What is an atomic pile?

The atomic pile is an early model of a nuclear reactor whose core consisted of layers of graphite blocks interspersed with uranium, designed to create a sustained fission reaction. The first atomic pile was created by Ernico Fermi and his colleagues at Columbia in 1942. It consisted of a stack of pure graphite bricks surrounding a neutron source. This first step enabled the examination of graphite’s effect on neutron activity: absorption and re-emission, quantities, fissions. Later, they added uranium pieces in some of the graphite bricks.