Fragility analysis and probabilistic safety performance evaluation of nuclear containment structure under local prestressed tendons fracture conditions

Abstract

Prestressed tendon in nuclear containment structure may occur unexpected fracture during the service life of the nuclear power plant. Fracturing of the prestressed tendon will pose great threat to the integrity of the nuclear containment structure. Based on detailed three-dimensional finite element model of the nuclear containment structure and reasonable constitutive model, this study presents fragility analysis and probabilistic safety performance evaluation of the nuclear containment structure under prestressed tendon fracture conditions. Change for the compressive stress state of the concrete and ultimate pressure capacity of the nuclear containment structure is discussed. Fragility curve and probabilistic safety margin of the nuclear containment structure under prestressed tendon fracture conditions is analyzed. Results indicate that for different types of fractured prestressed tendons, the influence of hoop prestressed tendons is greater than that of vertical prestressed tendon. Meanwhile, as for fracture locations, equipment hatch is the most vulnerable location. Ultimate pressure capacity of the containment structure decreases by no more than 2% under prestressed tendon fracture conditions considered in this study, which means that the impact for fracturing of the prestressed tendons on ultimate pressure capacity of the nuclear containment structure is small. Considering various uncertainties, 95% percentile pressure capacity corresponding to the most unfavorable fracture condition is 3.27 times the design pressure and it can meet the requirement that safety margin larger than 2.5.