Multiscale simulation of the thermomechanical behavior of containment buildings of nuclear power plants

The prediction of the leakage rate of containment vessels in double-walled nuclear power plants is of particular importance given the role of the structure.As the third containment barrier, it must indeed guarantee a certain level of leak tightness in order to perform its function fully.Traditionally, the estimation of the leakage rate is based on simulation and includes a good knowledge of the hydric state (degree of saturation) and of the potential mechanical disorders (potential cracks).These quantities are then associated with transfer laws (generally damage -or crack openingpermeability) in a chained (thermo)hydric/mechanical approach.This paper describes the evolutions in the methodology used to predict the mechanical behavior of containment buildings, for which numerous developments have been made in recent years.After introducing a brief history of mechanical behavior simulation practices at this scale (direct application of damage mechanics for example), significant improvements, in terms of representativeness and performance of the mechanical calculation, will be discussed.A particular attention will be paid to scale change using evolving static condensation, from the containment buildings to Representative Structural Volume, on which the application of more refined approaches become possible.Finally, discussions on open issues are proposed towards simulating the behavior of a real structure.