sentences:  In 1951, the first nuclear fission power plant was the first to produce electricity at the Experimental Breeder Reactor No.1 (EBR-1), in Arco, Idaho, ushering in the "Atomic Age" of more intensive human energy use.However, if the mass is critical only when the delayed neutrons are included, then the reaction can be controlled, for example by the introduction or removal of neutron absorbers.