Study of Ru released under accidental conditions by overheated nuclear fuel: the emission of Ru and U

The emission of uranium and ruthenium oxides from overheated nuclear fuel i s a complex phenomenon which depends on the fuel matrix, on temperature, on the oxygen potential of the amosphere in contact and on the emission seque nce. All these factors influence the properties of particles before their d ispersion in the reactor containment building and in the environment: these properties are, among others, surface composition, particle size, and, as a consequence, weathering rates in the environment. Emission in air increas es the solubility of U-oxides mainly. This first paper describes the main p hysico-chemical characteristics of condensation particles released by overh eated U and Ru oxides mixtures, in small-scale laboratory simulations.