An archaeological glass initially fractured and altered for 1800 years in a marine environment is now being examined by the CEA because of its strong morphological similarity to the nuclear glasses used for immobilization of long-lived radionuclides (i.e. the presence of fractures and cracks formed during cooling, which significantly increase the surface area accessible to water). The issue concerns glass alteration by water, and in particular the different behavior of the external surfaces in contact with a solution highly renewed and the internal surfaces, which constitute a much more confined medium.

The preliminary results of this study are discussed. The cracks in the archaeological glass have been filled by crystallized alteration products formed jointly by elements from the glass and elements dissolved in seawater. The glass is distinctly less altered (by a factor of 10 to 100) on the internal surfaces generated by the cracks than on the external surfaces. The forward glass dissolution rate was measured at different temperatures on pristine glass samples and under conditions that allowed us to estimate the dissolution rate of the external surfaces under realistic conditions at about 200 μm in 1800 years. The implications of this study are then discussed.