Future fusion experiment and power plants, including ITER and DEMO, will operate with a mixed deuterium/tritium fuel. All current fusion experiments are unable to operate with Tritium, apart from JET. Understanding the effect of the change in the fuel mix on the fusion plasma is therefore paramount for making accurate predictions for fusion power plants. The starting point of this project is a unique set of JET experiments achieved with pure deuterium as fuel, mixed deuterium/tritium and pure tritium fuel [L. Frassinetti et al 2023 Nucl. Fusion 63 112009]. The aim of this project is to model the effect of the isotope in the JET pedestal and verify if the current theory can explain the experimental results. This will be done with the JOREK code [M. Hoelzl et al 2021 Nucl. Fusion 61 065001], a non-linear visco-resistive magnetohydrodunamic (MHD) code. JOREK represents the state of the art in European fusion plasma stability codes and it is a unique resource that will allow to investigate both the role of plasma resistivity, of plasma viscosity and diamagnetic flow in explaining the effect of the fuel mix in JET plasmas. The project will start by focusing on the linear stability of the plasma, which would be sufficient to identify the origin of the effect of the isotope mass in the JET pedestal. In a later stage, non-linear runs will allow a more in depth investigation of the effect of the isotope mass on important plasma phenomena such edge localized modes