Vaporization behaviour of a PuF₃-containing fuel mixture for the Molten Salt Fast Reactor

Highlights: •First partial vapour pressure results on a PuF₃-containing fuel mixture for the Molten Salt Fast Reactor. •First results on eutectic melting, liquidus and boiling point for the LiF-ThF₄-UF₄-PuF₃ (77.5–6.6-12.3–3.6 mol%) fuel mixture. •Second independent study on melting point and appearance potential of PuF₃. •New data on PuF₃ vapour pressure and enthalpy of sublimation. - Abstract: The mixture LiF-ThF₄-UF₄-PuF₃ (77.5–6.6-12.3–3.6 mol%), a fuel option for the Molten Salt Fast Reactor (MSFR), has been measured by differential scanning calorimetry (DSC) for determination of phase transitions, and by Knudsen effusion mass spectrometry (KEMS) for measurement of partial vapour pressures. The boiling point of the mixture was determined by extrapolation of total vapour pressure to 1 bar. Thermodynamic calculations were performed and compared with the experimental results. Novel experimental data on pure plutonium trifluoride are presented: melting point, vaporization enthalpy, vapour pressure and ionization energies by electron impact.