Alarms sound at Fermi 1; two fuel assemblies melt near Detroit

Fermi 1 had only reached commercial operation two months earlier, a prototype fast breeder reactor feeding power to the grid south of Detroit. On October 5, 1966, during a routine climb in power, a blockage in one of the reactor's lower support plate orifices choked off liquid sodium coolant to part of the core. Two of its 92 fuel assemblies overheated and partially melted before core temperature alarms finally alerted operators. The Atomic Energy Commission later confirmed no abnormal radioactivity escaped into the environment, but the reactor did not return to service until 1970…