A simplified fragility analysis methodology for containment structure subjected to overpressure condition

Abstract Nuclear containment structure plays a critical role of providing the leak proof boundary for preventing radioactive material leak into the environment during severe accident conditions. There is a growing demand to quantify the failure probability of containment structure under severe accident conditions. This paper mainly focuses on fragility analysis and performance evaluation of containment structure under severe accident conditions from an innovative perspective. An innovative log-expansion method is proposed based on reliability theory. The obvious advantage of the proposed method is that the computational work is greatly reduced without sacrificing accuracy. The validity of the proposed methodology is verified through cylinder structure subjected to hydrostatic pressure condition and containment structure subjected to overpressure condition, and the proposed methodology is compared with the more accurate but computationally demanding conventional Monte-Carlo sampling technique and Latin hypercube sampling technique. Results indicate that the proposed methodology can provide good estimation of fragility curve of containment structure with less computational work. The 95% non-exceedance pressure capacity of containment structure is 1.29 MPa, which meets the requirement of minimum margin not less than 2.5. Cumulative conditional failure probability (CCFP) of containment structure in this study is 0.0032, which indicates that this containment structure can meet the performance requirements under severe accident conditions.