Lottie Harding¹

Gary Wan¹, Jude Laverock¹, David T Goddard², Ross Springell¹

¹University of Bristol;

²National Nuclear Lab.

Abstract

Advanced Technology Fuels (ATFs) are a key concept in the drive to improve overall performance and safety in the nuclear industry. The 2011 Fukushima Daiichi accident highlighted the thermal limitations of the current UO₂-Zr system and, as such, significant effort is being invested in researching advanced fuels with improved thermal conductivities.

Uranium silicide (U₃Si₂) has been highlighted as a potential ATF, having improved thermal properties and increased uranium densities when compared with UO₂ [1]. However, there are significant discrepancies within the literature regarding the corrosive properties of U₃Si₂. Some studies indicate that uranium preferentially oxidises, resulting in a U-Si fuel type with a higher Si content [2, 3]. Whereas other studies suggest the formation of a uranium silicate, USiO₄ [4]. Understanding the surface oxidation is vital for assessing the structural integrity of the fuel, and is beneficial for dissolution studies. Furthermore, conducting analysis on this material is challenging, as the process required to produce U₃Si₂ in the bulk often results in the formation of multi-phased silicides [5,6]. In this regard, thin films offer significant potential, providing idealised surfaces on which single parameter studies can be conducted. Through varying the growth parameters, stoichiometry, grain size, and crystallographic orientation can also be controlled.

Here we present an investigation into the ambient corrosion of uranium silicide single crystals. Using DC magnetron sputtering, the U-Si phase diagram has been delicately mapped as a function of uranium content. The corrosion of U₃Si, U₃Si₂, U₃Si₅, USi₂¸ and USi₃ surfaces has been probed using x-ray diffraction and x-ray photoelectron spectroscopy; allowing for the oxidation thickness to be measured, and for an investigation into the dissolution behaviours to be observed. These studies have been vital in understanding the oxidation products that form on U-Si phases as a function of uranium content.

References

[1] K.A Terrani et al., Journal of Nuclear Materials, 512-519, 448, (2014)
[2] E. Jossou, et al., Physical Chemistry Chemical Physics 20.7, 4708-4720, (2018)
[3] J. H. Yang et al. ,Journal of Nuclear Materials 542, 152517, (2020)
[4] T Yan et al., Journal of Nuclear Materials 520, 1-5, (2019)
[5] Ki Hwan Kim et al., Journal of nuclear science and technology, (1997)
[6] J. Harp et al., Journal of Nuclear Materials, 728-738, (2015)
“

Event Timeslots (1)

Thursday – 16th September 2021
2:20 pm - 2:40 pm
Lottie Harding