Removal of nitrogen oxides, volatile radionuclides and aerosols formed in laboratory-scale denitration, calcination and solidification of simulated high-level wastes

An apparatus and procedure for the purification of gaseous effluents formed in the denitration, calcination and solidification of simulated high-level wastes were proposed and tested in a laboratory-scale apparatus. The purification procedure consisted of absorption and decomposition of nitrogen oxides, sorption of 106RuO4 and 137Cs vapour, and filtration of 106Ru, 137Cs and 85Sr aerosols. The absorption solution used was ammonium oxalate. As an inorganic sorbent silica-gel was used, as well as molecular sieves, ceramics and charcoal. A high efficiency filter made of glass and organic polymer (perchlorvinyl) microfibres, and a prefilter made of glass fibres, were used for filtration. In addition to the laboratory-scale apparatus for absorption and decomposition of the nitrogen oxides, a semipilot-plant-scale apparatus was proposed and constructed. By successive absorption, adsorption and filtration processes the concentrations of 106Ru, 137Cs and 85Sr were reduced by more than 4, 4 to 6 and more than 3 orders of magnitude, respectively; the efficiency of the removal of nitrogen oxides was 95 to 100%. (author)