Reactor engineering is a branch of engineering focused on the design, analysis, and operation of reactors, which are systems that facilitate chemical or nuclear reactions. In chemical engineering, reactors are used to produce various chemicals through controlled reactions, while in nuclear engineering, they are essential for generating energy through nuclear fission. Reactor engineers work to optimize the performance and safety of these systems, ensuring they operate efficiently and meet regulatory standards. They apply principles from thermodynamics, fluid mechanics, and materials science to develop reactors that can handle specific processes, such as those found in nuclear power plants or chemical manufacturing.