Question:  Walter Henry Zinn designed and built several new reactors, including one that produced sufficient electricity to illuminate four what?
Sentence (from "Experimental Breeder Reactor I"): At 1:50 p.m. on December 20, 1951, it became one of the world's first electricity-generating nuclear power plants when it produced sufficient electricity to illuminate four 200-watt light bulbs. Electricity had earlier been generated by a nuclear reactor on September 3, 1948 at the X-10 Graphite Reactor in Oak Ridge, Tennessee.
Relevant evidence: Yes