world's first nuclear-powered surface ship, a large icebreaker built by the Soviet Union in Leningrad (St. Petersburg) in 1957. The Lenin is 440 feet (134 m) long, displaces 16,000 tons, and cruises in normal waters at 18 knots (nautical miles per hour). It is powered by three nuclear reactors, two of which are normally used for operation and the third of which is kept in reserve. Despite high initial costs, nuclear propulsion proved to be highly advantageous because it allowed virtually unlimited cruising range under extremely severe conditions.