Fabrication, defect chemistry and microstructure of Mn‑doped UO2

Mn-doped UO2 is under consideration for use as an accident tolerant nuclear fuel. We detail the
synthesis of Mn-doped UO2 prepared via a wet co-precipitation method, which was refned to
improve the yield of incorporated Mn. To verify the Mn-doped UO2 defect chemistry, X-ray absorption
spectroscopy at the Mn K-edge was performed, in addition to X-ray difraction, Raman spectroscopy
and high-energy resolved fuorescence detection X-ray absorption near edge spectroscopy at the
U M4-edge. It was established that Mn2+ directly substitutes for U4+ in the UO2 lattice, accompanied
by oxygen vacancy (Ov) charge compensation. In contrast to other divalent-element doped UO2
materials, compelling evidence for U5+ in a charge compensating role was not found. This work
furthers understanding of the structure and crystal chemistry of Mn-doped UO2, which could show
potential advantages as a novel efcient advanced nuclear fuel.