SINTERED SILICA AEROGEL - A HOST MATRIX FOR LONG-LIFE NUCLEAR WASTES

An approach to nuclear waste fixation is to incorporate radioactive el ements in multicomponent oxide glasses containing silica, alumina, bor on and alkali. For long-lived nucleides, a new alternative approach is considered in order to evaluate durability of new matrices. High sili ca glasses present high chemical durability and stability associated w ith strength and thermal shock resistance. A process is described in w hich a porous, partially sintered silica aerogel is used as a host mat rix for actinides. The porous aerogel is soaked in a solution containi ng the wastes in nitrate salt form. Neodymium oxide is used to simulat e the actinide oxides. We investigate the effect of the porous network features (mechanical strength, pore size) on the ability of the mater ial to soak up the simulating salts. Composite materials (silica glass + simulating oxide) have been synthesized with Nd2O3 content close to 10 wt%. (C) 1998 Elsevier Science B.V. All rights reserved.