Impact of platinum group metals (Ru, Pd, Rh) on the dissolution of UO2

Abstract

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Impact of ruthenium metallic particles on the dissolution of UO2 in nitric acid

“…Therefore, the catalytic effect observed in both media was attributed to the presence of the Ru 0 nanoparticles in contact with UO 2 in this system. Similar conclusions were already stated by Cordara et al 17 when studying the dissolution kinetics of UO 2 pellets incorporating 3 mol.% of Ru particles under the same experimental conditions. However, according to Cordara et al 17 , the relative mass loss of UO 2 + 3 mol.% Ru pellet reached 19% after 20 days of dissolution in 0.1 mol L −1 HNO 3 solution at 60 °C against 90% in this work.…”

“…Similar conclusions were already stated by Cordara et al 17 when studying the dissolution kinetics of UO 2 pellets incorporating 3 mol.% of Ru particles under the same experimental conditions. However, according to Cordara et al 17 , the relative mass loss of UO 2 + 3 mol.% Ru pellet reached 19% after 20 days of dissolution in 0.1 mol L −1 HNO 3 solution at 60 °C against 90% in this work. The authors assumed that the positive impact of the PGM particles on the dissolution kinetics of UO 2 was linked to the reduction of nitrate ions to NOx at the particles/solution interface.…”

“…Ikeda et al 16 showed a significant increase in the dissolution rate of UO 2 powder in concentrated nitric acid (8 mol L −1 ) at 60 °C and in the presence of PGM metallic particles (0.09 wt.% of each element). More recently, Cordara et al 17 performed a multiparametric study on the dissolution of standard UO 2 pellets and pellets doped with 3 mol.% of PGM particles (1.1 mol. % Ru; 1.6 mol.% Rh and 0.3 mol.% Pd).…”

“…This reaction was slow, but it produced nitrogen species more oxidising than nitrates with respect to UO 2 leading to a strong acceleration of dissolution in the next kinetic step. The presence of PGM particles not only reduced the duration of the induction period, but also drastically changed the apparent activation energy of the dissolution reaction (from 87 ± 8 kJ mol −1 to 35 ± 12 kJ mol −1 ) 17 . This result traduced the change of the UO 2 dissolution mechanism caused by the presence of the PGM particles.…”

“…These particles were then introduced in suspension during UO 2 dissolution experiments. The dissolution experiments were performed in 0.1 mol L −1 HNO 3 at 60 °C, which corresponded to the conditions of the strong impact of Ru particles according to Cordara et al 17…”