The development of a mechanistic code on fission product behavior in the polycrystalline UO2 fuel

The current status of a mechanistic code (RTOP) on fission product behavior in the polycrystalline UO2 fuel is described. Outline of the code and implemented physical models is presented. The general approach to the code validation is discussed. It is exemplified by the results of validation of the models of oxidation and grain growth. The different models of intragranular and intergranular gas bubbles behavior have been tested and the sensitivity of the code in the framework of these models has been analyzed. An analysis of available models of the resolution of grain face bubbles is also presented.