ABSTRACT
Extending French nuclear power plants to 60 years requires verifying the long-term integrity of concrete containment buildings under Severe Accident (SA) conditions, namely, exposure to 150°C and 90% RH. An autoclave with an internal hydraulic jack was used to reproduce SA conditions, axial delayed strains were measured, and the in-situ Young’s modulus of concrete cylinders was determined. In parallel, a simplified thermo-hydro-mechanical (THM) model is developed assuming the gas phase is only composed of water vapor. The TH part includes temperature-dependent sorption and the change of porosity, density, and permeability. The mechanical model adopts Burger’s rheology to predict basic creep, drying creep, shrinkage, transient thermal deformation (TTD), and Young’s modulus degradation. A 2D homogeneous axisymmetric finite-element model is used to simulate the creep test. Experiments and simulations show rapid strain changes within the first 24 h, followed by a steady state, indicating that most strains accumulate early during SA exposure.
