Reactivity of Ru oxides with air radiolysis products investigated by theoretical calculations

Quantitative predictions of the release volatile radiocontaminants ruthenium (Ru) in environment from either nuclear power plants (NPP) or fuel recycling accidents present significant uncertainties while estimated by severe analysis codes. Observations Ru experimental modeling works suggest that main limitations relate to poor evaluation kinetics gaseous form RuO$_3$ and RuO$_4$. This work presents relativistic correlated quantum chemical calculations performed determine possible reactions pathways leading formation oxides under NPP accident conditions, as a result RuO$_2$ with air radiolysis products, namely nitrous nitrogen oxides. The geometries relevant species were optimized TPSSh-5%HF functional density, total electronic energies computed at CCSD(T) level extrapolations complete basis set CBS limit. reaction fully characterized localizing transition states all intermediate structures using internal coordinate algorithm (IRC). rate constants determined over temperature range 250-2500 K. It is revealed less kinetically limiting pathway fraction oxidation oxide, corroborating observations.