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On October 13, 2005, during a scheduled refueling outage, with fuel offload in progress, super particulate iodine noble gas (SPING) effluent monitor, SPING-1, was removed from service for required surveillance testing. Operations personnel failed to recognize that Technical Specifications (TS) require SPING-1 to be operable when the reactor building purge isolation valves are open and fuel movement is in progress in the reactor building. Sampling was performed and SPING-1 was returned to service. On October 14, 2005, prior to removing SPING-1 from service again for sampling, operations personnel recognized that this configuration was not allowed with fuel movement in progress in the reactor building and realized that the removal of SPING-1 from service the previous day resulted in operation prohibited by TS. This event can be attributed to inadequate guidance regarding the TS requirement to maintain SPING-1 operability during fuel movement in the reactor building.

Procedures will be revised to ensure SPING-1 is not removed from service during fuel handling operations in the reactor building unless TS requirements are satisfied.

Di 20.2201(b) 0 ❑ 20.2203(a)(3)(i) p 20.2201(d) 0 20.2203(a)(3)(ii) D 20.2203(a)(1) 0 20.2203(a)(4)

• 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A) L 20.2203(a)(2)(ii) 0 50.36(c)(1)(ii)(A)

• 20.2203(a)(2)(iii) 0 ❑ 50.36(c)(2) E 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii) ( 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A)

• 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B)

• 50.73(a)(2)(i)(C) 111 50.73(a)(2)(ii)(A)

• 50.73(a)(2)(ii)(B) 111 50.73(a)(2)(iii) U 50.73(a)(2)(iv)(A)

• 50.73(a)(2)(v)(A) 111 50.73(a)(2)(v)(B) U 50.73(a)(2)(v)(C) 111 50.73(a)(2)(v)(D) 11. L1CF CINITACT Pen TH78 LER

• 20.2203(a)(2)(vi) 0

• 50.73(a)(2)(i)(B) 0

• 50.73(a)(2)(v)(D)

On March 27, 2010, with Arkansas Nuclear One - Unit 1 (ANO-1) in Mode 6 for a refueling shutdown, visual examinations discovered indications of through wall leakage on an ANO-1 Reactor Coolant System (RCS) pressurizer level instrument tap nozzle.

Leakage was indicated by a small amount of dry boron on the lower portion of the nozzle bore with rust stains on the Alloy 600 nozzle and in the vicinity surrounding the nozzle outlet. Subsequent inspections and evaluation revealed minor corrosion of the nozzle bore and concluded that the failure mechanism for the degradation was Primary Water Stress Corrosion Cracking (PWSCC) of Alloy 600 material. A planned mitigation repair method for the affected nozzle was implemented to resolve this condition. Also, in accordance with Arkansas Nuclear One's Inservice Inspection program, the remaining 8 pressurizer nozzles were visually inspected and exhibited no indications of leakage or degradation. During the refueling outage, all 9 pressurizer instrument nozzles were replaced with materials that are resistant to PWSCC. The pressurizer nozzles with dissimilar metal butt welds (surge, spray, and safety valve nozzles) had previously been mitigated by a full structural weld overlay.

• 20.2203(a)(2)(vi) 0

• 50.73(a)(2)(i)(B) 0

• 50.73(a)(2)(v)(D)

On March 31, 2013, at approximately 0750 CDT, during lifting and removal of the Arkansas Nuclear One Unit 1 (ANO-1) original Main Generator Stator (Stator), the temporary lift assembly collapsed due to failure of one of the structural columns, resulting in the Stator falling onto the turbine deck (386' elevation) and rolling down into the ANO-1 train bay (354' elevation) adjacent to Arkansas Nuclear One Unit 2 (ANO-2).

The event resulted in one fatality, multiple injuries, structural damage to the ANO-1 and ANO-2 turbine buildings, and damage to non-vital systems and electrical equipment. At the time of the event, ANO-1 was in MODE 6 and ANO-2 was in MODE 1 at approximately 100 percent power. The event resulted in a loss of offsite power for ANO-1, with both Emergency Diesel Generators (EDGs) starting to supply safety loads.

ANO-1 decay heat removal was lost for approximately four minutes. ANO-2 automatically tripped off-line after the vibration from the dropped Stator resulted in the actuation of relays in the ANO-2 switchgear located adjacent to the train bay, subsequently tripping a reactor coolant pump motor breaker. After the reactor trip, emergency feedwater was manually initiated by ANO-2 Control Room Operators. As debris fell into the train bay, an 8-inch firewater pipe was ruptured and the Alternate AC Diesel Generator electrical tie to ANO-1 was severed. At 0923 CDT that same day, water intrusion from the ruptured firewater piping into a 4160 volt breaker resulted in an ANO-2 Startup Transformer lockout, de-energizing a safety bus. An EDG automatically started as designed and supplied the affected safety bus. An ANO-2 Notification of Unusual Event was declared at 1033 CDT due to fire or explosion from an electrical fault in the 4160 volt switchgear with indications of bus damage. After damage assessment and repairs, ANO-2 returned to power operation on April 28, 2013. ANO-1 returned to power operation on August 7, 2013.