Systems for Nuclear Auxiliary Power (SNAP) was an Atomic Energy Commission program with the goal of producing a portable and dependable power source centered around nuclear technology that could be utilized in land, sea, and space applications. The program aimed to provide a compact reactor—a necessity for space applications—and ran from 1955 until 1973, when it was discontinued.

In March 1949—75 years ago this month—the 25-kilowatt reactor known as Clementine reached full power. As an experimental reactor, it had a rather long and successful run. It was the world’s first fast neutron (high-energy) reactor and operated from initial criticality in 1946 to final shutdown in 1952.