Physical and mechanical characterization of irradiated uranium dioxide with a broad burnup range and different dopants using acoustic microscopy

Scanning acoustic microscopy is a non-destructive technique that allows determining the local material elastic properties by measuring the velocity of acoustic waves propagating in matter. High frequency acoustic waves are generated by a piezoelectric transducer, focused and then detected by the same transducer after having interacted with the sample. This technique has been employed in the past to assess different types of irradiated nuclear fuel and unirradiated chemical analogues of UO2 and it has enabled to relate the Rayleigh wave velocity of propagation with the Young's modulus and the density of the material. In the present study, thanks to new measurements on irradiated fuel and to analysis of data from the open literature, the variation of the density with burnup is determined up to ∼ 100 GWd·t−1M. The porosity is then determined taking account of the irradiated fuel matrix swelling. Finally, an expression is proposed describing Young's modulus as a function of burnup, that can be used in fuel performance calculation.