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Journal Articles

Spin conversion reaction of spin-correlated ${it ortho}$-positronium and radical in liquids

Hirade, Tetsuya

Proceedings of 8th Asia Pacific Symposium on Radiation Chemistry (APSRC 2020) (Internet), 2 Pages, 2020/04

The positrons injected in insulating materials make ionization at the end part of the track, forming excess electrons and radicals. When one of the excess electrons and the incident positron form positronium, the electron in the positronium and the unpaired electron in the radical have a spin correlation. By using this spin correlation, a quantum beat phenomenon that depends on the hyperfine coupling constant of the radical appears in the spin conversion reaction with the positronium. The spin-correlated radical and other radicals can be distinguished by a reaction using the positronium as a probe. It is possible to study the behavior of OH radicals in water and the state of cation radicals in room temperature ionic liquids.

Oral presentation

Oxidative uranium dissolution from UO$$_{2}$$ in the presence of adsorbed phthalic acid

Kumagai, Yuta; Jonsson, M.*

no journal, , 

Contact of water with spent nuclear fuel is anticipated in scenarios of failure of the repository system for the direct disposal of spent fuel. Upon the direct contact of water, the UO$$_{2}$$ matrix of the fuel is expected to gradually dissolve due to oxidation of uranium by the action of ionizing radiation. In this study, we examined effects of organic acid on the UO$$_{2}$$ dissolution by using phthalic acid as a model compound. We investigated oxidation of UO$$_{2}$$ by exposure to H$$_{2}$$O$$_{2}$$ in aqueous solution containing phthalic acid. Significant adsorption of phthalic acid on UO$$_{2}$$ was observed. The coverage of the surface was estimated to reach 80 %. The H$$_{2}$$O$$_{2}$$-exposure experiments revealed that adsorbed phthalic acid has no significant effect on the redox reaction by H$$_{2}$$O$$_{2}$$ on the UO$$_{2}$$ surface, despite the high surface density. H$$_{2}$$O$$_{2}$$ oxidation of UO$$_{2}$$ with adsorbed phthalic acid resulted in U dissolution to similar extents with the U dissolution measured in aqueous bicarbonate solutions.

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