Nuclear engineers are involved in the design, construction, and operation of nuclear power plants for power generation, propulsion of nuclear ships and submarines, and space power systems. Nuclear engineers are also involved in the handling of nuclear fuels, the safe disposal of radioactive wastes, and in medical uses of radioactive isotopes. Many of these engineers find industrial and medical uses for radioactive materials—for example, in equipment used in medical diagnosis and treatment. Many others specialize in the development of nuclear power sources for ships or spacecraft.