Aqueous corrosion of lanthanum aluminosilicate glasses: influence of inorganic anions

In order to confine specific long-life actinides, originating from high-level nuclear wastes, lanthanum aluminosilicate glasses are considered. The aqueous corrosion behavior of these glasses is studied under static conditions (T=96°C, duration between one and six months, glass surface area/leachate volume, S/V=0.3, 50 and 500 cm−1) by means of solution analysis (ICP-MS and spectrophotometry) and solid analysis (X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry). Tests performed at high S/V ratio lead to silicon releases of 10−3 moll−1 while lanthanum releases reach 10−4.5 moll−1. Phosphate anions are found to modify the dissolution, as an amorphous lanthanide phosphate is evidenced at the glass surface after the corrosion experiment. The lanthanide releases decrease in presence of phosphate, but the matrix dissolution process is not reduced.