SEISMIC SAFETY ANALYSIS OF NUCLEAR POWER PLANT CONTAINMENT STRUCTURES

Abstract

Containment system of a nuclear power plant is an engineered safety feature to meet one of the basic safety requirements of containing radioactivity. Structural design of nuclear containments is governed by the design pressure value and leak tightness requirements along with the external events such as earthquakes, wind, airplane crash and blast shock waves. Generally a secondary containment is provided to resist the loads associated with the external events except earthquakes that pervades through every structure.In this dissertation work, an attempt has been made to estimate the damage of the inner and outer containment structures under gradually increasing internal pressure load. The performance of the outer containment structure is also evaluated under strong ground motion. For internal pressure analysis, pressure load is applied to the inner surfaces of the containment structures that gradually increases from 0.0 to 0.4 MPa. The safety analysis of the outer containment structure under seismic excitation is performed using incremental dynamic analysis (IDA). Spectrum compatible time histories of two earthquake records normalized to 0.24g (MCE, Zone Was per IS 1893: 2002) are generated for this purpose. Finite element program ABAQUS is used for both pressure analysis and IDA. 3D model of both the containment structuresare made using 8 nodded brick element. To simulate the realistic behaviour of the structure, two layers. of reinforcement are provided in both longitudinal and hoop directions. Concrete damage plasticity model has been used to introduce nonlinearity. The damage caused by the increasing pressure and severe earthquake load is calculated in terms of damage index. The crack propagation for different PGA values is shown considering the Northridge Earthquake, 1994 as the input motion.Permanent deformation is observed in the structure both in horizontal and vertical direction for intensity more than 0.24g PGA.