Equation of State of High-Temperature Weakly Nonideal Flinabe (LiF-NaF-BeF2) Gas

Abstract

The molten salt Flinabe (LiF-NaF-BeF2) is proposed as a liquid wall material for future fusion reactors because of its many attractive aspects. High-temperature Flinabe gases (plasmas) appear in the inertial fusion energy chamber over a wide range of temperatures and pressures because of the absorption of X-rays and debris, emitted from the target microexplosion, within a very thin surface layer of the Flinabe liquid wall. The deposited energy heats the surface edge of the Flinabe wall to very high temperatures where vaporization, dissociation, and ionization take place and high-temperature plasma is generated. Equation-of-state (EOS) and ionization equilibrium data of the resulting high-temperature gas are needed to perform gas dynamics calculations and the required assessments of many research and development issues in nuclear fusion. Nevertheless, data for Flinabe EOS or ionization states are missing in the literature, and there is an immediate need to model and estimate these properties. In this paper, a self-consistent model for the ionization equilibrium and EOS of weakly nonideal high-temperature Flinabe gas is presented and used to compute the ionization equilibrium data and EOS of such an important material. Nonideality effects have been taken into account in terms of depression of the ionization potentials, coulombic correction to plasma kinetic pressure, and truncated partition functions. A reduced formulation and efficient algorithm to solve the set of nonlinear Saha equations subjected to the constraints of electroneutrality and conservation of nuclei have been used to generate ionization equilibrium and Flinabe EOS over a wide range of temperatures and pressures. A criterion for the validity of the assumption of local thermodynamic equilibrium (LTE) is applied to the results showing the regions of pressure-temperature phase-space over which the LTE assumption can be justified and accepted. Estimates of high-temperature Flinabe EOS and ionization states are presented and discussed.