SIMULANT EVAPORATION TRIALS TO SUPPORT AWE'S NEW RADIOACTIVE AQUEOUS WASTE TREATMENT PLANT

AWE's future radioactive aqueous wastes are to be treated by evaporation followed by encapsulation of the concentrates in cement for disposal. Pilot-scale trials using simulants were conducted to test the principle of this new operation. The simulants contained soaps and other surface active agents, and several inorganic species including calcium, magnesium, bicarbonate, chloride, sulphate, phosphate, silicate, and also for the third trial uranium, barium and strontium. It was found that the simulants could be concentrated to at least 20% w/w solids without undue problems due to corrosion or scaling. Foaming was encountered, and this was controlled with an anti-foam comprising a blend of synthetic waxes and non-ionic surfactants in a highly refined mineral oil. A silicone anti-foam was found to be ineffective, and there were indications that it promoted the coagulation of the suspended solids.