[en] The safety analysis of the US uranium enrichment facilities requires that postulated accidental releases of UF₆ be simulated. In order to predict the human health consequences of a postulated UF₆ release, two types of information are needed: (1) predicted toxicant concentrations and exposure durations at pertinent locations (calculated by a dispersion model), and (2) toxicity data which support the assessment of the human health consequences of a known exposure to a mixture of UF₆ and UF₆ hydrolysis products. This report describes the development of a Gaussian dispersion model for simulating UF₆ dispersion and the plans for developing a puff dispersion model