Multiscale modeling of fission gas behavior in U3Si2 under LWR conditions

In this work, we present a model of fission gas behaviour in U3Si2 under light water reactor (LWR) conditions for application in engineering fuel performance codes. The model includes components for intra-granular and inter-granular behaviour of fission gases. The intra-granular component is based on cluster dynamics and computes the evolution of intra-granular fission gas bubbles and swelling coupled to gas diffusion to grain boundaries. The inter-granular component describes the evolution of grain-boundary fission gas bubbles coupled to fission gas release. Given the lack of experimental data for U3Si2 under LWR conditions, the model is informed with parameters calculated via atomistic simulations. In particular, we derive fission gas diffusivities through density functional theory calculations, and the re-solution rate of fission gas atoms from intra-granular bubbles through binary collision approximation calculations. The developed model is applied to the simulation of an experiment for U3Si2 irradiated under LWR conditions available from the literature. Results point out a credible representation of fission gas swelling and release in U3Si2. Finally, we perform a sensitivity analysis for the various model parameters. Based on the sensitivity analysis, indications are derived that can help addressing future research on the characterization of the physical parameters relative to fission gas behaviour in U3Si2. The developed model is intended to provide a suitable infrastructure for the engineering calculation of fission gas behaviour in U3Si2 that allows for exploiting a multiscale approach to fill the experimental data gap and can be progressively improved as new lower-length scale calculations and validation data become available.

BARANI Tommaso;  PASTORE Giovanni;  PIZZOCRI Davide;  ANDERSSON David;  MATTHEWS C.;  ALFONSI A.;  GAMBLE K.A.;  VAN UFFELEN Paul;  LUZZI Lelio;  HALES Jason; 

2019-09-10

ELSEVIER SCIENCE BV

JRC114572

0022-3115 (online),   

https://publications.jrc.ec.europa.eu/repository/handle/JRC114572,   

10.1016/j.jnucmat.2019.04.037 (online),