A theoretical study of Ti nanoparticle effect on sodium water reaction: Using ab initio calculation

• We report effectiveness and possible mechanisms of Na atom and Ti nanoparticle surface interaction to the sodium water reaction.
• Chemical interaction between Na atom and Ti nanoparticle surface was evaluated by ab initio calculation with density functional theory.
• Covalent like metallic Na adsorbed atomic layer onto Ti(0 0 0 1) surface was found and its strength was evaluated as 1.65 eV.
• We postulate that strong chemical interaction between Na atoms and Ti NP surface increase both hydration energy and activation energy required initiate SWR.

The sodium–water reaction (SWR) is a serious impediment to development of sodium fast cooled nuclear reactors. The reaction can be suppressed by suspending 2 at% of 10-nm Ti nanoparticles (NPs) in liquid Na, but the mechanisms by which the Ti NPs suppress the SWR are not known. In this study, ab initio calculation revealed a strong chemical bond with interaction strength 1.65 eV (64.5 kT at 298 K) between Na atoms and the Ti NP surface. We postulate that this interaction with Ti atoms causes a layer of Na atoms to form on the Ti NP surface, and that this layer increases both hydration energy and the activation energy required to initiate SWR. As a result, these interactions suppress the SWR by reducing effective reaction area.