Safety Analysis of Nuclear Concrete Containment Structures

摘要

The objective of this work is to present a procedure for calculating the reliability of a concrete containment structure in terms of a safety index when the random variables entering into the design equations are defined by their probability distribution function. This is accomplished by means of mapping the random variables into standardized Gaussian variables. The evaluation of the safety index is greatly facilitated by selecting a polynomial function to approximate the transformed variable. The proposed approach provides a means for extension of the reliability index from second moment formats towards a probabilistic format. The procedure is illustrated for a post-tensioned concrete containment structure considering failure modes typical of those for cylindrical shells. Selected design cases involving structural loads caused by the seismic motions and the loss-of-coolant accident are treated. In addition, this work includes a brief assessment of failure modes and an evaluation of uncertainties in physical properties of materials and load parameters. A Monte Carlo simulation method was used to predict the stochastic response characteristics of concrete containment considering the effect of the randomness of the soil characteristics and concrete stiffness.