Design of an experimental erosion test section in lead

To support the transition towards low-carbon energy systems, new reactor concepts are being developed to offer greater flexibility and reduced construction costs. Among these, the Lead-cooled Fast Reactor (LFR) stands out for the favourable properties of lead as a coolant and its potential for simplified design. Despite its advantages, several technical challenges remain. This thesis focuses on one of them: the erosion corrosion phenomena induced by heavy liquid metal flow on protective layers within reactor components. One important aspect to investigate is the erosion that the heavy liquid metal flow can induce on the passive-corrosion layers present along the fuel bundles and along the heat exchanger tubes. This can be a problem if it is not controlled, because the corrosion layer helps to protect the base material. For this reason, a fluid-dynamic study on the design of a specific test-section is performed. In this thesis a test section is designed that permits to understand through CFD analysis the stresses and the velocity fields achieved in specific typical representative geometries, trying to study and stretch the rule of thumb erosion limit of 2 m/s now adopted in the reactor design. This study aims to determine whether this can be relaxed and at what condition. During this thesis only the design and the CFD simulation work is performed. The test section will be placed into the lead loop for a long period, then it will be extracted and analysed to understand where erosion takes place. With the experimental information and knowing the condition inside the test section given by the CFD analysis, it will be possible to learn more on the erosion behaviour of liquid lead. Particular attention was given to areas with high velocity, shear stress and turbulence kinetic energy, which are likely to influence erosion corrosion phenomena. The design of the test section includes as representative geometries an array of cylinders in crossflow, two plates with holes and three inclined plates. Key findings include: -??the array of cylinders permits to reach gradually high velocities. It shows less chaotic flow in the first columns making erosion corrosion coupling more straightforward, while the last columns exhibit high turbulence and velocity peaks; -??plates with holes give interesting results in terms of shear stress in the restrictions. They generate the highest shear stress in the test section, especially in rounded restrictions, which also reach the highest velocities. Sharp restrictions, despite lower velocity, still produce high shear stress and should be avoided in design; -??inclined plates permit to study the influence of the flow angle which can form with the solid surface. The 45° inclined plate shows expected shear stress peaks, but elevated TKE values upstream must also be considered. These results provide a valuable foundation for interpreting future experimental data and refining design criteria for erosion corrosion mitigation in LFR systems.