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US Army Engineer Reactors Group letterhead

The Army Nuclear Power Program (ANPP) was a program of the United States Army to develop small pressurized water and boiling water nuclear power reactors to generate electrical and space-heating energy primarily at remote, relatively inaccessible sites. The ANPP had several notable accomplishments, but ultimately it was considered to be "a solution in search of a problem." The U. S. Army Engineer Reactors Group was the entity that managed this program and it was headquartered at Ft. Belvoir, VA. The program began in 1954 and had effectively terminated by about 1977, with the last class of NPP operators graduating in 1977. Work continued for some time thereafter either for decommissioning of the plants or placing them into SAFSTOR (long term storage and monitoring before decommissioning). The current development of small modular reactors has led to a renewed interest in military applications.[1][2]


There was interest in the possible application of nuclear power to land-based military needs as early as 1952. A memo from the Secretary of Defense, dated 10 Feb 1954, assigned the Army the responsibility for "developing nuclear power plants to supply heat and electricity at remote and relatively inaccessible military installations." The Department of the Army (DA) established the Army Nuclear Power Program and assigned it to the Corps of Engineers.[3]

The Atomic Energy Act of 1954 made the Atomic Energy Commission responsible for R&D in the nuclear field, so that the ANPP then became a joint interagency 'activity' of the DA and the AEC. When the Atomic Energy Act was revised in 1954, Paragraph 91b authorized the Department of Defense to obtain special nuclear material for use in defense utilization facilities. The focus of the Army Nuclear Power Program was on power production facilities while the Naval Reactors Program concentrated on nuclear propulsion for submarines and ships. On 9 April 1954 the Chief of Engineers established the US Army Engineer Reactors Group to perform the missions assigned by DA. Essentially, these missions were to:[3]

  • conduct R&D, with the AEC, on nuclear power plant development;
  • operate the Corps of Engineers nuclear power plants;
  • carry out training in support of the plants;
  • provide technical support to other agencies as required;
  • develop programs for application of nuclear reactors to military needs.

In a Department of the Army Approved Qualitative Materiel Development Objective for Nuclear Power Plants, dated 7 January 1965, these objectives were stated for the program:[3]

  • Reduction or elimination of dependence on [fossil] fuel sources.
  • Reduction or elimination of logistic burden necessary to support conventional power plants.
  • Reliable operation.
  • Infrequent refueling and maintenance.
  • Reduced crew size, with ultimate goal of unattended operation.
  • Transportability, mobility, and reaction times compatible with the mission or equipment to be supported.
  • Improved cost-effectiveness.

The AEC ultimately concluded that the probability of achieving the objectives of the Army Nuclear Power Program in a timely manner and at a reasonable cost was not high enough to justify continued funding of its portion of projects to develop small, stationary, and mobile reactors. Cutbacks in military funding for long-range research and development because of the Vietnam War led the AEC to phase out its support of the program in 1966. The costs of developing and producing compact nuclear power plants were simply so high that they could be justified only if the reactor had a unique capability and filled a clearly defined objective backed by DOD. After that, the Army's participation in nuclear power plant research and development efforts steadily declined and eventually stopped altogether.[4]

List of ANPP plants

Eight reactors / plants were constructed. In this list MWe = megawatts electrical; kWe = kilowatts electrical. Any power plant, nuclear or otherwise, has an efficiency with which thermal energy can be converted to electrical energy. This thermodynamic efficiency is usually in the 30-40% range, but for the ANPP reactors was, for various reasons, more often about 20%. Also, the electrical energy available outside the plant is limited by (1) the need in some designs to extract steam for space heating, and (2) in all cases the need to supply electrical power to the plant itself (station service); in other words, "It takes electricity to make electricity."

Due to the requirement for a small physical size, all these reactors other than the MH-1A used highly enriched uranium (HEU). The MH-1A had more space to work with, and more weight-carrying capacity, so this was a low-enrichment reactor; i.e., larger and heavier. The MH-1A was briefly considered for use in Vietnam, but the idea of anything nuclear in Vietnam was quickly rejected by the State Department.[3]

The plants are listed in order of their initial criticality. See the gallery of photos in the next section. Sources for this data include the only known book on the ANPP, by Suid,[5] and a DOE document.[6]

  • SM-1: 2 MWe. Fort Belvoir, VA, Initial criticality April 8, 1957 (several months before the Shippingport Reactor) and the first U.S. nuclear power plant to be connected to an electrical grid. Used primarily for training and testing, rather than power generation for Ft. Belvoir. The plant was designed by the American Locomotive Company (renamed ALCO Products, in 1955), and was the first reactor developed under the Army Nuclear Power Program. See the SM-1 image gallery, below. This plant was a tri-service training facility, with both the US Navy and Air Force sending personnel to be trained on shore-based facilities (the Navy had a different stand-alone program for ship-based nuclear power, which is still in operation). The SM-1 and associated training facilities at Ft. Belvoir were the only training facility for shore-based military power plants. The plant cooled its condensers using the waters of Chesapeake Bay. For about the first 10 years of its operation, the SM-1 unknowingly released tritium into the waters of Chesapeake Bay, until the development of the Packard Tr-Carb detector, which was the first capable of detecting the low-energy beta decay of tritium. The instrumentation in the SM-1 pre-dated the development of solid-state devices and used vacuum tubes.
  • SL-1: Boiling water reactor, 300kWe, National Reactor Testing Station, Idaho. Initial criticality August 11, 1958. Site of the only fatal accident at a US nuclear power reactor, on January 3, 1961, which destroyed the reactor. The SL-1 was designed by the Argonne National Laboratory to gain experience in boiling water reactor operations, develop performance characteristics, train military crews, and test components. Combustion Engineering was awarded a contract by the AEC to operate the SL-1 and in turn employed the Army's military operating crew to continue running the plant. This BWR was specifically designed to power DEW line stations. Three men were killed when this reactor plant went from shutdown to prompt critical during a maintenance procedure. The accident happened when a control rod jammed during refueling. Two men entered the containment facility to unjam the rod. In so doing, they withdrew the rod. The core instantly went critical and the cooling water, which also served as the moderator, flashed to steam. The rod pinned one man to the ceiling and the steam flash killed the other. After the accident, the third man left the control room and entered the containment, where he was killed by the radiation. This accident was important in the development of commercial power because future designs prevented the core from going critical with the removal of a single rod.
  • PM-2A: 2 MWe, plus heating. Camp Century, Greenland. Initial criticality October 3, 1960. The first "portable" nuclear power reactor. Brought to Greenland in parts, assembled, operated, disassembled, shipped back to CONUS.[7] The PM-2A in Camp Century, Greenland, was designed by the American Locomotive Company to demonstrate the ability to assemble a nuclear power plant from prefabricated components in a remote, arctic location. The pressure vessel was subsequently used to investigate neutron embrittlement in carbon steel. This plant was shut down 1963-1964. PM-2A operated at a uranium-235 enrichment of 93 percent.[8]
  • ML-1: first closed cycle gas turbine. Initial criticality was on March 30, 1961. Designed for 300 kW, but only achieved 140 kW. Operated for only a few hundred hours of testing. The ML-1 was designed by Aerojet General Corporation to test an integrated reactor package that was transportable by military semi-trailers, railroad flatcars, and barges. This reactor was shut down in 1965.
  • PM-1: 1.25 MWe, plus heating. Sundance, Wyoming. Owned by the Air Force, this pressurized water reactor was used to power a radar station. Initial criticality was on February 25, 1962. The PM-1 was designed by the Martin Company and provided electric power to the 731st Radar Squadron of the North American Air Defense Command (NORAD). This plant was shut down in 1968. PM-1 operated at a uranium-235 enrichment of 93 percent.[9]

PM-1 Nuclear Power Plant

  • PM-3A: 1.75 MWe, plus heating and desalinization. McMurdo Station, Antarctica.[10] Owned by the Navy. Initial criticality March 3, 1962, decommissioned 1972. The PM-3A, located at McMurdo Sound, Antarctica, was designed by the Martin Company to provide electric power and steam heating to the Naval Air Facility at McMurdo Sound. PM-3A operated at a uranium-235 enrichment of 93 percent.

The PM-3A (Portable, Medium-power, 3rd generation) was a plant installed to provide power for the McMurdo Base in Antarctica. During the 1970 to 1971 winter, it achieved a world-record power run. It was one of the first shore-based power plants to use solid-state equipment. The PM-3A was not operated by the Army, but was under the NAVFAC (Naval Facilities Engineering Command "Sea Bees"), shore-based power division of the US Navy. Although the majority of the personnel were Navy, the PM-3A was a tri-service stationing. For 1970-1971, there was an Army Sergeant and an Air Force Sergeant stationed with the crew. The plant was air-cooled with the condensers and fan units running glycol. Waste heat was also used for desalination using vacuum flash distillation. The reactor was located in buried tanks in the ground. After decommissioning, the plant was cut into pieces and transported to the US for burial. The soil surrounding the tanks had become radioactive; so it was also removed and transported to Port Hueneme Naval Base, California, where it was incorporated into asphalt pavement.

  • SM-1A: 2 MWe, plus heating. Fort Greely, Alaska. Initial criticality March 13, 1962. The SM-1A at Ft. Greely, Alaska, was designed by ALCO Products and was the first field facility developed under the Army Nuclear Power Program. This site was selected to develop construction methods in a remote, arctic location. This plant was shut down in 1972. SM-1A operated at a uranium-235 enrichment of 93 percent.

MH-1A control room simulator

  • MH-1A: 10 MWe, plus fresh water supply to the adjacent base. Mounted on the Sturgis, a barge (no propulsion systems) converted from a Liberty ship, and moored in the Panama Canal Zone. Initial criticality at Ft. Belvoir VA (in Gunston Cove, off the Potomac River), January 24, 1967. It was the last of the eight plants to permanently cease operation. The MH-1A was designed by Martin Marietta Corporation. It remained moored at Gatun Lake in the Panama Canal from 1968 until 1977, when it was towed back to Ft. Belvoir for decommissioning. It was moved to the James River Reserve Fleet in 1978 for an expected 50 years of SAFSTOR. This reactor used low-enrichment uranium (LEU) in the range of 4 to 7 percent. The MH-1A had an elaborate analog-computer-powered simulator installed at the Training Division, USAERG, Ft. Belvoir. The MH-1A simulator was obtained by Memphis State University Center for Nuclear Studies in the early 1980s, but was never restored or returned to operational service. Its fate is unknown after the Center for Nuclear Studies closed.

Key to the codes:

  • First letter: S - stationary, M - mobile, P - portable.
  • Second letter: H - high power, M - medium power, L - low power.
  • Digit: Sequence number.
  • Third letter: A indicates field installation.

Of the eight built, six produced operationally useful power for an extended period. Many of the designs were based on United States Naval reactors, which were proven compact reactor designs.[citation needed]

Gallery of ANPP plant photos

ANPP significant accomplishments

References for this list include the DOE document,[6] the Suid book,[5] and the Briefing Book.[3]

  • Detailed designs for pressurized and boiling water reactors, as well as gas-cooled and liquid-metal cooled reactors.
  • First nuclear power plant with a containment structure (SM-1)
  • First use of stainless steel for fuel element cladding (SM-1)
  • First nuclear power plant in the US to supply electrical power to a commercial grid (SM-1)
  • First in-place reactor vessel annealing, using nuclear heat source, in the US (SM-1A)
  • First steam generator replacement in US (SM-1A)
  • First pressure-suppression containment (SM-1A)
  • First operational boiling-water reactor power plant (SL-1)
  • First portable, pre-packaged, modular nuclear power plant to be installed, operated, and removed (PM-2A)
  • First use of nuclear power for desalinization (PM-3A)
  • First land-transportable, mobile nuclear power plant (ML-1)
  • First nuclear-powered closed-loop (Brayton) gas turbine cycle (ML-1)
  • First floating (barge-mounted) nuclear power plant (MH-1A)

Nuclear power plant operator training

The Nuclear Power Plant Operator Course (NPPOC) was conducted at Ft. Belvoir. Applicants for the program were enlisted men who had to commit to serving a minimum of two years after completion of training. The requirements for admission to the NPPOC included aptitude test scores at least as stringent as those required for admission to Officer Candidate School.[11] Over 1,000 Nuclear Power Plant operators were licensed between the years 1958 through 1977. The NPPOC was an intense and academically challenging year-long course.[12]

The training was in three phases of four months each: (1) Academic; (2) Operator; (3) Specialty. Academic phase was eight hours per day of classroom work on Electrical, Mechanical, Nuclear Engineering. Operator phase was at the SM-1, and was shift work both on the "floor" of the plant (i.e., as an "Equipment Operator") and in the control room (Control Room Operator). Specialty phase was one of Mechanical, Electrical, Instrumentation, or Health Physics / Plant Chemistry. The plants were maintained by the operator personnel, trained in these plant maintenance specialties. On graduation from the NPPOC, an individual was "licensed to learn" how to operate a nuclear power plant. A series of badges worn on uniforms designated the individual's progress through the training program.

Nuclear-powered fuel depot

This material is extracted from an article in Army Logistician[4] It is also discussed in the Briefing Book,[3] Section III-C.

In November 1963, an Army study submitted to the Department of Defense (DOD) proposed employing a military compact reactor (MCR) as the power source for a nuclear-powered energy depot, which was being considered as a means of producing synthetic fuels in a combat zone for use in military vehicles. MCR studies, which had begun in 1955, grew out of the Transportation Corps' interest in using nuclear energy to power heavy, overland cargo haulers in remote areas. These studies investigated various reactor and vehicle concepts, including a small liquid-metal-cooled reactor, but ultimately the concept proved impractical.
The energy depot, however, was an attempt to solve the logistics problem of supplying fuel to military vehicles on the battlefield. While nuclear power could not supply energy directly to individual vehicles, the MCR could provide power to manufacture, under field conditions, a synthetic fuel as a substitute for conventional carbon-based fuels. The nuclear power plant would be combined with a fuel production system to turn readily available elements such as hydrogen or nitrogen into fuel, which then could be used as a substitute for gasoline or diesel fuel in cars, trucks, and other vehicles.
Of the fuels that could be produced from air and water, hydrogen and ammonia offer the best possibilities as substitutes for petroleum. By electrolysis or high- temperature heat, water can be broken down into hydrogen and oxygen and the hydrogen then used in engines or fuel cells. Alternatively, nitrogen can be produced through the liquefaction and fractional distillation of air and then combined with hydrogen to form ammonia as a fuel for internal-combustion engines. Consideration also was given to using nuclear reactors to generate electricity to charge batteries for electric-powered vehicles—a development contingent on the development of suitable battery technology.
By 1966, the practicality of the energy depot remained in doubt because of questions about the cost-effectiveness of its current and projected technology. The Corps of Engineers concluded that, although feasible, the energy depot would require equipment that probably would not be available during the next decade. As a result, further development of the MCR and the energy depot was suspended until they became economically attractive and technologically possible.

Although the nuclear-powered fuel depot was never taken beyond this point, the concept was technically sound but to this day remains too expensive to realize, even though fuel cell technology has advanced significantly since the suspension of the program. However, there remains the possibility that a similar approach might be used in the coming decades, as fuel cells become more proven and oil becomes more expensive.

SM-1 photo gallery

See also


  1. Nuclear Power: An Option for the Army's Future
  2. COL Paul E. Roege - Can nuclear energy fill critical gaps in the military energy portfolio? @ TEAC3 - YouTube
  3. 3.0 3.1 3.2 3.3 3.4 3.5 Army Nuclear Power Program: Past, Present, Future. A briefing document prepared and presented to the Ad Hoc Study Group of the Army Scientific Advisory Panel, 10–11 February 1969
  4. 4.0 4.1 Pfeffer, Macon, Nuclear Power: An Option for the Army's Future, Army Logistician, PB 700-01-5, Vol 33, Issue 5, Sept/Oct 2001, retrieved from [1] on January 30, 2009
  5. 5.0 5.1 Suid, L. H., The Army's Nuclear Power Program: The Evolution of a Support Agency, Greenwood (1990), ISBN 978-0-313-27226-4
  6. 6.0 6.1 Office of the Deputy Administrator for Defense Programs (January 2001). "Highly Enriched Uranium: Striking A Balance - A Historical Report On The United States Highly Enriched Uranium Production, Acquisition, And Utilization Activities From 1945 Through September 30, 1996". U.S. Department of Energy, National Nuclear Security Administration. Retrieved 2009-06-13. 
  7. PM-2A
  8. Atomic Energy, Volume 9, Number 4 - SpringerLink
  10. Antarctic Environmental Awareness Pages
  11. Suid, p. 36

External links

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