An investigation by Entergy Corp. and an independent engineering firm has determined that insulation in a transformer failed at Indian Point Energy Center on May 9, which resulted in a series of events that ultimately led to about 3,000 gallons of oil reaching the Hudson River.
A preliminary investigation conducted by Indian Point”™s owner, Entergy, found “a failure of insulation” ”“ a paper insulation wrapped around copper windings ”“ caused a short circuit that resulted in the combustion of dielectric fluid inside the transformer. The findings were released Tuesday afternoon.
The Unit 3 nuclear reactor automatically shut down as the transformer caught fire twice. Overhead sprinklers were activated and the leaking oil, in addition to the water and foam used to extinguish the fires, overflowed the moat system. The moat is designed to catch fluids from the transformer, which holds 24,300 gallons of dielectric fluid.
The U.S. Coast Guard and National Oceanic and Atmospheric Administration estimated that 3,000 gallons of the transformer fluid leaked into the river. Entergy officials and contractors estimated 8,300 gallons of fluid was recovered from the moat and the immediate areas or combusted. Environmental engineers are continuing to search for the remaining 13,000 gallons, presumed to be on-site, according to Jerry Nappi, an Entergy spokesman.
The Coast Guard and the state Department of Environmental Conservation looked into 25 areas on the river”™s shoreline where oil sheens were spotted and reported. Six of those sites ”“ as far as 2 to 3 miles from the plant ”“ required remediation, a process that included using absorbent mats or similar materials to collect the oil. Oil booms have also been placed in the river to absorb the transformer fluid.
The transformer has been replaced, and Unit 3 was brought back online May 25 after being shut down for 16 days. The cause of the insulation failure is not yet known, but the combusted transformer will be shipped, Nappi said, to an engineering expert who will analyze the device.
“The issue of transformer failures is not unique to nuclear power plants because similar transformers are in use at natural gas, coal, wind generating, wind-powered plants,” Nappi said. “So it”™s an industrywide issue, that”™s being tackled at a higher level.”
Indian Point has had transformer failures in the past, most recently in 2010 and 2007, but they were problems outside the main body of the transformer.
