Evaluation of glass as a matrix for solidifying Savannah River Plant waste: properties of glasses containing Li2O

Properties of waste forms made of borosilicate glass containing Li2O combined with both simulated and actual Savannah River Plant (SRP) waste sludges were studied. The glass former, Frit 21, is presently the leading candidate for vitrifying SRP waste in a proposed process for long-term waste management. Devitrification of waste forms was inhibited by sludge components uranium and nickel, but was promoted by aluminum. Devitrification increased the leach rate of waste forms containing simulated sludges up to a factor of 20 in high-temperature leach tests and could be qualitatively correlated with the leach rate of waste forms containing actual sludges in room temperature tests. Room temperature leach rates were diffusion controlled throughout a 100-day test. Although sulfate solubility in Frit 21-sludge melts could be raised from 1 wt % to 2.5 wt % by slight modifications of the frit, this should not be necessary since Na2SO4 washes from actual sludges to levels below 0.5 wt %. It was demonstrated that waste forms can be dissolved in boiling 5M HNO3 if waste recovery becomes necessary. 13 figures, 12 tables