Reliability-based shape optimization of pressure vessels using an isogeometric approach

The design of pressure vessels, including nuclear components, must satisfy safety margins and regulatory requirements, while uncertainties from manufacturing and operation strongly influence structural integrity. Conventional safety-factor–based methods ensure conservatism but often lead to excessive thickness, increased cost, and degraded performance. This study proposes a reliability-based shape optimization framework using isogeometric analysis (IGA) to incorporate manufacturing uncertainties directly into the design phase. Control points of the IGA model are treated as probabilistic design variables, and reliability-based design optimization (RBDO) with sampling-based approach is employed to evaluate structural failure without analytical sensitivities. The computational cost of sampling is reduced by IGA's exact geometry, superior convergence, and mesh-free design updates. Furthermore, dynamic Kriging constructs accurate surrogate models with a limited number of samples, further reducing computational cost. The first example verifies the accuracy of IGA by comparison with finite element method (FEM) under identical conditions, and the second example demonstrates the efficiency of the proposed IGA-based RBDO procedure. Finally, the method is applied to the shape optimization of a set-in nozzle of a reactor pressure vessel, confirming its applicability to nuclear component design.