The Nuclear Regulatory Commission (NRC) has issued Entergy (NYSE:ETR) two ‘yellow’ findings, of substantial safety significance, following its investigation of a fatal heavy equipment accident last year at the dual-unit Arkansas Nuclear One station in Russellville, Ark.
The NRC evaluates regulatory performance at commercial nuclear plants with a color-coded process that classifies inspection findings as green, white, yellow or red in order of increasing safety significance.
NRC had initially issued a more serious ‘red’ finding as well, but after a May 1 meeting with Entergy officials decided that ‘yellow’ was an appropriate reflection of the risk significance at Arkansas Nuclear One station’s Unit 1 and 2.
There is no fine associated with the yellow finding, an NRC spokesperson said June 26. The NRC will determine the appropriate level of agency oversight and notify Entergy officials of the decision in a separate letter.
“Entergy is dedicated to the safe operation of Arkansas Nuclear One, and we take the NRC’s findings very seriously,” the company said in a statement. “We are committed to learning from this tragic incident, sharing our knowledge with the industry, and ensuring that it never happens again,” Entergy added.
Workers were moving a 525-ton component out of the plant’s turbine building during a maintenance activity when a temporary lifting assembly collapsed on March 31, 2013, causing the component to fall, damaging plant equipment, killing one person and injuring eight others.
The worker killed was employed by a contractor. The Arkansas Nuclear One Unit 1 facility did not return to service until August 2013. More than a year ago, Entergy said the accident could cost anywhere from $130m to $215m.
Unit 1 was in a refueling outage at the time. Entergy officials declared a Notice of Unusual Event, the lowest of four emergency classifications used by the NRC, because the incident caused a small explosion inside electrical cabinets.
The damaged equipment caused a loss of off-site power. Emergency diesel generators were relied upon for six days to supply power to cooling systems.
Unit 2, which was operating at full power, automatically shut down when a reactor coolant pump tripped due to vibrations caused by the heavy component hitting the turbine building floor when it fell. Unit 2 never completely lost off-site power, and means existed to provide emergency power using the diesel generators.
The NRC conducted an Augmented Team Inspection, prepared a detailed chronology of the event, evaluated the adequacy of licensee actions in response to the incident, and assessed the factors which may have contributed to the incident.
Worker safety issues are the responsibility of the Occupational Safety and Health Administration (OSHA), which conducted an independent inspection of the incident. The NRC determined that the lifting assembly collapse resulted from the licensee’s failure to adequately review the assembly design and ensure an appropriate load test in accordance with its procedures or approved standards.
The NRC team’s report was the subject of a May 9 meeting in Russellville.
“The augmented inspection team concluded that after the event occurred, the plant safety systems responded as designed, all assumptions in the accident analysis appropriately bounded the event, and no unanalyzed condition existed. The augmented inspection team identified ten unresolved items requiring follow-up inspection to determine the existence and significance of any associated performance deficiencies,” according to the 46-page NRC report.
ANO is a nuclear station that includes two pressurized water reactors (PWRs) in Russellville, Ark. Together Units 1 and 2 can generate more than 1,800 MW.