From the perspective of the current book, nuclear reactors are boilers. They either act as steam boilers for Rankine steam cycle power plants (conventional deployment) or as heat exchangers to increase the temperature of the power cycle’s working fluid. As far as the second variant is concerned, it has not progressed from paper to practice. The power cycle in question is a closed cycle gas turbine. There are several candidates for the working fluid in such a cycle with supercritical CO2 being a prime candidate. This chapter covers the application of gas/steam turbine technology to nuclear power and other possibilities such as methane pyrolysis.