Aqueous leachability of lanthanide and plutonium titanates

The leachabilities of titanate and zircono-titanate solid solutions, Ce₂Ti₂O₇, Er_1.78Ce_0.22Ti₂O₇, Er_1.78Pu_0.22Ti₂O₇ (9.5 wt% Pu) Er_1.78Ce_0.22Ti_0.5Zr_1.5O₇, SrCe₂Ti₄O₁₂, SrPu₂Ti₄O₁₂ (50.7 wt% Pu) and Sr₂Ce₂Ti₅O₁₆, have been investigated in WIPP 'A' brine, 0.1 M NaCl, and 0.1 M HCl solutions using a modified MCC-3 procedure with a duration of 60 days. The concentrations of plutonium leached by the brine were less than 1 ppm. Where cerium was used as a surrogate for plutonium, its concentration in WIPP brine was below the limit of detection (10 ppm) established for the inductively coupled plasma (ICP) atomic emission spectrometer used. Concentrations of strontium leached by WIPP brine from stable strontium-containing titanate compounds, considered as possible immobilizers of both ⁹⁰Sr and actinide elements, were on the order of 30-60 ppm.