The supercritical carbon dioxide (S-CO₂) Brayton cycle, coupled with a sodium-cooled fast reactor (SFR), has been identified as a new and innovative energy conversion technology that could contribute to improving the economics of advanced nuclear energy. For these reactors, a new generation of compact, highly-efficient heat exchangers (HXs) will be employed that show great promise in improving the safety and cost of SFRs; however, small HX leaks could still occur. SNAKE is designed to study S-CO₂ leakage into sodium.