Evaluation of UF6 vapor release in postulated accident

The rupture of UF6 gas line connected to hot UF6 cylinder, being one of various accidents in UF6 vapor leak-out, is considered as a postulated accident for uranium enrichment plants. For this type of rupture, we will estimate the amount of UF6 vapor release based on a simplified calculation model and then make an evaluation of UF6 vapor release through a ventilation system of feed vaporization facility. Assuming an instantaneous steady state for the change of UF6 states, an unsteady state thermodynamics process is solved. Numerical examples show that about 52% of the initial UF6 quantity are vaporized at 800C (the temperature of the liquid UF6 in the cylinder). Furthermore, by using the amount of released UF6 vapor and the collection capacity of HEPA filter for HF gas, the amount of gaseous UO2F2, HF which may be dissipated to the environment are conservatively estimated. (auth.)