Experimental and theoretical study on the heat flush method for helium isotope separation

As a rare strategic resource, He-3 has wide applications in critical fields such as national security, medicinal imaging, and frontier science. However, there is currently a global shortage of He-3. The heat flush method is a promising technology for helium isotope separation because of its simple structure and scalability. Nevertheless, existing studies have mainly focused on feed gases with low He-3 concentrations and have largely been limited to preliminary experiments, with insufficient systematic analysis of the separation mechanism and key operating parameters. To address these limitations, this study focuses on relatively high-concentration He-3 gas sources commonly associated with tritium systems and recovered gases, such as He-3/He-4 mixtures with an initial He-3 concentration of 0.5%. An analytical expression for the steady-state He-3 concentration distribution in the heat-flush tube was derived. A 1.4 K cryogenic experimental system was developed, achieving a maximum He-3 concentration of 52.1% with a corresponding recovery rate of 43.4%. By combining theoretical calculations with CFD simulations, the effects of bath temperature and heat flux on the separation performance were systematically investigated. These results provide both theoretical guidance and experimental support for optimizing the heat-flush process in practical applications.