Modeling of the Behavior of a UF6 Container in a Fire-DIBONA Code

Uranium hexafluoride (UF6), the raw material from which the fuel for nuclear power stations is obtained, is stored in the solid state in industrial containers called 48Y. The International Atomic Energy Agency (IAEA) envisages a revision of current regulation and suggests that a container withstands a specific fire test (engulfing fuel fire of soooc for half an hour, for a steel emissivity of 0.8 and flame emissivity of0.9). To study the safety of the containers under these conditions, a numerical model was elaborated by the French Atomic Energy Commission (CEA). A 2-D model using the finite element computation code ANSYS was therefore developed. It takes into account thermal and mechanical phenomena as well as mass transfers. Recently some tests have been performed on a Tenerife container (Saroul et al. 1995), and our model bas to be validated with this results. As the analysis and the interpretation of physical phenomena have been carried out (Pinton et al. 1995) therefore this document will only show bow these phenomena have been introduced in the numerical model. This paper is chiefly concerned with the study of thermobydraulic behavior inside the container, with no reference to the mechanical aspects of the problem. The extrapolation to a IAEA fire test on 48Y will be a future step. Note that this model is the pursuit of the work begun by DURET B. (1992). So, only the new developments will be more detailed.