Leaching and migration of Np, Pu and Am from alpha-doped SON68 HLW glass in contact with dense clay

In the frame of an integrated in situ test on the alteration of the SON68 reference glass in realistic disposal conditions, the leaching of Np, Pu, and Am from α doped SON68 glass samples and their migration in three different backfill materials at high density was measured. All backfill materials proved to be efficient barriers against radionuclide migration. The addition of powdered glass frit to Ca-bentonite clay decreased the glass alteration by two orders of magnitude, and resulted in a concomitant decrease of the radionuclide leaching in comparison with dried Boom Clay, which is the more agressive backfill. All actinides were selectively retained in the gel, but the retention degree was lower for Np than for Pu and Am.