Metallic alloys used in nuclear power plants are under permanent irradiation which causes fast modification of their microstructure through a large variety of defects interacting with each other: interstitials, vacancies, point defect clusters, dislocations, grain boundaries (GBs), etc. In particular, segregation of atoms in these conditions can be observed at GBs, which can alter the structural integrity of the materials. Despite the numerous improvements achieved so far to understand radiation-induced segregation (RIS) at GBs through cutting-edge experimental or modelling tools, several observations remain unexplained. This might be due to the huge diversity of GB structures and the resulting difficulty to correctly describe their interactions with solute and point defect (PD) diffusion. Recently, phase-field (PF) approaches have been developed to predict RIS behaviour in binary alloys for different conditions. However, in their formalism, the description of GB was still basic since the thermodynamic and elastic properties of the GB and the bulk phase were supposed to be the same, the GB being treated as a simple absorbing plane for PDs (“planar sink” model). As a consequence, these approaches fail to predict thermal segregation, which may interplay with RIS resulting in complex segregation profile at GBs. To overcome the limitations of this “planar sink” model, we first propose in this work to better describe the thermodynamic heterogeneities between the bulk phase and the GB. For this purpose, a density-based model recently proposed in the literature is adopted, allowing to recover the well documented “W-shape” segregation profile observed experimentally under irradiation. Secondly, the elastic relaxation at the GB is modelled by different approaches, among which the Read and Shockley one for low angle tilt GBs, inducing complex segregation behaviours analysed in detail. Case studies will be presented on Fe Cr and nickel base model alloys for nuclear applications.