Reliability Analysis of the Ductile Fracture of Overpacks for High-Level Radioactive Waste in Repository Conditions

Abstract

In France, a deep geological repository project is under development for radioactive waste management. The lack of knowledge from similar facilities and the large time scales involved result in uncertainties about the repository environment in operating conditions. The reliability methods are dedicated to dealing with such problematics and are used in this work to study the behavior of the overpack containing high-level radioactive waste. Its function is to isolate the waste from the environment for the first 500 years. The analysis is based on a finite-element model of the system integrating the time-related degradation of the system and considers a ductile fracture criterion. The stochastic structural model includes uncertain and time dependent corrosion rates and mechanical loading. A Kriging metamodel is calibrated in order to predict the behavior of the finite-element model with a much smaller computation time. The failure probability of the system is estimated using Monte Carlo simulations based on the results of both the finite-element model and the Kriging metamodel. The behavior of the system and the parameters having a first order influence on its performances are investigated through a sensitivity analysis.