Leaching behaviour of Cs, Sr, and Eu nitrates from Fe-rich polymers: Influence of precursor composition, presence of CeO2 nanoparticles, and the effect of high-dose gamma irradiation

Abstract

The extended half-lives and potential for environmental contamination of radionuclides in liquid nuclear waste make radioactive waste management a major concern for society and the nuclear industry. One prospective solution for efficiently managing liquid nuclear waste is the use of Alkali-Activated Materials (AAMs). The immobilisation ability of AAMs largely depends on their composition and the effect of the introduced radionuclides on the structure itself. The purpose of this work is to investigate the leaching behaviour of radioactive simulants such as strontium (Sr), caesium (Cs), and europium (Eu) nitrates from iron-rich slag-derived AAM samples, explore the impact of CeO2 nanoparticles`nanoparticles`presence as well as the effects of gamma irradiation on the structure and leachability of the contaminants. CeO2 nanoparticles are investigated for preconcentrating radionuclides from liquid nuclear waste and have been previously used in isolating and absorbing Eu 3+. Samples received a cumulative dose of 6.5 MGy of radiation from a cobalt-60 (60 Co) source. Potential changes in mechanical characteristics and microstructure were investigated by SEM analysis and nanoindentation. The leaching tests revealed significant variability in the release of elements such as Fe, Na, Al, Cs, Sr, Eu, and Ce across different samples, influenced by the slag composition and the presence of CeO₂ nanoparticles. No appreciable variations were observed in the dopant or structural element releases from the irradiated and non-irradiated samples. Irradiation had no effect on the materials' hardness and a limited effect on elastic modulus. From this perspective, the produced AAMs are suitable candidates for nuclear waste immobilisation.