Evaporation Properties of FLiNaK with Plasma Interaction

Abstract

Evaporation properties of FLiNaK (LiF 46.5 mol% + NaF 11.5% + KF 42 mol%) were investigated with hydrogen plasma interaction. To prevent massive evaporation of molten salt of flowing wall in fusion device, evaporation property of molten salt should be researched. However vapor pressure of FLiNaK has been studied for liquid state without consideration of interaction with plasma. We measured evaporation property of FLiNaK with hydrogen plasma interaction. Vapor component of FLiNaK were detected with OES(Optical Emission Spectroscopy) and RGA(Residual Gas Analyzer). The film deposited on wafer samples were investigated with EDS(Energy Dispersive Spectrometer) to determine vapor component. Hydrogen plasma was generated with 500W ECR source and the molten FLiNaK was contained with heated crucible of diameter of 46mm and depth of 40mm. OES data showed several peaks of total component of FLiNaK. Those were emission lines of F, Li, Na and K. RGA data also showed FLiNaK components with plasma interaction. Without plasma interaction, the deposited film was mostly KF at molten salt temperature of 973K. The components of deposited film during plasma interaction were similar with the original FLiNaK sample. The evaporated mass became higher with plasma interaction while the remained FLiNaK at crucible still hold similar molar percentage. In this paper, plasma-enhanced-evaporation of FLiNaK was qualitatively discussed.