While Chicago Pile-1 demonstrated the feasibility of nuclear reactors, the Manhattan Project's goal of producing enough plutonium for atomic bombs required reactors a thousand times as powerful, along with facilities to chemically separate the plutonium bred in the reactors from uranium and fission products. An intermediate step was considered prudent. The next step for the plutonium project, codenamed X-10, was the construction of a where techniques and procedures could be developed and training conducted. The centerpiece of this was the X-10 Graphite Reactor. It was air-cooled, used nuclear graphite as a neutron moderator, and pure natural uranium in metal form for fuel.