A rare look at South Dakota’s first and only nuclear power plant called Pathfinder

Eye on KELOLAND

Right now about 25 percent of the power we use in our homes in South Dakota is generated by two nuclear power plants in Minnesota. Northern States Power constructed the plants in the 1970s. However, they might not have been built if it weren’t for a project in South Dakota called Pathfinder.

It was a small nuclear power plant built near Brandon in the early 1960s. It all started in the 1950s with a program called Atoms for Peace.

It was President Dwight Eisenhower’s idea to allow technology being used by the Navy to power submarines to become available for commercial purposes. Power companies including NSP, or Northern States Power saw the potential, and ramped up research. Today there are 58 nuclear power plants operating in the U.S. This is not one of them. It is the Angus Anson Power Plant near Brandon, which generates electricity by burning natural gas.

But in 1966, this same site was home to South Dakota’s first, last and only nuclear power plant. The plan for the plant was submitted to the U.S. Atomic Energy Commission and Northern States Power in August of 1959 by Allis Chalmers Manufacturing, which around here, most of us know as a tractor company. At that time Allis Chalmers had an Atomic Energy Division

This is rare photo of the plant under construction taken on November 2nd of 1960.

Courtesy: Xcel

10 months later they loaded the reactor vessel into the reactor building.

Like all nuclear power plants, Pathfinder’s core superheated water which turned into steam. That steam turned turbines which generated electricity. Pathfinder incorporated a technology called the steam “superheater”. Jim Wilcox is a historian and former Xcel employee.

“I think we determined that the economics panned out quite well, the steam superheater turned out to be more problematic, it was a technology that was ahead of its time, and has not been adopted by any other nuclear power plants since, said Wilcox.

In South Dakota just under half of our power comes from the hydro-electric plants along the Missouri River. Pathfinder might have gone on to power homes in South Dakota, however repeated failure in the steam separators caused the plant to shut down and eventually led to the decision to close the plant.

“I think we would classify Pathfinder as a research project. You know it began construction in the late ’50s, went online in 64, and then operated for 3 years, intermittently for testing purposes, for research purposes,” said Wilcox.

Not only did NSP gain knowledge about generating nuclear power, According to Pam Gorman Prochaska, Director of Xcel’s Nuclear Fleet Operations, it gained something even more valuable from Pathfinder.

“We at NSP were able to take employees that had worked at Pathfinder and transfer that knowledge and the skills that they had learned operating Pathfinder, when we opened up the two nuclear power plants that are still operating today in Minnesota, at the Monticello and the Prairie Island Nuclear plant,” said Prochaska.

The Minnesota plants, built in the early ’70s, use slightly different technology and are much larger than pathfinder.

A natural concern when people find out there was a nuclear power plant near Brandon is “what about radiation.”

“We have a federal regulator, the Nuclear Regulatory Commission, and they’ve come in and said that there’s no residual radiation at the plant and its not deemed a nuclear site any longer,” said Prochaska.

This report filed by the Nuclear Regulatory Commission’s, Advisory Committee on Nuclear Waste in 1990 talks about the radiation levels at Pathfinder being so low, there was concern workers would become too relaxed in their safety precautions. The report urged the Commission to monitor the deconstruction closely.

“The reactor itself was removed in 1991,” said Wilcox.

The rest of Pathfinder was taken down and moved in the early 2000s.

“And the piping and all the other equipment which was at a level low enough to be handled by people physically without any protective gear,” Wilcox added.

Pathfinder was a source of pride, not only for the workers but for the community. At the time, brochures promoting Sioux Falls mentioned the atomic plant as a place to see along with the Battleship Memorial.


Big Sioux provided enough water for a small plant like Pathfinder, it could not support today’s larger plants. So, while nuclear power is a part of Sioux Falls’ past, it doesn’t appear it will ever be part of the future.

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