Experimental Reactors

Over the course of its 24-year history the Army Nuclear Power Program (ANPP) built or operated the SM-1 at Fort Belvoir, the MH-1A Sturgis, and 6 other experimental reactors. The power plants reflected the ANPP’s mission to develop and test innovative reactor designs that were easily transportable and could operate in remote locations.


SL-1 (Stationary Low Power Reactor Prototype Number 1) was a small experimental reactor and the only boiling water reactor in the Army Nuclear Power Program. The Atomic Energy Commission (AEC) designed the reactor, but the Army operated and maintained it at the AEC’s National Reactor Testing Station near Arco, Idaho. SL-1 became operational on August 11, 1958. On January 3, 1961, a non-nuclear explosion, likely caused by operator error, destroyed the reactor. It was the only nuclear-related accident in the history of the Army’s nuclear program.

ML-1 (Mobile Low Power Reactor Prototype Number 1) was to be a nuclear power plant easily transported over land. To reduce the reactor size, the Army used a closed-cycle gas turbine, a completely new design. The reactor, designed at Ft. Belvoir and tested at the National Reactor Testing Station, began intermittent operations in 1961, but problems plagued the reactor and the Army discontinued the ML-1 program in 1965.

SM-1A (Stationary Medium Power Reactor Number 1A) at Ft. Greely, Alaska, was modeled after the SM-1 reactor at Ft. Belvoir. It began operation on March 13, 1962, and provided power and heating for the installation for a decade until deactivation in 1972. Notably, the large earthquake in Alaska on March 27, 1964, caused no damage to SM-1A.

PM-2A (Portable Medium Power Reactor Number 2A) was the power plant for the U.S. Army’s Camp Century, a year-round experiment station under Greenland’s ice cap. Construction began in 1960 in extremely challenging conditions and was the first true test of the Corps’ portable nuclear power plant concept. Components arrived by ship, aircraft, and cargo sleds for assembly at the installation. The PM-2A became operational on October 3, 1960. Camp Century converted to summer-only operations in 1962, making PM-2A unnecessary. The Army deactivated and disassembled the plant that year and transported it back to the U.S.

PM-3A (Portable Medium Power Reactor Number 3A) provided electricity, steam heat, and desalinized water for the U.S. Navy base at McMurdo Sound, Antarctica. Operated by Navy personnel, PM-3A began generating power on March 3, 1962, and was deactivated and removed in 1972.

PM-1 (Portable Medium Power Reactor Number 1) provided power for the U.S. Air Force Sundance Radar Station in Wyoming, part of the North American Defense Command. As with the other portable reactors, the PM-1 arrived in components to be assembled on site. With technical support from the Army Engineers, the Air Force plant operated from February 25, 1962, until April 1968, when the Sundance station closed.

Apr. 2017


Visit the other pages of the Army Nuclear Power Program Virtual Exhibit

SM-1 Booties

Exhibit Home

SM-1 Dedication

Origins of the ANPP

Sturgis Core

Nuclear Power Generation

SM-1 Control Panel

SM-1 Ft. Belvoir


MH-1A Sturgis


Shutdown & Legacy