An approach to modelling fuel behaviour using data from some international high burnup fuel programmes

The well-defined fuel rod tests from the international research programmes TRIBULATION and High Burnup Effects Programme have provided a large amount of fuel performance data for computer code verification and validation. This report describes the calculation approach used to simulate the fuel rod deformations and fission gas release focused on some rods irradiated to high burnups. The TRANSURANUS computer code was used for the calculations. In a first phase the fuel densification input parameter as well as the fuel swelling and clad creep-down rates have been adjusted in order to reproduce the measured end-of-life clad dimensional changes. The agreement was very good. The experimental fission gas releases were then compared with the values predicted by three different models. Besides the standard model URGAS also the Halden model as well as the one from Framatome were implemented in TRANSURANUS. A significant discrepancy was found not only between the different models but also between the measured fission gas release values. The achieved result was discussed and some conclusions from this first step on the way to develop a new model at PSI to be used with TRANSURANUS were drawn. (author). 11 refs, 4 figs