BUCHANAN, N.Y. -- A failure of insulation caused a main transformer at the Indian Point nuclear power plant’s Unit 3 to short circuit and catch fire on May 9 in Buchanan, Entergy announced Tuesday.
The company also said its internal investigation confirmed that water and foam used to extinguish the fire, together with fluid from the transformer on the plant’s non-nuclear side, exceeded a containment system’s capacity, Entergy said.
Since the fire and the plant’s safe shutdown, the transformer has been replaced, Unit 3 has returned to service, and no remediation was warranted at most locations of reported sheens from fluids that reached the Hudson River.
“We have been working closely with independent engineers, and with federal and state agencies, to address issues surrounding the May 9 transformer failure, and corrective actions are well under way,” said Bill Mohl, president of Entergy Wholesale Commodities, the Entergy business unit that owns Indian Point. “These actions reinforce our commitment to environmental responsibility and transparency, as well as the continued safe, secure and reliable operation of Indian Point.”
Entergy’s engineers and an independent engineering firm traced the transformer problem to the failure of internal insulation that caused a short circuit in a high-voltage winding coil, Entergy said.
Indian Point’s transformers are tested routinely for signs of degradation but no immediate problems were identified prior to May 9 in the unit that failed, according to Entergy.
Entergy’s investigation into the release of the transformer’s dielectric fluid -- a clear mineral oil that acts as an electrical insulator and coolant -- to the ground and ultimately the Hudson River confirmed that automatic sprinkler systems dispensed more water than the capacity of the moat containment system. Some of this fluid mixed with firefighting water and foam, and then flowed from the moat into a storm drain leading to the plant’s discharge canal and ultimately the Hudson River.
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