Static and dynamic leach tests with depleted and alpha doped UO2 in contact with three kind of alkaline solutions (pH 11.7 to 13.5) were performed to estimate the spent fuel dissolution rate in the high pH conditions of the Belgian Supercontainer concept. In this paper, results are entirely focused on static tests with depleted and alpha doped UO2. We observe (1) Dissolved concentrations increase with pH due to peroxidised U(VI), more soluble at higher pH (2) Ultrafiltred concentrations at 10-9 to 10-7 mol.L-1 seem undersaturated with Ca-uranate at all pH, but ultrafiltred U(IV) is probably only a small fraction of the total ultrafiltred concentration, (3) Colloid concentrations are high at 10-6 to 10-4 mol.L-1, presumably U(IV), (4) Alpha radiation causes higher oxidative dissolution with an increase of total uranium release in solution, (5) No effect of metallic iron at high pH, (6) Oxidative dissolution may be important for longer time at high pH, because of the weak reducing capacity of high ph solutions, (7) non-oxidative dissolution may be accelerated by colloids, (7) Long term dissolution rate still difficult to assess.
|Conference||Cementitious Materials in Safety Cases for Geological Repositories for Radioactive Waste: Role, Evolution and Interactions|
|Period||2009-11-17 → 2009-11-20|