Comparing the Corrosion of Uranium Nitride and Uranium Dioxide Surfaces with H2O2

TL;DR

This study compares the corrosion rates of uranium nitride and uranium dioxide surfaces under simulated radiolytic water conditions, revealing that UN corrodes more slowly than UO2, which has implications for nuclear fuel safety.

Contribution

It provides the first comparative analysis of radiolytic corrosion rates of UN and UO2 using H2O2 as a water radiolysis surrogate.

Findings

UN has a lower corrosion rate than UO2 in 0.1 M H2O2.

Corrosion rates measured were 0.020 and 0.083 A/s for UN and UO2, respectively.

U2N3 shows a much higher corrosion rate, indicating different stability profiles.

Abstract

Uranium mononitride, UN, is considered a potential accident tolerant fuel due to its high uranium density, high thermal conductivity, and high melting point. Compared with the relatively inert UO2, UN has a high reactivity in water, however, studies have not considered the significant effect of radiation, which is known to cause corrosion of UO2. This study uses 0.1 M H2O2 to simulate the effects of water radiolysis in order to compare the radiolytic corrosion rates of UO2, UN, and U2N3 thin films at room temperature. X-ray reflectivity was used to investigate the changes in film morphology as a function of H2O2 exposure time, allowing changes in film thickness and roughness to be observed on the Angstrom length-scale. Results showed significant differences between UO2, UN, and U2N3, with corrosion rates of 0.083(3), 0.020(4), and 0.47(8) A/s, respectively, showing that UN corrodes more slowly than UO2 in 0.1 M H2O2.