Samples of real irradiated (i-)graphite from bushings of RBMK reactor after several types of decontamination treatments were put in contact with aqueous solutions modelling underground water of Nizhnekansky massif (Russia) equilibrated with bentonite for periods up to 1.5 years. Leach rates of radionuclides and evolution of graphite surface morphology and oxidation state were monitored using nuclear spectroscopy, SEM and XPS. After the experiment, less than one third of surface carbons remains unoxidised. Extensive precipitation of secondary phases (alumosilicates, carbonates) was observed on some samples and is possibly correlated with surface oxidation extent. The leach rates of dose-forming 14C and 36Cl are comparable with the leach rates of radionuclides in glassy waste forms. According to the current study i-graphite could be regarded as a waste form, which is suitable for near-surface disposal.

Results of characterization of 238Pu-doped Eu- and La-monazites using single crystal XRD, Raman and XAFS spectroscopy and TEM are presented. It is shown that despite significant accumulated doses (up to 9x1018 α-decays/gram) the Eu-monazite remains a single crystal. Unusual foamy structures are observed by TEM and are interpreted as recrystallisation of domains damaged by recoil U-ions. Partial recrystallisation of the surface material is also supported by Raman and luminescence data.