Robert Mariani

The fuel cladding chemical interaction (FCCI) phenomenon is potentially the main factor restricting the application of metallic fuels in liquid sodium cooled fast reactors. The understanding of the lanthanide (Ln) transport behaviors in liquid Cs filled pores in U-Zr fuel is essential for understanding FCCIs. By using ab initio molecular dynamics, fundamental properties of the metallic system Cs-Ln, such as density of states and coordination number, have been studied. Then, the Ln diffusivities in liquid cesium and the solution viscosity were calculated. For validating the model, the viscosity of the pure liquid Cs which has been well measured is also calculated at three temperatures, which indicates the present model has a high accuracy in calculation of viscosity and self-diffusivity of Cs in liquid Cs.

For liquid-sodium-cooled fast nuclear reactor systems, it is crucial to understand the behavior of lanthanides and other potential fission products in liquid sodium or other liquid metal solutions such as liquid cesium-sodium. In this study, we focus on lanthanide behavior in liquid sodium. Using ab initio molecular dynamics, we found that the solubility of cerium in liquid sodium at 1000 K was less than 0.78 at. %, and the diffusion coefficient of cerium in liquid sodium was calculated to be 5.57 × 10−9 m2/s. Furthermore, it was found that cerium in small amounts may significantly alter the heat capacity of the liquid sodium system. Our results are consistent with the experimental results for similar materials under similar conditions.