In 1891, Mitsubishi Heavy Industries - Yokohama Machinery Works was started as Yokohama Dock Company, Ltd. Its main business was ship repairs, ... From its inception, the Mitsubishi Nagasaki shipyards were heavily involved in contracts for the Imperial Japanese Navy. .... It also operates a nuclear fuel manufacturing plant in Tōkai, Ibaraki which processes 440 Metric tons of Uranium per year.