Preliminary evaluation of the flooding effects on an existing PWR

The aim of the study is the evaluation of the structural effects induced by a severe flooding or tsunami (which is one of the external events to be considered for the safety margin reassessment purpose according to the International requirements, after the Fukushima accident) in an outer containment walls of a typical PWR. The hydrodynamic forces exerted by the breaking waves, characterizing the inundation phase of tsunami/flooding phenomenon, are calculated in agreement with ASME rules. Therefore to evaluate the consequences and damages, if any, induced by the breaking water waves which have arisen on an existing PWR containment building, non linear analyses (by using an adequate FEM code) were performed simulating the impact forces of the water waves in terms of pressure. Moreover a FSI analysis was carried out in order to verify the adequacy (and consistency) of the methodology adopted in the evaluation of the pressure forces mentioned above. To analyze the performances of the containment building suitable reinforced concrete material properties and damage phenomena features were considered. The results obtained highlighted that the tsunami effects are strongly dependent on the wave height, flow velocity, hydrodynamic phenomena and on the geometry and material behaviour of the analyzed structures. Finally they showed that the containment building considered seemed capable to withstand the flooding/tsunami effects without loss of the integrity of PWR containment structure