Fragility analysis of APR-1400 nuclear containment structures under internal pressure

This study aims to investigate the key factors influencing the pressure fragility of APR-1400 nuclear containment structures, incorporating a broad set of uncertainty parameters. A total of 15 variables were considered, encompassing material properties such as strength, modulus of elasticity, and density, as well as prestressing loads. In-depth investigations into the behavior of containment structures under internal pressure have suggested a liner plate strain of 0.4 % in the global free field as an appropriate limit state for estimating the ultimate pressure at failure. Fragility analysis based on this limit state revealed that while the median ultimate pressure (approximately 1.2 MPa) is slightly higher than previously reported, other pressure levels exhibit significant differences in failure probability, likely due to the broader range of uncertainty parameters considered in this study. A sample size analysis indicated that a minimum of 70 samples is required to generate a fragility curve similar to that produced using 100 samples. Sensitivity analysis identified the elastic modulus of the liner plate and the concrete tensile strength as the most influential factors on the pressure fragility, whereas the material densities had minimal impacts. Considering a cumulative 90 % sensitivity index, it is recommended to exclude the densities of all materials and the modulus of elasticity of the tendons in the fragility analysis of nuclear containment structures under internal pressure.