Speaker
Description
Radioactive wastes, especially high-level waste (HLW) and intermediate-level waste (ILW), generated predominantly in nuclear fuel cycles contain a wide variety of radionuclides including long-term radionuclides and the wastes contain also various chemicals, often complexation agents used for decontamination purposes. Due to the presence of large quantities of long-term radionuclides, HLW and ILW have to be stored in deep geological repositories. Design of such repositories has to ensure long-term isolation of radioactive waste from the biosphere. In order to satisfy this condition, multibarrier approach is applied. However, such an approach is not perfect, the fail is possible and therefore radionuclides might enter environment. The mobility of radionuclides in the environment is affected especially by their speciation. Knowledge of speciation is therefore crucial in terms of deep geological repository design and protection of the environment. Therefore, this work is focused on the study of complexation of europium commonly used as a chemical analogue of trivalent actinides. Disodium salt of ethylenediaminetetraacetic acid (EDTA), glycolic acid, succinic acid and phthalic acid were used as complexation agents and the study was performed by means of time-resolved laser-induced fluorescence spectroscopy method (TRLFS). Europium complexation with complexation agents mentioned above was studied with varying pH and in the case of succinic and phthalic acid also with varying ligand-to-metal ratio.
These experiments served as a basis for europium distribution diagrams acquistion, for determination of luminiscence spectra as a function of pH and ligand-to-metal ratio and the mean lifetime measurements were used for determination of number of water molecules surrounding europium, the mean lifetimes of resulting complexes and indentification of europium complexes. Finally, time-resolved luminiscence spectral characteristics of indentified complexes were determined and deconvolution of luminiscence spectra of the identified complexes was performed.
