Influence of Alloying Elements and Chloride Concentration on the Galvanic Corrosion of Ferrous Alloys Coupled to Graphite for SMR Waste Applications

Abstract As the deployment of small modular nuclear reactors (SMR) in Canada approaches, waste management considerations become increasingly critical. This study investigates the potential degradation mechanisms during the initial dry storage phase of TRISO fuel waste storage containers. Specifically, this research explores the possible galvanic corrosion of the graphite outer casing of TRi-structural ISOtropic (TRISO) fuel and the carbon steel storage material, resulting from the ingress of air/water. Proximity to water sources can exacerbate corrosion, particularly due to the presence of Cl ions. Additionally, water radiolysis may lead to the formation of hydrogen peroxide and nitric acid, further influencing corrosion rates. This study examines the galvanic coupling between graphite and ferrous alloys under varying concentrations of NaCl to identify concentrations that may significantly impact material integrity. Electrochemical testing along with immersion testing were employed to determine the extent of galvanic coupling at varying NaCl concentrations.