The Interaction Between Nuclear Waste Glass and Ordinary Portland Cement

Abstract

The interaction between simulated reference waste glasses SON68 and SM539, and cement has been studied in suspensions of ordinary Portland cement and synthetic cement water with pH 13.5 at 30°C. The cement appears to trigger glass dissolution by consumption of glass matrix components. This leads to fast glass dissolution at a constant rate with formation of a porous gel layer on the glass. A glass dissolution model has been proposed considering that the silicon coming from the glass reacts with portlandite to form C‐S‐H phases. The transformation of C‐S‐H into C‐A‐S‐H phases is a second parallel driving force especially for the Al‐rich SM539 glass. After consumption of the portlandite, the glass alteration rate is expected to decrease.

Transport- and surface reaction-controlled SON68 glass dissolution at 30°C and 70°C and pH=13.7

“…On one hand, a high pH will accelerate the hydrolysis of the silicate network; on the other hand, Ca can improve the long-term durability of glass due to formation of a passivating Ca-enriched gel layer at the glass interface (Utton et al, 2013;Chave et al, 2011). However, Ca can also promote glass alteration (Rajmohan et al, 2010;Gin et al, 2012;Ferrand et al, 2013). At a high surface-area-to-volume ratio of 10,000 m À1 , Ca reduced the initial dissolution of rate of UK HLW glass by an order of magnitude (Corkhill et al, 2013).…”

“…The effect of Ca in YCWCa containing cement powders with different cement to glass ratios has been studied by Ferrand et al (2013). In Ferrand et al (2013), cement powders served as a Ca reservoir.…”

“…In Ferrand et al (2013), cement powders served as a Ca reservoir. As long as the solution was saturated with respect to portlandite, the leaching rate of the glass dissolution indicator, Li, decreased with the decrease of Ca concentration in the solution.…”

“…When the Ca concentration was below 0.4 mmol/L, the Li release rate became constant. However, due to conglomeration of the cement and glass powders (Ferrand et al, 2013;Andriambololona et al, 1992), it is difficult to relate glass alteration rate to the amount of cement. It should be noted that despite this promoting effect of Ca, glass corrosion rate is well below the value that could be expected from the same pH in the absence of Ca (Andriambololona et al, 1992).…”

“…In the experiments with cement powders (Ferrand et al, 2013) due to B sorption onto cement, Li concentration in the solution was used as a dissolution indicator. In the model, if the solution became super-saturated with respect to a secondary phase, after each dissolution timestep this phase could precipitate out of the solution.…”