Fractionation of UF6 and daughter progeny in storage cylinders from external heating

Abstract

Uranium hexafluoride (UF₆) is a significant concern for material accountancy and verification in the international safeguards community. Verification of the contents of UF₆ cylinders is generally attempted with gamma spectroscopy but the current methods assume a uniform, homogeneous UF₆ mass distribution within the cylinder. In this work, it was found experimentally and confirmed via modeling, that under an external heat load (the sun), the UF₆ and its daughter products undergo fractionation in the cylinder. This fractionation of the UF₆ and daughter products can cause an errant measurement of the enrichment of the cylinder when using the current verification methods.