A thermal/electrical power converter includes a gas turbine with an input couplable to an output of an inert gas thermal power source, a compressor including an output couplable to an input of the inert gas thermal power source, and a generator coupled to the gas turbine. The thermal/electrical power converter also includes a heat exchanger with an input coupled to an output of the gas turbine and an output coupled to an input of the compressor. The heat exchanger includes a series-coupled super-heater heat exchanger, a boiler heat exchanger and a water preheater heat exchanger. The thermal/electrical power converter also includes a reservoir tank and reservoir tank control valves configured to regulate a power output of the thermal/electrical power converter.