Experimental Breeder Reactor II was a sodium-cooled fast-neutron reactor in Idaho developed by Argonne National Laboratory to demonstrate an integrated breeder-reactor system with on-site fuel reprocessing and a closed fuel cycle. Beginning operation in 1964 and reaching criticality in 1965, it tested recycling metallic uranium fuel, reached full power in 1969, and over its lifetime produced more than two billion kilowatt-hours of electricity while supplying power and heat for Argonne National Laboratory-West. Later it served as a test bed for the Integral Fast Reactor concept and became especially significant for 1986 passive-safety tests in which it shut itself down without damage or operator action.