Bad Insulation Caused NY Nuke Fire, Spill

Tuesday, July 7, 2015 @ 03:07 PM gHale

An insulation failure in a transformer caused the fire at a New York nuclear plant May 9 resulting in a spill of 3,000 gallons of oil into the Hudson River.

Entergy, the operator of Indian Point Energy Center, said the failed insulation — made of special paper — caused a short circuit in a high-voltage coil. The company regularly inspects its paper insulation for signs of degradation, but investigators found no problems before the fire near the Unit 3 generator.

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No radiation released during the fire in Buchanan, NY, and the generator automatically shut down as designed. The reactor resumed service May 25. Entergy said it will continue its analysis of the paper insulation.

“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,” he said.

The transformer contained 24,300 gallons of dielectric fluid, a clear mineral oil that serves as a cooling agent and insulation. Workers recovered about 8,300 gallons of oil from the moat beneath the transformer, inside the transformer, drains and areas around the transformer yard, or ended up burned in the fire.

Contractors are investigating the transformer yard and other areas on site to see whether they can recover more transformer oil and prevent any potential migration. Six shoreline locations required environmental cleaning, which they completed June 5.

In another investigation related to the fire, Entergy staffers looked at why water from fire sprinklers accumulated in a building that contains electrical equipment powering some of the plant’s safety systems. The company concluded some sprinkler valves malfunctioned and didn’t automatically close as designed.

None of the electrical systems ended up damaged by the water. As a result of the investigation, Entergy is modifying its preventive maintenance and testing to ensure the sprinkler valves operate properly.

The U.S. Nuclear Regulatory Commission began a special inspection of Indian Point related to the accumulated water on May 19. That inquiry continues.

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