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Journal Articles

Impact of stoichiometry on the mechanism and kinetics of oxidative dissolution of UO$$_{2}$$ induced by H$$_{2}$$O$$_{2}$$ and $$gamma$$-irradiation

Kumagai, Yuta; Fidalgo, A. B.*; Jonsson, M.*

Journal of Physical Chemistry C, 123(15), p.9919 - 9925, 2019/04

 Times Cited Count:20 Percentile:63.7(Chemistry, Physical)

Radiation-induced oxidative dissolution of uranium dioxide (UO$$_{2}$$) is one of the most important chemical processes of U driven by redox reactions. We have examined the effect of UO$$_{2}$$ stoichiometry on the oxidative dissolution of UO$$_{2}$$ induced by hydrogen peroxide (H$$_{2}$$O$$_{2}$$) and $$gamma$$-ray irradiation. By comparing the reaction kinetics of H$$_{2}$$O$$_{2}$$ between stoichiometric UO$$_{2.0}$$ and hyper-stoichiometric UO$$_{2.3}$$, we observed a significant difference in reaction speed and U dissolution kinetics. The stoichiometric UO$$_{2.0}$$ reacted with H$$_{2}$$O$$_{2}$$ much faster than the hyper-stoichiometric UO$$_{2.3}$$. The U dissolution from UO$$_{2.0}$$ was initially much lower than that from UO$$_{2.3}$$, but gradually increased as the oxidation by H$$_{2}$$O$$_{2}$$ proceeded. The $$gamma$$-ray irradiation induced the U dissolution that is analogous to the kinetics by the exposure to a low concentration (0.2 mM) of H$$_{2}$$O$$_{2}$$. The exposure to higher H$$_{2}$$O$$_{2}$$ concentrations caused lower U dissolution and resulted in deviation from the U dissolution behavior by $$gamma$$-ray irradiation.

Oral presentation

H$$_{2}$$O$$_{2}$$ and $$gamma$$-ray induced oxidative dissolution of stoichiometric UO$$_{2.0}$$

Kumagai, Yuta; Fidalgo, A. B.*; Jonsson, M.*

no journal, , 

We have investigated the effect of UO$$_{2}$$-hyper-stoichiometry on the oxidative dissolution upon H$$_{2}$$O$$_{2}$$ exposure and by water radiolysis. The oxidative dissolution of UO$$_{2}$$ is anticipated in the concept of geological disposal of spent nuclear fuel and also in the direct contact with coolant water after a severe accident. However, our understanding on the dissolution kinetics has so far not taken the hyper-stoichiometric nature of UO$$_{2}$$ into account. Thus, we have studied the oxidative dissolution of hyper-stoichiometric UO$$_{2.3}$$ and stoichiometric UO$$_{2.0}$$ and compared the results. The results show that the UO$$_{2}$$ stoichiometry largely affects the kinetics of oxidative dissolution. The oxidation of stoichiometric UO$$_{2.0}$$ in water proceeded fast accompanied with low initial U dissolution, but gradually the reaction became slower and U dissolution became more significant.

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