Determining the redox and mechanism for incooperation of Cs into UO2 nanoparticles via HERFD XANES and EXAFS spectroscopy

In the present proposal, HERFD-XANES and EXAFS measurements are sort at BM20 to determine the chemical state and
mechanism of incorporation of caesium in UO2 nanoparticles. Such nanoparticles are found after a high burn-up time of UO2 and referred to
as high burnup structures (HBS) which is a part of spent nucleal fuel (SNF). Scanning electron microscopy (SEM) and Powder X-ray diffraction
(PXRD) measurements suggests incorporation of caesium into the crystal lattice. However, the mechanism for incorporation, particularly the
local chemical structure is unclear and will affect their stability in SNF disposal scenario, hence HERFD-XANES and EXAFS measurement are
sought on the U M4-edge and Cs L3-edge to determine changes. This work has implications for the storage and safety of SNF particularly in
the context of the “instance release fraction” in which caesium is a part of and to draw appropriate conclusions for the storage of SNF.