Thermodynamics of water sorption on PuO2: Consequences for oxide storage and solubility

Thermodynamic data for hydrous and anhydrous PuO2+x(s)

“…PuO 2 (cr) cannot be oxidised by O 2 (g) in the absence of H 2 O(l) or H 2 O(g) that is required to obtain a surface layer of hydrous oxide. The standard molar Gibbs energy for the hydration of the bulk PuO 2 (cr) is of course positive, but r G • m for surface hydration is negative [22]. Hence in the presence of both water and oxygen, PuO 2 (s) is partially oxidized to PuO 2+x (s) by reaction (2) as reported by Haschke et al [2,3].…”

Hydrothermal Growth and Thermal Property Characterization of ThO2 Single Crystals

“…5 Under anoxic conditions in the nuclear reactor chamber this can form H 2 gas. 6 Expansion of the gas can cause cracks to form in the fuel rod, which will inevitably increase the corrosion rate when the fuel is exposed to water or oxygen. 7 Once the fuel rod has been penetrated the formation of higher oxides of uranium is very likely.…”

“…It has been shown that thoria ceramics may have many surface defects which promote disassociation of water . Under anoxic conditions in the nuclear reactor chamber this can form H 2 gas . Expansion of the gas can cause cracks to form in the fuel rod, which will inevitably increase the corrosion rate when the fuel is exposed to water or oxygen .…”

Corrosion of UO2 and ThO2: A quantum-mechanical investigation

“…The presence of defects or the use of polycrystalline materials tends to favor the dissociation of water [19] which is important because the interaction of water with actinide-oxide surfaces (e.g. PuO 2 ) can potentially produce free H 2 gas under anoxic conditions via the dissociation of water [28]. Furthermore, once a fuel rod is breached, water can accelerate the corrosion process in an oxidizing environment [22,26] leading to the formation of higher oxide phases accompanied by volume changes, fuel cladding failure, and ultimately radionuclide release [24].…”