Importance of uncertainty quantification in nuclear fuel behaviour modelling and simulation

•A short description of nuclear fuel behaviour and its modelling in a fuel performance code.•A list of uncertainty sources in fuel behaviour modelling area.•Some examples of uncertainty quantification in modelling.•Some requirements for a generalization of uncertainty quantification in the future. Fuel performance codes describe the physical phenomena occurring in fuel during its irradiation in steady-state and transient conditions. In this paper, the principles of the modelling of nuclear fuel behaviour are presented. Many reasons show that it is also important to consider uncertainties in the fuel modelling process. It can be experimental reasons (validation database and material properties determination), uncertainties in the modelling process itself (lack of knowledge for example). This paper also presents several applications of uncertainty quantification and sensitivity analysis applied to fuel behaviour modelling. The first example is about the validation process of the fuel performance code, which results in a quantification of the uncertainty of the calculated quantities. The second application is about the use of the code in safety analysis to determine probabilities of failure considering epistemic and random uncertainties. In the last application, we show how important it is to quantify modelling uncertainties in the calibration process of complex physical models.