Sorption characteristics of ferrocyanide nanoparticles to metal ions in nitric acid solution for development of vitrification processes of high level radioactive nuclear wastes
J. Onoe, S. Watanabe, M. Harigai, Y. Inaba, and K. Takeshita
Nagoya University, Tokyo Institute of Technology
Abstract
High-level radioactive nuclear liquid wastes (HLLW: radioactive metal ions in 2 M nitric acid solution) are generated in the reprocessing of spent nuclear fuels or in the decommissioning of nuclear reactors. In the process of producing the vitrified objects containing the wastes by using a glass melter, platinum-group metals (PGMs) [especially, ruthenium (Ru), rhodium (Rh), and palladium (Pd)] and molybdenum (Mo) cause serious problems: PGMs tend to be accumulated on the sidewall surface of the melter, whereas Mo compounds, so called yellow phase, are formed in the vitrified object. These issues result in (i) degradation of vitrified objects due to heterogenization and (ii) an increase in both disposal space and processing costs in conjunction with additional vitrified rods obtained by flushing the glass melter. To solve these issues, we have developed a process for efficient removal of PGMs and Mo from HLLW prior to introducing into the glass melter, using metal hexacyanoferrates (HCF) as a sorbent [1-3]. It is important to reveal the sorption mechanisms of PGMs and Mo for design of high performance HCF sorbents. In this talk, we will present the results on the sorption characteristics of Prussian blue (PB) nanoparticles, one of the HCFs, to the above metal ions in nitric acid solution, obtained using various spectroscopies and first-principles calculations. [1] S. Watanabe et al., J. Appl. Phys. 119, 235102 (2016). [2] S. Watanabe et al., AIP Adv. 8, 045221 (2018). [3] S. Watanabe et al., Chem. Phys. Lett. 723, 76–81 (2019).
Keywords: ferrocyanide nanoparticles, sorption characteristics, nuclear wastes, vitrification processes
Topic: DV-Xa Method