Modeling downwind hazards after an accidental release of chlorine trifluoride

Chlorine trifluoride (ClF3,) is a chemical compound used in the gaseous diffusion process to enrich uranium at two plants, one in Portsmouth, Ohio and the other in Paducah, Kentucky. Although highly unlikely, a breach in ClF3, storage cylinders or tanks would result in a potential release of ClF3, to the atmosphere. The fate of ClF3, once released to the atmosphere, is a primary concern for plant managers and safety engineers at the plants because of its extreme toxicity. There are many atmospheric dispersion models typically used to model the release of inert airborne contaminants; however, ClF3 is highly reactive with water vapor in the atmosphere, and therefore, these models would not accurately predict atmospheric concentrations of ClF3 downwind of a potential release. Additionally, these models do not predict the formation of reaction products that also are toxic [i.e., hydrogen fluoride (HF) and chlorine dioxide (ClO2)]. An atmospheric chemical reaction model was developed to predict release hazards associated with an accidental release of ClF3. Experimental results indicating that ClF3, reacts with atmospheric water vapor in two reaction sequences were incorporated into the model. The first reaction sequence, termed excess ClF3, occurs when the molar ratio of ClF3, to water vapor is greater than two-thirds. The second sequence, termed excess water vapor, occurs when the molar ratio is less than or equal to two-thirds. The ClF3, reaction model was incorporated into the AEROPLUME near-field jet dispersion model which is part of HGSYSTEM (a system of models used to simulate near-field, heavy-gas, and neutrally buoyant dispersion from accidental releases). Many simulation exercises were run to test the model, showing rapid formation of HF and ClO2 after an atmospheric release of ClF3. At distances beyond the first several meters from the release point, HF and ClO2, concentrations pose a greater threat to human health than do ClF3 concentrations. For most of the simulations, ClF3, concentrations rapidly fall below the IDLH (i.e., within about 20 m). For releases occurring in ambient conditions with low relative humidity and/or ambient temperature, CIF3 concentrations exceed the IDLH up to almost 500 m.