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How an outage helped Prairie Island save millions

November 27, 2018 GMT

RED WING — Just in time to power all those Christmas lights, the Prairie Island Nuclear Plant completed its scheduled outage in October with improvements for the plant’s future.

The outage, planned for more than four years, was a routine refueling that came with several upgrades, said Scott Sharp, site vice president at the plant. A big part of that planning included installing a new generator in Unit 1, replacing the original generator that lasted for 45 years.

“The number one item is the reliability,” Sharp said. “It was one of the older generators out there in the nuclear industry that hadn’t had major maintenance performed on it.”


If a generator were to go offline due to a failure, it could take months to repair, Sharp said. The new generator is more efficient — adding a couple of extra megawatts of power — but it’s the ease of maintenance of the new generator that will help the most.

“Part of what’s easier on it is better diagnostics,” he said. “We can more proactively get on it and do those repairs. Technology has come a long ways. Even though the basic design is the same.”

In addition to replacement of the aged generator, the outage involved a new fuel project that could save the plant $70 million over the next 15 years.

The uranium pellets that make up the fuel rods have additives that help the fuel react, Sharp said. Engineers at Prairie Island developed a formula of multiple additives that make the fuel react more efficiently. “Our engineers are always trying to be innovative,” he said. “We’re able to use more of the fuel in the core, so we put less in. Instead of 18 months on a fuel cycle, now we can go 24 months.”

That will reduce the number of fueling outages, Sharp said. “It’s about $70 million we will be saving the customers on that one change.”

Prairie Island engineers have shared their new formula with Westinghouse, the company that produces the fuel pellets, and the innovation could help nuclear plants across the country.

“Depending on the style of plant, if this works out for their design, it could save money all across the industry,” Sharp said. “We want to encourage our employees to find better ways of doing things without giving up safety and reliability.”

With the upgrade, the plant has now replaced both of its original generators. While the plant lasted 40-plus years on its original generators, the new ones only must last until the current nuclear licenses on the two units – currently licensed through 2032 and 2033 – run out.

That is, of course, unless the plant applies for new licenses.

That decision, Sharp said, has not yet been made.

“If we can get 40-plus years out of this one, our consumers will be pleased,” he said, adding that the decision to apply for a further license has not been made. “We made this decision to make sure we’re reliable through the end of our license.”