A Serpent/OpenFOAM coupling for 3D burnup analysis

In nuclear reactor analysis, a relevant challenge is to achieve a suitable global description of nuclear systems through the coupling between neutronics and thermal hydraulics. Indeed, a multi-physics approach improves the reactor safety analysis and the design of different types of nuclear systems; in addition, it allows the investigation of physical effects at different scales of time and space. In this context, a challenging task is the development of multi-physics tools to study the fuel cycle. This paper presents a modelling approach for 3D burnup analysis with the Serpent Monte Carlo code that implements an external interface for the coupling with OpenFOAM, importing material temperatures and density field. We adopt CFD to simulate thermal hydraulics for its high flexibility that simplifies the management of input data. In addition, the coupling with a Monte Carlo code assures a natural description of the different physics phenomena of nuclear reactors. We carry out the burnup calculations for one year of burnup of a PWR fuel cell, composed of an UO2 pin surrounded by water. We compare the results to those obtained from simulations that adopt uniform temperature and density distributions. The results show that thermal hydraulics feedback influences the spatial distribution of the reaction rates over the time, leading to a remarkable effect on the nuclide density field along the radial and axial direction. In future works, we plan to extend the analysis for fuel assembly design.