A Serpent2-SUBCHANFLOW-TRANSURANUS coupling for pin-by-pin depletion calculations in Light Water Reactors

•Serpent2-SUBCHANFLOW-TRANSURANUS mesh-based object-oriented geometry-agnostic coupling.•Fully coupled semi-implicit depletion scheme for pin-by-pin modelling.•Improvement of the fuel solution using a fuel-performance thermome-chanic methodology.•Assessment of the modelling approach comparing the results with Serpent2-SUBCHANFLOW.•Pin-by-pin fuel-assembly calculations, towards full-core problems. This work presents the development of a coupling scheme for Serpent2, a continuous-energy Monte Carlo particle transport code, SUBCHANFLOW, a subchannel thermalhydraulics code, and TRANSURANUS, a fuel-performance code, suitable for large-scale high-fidelity depletion calculations for Light Water Reactors. The calculation method is based on the standard neutronic-thermalhydraulic approach, replacing the simple fuel-rod solver in SUBCHANFLOW with the more complex thermomechanic model of TRANSURANUS. The depletion method is fully coupled and semi-implicit, and the implementation relies on an object-oriented design with mesh-based feedback exchange. The results of the three-code system for a 360-day depletion calculation of a VVER-1000 fuel assembly with a pin-by-pin modelling approach are presented and analyzed. The performance of this tool, as well as the bottlenecks for its application to full-core problems, are discussed.