Abstract: An improved process and apparatus are disclosed for the supercritical water oxidation of organic waste materials which avoids or at least substantially reduces the corrosion and solids deposition problems associated with prior art techniques. According to this invention, externally heated supercritical water is fed to a platelet tube reactor to both protectively coat its inner surface and heat the waste stream to oxidation reaction conditions. Higher reaction temperatures can be used as compared to prior art processes, which significantly improves the reaction rate and permits smaller reactors to be used. The protective film of water on the reactor inner surface, coupled with the elimination of preheating of the waste material, substantially reduces solids deposition and corrosion.