Modeling hydrogen and helium entrapment in flowing liquid metal surfaces as plasma-facing components in fusion devices

In a fusion reactor, the ability to use liquids as plasma-facing components (PFCs) depends on their interaction with the plasma and the magnetic field. One important issue for the moving liquid is the ability to entrain particles that strike the PFC surface (helium and hydrogen isotopes) while accommodating high heat loads. To study this problem, an analytical model and a two-dimensional comprehensive numerical model have been developed and implemented in the HEIGHTS computer simulation package. The models take into account the kinetics of particle injection, motion and interactions with the liquid lattice, and the ultimate release from the surface. The models were used to investigate an important issue, whether He particles can be pumped by the PFC liquid rather than requiring a standard vacuum system. Hydrogen isotope (DT) particles that strike the surface will likely be trapped in the liquid-metal surface (e.g., lithium) due to the high chemical solubility of hydrogen. The impinging He particles in the established low-recycling regime at PFCs could be harder to pump using the standard vacuum pumping techniques. The analysis results indicate a reasonable chance of adequate helium self-trapping in flowing lithium as PFC without active pumping. (C) 2002 Published by Elsevier Science B.V.