Sioux Falls’ Nuclear Experiment

Posted: Saturday, March 19, 2011 at 4:41 pm
By: Doug Lund
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 I suppose I’m just going to have to give in and jump on the wind generator bandwagon as an alternative energy source now that the disaster in Japan has soured public opinion on Nuclear energy even more.

Steve Hemmingsen, who lives in the shadow of a gazillion of those unsightly(my opinion) electric generating whirligigs spinning away on every southwest Minnesota hillside, recently reminded me about how Sioux Falls was once a real pioneer in the development of nuclear power; a “Pathfinder” in both name and mission.

Back in the 50’s and 60’s about all we knew of atomic power was the fact that Russia and the United States had a bunch of intercontinental ballistic missiles pointed at one another promising mutual annihilation if either side got too pushy.

atomic plant oneBut there were others at the same time trying to downplay the bombs and tout the POSITIVE side of nuclear energy as an economical, clean, relatively safe source for generating electricity. After all, the U.S. Navy had already proven that it was feasible with the launching of “Nautilus” the first nuclear powered submarine in 1955; the beginning of our nuclear Navy.  

Northern States Power Company along with other investor owned utilities wanted to be in on the ground floor so it applied for and received permission to build a small nuclear plant just northeast of the growing and industrially ambitious city of Sioux Falls. It would be one of the first all nuclear generating stations in the country and serve as a guinea pig for the utilities to  find out how to run a nuke plant and demonstrate the feasibility of building more.  The chamber of commerce was all for it; believing the facility would attract new people and business to our “modern progressive” community. The chamber even used Pathfinder in the tourist brochure of “must see” places in Sioux Falls.

atomic pathfinder two

“Pathfinder” went on-line in 1966 but almost immediately began having mechanical problems.  In fact, it only ran at maximum output ONE time and then for just a half hour. Within a year, it was decided that the plant was too costly to maintain and not all that safe so the reactor, manufactured by Allis/Chalmers (the tractor people) was shut down and converted to use natural gas and oil as fuel to make steam for powering the turbines.  Here’s what Atomic Power Resources Associates official blog has to say about Pathfinder: “This plant, was one of the most troubled in history because of the design of the reactor which was one of only two ever built here that attempted to use nuclear superheating of the steam in the reactor core. The plant was never successful and never passed full power tests, and was never put on the grid of Northern States Power for any measurable time before being terminated.

But NSP did learn from Pathfinder’s problems and went on to build several more nuclear power plants. Just no more in South Dakota.  It took 24 YEARS for the reactor to cool enough to be safely removed from the building and hauled off to a nuclear waste disposal site in Washington State. I remember during those years there were lots of whispers and rumors about Pathfinder occasionally leaking little poofs of radiation. One story that went around was that the plant had once come close to a melt down. I think that was probably right after the movie, China Syndrome, came out. To my knowledge, though, no such evidence ever surfaced.

In 1994, Pathfinder was renamed for NSP executive, Angus Anson, who was killed in the same plane crash that claimed the life of Governor George Mickelson. The plant is still there and still used by Xcel as a backup.. providing extra electricity during those scorching humid summer days when everybody’s air conditioner is cranked up on high.

I suppose if you live near the Buffalo Ridge when it’s hot like that, you could go stand in front of one of those mega million dollar giant fans that pepper the landscape. I’m sure they must generate a nice breeze along with a little electricity.


  1. rdl says:

    Yes those wind generators do bother a few people. I have a home on the Buffalo ridge so see them often; but at night the just disappear except for the blinking red lights. I have heard that they use a special white paint. When a cloud’s shadow covers them and on cloudy days the tower do turns a lite gray and almost disappears.

  2. hardass says:

    i remember this place….my class back then took a “field trip” when it was fired up and at that time it was a marvel of technology…..we all got some little trinket that was given away at that time to commemorate our visit……in fact….at that time i had only on a few occasions ever seen anything so astoundingly elaborate!!!!….and those were my earlier visits to the “Captain 11″ show…now there was something amazing!!!!!

  3. Gene says:

    Reddi Killowatt

  4. Doug Lund says:

    Willie Wirehand

  5. Hemmingsen says:

    Doug, you really should come up more often. Now they have metasticized west of us into South Dakota, which is about three blocks away. As rdl points out, we are watching the formation of a new galaxy on the horizon made up of all red stars. At least they don’t stick. They could all be hog farms.

  6. Hemmingsen says:

    Maybe there is a karma to it. This as we were about to pick up nuclear power again; BP as we were finally going to drill for oil offshore. I suppose if we tap that Alaskan tundra we’ll have a quake up there as soon as the oil starts flowing.

  7. Hemmingsen says:

    By the way, I’m still for all three, providing we learn the lessons that apply.

  8. M. Peterson says:

    I worked at the Allis-Chalmers Nuclear Power Plant in Greendale, Wisconsin 1959-1962 as a secretary, while the company was building the Pathfinder Nuclear Reactor for Sioux Falls, SD. I was one of a few typists that typed all the manuals on how the reactor was built and how it would operate. I always wondered if it was still in operation, so recently did some research about it and was very surprised to see the short time it was in operation. I was very sorry to read that seeing what went into building it, man power, time and money.

  9. Charlie Smith says:

    “I suppose if you live near the Buffalo Ridge when it’s hot like that, you could go stand in front of one of those mega million dollar giant fans that pepper the landscape. I’m sure they must generate a nice breeze along with a little electricity.”

    Actually, they decrease the breeze. Energy in the wind is proportional to the velocity to the third power, extract some energy and it must slow down. Not much written on what affect it will have on climate.

  10. M. Peterson says:

    I wonder who paid Allis-Chalmers for the Pathfinder Nuclear Reactor? The government? Does anyone know?

  11. Matt Fischer says:

    Don’t know who paid for it, but Allis-Chalmers made a lot of electrical distribution equipment thru 1984 when Siemens of Germany bought out their electric division. Doug–Thanks for mentioning Pathfinder. Haven’t heard that name in years. I remember when you (or maybe Hemmingsen) did a story about the removal of the fuel from the plant. Trip down memory lane. . .

  12. Will Davis says:

    The blog you quoted is mislabeled; it is ATOMIC POWER REVIEW, and I am the owner. Further, it is the product of Atomic Power Research Associates.

    Allis-Chalmers, frankly, was in way over its head with the Pathfinder station. The original contract for what would become Pathfinder specified superheated steam, in order to keep complexity of the turbine equipment to a minimum, and as a result said contract specified a boiling water reactor producing saturated steam which then would have been superheated by either a coal-fired or else an oil-fired superheater. (ConEd’s Indian Point 1 nuclear plant used an oil fired superheater; Rural Co-Op’s Elk River nuclear plant used a coal fired superheater.) However, Allis-Chalmers decided to go for broke and convert the reactor design to include superheating elements in the core in a two-pass arrangement, with forced water recirculation. The many problems this introduces are too numerous to explain here, but A-C was definitely challenged beyond its capacity to cope by the design … as well as by the fact that it decided to act as architect-engineer for the whole power station, a giant job best handled either by major experienced constructors (Bechtel, Burns & Roe) or else very large utilities with vast experience (Detroit Edison.) In the end, it was too much.

    You can still see where the reactor building was at the plant. The building is gone, but there’s a circular concrete pad right where it sat.

  13. Will Davis says:

    @M Peterson: The Pathfinder project was mostly paid for by private investment. Northern States Power was the owner-operator and paid the construction costs. There was a consortium of a number of utility companies that paid in some money for R&D work, known as Central Utilities Atomic Power Associates. However, the plant was also built as a part of the 3rd round of the Atomic Energy Commission’s “Power Demonstration Reactor Program” which gave monetary incentive to builders of new plants, in the form of waivers for fuel costs (all nuclear fuel was owned by the AEC, hence the Federal Government) for five years, and another contribution of cash for R&D work. I would like to amend my previous comment with the note that Allis-Chalmers DID retain Pioneer Service and Engineering Co. as a consultant for architectural and engineering services but acted much more like Detroit Edison during construction of that company’s Fermi No. 2 plant than any normal relationship would have dictated. A-C also contracted Fegles Construction Company as its General Contractor for the site.

    Because of all the problems and all the work A-C took on itself the construction of Pathfinder was very protracted. The proposal was floated for this plant in May 1957, with construction beginning two years later. We see how long it took to get testing done and finally decide to kill the project by the information in the article above.

  14. Dick Davie says:

    I worked on the design of the Pathfinder plant at Allis
    Chalmers. Did plant systems design including reactor water purification system.Ended up in design of the second low enrichment reactor superheater core.I also did the leak testing of the containment vessel. Left the division before the plant started up. I never heard anything about it after that. I’d like to know , in more detail, just what problems were encountered with the plant and the reactor. Any idea where I could find that information?

  15. cody says:

    I was born after the plant was shutoff, but i wouldn’t want to live anywhere near the plant. Nuclear plants have always terrified me!

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