Oh my say it’s not so, Shippingport was not the first reactor to put power on the grid!!!!!!!
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. 
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.
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.
The plants are listed in order of their initial criticality.
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. 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.
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.
PM-3A: 1.75 MWe, plus heating and desalinization. McMurdo Station, Antarctica. 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 personal were Navy, the PM-3A was a tri-service stationing. For 1970-1971, there was an Army Sargent and an Air Force Sargent 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. An interesting aside is the plant was located on the flanks of Mt. Erebus, the only active volcano in Antarctica, an excellent geothermal source.
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.
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. The MH-1A had an elaborate analog-computer-powered simulator installed at the Training Division, USAERG, Ft. Belvoir.
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.