Ranking of LMFR Coolants by Degree of Preference

A new approach to ranking the coolants of a liquid metal fast reactor (LMFR) by degree of preference is proposed and implemented. The approach involves comparing the optimal LMFR layouts with different coolants and compatible structural materials. The layouts were obtained in solving mathematical programming problems with restrictions in the same formulation. The problem is solved in three stages. At the first stage, on the basis of an elementary analysis of the physicochemical properties and cost, unacceptable metals with a high cost (rare metals), a small wide range of operating temperatures, a low boiling point, and high induced activity were excluded. The second stage involves obtaining the optimal layout of LMFR with different coolants. Then, using lexicographic methods for solving multicriteria problems, a coolant ranking procedure is carried out based on a comparison of the optimal LMFR layouts. The third stage involves the analysis of preferred options. Depending on the power and purpose of the reactor, the most preferred coolants are different. For medium and high power reactors, lead extracted from thorium ores is most preferred. For low power reactors, lead from polymetallic and lead ores is preferred. In such reactors, the use of lead of uranium ores is possible. For high- and very-high-temperature low power reactors, gallium and its alloys, including gallium-lead alloys, are preferred. For space reactors, a coolant based on the eutectic Na-K-Cs alloy is more preferred.