Vapor condensation study for HIF liquid chambers

Abstract

This paper presents the experimental study of transient cooling and condensation of the prototypical material flibe under conditions relevant to Heavy Ion Fusion (HIF) power plants. Superheated vapor is generated by a high-current, pulsed electrical discharge over a pool of liquid flibe. The excited vapor expands inside a temperature-controlled chamber designed to scale the initial density of the generated vapor, the initial energy density and the surface area available for condensation, considering HYLIFE-II as the reference design. Clearing rates are evaluated from the measured pressure history. Mass spectroscopy is used to characterize the composition of the residual gases. SEM analysis of material deposited on witness plates is also presented, showing that interface phenomena during the initial expansion phase depend on the orientation of the condensation surface relative to the gas velocity. The results show that chamber clearing can be characterized by an exponential decay with a time constant of 6.58 ms. However, the equilibrium pressure is one order of magnitude higher than the desired HIF base pressure because of the presence of non-condensable impurities dissolved in the material available for the experiments. If the exponential decay is applied to the pressure range of the reference design, the resulting period for chamber clearing is 60 ms. The conclusion is that condensation rates of flibe vapor are sufficiently fast to allow HIF power plants repetition rates, and that the main issue for flibe vapor condensation lies in the control of the impurities dissolved in the salt.