[en] In early 1943, as part of the Manhattan Project, plans were made to build an air-cooled nuclear experimental pile, a chemical separations pilot plant, and supporting laboratories on an isolated tract known as X-10. These major installations became the prime function of the Clinton Engineer Works, now known as Oak Ridge National Laboratory (ORNL). Since that time, Building 3019 (formerly known as Building 205) has served as a pilot plant in the development of several radiochemical processes that have found plant-scale application in both government and commercial facilities on a worldwide basis. In addition to the process development role, the facility's operations have also produced large quantities of product materials (plutonium, uranium of all isotopes, thorium, and special isotopes) while processing highly irradiated fuel. A series of decisions relating to the fate of Building 3019 are currently required. Before these decisions can be prudently made, an understanding of the historical and programmatic background is necessary to establish the extent of the contribution made in support of the government's missions. Accordingly, this report outlines the scope and objectives of a pilot plant in process development and interim production and relates these functions to both the history and technology development of the reprocessing segment of the nuclear fuel cycle. The specific role of, and contributions made by, the operations within Building 3019 since 1943 are presented and documented