The Adsorption Behavior of the Fission Product of Cs and Graphite in the HTR-10 Primary Loop: Electronic Structure and Interaction Properties

Abstract

Understanding radioactive dust behavior is essential for nuclear safety assessments, particularly in high-temperature pebble-bed reactors. Current knowledge gaps in microscopic interaction mechanisms under extreme conditions have hindered progress in this field. Our study bridges this gap through systematic modeling of cesium-graphite systems, focusing on the adsorption behavior of cesium's predominant chemical forms (Cs₂, Cs₄, Cs₂CO₃, and CsOH) on graphite clusters, guided by thermodynamic predictions for reactor conditions. The results demonstrate that atomic cesium exhibits superior adsorption affinity due to dominant electrostatic interactions, while molecular forms (Cs₂CO₃/CsOH) show reduced adsorption capacity as their oxygen atoms create an energetic barrier that counteracts the combined effects of dispersion and electrostatic forces. Temperature-dependent analysis reveals atomic cesium remains stably adsorbed on graphite surfaces below 627 K. These findings provide both a predictive framework for fission product morphology in radioactive dust and fundamental insights into interfacial interactions that govern cesium adsorption behavior—critical knowledge for enhancing nuclear reactor safety protocols.