The U.S. Nuclear Regulatory Commission (NRC) has announced that a team of its inspectors will seek to better understand the presence of water in an electrical supply room at Entergy’s (NYSE: ETR) Indian Point 3 nuclear power plant following a main transformer failure earlier this month.
Indian Point 3 safely and automatically shut down following the failure of one of two main electrical transformers around 6:00 p.m. on Saturday, May 9. Plant operators declared an “Unusual Event” - the lowest of four levels of emergency classification used by the NRC - at 6:01 p.m. because of a fire that erupted following the transformer failure. Automatic sprinkler systems, along with trained onsite personnel were able to extinguish the fire, and operators terminated the alert at 9:03 p.m.
Entergy reported no injuries and no release of radiation due to the event.
Starting Tuesday, May 19, a three-member NRC Special Inspection Team will report to the Indian Point facility to review the issue. The room in question contains electrical equipment that provides power to plant safety systems.
“None of the electrical equipment became wet or experienced any damage or failures as a result of the water,” said NRC Region I Administrator Dan Dorman. “Nevertheless, the NRC inspectors will be tasked with gathering information on how the water accumulated in the room and the potential for impacts had there been a significantly larger volume of water.”
NRC said inspectors will be reviewing whether the fire suppression system for the transformer or efforts by the plant’s on-site fire brigade and off-site firefighters, among other things, may account for the water observed in the electrical equipment room.
A report summarizing the findings of the Special Inspection Team will be issued within 45 days after the conclusion of the inspection.
Separately, an oil leak into the Hudson River has also been associated with the event, but was not listed among the areas of focus in the NRC’s Special Inspection announcement. Entergy said Friday preliminary assessments of the system designed to catch the transformer's dielectric fluid following a failure, along with areas around the transformer, indicated approximately 8,300 gallons of dielectric fluid have been recovered or were combusted during the fire. Currently, 16,000 gallons of fluid remains unaccounted for.
“Visual observations in the discharge canal and the Hudson River have not indicated significant quantities of transformer oil, and further investigation and aggressive recovery efforts at the site will continue,” said Entergy in a statement on its site. “These efforts likely are anticipated to take several months, and will be coordinated with the New York State Department of Environmental Conservation (NYSDEC).”
Dielectric fluid is a clear, light mineral oil that acts as an electrical insulator and coolant inside transformers when they are operational.
Indian Point 3 remains offline while work to replace the transformer continues. Unit 2 continues to operate at full power.