Fragility analysis of prestressed concrete containment under severe accident condition

Abstract

Nuclear containment structure is the most important shielding structure in nuclear power plant, the main function of the containment structure is to prevent the leakage of radioactive materials into environment during the accident conditions, it is of great significance to gain insight into the performance of the containment under severe accidents. This paper presents fragility analysis of prestressed concrete containment vessels under severe accidents. Firstly, detailed three-dimensional finite element model of the containment is established, material nonlinearity and non-uniform effective prestressing distribution along the prestressed tendons is also considered. Secondly, Latin hypercube sampling technique combined with MATLAB program and python script is developed to update the material parameters in ABAQUS input files to generate 30 random samples. Fragility curves of five critical locations with consideration of aleatory uncertainty and epistemic uncertainty and fragility curves with different confidence levels had been thoroughly investigated. Finally, sensitivity analysis for input random variables had been conducted to provide better understanding of the significance of the various random parameters. Results indicate that functional failure of containment is dominated by the location of equipment hatch. The difference between the HCLPF pressure capacity obtained from the composite fragility curve and the lower bound pressure capacity of the containment obtained from fragility curve with 95% confidence is small. The lower bound pressure capacity and upper bound pressure capacity is 0.837 MPa and 1.259 MPa, respectively. Sensitivity analysis of the input random variables reveale that modulus of elasticity of prestressed tendon make most contribution to the pressure capacity of the containment.