Physical Chemistry and Technology of Alkaline Liquid-Metal Coolant: A Retrospective-Perspective Look

The results of studies on the physical chemistry, mass transfer, and technology of alkali liquid-metal coolant are reported. The state of the coolant is determined by the interaction coolant-impurities-structural materials- protective gas. The impurity sources and their intensity were determined: sodium and sodium-potassium alloy – oxygen, hydrogen (tritium), carbon, products of corrosion of structural materials, nitrogen, and the protective gas, lithium- nitrogen. The following data were obtained on the impurities in the coolant: form, equilibrium concentration, solubility, reaction kinetics, and mechanisms of heterogeneous and homogeneous mass transfer. It was shown that the required concentration of the impurities in sodium and the sodium-potassium alloy guaranteeing the design-basis parameters and a low rate of corrosion of the structural materials is achieved on purification by means of cold traps. Deeper purification of coolants in high temperature NPF intended for use in space is achieved by means of getters (hot traps). The behavior of tritium and hydrogen in the sodium loops in NPP with fast reactors was studied. A new combined system is proposed for purification from impurities in high-temperature NPF for hydrogen production at sodium temperature ~900°C.