'•'i Transport and Reaction Kinetics at the Glass Solution Interface Region: Results of Repository-oriented Leaching Experiments

MAP DE87 006975 Repository-oriented leaching experiments involving Savannah River Laboratory (SRL) 165 type glass under a 7-radiation field (1 * 0.2 x 104 R/h) have been performed by the Nevada Nuclear Waste Storage Investigations (NNWSI) project. In this communication, we discuss glass surface analyses obtained by SEM, nuclear resonance profiling, and SIMS together with leachate solution data 1n relation to a mechanism that couples diffusion, hydrolysis (etching and gelation), and precipitation to qualitatively describe the release of different glass components to the leachant solutions. The release of mobile (e.g., Li) and partly mobile (e.g., B) species 1s controlled primarily by Interdiffusion with water species across the Interdiffusion zone. Glass components that are immobile 1n the Interdiffusion zone are released to the solution by etching. For prediction of long-term steady-state concentrations of glass components with low solubility, the relative rates of release from the glass and secondary mineral precipitation must be taken Into account.