Adsorption of Sr on electrochemical deconsolidation products of matrix graphite

Abstract

With the development of high-temperature gas-cooled reactor (HTGR), the disposal of its spent fuel elements will become an important factor that affects its industrialization. As one of alternative routes for head-end process of HTGR spent fuels’ reprocessing, electrochemical deconsolidation method separates TRISO fuel particles from matrix graphite (MG) and produces electrochemical deconsolidation product (EDP) with larger surface area than MG and abundant functional groups. In this paper, the chemical composition and structure of EDPs obtained in HNO3 with concentrations of 4%, 34% and 68% were studied, and the application of EDPs on strontium ions (Sr2+) adsorption was investigated. The results showed that EDP-4% with more carbonyl groups on the surface possessed the largest Sr2+ capacity of 44.8 mg/g at pH 5, while EDP-34% containing more hydroxyl and epoxy groups had the smallest capacity of 9.6 mg/g. The capacity for EDP-68% lay in the mid value of 19.5 mg/g. Density functional theory (DFT) calculations and adsorption experiments jointly evidenced that the type and amount of functional groups both significantly impacted the Sr2+ adsorption. The proposed adsorption mechanism provides theoretical foundation to evaluate the distribution of 90Sr during HTGR spent fuels’ electrochemical deconsolidating.