Numerical Strategy for Forecasting the Leakage Rate of Inner Containments in Double-Wall Nuclear Reactor Buildings

In the context of life extension of nuclear reactor buildings while ensuring safety and regulatory requirements, a numerical strategy is proposed to compute and forecast the air leakage rate evolution of inner containments in double-wall reactor buildings under standard long-term operation. In order to reduce the numerical cost of such complex computations, the proposed strategy is based on a coarse but adapted mesh together with a chained weakly-coupled thermo-hydro-mechanical modeling. The total leakage rate is then computed with a specially-designed tridimensional finite element based on a non-linear thermal analogy.This methodology is used to model the behavior of the VeRCoRs mock-up, a simplified nuclear reactor building at scale 1:3, built and monitored by EDF. Results obtained until the first pre-operational pressurization test have been discussed in a dedicated benchmark organized by EDF. The proposed methodology provides delayed strains and leakage results in good agreement with available experimental data. A blind prolongation until the first decennial test of the mock-up is presented and analyzed.