Processing High-Level Liquid Waste by Super-High-Temperature Method, (III)

Abstract

The process constituting the elements of the method for treating high-level liquid waste with addition of reducing agent at temperatures above 1,873 K were examined applying thermogravimetry and X-ray diffractometry to sample mixtures of the platinum metal oxides RuO2, Rh2O3, PdO and of Re2O7, with and without addition of TiN as reducing agent. The addition of TiN reducing agent proved to induce reduction of the platinum metal oxides at temperatures far below those of thermal decomposition occurring in the absence of reducing agent. The presence of reducing agent further proved to reduce Re2O7 to ReO3 at 373K, to ReO2 at 773 K and to Re metal at 1,073 K. At around 773 K disproportionation reconverted part of the ReO3 formed at 373K to ReO2 and Re2O7. Thus, sublimation of the Re2O7 in starting material which occurs at 523 K in the absence of TiN was eliminated, and occurred only at 773 K on the Re2O7 that was regenerated at that temperature by disproportionation of the converted ReO3. Alloys of Ru, Rh and Pd resulting from the above treatment with TiN proved to agree with what is indicated from phase diagrams. Among the alternative compounds existing in the Rh-Ti and Rh-Ti binary systems, however, solely Ru-Ti proved to have been produced.