SOURCE IST 2.0 Model Uncertainty for Noble Gases

Abstract

SOURCE IST 2.0 was developed based on models aimed to describe the formation of fission products, diffusion and release of the fission product from pellet, evaporation and release from the failed fuel element. The fission product release fraction is the key parameter predicted by SOURCE. An integrated uncertainty for this parameter, which accounts for SOURCE models' uncertainties was evaluated in order to assess the overall uncertainty of the code for noble gases. The combination of the models’ uncertainties is performed using the GRS methodology, according to which each uncertainty is treated as an independent variable that can evolve following a specific statistical distribution. The model’ uncertainties analysis is useful for best estimate application of the code and for sensitivity studies and will rationalize the code accuracy assessment. Also, the models’ uncertainties analysis will reveal areas for further development of the code.