Fission product speciation across a UO2 spent nuclear fuel

This article presents the preparation, the realization and the results of the first X-ray absorption spectroscopy analysis of a bulky irradiated UO2 sample. The studied sample was taken from a high burnup fuel rod irradiated for 5 years in a nuclear reactor. HERFD-XANES spectra at the K edge of molybdenum and at the L3 edge of c AE sium were measured at different radial positions of the original pellet. Important information on the chemical forms of Mo in the spent fuel could be obtained: Mo is mainly in the form of two metallic phases, or in solution in UO2 , the nature of these dissolved species is discussed in details. At the Cs L3 edge, several experimental difficulties were encountered for this first experiment, and the data obtained, although promising, are more difficult to interpret. They show, nonetheless, that the c AE sium is in the same chemical form(s) in the center and on the periphery of the pellet, probably predominantly dissolved in UO2.

Automated summary

This article presents the preparation, the realization and the results of the first X-ray absorption spectroscopy analysis of a bulky irradiated UO2 sample. The study found that molybdenum in the spent fuel exists mainly in the form of two metallic phases or in solution in UO2, with detailed discussion on the nature of these dissolved species. At the cesium L3 edge, experimental difficulties were encountered, but the results indicate that cesium is likely predominantly dissolved in UO2 in both the center and periphery of the pellet.