Nuclear Engineers-What They Do. Nuclear engineers research and develop the processes, instruments, and systems used to derive benefits from nuclear energy and radiation. They design, develop, monitor, and operate nuclear plants to generate power.They may work on the nuclear fuel cycle the production, handling, and use of nuclear fuel and the safe disposal of waste produced by the generation of nuclear energy or on the development of fusion energy.hey design, develop, monitor, and operate nuclear plants to generate power. They may work on the nuclear fuel cycle the production, handling, and use of nuclear fuel and the safe disposal of waste produced by the generation of nuclear energy or on the development of fusion energy.