A super critical water oxidation reactor (SCWOR) serves as an extremely efficient power source in a power plant by coupling the various output streams in thermal communication with multiply staged or cascaded compressor- expanders that are themselves mechanically coupled to a motor or generator. In one embodiment heat from a re-circulating liquid brine loop either directly or indirectly preheats the exhaust gases of the SCWOR prior to expansion. In another embodiment the heat of compression is used to preheat the effluent of an expander prior to a subsequent expansion stage. The re-circulating brine loop also preferably preheats expander effluent prior to a subsequent expansion stage.
