Overview of Code Structures, Challenges and Available Methodologies for Treatment of Model Uncertainty in Severe Accident Calculations

In spite of being a significant source of uncertainty, “Model Uncertainty” is ignored in most of engineering applications. The influence of model uncertainty is most pronounced for areas with limited knowledge and complex simulations structures like severe accident calculations; however lack of a systematic methodology makes this assessment a challenge. The present study is devoted to the treatment of model uncertainty in severe accident analysis for nuclear power plants. After a review of available methodologies for model uncertainty treatment in different applications, the unique features are described for the severe accident problems with supportive examples from the real calculations. By reviewing available approaches in engineering and science as well as the structure of severe accident codes, challenges are discussed for model uncertainty assessment in this area. This paper initiates a systematic examination at the subject.