Historic Army SM-1 Nuclear Plant in Photos

by Will Davis

It was released this week that the US Army Corps of Engineers has decided to enter into the process of decontaminating and dismantling the historic SM-1 nuclear plant at Fort Belvoir, Virginia.  This early military prototype plant isn’t often discussed or even remembered today, so let’s look at the history of this project through photos.

SM1 external view

APPR, later redesignated as the SM-1.

After having been tasked by the US Atomic Energy Commission in 1952 with exploring uses of atomic energy, the US Army paired its Army Corps of Engineers with Oak Ridge National Laboratory to design a conceptual nuclear plant which, small in output, could be transported anywhere by airplane and then constructed and operated.  In 1954, ALCO Products, formerly one of the world’s largest railroad locomotive builders (its name was a contraction standing for American Locomotive Company) decided to form a nuclear power department and get into the business.  Amazingly, when the AEC and US Army decided to go ahead with the packaged reactor project that year ALCO got the contract – although it was said at the time to have been a case of underbidding on the part of ALCO to ensure it could get a foot in the door in this new business.  Construction partner on the project was Stone & Webster Engineering (which itself bid a $1 fee for engineering the Shippingport Atomic Power Station for exactly the same reasons ALCO bid low on this project.)  The designation for this project was to “APPR,” or Army Packaged Power Reactor.

SM1 ALCO press photo

This is an extremely rare ALCO Products press photo from my collection.  The original caption is as follows:  “First views approved for publication of the Army Package Power Reactor designed by American Locomotive Company under a contact received from the Atomic Energy Commission in December, 1958.  The APPR will be a prototype of the first atom-powered generating plant built so that its components can be transported by air to remote bases in any part of the world.  The US Army’s first atomic reactor will be erected at Ft. Belvoir, Va., headquarters of the Army Corps of Engineers, and should be in operation in about three years.  It will probably be the nation’s first exportable peaceful application of atomic energy.  According to Adm. Lewis L. Strauss, chairman of the AEC, the contract is the first of its kind to be let on a fixed-price basis and as such is an important step in the development of power reactor technology.  ALCO was successful bidder among 18 companies seeking the contract, which will be administered by Schenectady Operations of the AEC.

The design developed for the APPR centered around a small, highly enriched 10,000 Kwt reactor using plate type fuel, which supplied heat to a single U-tube type steam generator.  The plant’s intent was to furnish both electric power and space heat for remote installations (such as research or remote radar or weapons stations), but since Fort Belvoir required no space heat a 2000 Kwe turbine generator was installed to absorb the small plant’s entire output.  The plant was then rated 1855 Kwe net, which was supplied to the local Fort Belvoir base grid.

Construction of the plant began under the $3,500,000 fixed price contract on October 5, 1955; the plant was first started up less than two years later, on April 8, 1957.

SM1 System Diagram

System diagram giving significant parameters for this diminutive, single loop PWR plant. The reactor vessel was just about 47 inches inside diameter and was fabricated of carbon steel with a 304 stainless welded overlay in ALCO’s own shops. The steam generator, designed to provide slightly superheated steam, had to be partially dismantled and fitted with different internal equipment after early plant testing revealed operating deficiencies. After this, the equipment performed to specification.

After achieving full power operation on April 20, 1957 the plant was placed in full operation, both conducting various physics and core tests and, very importantly, acting as a working nuclear power classroom for many students of all branches of service and even for civilians.  The design led to a small family of portable PWR reactors and plants; several were built and operated with mixed success.

Operationally the plant, which in 1959 was redesignated from APPR to SM-1 to match new Army parlance, proved to be very impressive.  The plant demonstrated an ability to ride out a full load rejection without scramming simply by reducing fission rate on moderator temperature alone.  It also showed that the nuclear portion of the plant could respond to load change at any rate that the throttle equipment of the turbine generator could apply.  Truly, the consortium of the Corps of Engineers, ALCO, and Oak Ridge had developed a remarkable plant – a plant whose characteristics are being called for again even now in 2019.

SM1 Primary Plant

Arrangement of SM-1 equipment inside the primary shield.

The plant continued to be operated by ALCO for three years, being refueled for the first time in April 1960.  ALCO’s contract ended and control of the project was given to the Army Corps of Engineers in July, 1960 who would retain operating responsibility permanently.  During these early changes and the succeeding several years various further tests were carried out, although as time wore on the reduction of funding to the Army’s nuclear program overall tended to steadily reduce any testing or experimentation.  The plant’s original analog, magnetic amplifier I&C equipment had proven somewhat troublesome (the reactor scramming more often than desirable on spurious period scrams, for example) and one major investment was made in 1964 to solve this when transistorized I&C equipment from Bendix was installed.

SM1 external view press photo

The compact SM-1 plant is quickly recognizable in photos not just because of the rather unique plant building layout but also because of the 3 foot thick shielding concrete belt outside the containment. The containment, a steel cylinder topped and based with hemispheres, is 64 feet high and 36 feet wide. It also has another two feet of shielding concrete inside.

By the early 1970’s the Army had little further use for atomic energy, having had its remote operating plans more or less cancelled by the rapid development of other technologies. (For example, the shift to ballistic missiles had rendered the DEW Line, or Defense Early Warning system, obsolete; it was replaced by the BMEWS or Ballistic Missile Early Warning System that didn’t need remote radar stations dotting the arctic.)  The decision was made to shut down the SM-1 in 1973; the plant was defueled and placed in storage, awaiting the day when it would finally be dismantled.  With the recent moves by the Army Corps of Engineers, it appears that this day is approaching; it’s good, then, to remember this historic, early plant and its contributions.  It’s also sobering to think that a portable, load following unitized plant being asked for in some quarters today was already built a half century ago and worked extremely well.

For much more information see the US Army Corps of Engineers’ page on the SM-1 and the process now underway to fully decommission the plant and site. 

In addition to press photos and materials, sources for the above article include:

Annual Report to Congress of the Atomic Energy Commission, 1964.

The Atomic Energy Deskbook, John F. Hogerton; Reinhold Publishing, New York, 1963.

Nuclear Reactor Plant Data, Volume One – Power Reactors; American Society of Mechanical Engineers, 1958.

Nucleonics, February 1959 and May 1959.

Feel free to include a constructive comment for the author below.

Will DavisWill Davis is a member of the Board of Directors for the N/S Savannah Association, Inc. He has been a contributing author for Fuel Cycle Week, and he used to write his own popular blog Atomic Power Review. Davis is also a consultant and writer for the American Nuclear Society, and serves on the ANS Communications Committee and the Book Publishing Committee. He is a former U.S. Navy reactor operator and served on SSBN-641, USS Simon Bolivar.  His popular Twitter account, @atomicnews is mostly devoted to nuclear energy.  He has an Instagram at @williamdavis5500, but that’s mostly dog photos.

12 thoughts on “Historic Army SM-1 Nuclear Plant in Photos

  1. Will Davis

    Bill, I really appreciate this first hand account. This is a classic example of the comments on a post adding measurably to the history. Thank you!

  2. Will Davis

    Randy, thanks for the kind words – and I agree. So much was already done and, unfortunately, then forgotten. I’d be open to helping set up a course on nuclear power history but I seriously doubt if anyone would take me up on that, these days.

  3. Will Davis

    Tom, I can’t answer that directly but I see that a few other people involved in some way have responded in the comments. You might wish to try to contact them and re-establish a network of APPR folks!

  4. Will Davis

    Except that both were generally conceived as designs whose major components could be transported to a remote area and then set up, there were no similarities. The SL-1, originally ALPR, was designed by Argonne National Laboratory and was a direct cycle, natural circulation boiling water reactor providing steam heat and electric power in an essentially shrouded but not vapor tight enclosure. In all these respects it was different from the plant built at Fort Belvoir.

  5. Paul M Krishna

    Back in 1963, as a young man with a fresh M.S. degree in Nuclear Engineering, my first job was a Reactor Engineer in the U.S. Army Nuclear Power Field Office at Fort Belvoir, VA. In that job we supported SM-1 and all other reactors including the floating nuclear power plant “Sturgis”, under the jurisdiction of the Army. Your article captured the history of SM-1 and brought back nostalgic and very pleasant memories of my tenure at the NPFO. Thank you very much .

  6. Thomas Williamson

    I worked on the APPR for ALCO in ’57-’58 in Schnectady. This is a good story but would like to have seen names of some of the people involved. Example Dr. Reed Johnson is still an ANS member. I wonder if aany others are still active.
    Tom Williamson

  7. Paul A. Sanchez

    Will, I look forward to all your articles and blogs. I love studying our early nuclear history and your work is very much appreciated!

  8. Milt Klein

    Memories! I was personally involved in the process of awarding the contract for the APPR. I was then working at the AEC’s Chicago Operations Office which managed the process in cooperation with the Army Corps of Engineers. As your article notes, the award process was ground-breaking as a competitively bid award.of a nuclear plant.

  9. Randy Reames

    Very interesting, Will!

    It’s always intriguing but slightly disheartening to hear about old nuclear projects; every nuclear technology and application seems to have been developed and thoroughly tested half a century ago. It’s a shame that we weren’t able to deliver on Eisenhower’s dream for nuclear technology to drive development and prosperity across the world.

    I believe that nuclear undergraduate programs throughout the US should include courses in nuclear history, geopolitics, and business. Nuclear engineers and nuclear professionals have tremendous benefits to deliver to the world, and often don’t have enough perspective to realize it in my opinion.

    Thanks for all you do!

  10. William Saylor

    Will,
    Thanks for the article. I was a Captain and was the last Director of the Nuclear Power Plant Operators Course from 1977 -1979. My office was in the SM-1 and we had a couple of classes down there. In early 1977 we had towed the Sturgis back from Panama and decommissioned it at Ft Belvoir. That was the last operating reactor. I changed the curriculum to Prime Power Production and we kept the year-long school format to train enlisted students in the same specialties (electrical, mechanical, instrumentation, and health physics) but for multi-megawatt diesel and gas turbine power plants. This ultimately became the core group of the 249th Eng Bn that does that kind of work to this day (I think they still do). We deployed 4.5 MWe diesel plants during the 1978 coal strike. Sent a 2 MWe diesel plant to support cleanup at Eniwetok. Sent a 2 MWe (Solar gas turbines) to Kodiak Island after a 1978 fire during crab season). I still had Navy students from the Navy MUSE program at Port Hueneme. We built an 8 MWe training plant with 1.5 MWe EMDs, 500 kWe Caterpillars, and 750 kWe Solar gas turbines. Tremendous history and talent inthat group and I was lucky to spend 2.5 years with them.
    Thank you,
    Bill Saylor

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