Study on Influence of Increase in Surface Area by Cracking on Glass Dissolution for HLW Performance Assessment

Ebina, Takanori*; Makino, Hitoshi 

Cracking of the glass that occurred during cooling in the vitrification process would cause increase in surface area of vitrified wastes and potential impact of the cracking on glass dissolution have been discussed.In the current performance assessments of HLW,increase in glass dissolution has been assumed to proportionate to increase in the surface area.On the other hand,leaching experiments on a full-scale simulated glass block with numerous cracks have shown that only a fraction of the crack surface contributed to glass dissolution. In this study,we developed a simple model and carried out sensitivity analysis for influence of increase in surface area on glass dissolution. Results show that increase in surface area in a fractured glass block does not impact on glass dissolution proportionately.Instead of surface area,ratio of the outside surface area and aperture of fractures that could control diffusion behavior through fracture have impact on glass dissolution.Under the condition of leaching experiments on a full-scale simulated glass block with numerous cracks,a few times increase in glass dissolution was estimated by the developed model,and that was consistent with the experimental results.