Caption:
Researchers working on CP-5 at Argonne National Laboratory. Chicago Pile 5 (CP-5) was the last of the line of Chicago Pile research reactors which started with CP-1 in 1943. CP-5 operated from 1954-1979. It was a thermal-neutron reactor using enriched uranium as fuel and heavy water as coolant and as a neutron moderator. It produced neutrons for use in research. Cleanup and decommissioning of the site of CP-5 was completed in 2000.