The behaviour of waste glass was investigated under open site disposal
conditions. This glass was produced by vitrification of intermediate level
radioactive waste from nuclear power plants. Two types of borosilicate
glasses were obtained for two different reactor wastes, WWER and RBM.K.
Leaching and alteration mechanisms are discussed as well as the data
processing technique used for these long term tests. The decay of
radionuclides was accounted for in order to obtain correct results. The
leaching factors obtained can be used for the assesment of radionuclide
retention. Discontinuous leaching of Cs-137 has been observed during more
than 8 years testing time. The fluctuating leaching rate depends on glass
composition. The average leaching rate remains within (0.4 – 4) μg/sq.
Alteration of waste glass includes the formation of surface layers and
cracks on the glass surface. SEM analysis of glass was used to show these
surface layers. The thickness of the layers was determined to be within 2–6
μm. The structure of these layers depends on glass composition and the