Process for incineration and in can vitrification: Glass melt/liquid metal interactions and the multiphasic package

Abstract

A process for incineration and in can vitrification was studied as a potential conditioning solution for nuclear fuel cycle wastes consisting of various mixtures (organics, minerals, and metals including Al) contaminated with actinides (mainly U, Pu). The organic matter was first incinerated, followed by melting of the metallic phase and ashes together with an aluminosilicate glass as a vitrification additive. This resulted in the formation of a multiphasic glass/metal package containing the actinides without organic material. During the process, interactions between liquid metal and the glass melt led to redox reactions (aluminum oxidation, silica reduction…) and the reductive environment induced sodium volatilization. Characterization of the upper layer of glass–ceramic material with 53 wt% Al2O3 showed crystallizations and metallic inclusions. The lower metallic part of the package showed demixing of the Cu-rich liquid phase and the formation of three metallic phases (stainless steel-rich, copper-rich, and Cr-Fe). Based on the results acquired, a waste package description consistent with the proposed glass/metal interaction mechanisms was obtained.