Plasma fueling efficiency and fuel cycle implications for a fusion pilot plant

A fusion pilot plant with high fusion power will require high DT fuel burn efficiency that is dependent on efficient fueling and the ability to efficiently pump the plasma exhaust neutrals including the helium fusion byproduct and any impurities. The DT burn fraction is strongly affected by the global recycling and the fueling efficiency. Recycling is anticipated to be lower in a burning plasma that present day experiments due to the hotter edge and dense scrape off layer limiting the ionization to mostly occurring outside the separatrix. The fueling efficiency can be influenced by the reactor design to use high speed pellets that can penetrate into hot burning plasmas and utilize the gradB and curvature drift to maximize the fuel deposition depth. The pumping of exhaust gas will require a pumping system that has a helium pumping speed comparable to the hydrogenic pumping speed. A continuous cryopump has been developed that demonstrates this capability and is a candidate for future pilot plan deployment. rocessing of the exhaust gas and efficient recirculation must be carefully designed into the fusion pilot plant fuel cycle in order to keep the plant DT inventory at manageable levels. Impurities from the plasma must be effectively separated from the exhaust in order to recirculate the unburned fuel. Makeup of burned DT has to be done in real time to maintain the appropriate isotopic mix. A concept for the entire plasma fuel cycle that meets these requirements is presented.