A comparison of actinide halides for use in molten salt reactor fuels

Abstract

Recent years have seen a renewed interest for molten salt reactor (MSR) technologies. It is noticeable, though, that all MSR projects feature either fluoride or chloride melts for the fuel salt while the use of heavier halides -- bromine and iodine, namely – is scarcely mentioned with the argument that their capture cross section is too high. This paper thus intends to update the status of bromide and iodide salts as potential nuclear salts through a more in depth comparison of these melts with respect to more “standard” fluoride and chloride compounds. A literature review of the main thermodynamic properties of a few sodium halides, uranium halides and plutonium halides is presented to support the potential existence of liquid melts for bromides and iodides. The existence of stable critical neutronic configurations is then discussed showing that both bromide and iodide salts might constitute reasonable candidates for burner cores. The radiotoxicity of most dangerous and/or oxidizing activation products is finally analyzed showing that iodide salts are comparable with their fluoride and chloride analogs. The use of bromide salts, though, leads to an increase in gamma emission.