Sorption and fixation of biotoxic radionuclides on zeolites for decontamination of the spent fuel elements cooling medium

The batch adsorption of cesium and strontium radionuclides on natural zeolite (clinoptilolite) from Nizny Hrabovec (East Slovakia) was investigated with a view of decontamination of water from the long-time storage pool of spent fuel elements at the A-1 nuclear power plant at Jaslovske Bohunice. The sorption rate of strontium is slightly less than that of cesium but the equilibrium distribution ratio is fairly high for both elements (D=105 dm3kg-1). The adsorption follows the Freundlich-Langmuir isotherm, and batch adsorption of macroamounts of the ions can be optimized semi-empirically. The influence of competing ions (K+, Na+, Ca2+, Mg2+) should not prevent efficient sorption of the radionuclides in the course of pool water decontamination. A technological scheme with periodic batch adsorption and recirculation of the filtrate was proposed to minimize the necessary storage volume. Experiments with sorbent fixation in either bitumen or cement matrix indicated the cement matrix to be more suitable as regards radiation stability. The leaching properties of the cement-zeolite composite are satisfactory and meet the standards of the regional storage site at Mochovce. (author) 24 refs