Structural and phase evolution in U3Si2 during steam corrosion

• Published in: Corrosion science 2022-08, Vol.204, p.110373, Article 110373
• Main Authors: Liu, Jiatu, Burr, Patrick A., White, Joshua T., Peterson, Vanessa K., Dayal, Pranesh, Baldwin, Christopher, Wakeham, Deborah, Gregg, Daniel J., Sooby, Elizabeth S., Obbard, Edward G.
• Format: Article
• Language: English
• Subjects: A: Intermetallics; B: modelling studies; C: effects of strain, hydrogen absorption, oxidation, reactor conditions; Corrosion; Density functional theory; Deuteration; Grain boundaries; Neutron diffraction; Nuclear fuels; Uranium dioxide; Uranium silicide
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2022.110373

U3Si2 nuclear fuel is corroded in deuterated steam with in situ neutron diffraction. Density functional theory is coupled with rigorous thermodynamic description of the hydride including gas/solid entropy contributions. H absorbs in the 2b interstitial site of U3Si2Hx and moves to 8j for x ≥ 0.5. Hydriding forces lattice expansion and change in a/c ratio linked to site preference. Rietveld refinement tracks the corrosion reactions at 350–500 °C and preference for the 8j site. Above 375 °C, formation of UO2, U3Si5 and USi3 take place in the grain boundaries and bulk. Hydriding occurs in bulk and precedes other reactions. [Display omitted] •In situ neutron diffraction measures U3Si2 corrosion in deuterated steam.•Rigorous thermodynamic description of hydride using key entropy contributions.•H absorption at 2b interstitial site of U3Si2Hx, moves to 8j site for x ≥ 0.5.•From 350 °C, U3Si2Hx fragmented by 1–2% anisotropic lattice expansion.•From 375 °C, UO2, U3Si5 and USi3 form in bulk and in grain boundaries.