Water degradation of glass waste forms has been studied extensively under a
variety of conditions including of bulk glass immersed completely in static or
dynamic water. In practice, the vitrified nuclear waste cracks as soon as poured
into a container because of differences in thermal expansion coefficients. In
addition, in repository the canisters may be only partially immersed in water.
Later, water condenses on the surface of glass which corrodes releasing ions. In
this work experiments have been performed to understand these effects on the
degradation of International Simple Glass (ISG). Simulated cracks were found to
develop pitting corrosion in the crack openings when tested by immersing ISG in
water. Under load, these pits concentrated stress and grew as large planar
cracks inside the glass. The condensation of water on glass surfaces leads to
formation of pits and growth of calcium silicate crystals.