Prairie Island nuclear plant shut down Unit 1 after operators declared its two backup diesel generators inoperable Tuesday.
Staff determined during routine testing that both generators had exhaust leaks, Xcel Energy media relations spokeswoman Mary Sandok confirmed. That deemed them inoperable, and the plant filed an incident report of the safe shutdown with the Nuclear Regulatory Plant.
Prairie Island has other backup protection, including diesel generators and turbine-driven and portable pumps, the company said in the statement issued at 2:30 p.m. There was no radiation leak or danger to the public.
Prairie Island Tribal Council President Johnny Johnson called the loss of both generators “not acceptable.”
“A failure of the back-up diesel generators can affect all other safety features that rely on the electricity that they generate,” he said.
The plant has had more than 30 reported incidents of failing equipment, security breaches, human performance problems and operating errors in recent years, he said.
The emergency diesel generators did not fail, Sandok said. Plant workers test equipment regularly, and during this week’s test they determined both generators had defects.
“When it comes to important equipment, the nuclear industry has no tolerance for any imperfections, so operators shut the unit down to repair the generators,” she said.
As of 7 p.m. Tuesday, one diesel was operable and the other one was repaired and awaiting testing.
“Despite these assurances, today’s unplanned shutdown – and the unusual white steam clouds released throughout the day during the reactor shutdown – are ominous reminders of the fact that the 40-year-old Prairie Island Nuclear Generating Plant operating a half-mile from our homes relies on aging technology,” Johnson said.
An unrelated outage also occurred Tuesday at the Monticello plant to repair a gasket on a pipe flange. The plant had been operating at 10 percent power since the weekend as workers investigated leakage to a collection point inside the plant’s containment structure.