Simulation of the behaviour of nuclear fuel under high burnup conditions

•Increasing the time of nuclear fuel into reactor generates high burnup structure.•We analyze model to simulate high burnup scenarios for UO2 nuclear fuel.•We include these models in the DIONISIO 2.0 code.•Tests of our models are in very good agreement with experimental data.•We extend the range of predictability of our code up to 60 MWd/KgU average.

In this paper we summarize all the models included in the latest version of the DIONISIO code related to the high burnup scenario. Due to the extension of nuclear fuels permanence under irradiation, physical and chemical modifications are developed in the fuel material, especially in the external corona of the pellet. The codes devoted to simulation of the rod behaviour under irradiation need to introduce modifications and new models in order to describe those phenomena and be capable to predict the behaviour in all the range of a general pressurized water reactor. A complex group of subroutines has been included in the code in order to predict the radial distribution of power density, burnup, concentration of diverse nuclides and porosity within the pellet. The behaviour of gadolinium as burnable poison also is modelled into the code. The results of some of the simulations performed with DIONISIO are presented to show the good agreement with the data selected for the FUMEX I/II/III exercises, compiled in the NEA data bank.