Chapter 4 A New Approach to Energy Conversion Technology A nuclear reactor produces and controls the release of energy from splitting the atoms of uranium. Uranium-fueled nuclear power is a clean and efficient way of boiling water to make the steam that drives turbine generators. Except for the reactor itself, a nuclear power station works like most coal- or gas-fired power stations. 4.1 Power Conversion Study and Technology Options Assessment In the USA, most reactor design and development for the generation of electrical power derived from early nuclear naval research, when it was realized that a compact nuclear power plant would have great advantages for submarine-driven nuclear propulsion systems. To have such a power plant on board would make possible long voyages across the oceans at high speeds without having to resurface at frequent intervals. Operating temperatures of conventional light water reactors (LWRs), 280–320  C, limit power conversion systems to producing pressurized steam that drives a condensing steam turbine. After employing thermal recovery measures, nuclear plants using this Rankine cycle see a net plant efficiency of around 32–34 %. Comparatively, gas turbines with turbine inlet temperatures of up to and greater than 1400  C have simple cycle efficiencies of around 40 % that can be boosted to around 60 % in a combined cycle. The ability of the combined cycle or Brayton with recuperator cycle to drastically improve net plant efficiency is an especially appealing feature to employ with a nuclear power source, given the very low fuel costs for nuclear energy, but has previously been technically infeasible given the high operating temperature requirements of a combined cycle (Fig. 4.1). © Springer International Publishing Switzerland 2016 B. Zohuri, Nuclear Energy for Hydrogen Generation through Intermediate Heat Exchangers, DOI 10.1007/978-3-319-29838-2_4 123