Defect chemistry and radiation behaviour of Gd-doped UO₂

Ritesh Mohun

D. J. Bailey, S. Sun, C. Gausse, M. Cole, H. Smith, J. McCloy, M.H. Weber, M.C. Stennett, N.C. Hyatt & C.L. Corkhill

University of Sheffield & Washington State University


The irradiation behaviour of pure UO2 is rather well experimentally characterised, but little is known about the irradiation response of UO2 doped with fission products, such as rare-earth elements (REEs). In this study, we aimed to investigate the irradiation effects on trivalent REE-doped UO2 pellets in an attempt to predict whether the structural stability of spent nuclear fuels is altered by the radiation damage from alpha decay during the long-term storage in geologic repositories. The objective was first to quantify the defect chemistry when Gd-dopant, at concentrations ranging from 8 to 15 mol.%, is introduced in the UO2 matrix, and then to investigate how the intrinsic defect configuration is changed when these solid solutions are exposed to 1 MeV Kr-ion irradiation conditions.
For this purpose, several Gd-doped UO2 pellets were prepared through the wet chemistry co-precipitation route, and SEM images revealed a significant modification of the initial UO2 microstructure induced by the incorporation of the dopant. The lattice defect chemistry was then studied by means of X-ray diffraction, XANES and Raman spectroscopy, and allowed us to quantify the presence of both U5+ species and oxygen vacancy-type defects formed to compensate for the charge.
Post-irradiation measurements were performed and highlighted the excellent radiation stability of fluorite-type nuclear fuels. Positron annihilation spectroscopy was used to compare the irradiation response of UO2 and the Gd-doped solid solutions and also to investigate the effect of microstructure on the irradiation-induced lattice defects. In this talk, an attempt is made to detail the relevant mechanisms occurring near the defect-boundary interfaces to highlight the precise role of dopant and grain boundaries modifying the defects behaviour and their subsequent evolution in fluorite structure relevant to nuclear fuels.

Event Timeslots (1)

Thursday – 16th September 2021
Ritesh Mohun