Thermochemistry of Polonium Evaporation from LBE

Polonium is formed in relatively large quantities in lead-bismuth eutectic (LBE) cooled nuclear systems. Because of its radiotoxicity and volatility, a good understanding of the chemical equilibria governing polonium release from LBE is required. In this work, a set of thermochemical data is derived for the chemical species involved in the equilibrium between a solution of polonium in LBE and its vapor in inert conditions. The data were obtained by matching thermochemical models with experimental vapor pressure measurements and ab initio results. The dilute-limit activity coefficient of dissolved polonium in LBE is estimated, as well as the solubility of solid lead polonide in LBE. The results indicate that polonium evaporates from LBE according to the experimentally determined Henry’s law, up to dissolved polonium concentrations well above that expected in LBE cooled nuclear systems.

Critical Comments on “Assessment of the Thermodynamic Properties of DL-p-Mentha-1,8-diene, 4-Isopropyl-1-Methylcyclohexene (DL-Limonene) by Inverse Gas Chromatography (IGC)”

A polemic is given regarding the calculated thermodynamic quantities reported in the published paper by Farschi and coworkers. The graph used to calculate the molar heat of sorption of organic probe molecules onto the liquid DL-limonene stationary phase erroneously plots the reciprocal of the centigrade temperatures, rather than the reciprocal of the Kelvin temperatures. Molar heats of vaporization of the organic probe molecules reported in the paper are abnormally small and are not in accord with published values determined from calorimetric and vapor pressure measurements.