Americium and trivalent Lanthanides incorporation in high-level waste glass-ceramics

International audienceThe incorporation and partitioning of americium and trivalent lanthanides were investigated in aluminoborosilicate glass-ceramics with apatite-like silicate crystals of general formula Ca$_2$(Ln,Am)$_8$(SiO$_4$)$_6$O$_2$. A microstructural and structural study of two glass-ceramics containing Am$_2$O$_3$ - La$_2$O$_3$ or Nd$_2$O$_3$ - La$_2$O$_3$, respectively, was carried out by XRD, SEM-EDS and EMPA so as to assess a comparison of Lanthanides and Actinides partitioning into apatite crystals and residual glass. Moreover, Raman analyses of residual glasses were performed to compare the role of Am and Nd on the glassy structure. Results put forward that shape, composition, Ln-Am stoichiometry and cell parameters of apatite crystals of both (Am-La) and (Nd-La) glass-ceramics are very close. This paper thus shows similar results for (Am-La) and (Nd-La) glass-ceramics in terms of apatite - glass partitioning and in terms of structural role on glassy structure. It can be therefore put forward that Nd$^{3+}$ and Am$^{3+}$ behaviors are close, either in the glass or in the crystalline structure