Fracture Assessment of DEMO Divertor Components Under Thermo‐Mechanical Loads

Nuclear fusion represents a promising pathway toward large‐scale, sustainable, and low‐impact energy production. However, the extreme operating conditions within fusion reactors, characterized by high temperatures, intense neutron irradiation, and severe mechanical and magnetic loads, place significant demands on the structural integrity of the most critical components. This study presents a fracture mechanics assessment of the nuclear reactor DEMO divertor, a component subject to severe thermo‐mechanical and electromagnetic loads. A finite element model was developed to simulate divertor behavior under realistic thermal and mechanical conditions. Critical regions were identified through global model analysis, with a subsequent submodeling for detailed investigations. Semi‐elliptical surface cracks were introduced in these local submodels, and stress intensity factors along the crack front were evaluated, using linear elastic fracture mechanics. Crack propagation simulations were performed to reflect realistic operational scenarios. Fatigue life was estimated using Paris’ law, predicting the number of cycles required for cracks to reach critical dimensions. A multi‐ crack growth analysis was performed to investigate the simultaneous presence of two cracks located in adjacent critical regions, while an elastoplastic material model was implemented to analyze the deviations from the linear elastic behavior. These findings contribute to improving the structural reliability and lifetime prediction of divertor components in future fusion reactors.