 15, 2016, at 0958, Operations declared the affected components inoperable, implemented Enforcement Guidance Memorandum (EGM) 15-002, "Enforcement Discretion for Tornado-Generated Missile Protection Noncompliance", along with necessary compensatory measures, and subsequently declared the affected equipment operable but non-conforming.

The cause of this issue was unclear and changing regulatory requirements during original plant licensing that led to an inadequate understanding of the regulatory guidance with respect to tornado missile protection design requirements.

Interim corrective actions include implementation of compensatory strategies. Plant modifications and license basis changes are being evaluated to resolve outstanding issues.

On April 26, 2017, Arkansas Nuclear One, Unit 1 (ANO-1), was operating normally at 100% rated thermal power.

The 500kV transmission line to the substation at Pleasant Hill, Arkansas was out of service for planned maintenance.

The area around the plant was experiencing severe weather from thunderstorms and tornado warnings had been issued from the National Weather Service for the four county area.

At approximately 1002 CST switchyard breakers for 500kV lines opened on fault current. High winds had damaged the transmission towers approximately 16 miles away from ANO and caused phase to ground faults. This resulted in a loss of all offsite power lines to the 500kV bus. The autotransformer also locked out as designed when the 500kV transmission lines faulted.

The Reactor Operator initiated a manual reactor trip about 8 seconds after the 500kV lines tripped and prior to the reactor protection system initiating an automatic trip. During this time both emergency diesel generators (EDGs) (EK) started as expected. EDG #2 re-energized one Engineered Safeguards bus. EDG #1 ran unloaded until shutdown.

The plant was stabilized in Mode 3 with Emergency Feedwater (EFW) pumps supplying the steam generators, maintaining the water level at the natural circulation setpoint.