Monitoring of alpha-decay radiation damage in a 241Am-doped glass-ceramic material

The evolution under alpha-decay radiation of a 241 Am doped aluminoborosilicate glass-ceramic was in-vestigated in hot cells DHA-ATALANTE facility in CEA. The cumulative La2O3 -Am2O3 solubility limit was voluntarily exceeded, leading to the formation of apatite-like silicate crystals. The crystals, with a hexagonal-shaped morphology, that is characteristic of apatite crystals, have a composition and a cell pa-rameter close to those expected for an apatite phase of stoichiometric composition Ca2(La,Am)8(SiO4)6O2. Structural and microstructural evolutions under alpha self-irradiation were followed for 8 years by regu-larly analyzing the crystals and the residual glassy matrix. The evolution of the X-Ray Diffraction (XRD) patterns is the result of a progressive radiation-induced amorphization in apatite crystals. The fully amor-phous state is reached at an alpha-decay dose of around 3 x 10 18 alpha/g. Raman analyses suggest a modi-fication of the connectivity of the SiO4 tetrahedra of apatite crystals, with a transition from isolated SiO4 units in the crystalline state to connected SiO4 units in the metamict state. The crystalline-to-amorphous transformation is accompanied by an increase in macroscopic volume (swelling), highlighted by RAMAN imaging. This macroscopic dimensional change is also associated to a decohesion of the crystals from the glassy matrix, observed by Scanning Electron Microscopy (SEM). However, optical and SEM images of the glass-ceramic surface do not reveal any significant cracks in the residual glass under alpha self-irradiation, thus showing a quite good stability of this glass-ceramic material.(c) 2023 Published by Elsevier B.V.