VIDEO: Entergy updates cause of nuclear power plant transformer fire

An Entergy (NYSE: ETR) investigation concludes that an insulation failure led to the transformer fire at the Indian Point nuclear power plant Unit 3 in New York.

The failure caused a high-voltage winding coil in the main transformer to short circuit and catch fire May 9. Entergy says Indian Point’s transformers are inspected regularly, and there were no immediate signs of any issues prior to that day. Entergy is reviewing initial findings to identify potential corrective actions.

Entergy says that automatic sprinkler systems put out more water than what could be held in a moat containment system and, combined with water and foam used to put out the fire and leaking transformer fluid, exceeded a containment system’s capability. Some of that flowed into a storm drain that led to the plant’s discharge canal and ultimately the Hudson River. The U.S. Coast Guard, using data from the National Oceanographic and Atmospheric Administration (NOAA), estimated about 3,000 gallons of dielectric fluid leaked into the river. About 8,300 gallons of fluid was recovered from the moat beneath the transformer, inside the transformer, drains and areas around the transformer yard, or were combusted.

Contractors placed sorbent and protective booms in and outside of the discharge canal and removed fluid that had spilled in the transformer yard, storm drains and adjacent areas. Contractors also inspected approximately 25 locations of shoreline sheens reported to state authorities. Of those, 19 did not require remediation.

Since the incident, workers have replaced the transformer and returned the unit to service.

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