Earthquake's induced sloshing may lead to dangerous effects in a nuclear reactor pool during seismic events. The objective of this thesis is to investigate sloshing processes in the Advanced Lead Fast Reactor European Demonstrator (ALFRED).\\
Model scale experiments (1:18.4) have been carried out. The model of ALFRED is a reproduction in plexiglass of the very hot plenum of the actual demonstrator, based on Froude number scaling. Distilled water is used in similarity with the lead in the demonstrator. The model consists of an annular tank, as nuclear pool and internal primary core are simply reproduced. In the peripheral, nine cylinders are distributed and represent the internal structures of the demonstrator. The dominating sloshing processes take place above the diaphragm.\\
Harmonic base excitation in one Degree of Freedom (DoF) forms the basis of the present investigations. Nonlinear free-surface physics have been identified for different water depths, forcing amplitudes and frequencies outside and at/near to the fundamental resonance of the system. The wave-structure interactions add complexity to the sloshing processes, altering the skewness of the free-surface orbits.\\
Further, idealized norm-based earthquakes test series have been undertaken. These tests contain base excitation signals outside and close to the fundamental system frequency. The analysis of the seismic base excitation test series performed in 1-3 DoFs exhibits highly nonlinear and random behaviour. The short duration input signals add further to the randomness of the sloshing processes. Violent sloshing motions were detected for several events, especially related to the increasing amplitudes/intensity of earthquakes’ excitation signals close to the fundamental frequency. Additionally, a hazard condition in the primary nuclear reactor has been simulated by removing three of the internal cylinders (steam generators). In these parametric studies and via comparisons, a highly damped system was identified.\\
A preliminary full-scale assessment has been done both for the harmonic base excitation test series and for the norm-based earthquakes test series. The maximum ground accelerations and associated maximum amplitudes have been computed to perform a scale effect assessment based on the Froude scaling.
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Keywords: \textbf{sloshing}, \textbf{experimental investigation}, \textbf{nuclear reactor}, \textbf{earthquakes}, \textbf{nonlinear physics}