Code-to-Code Benchmarking of PCMI among High-Fidelity Fuel Performance Codes

This paper presents a benchmark study of high-fidelity fuel performance codes conducted within the European OperaHPC project. The collaboration involves EPFL, CEA, and VTT, which report results using the codes OFFBEAT, ALCYONE, and BISON, respectively. The focus of this benchmark is the analysis of pellet-cladding mechanical interaction during both base irradiation and a subsequent power ramp. The test case is a PWR rodlet consisting of ten pellets, subjected to a simplified irradiation history derived from the K11-5 ramp test. ALCYONE employs a multi-layered simulation strategy with its characteristic 3D single-fragment model for each axial slice. On the other hand, OFFBEAT and BISON adopt a 2D axisymmetric discrete-pellet approach. The evolution of cladding deformation and stress is presented through cladding displacement and equivalent stress profiles at selected time points throughout irradiation. Fuel centerline temperatures are also analyzed. The results indicate the level of agreement between the codes. Differences are discussed, and potential sources of these discrepancies are identified.