Chicago Pile-1 - Reactor

Reactor

The reactor was a pile of uranium and graphite blocks, assembled under the supervision of the renowned physicist Enrico Fermi, in collaboration with Leó Szilárd, discoverer of the chain reaction. It contained a critical mass of fissile material, together with control rods, and was built as a part of the Manhattan Project by the University of Chicago Metallurgical Laboratory. The shape of the pile was intended to be roughly spherical, but as work proceeded Fermi calculated that critical mass could be achieved without finishing the entire pile as planned.

A labor strike prevented construction of the pile at the Argonne National Laboratory, so Fermi and his associates Martin Whittaker and Walter Zinn set about building the pile (the term "nuclear reactor" was not used until 1952) in a rackets court under the abandoned west stands of the university's Stagg Field. The pile consisted of uranium pellets as a neutron-producing "core", separated from one another by graphite blocks to slow the neutrons. Fermi himself described the apparatus as "a crude pile of black bricks and wooden timbers." The controls consisted of cadmium-coated rods that absorbed neutrons. Withdrawing the rods would increase neutron activity in the pile, leading to a self-sustaining chain reaction. Re-inserting the rods would dampen the reaction.