SEISMIC. ANALYSIS OF NUCLEAR REACTOR CONTAINMENT STRUCTURE

Abstract

The reactor containment structure contains the nuclear reactor as well as other equipment and pipings. It plays an important role in preventing dissipation of radioactive substances to exterior by bearing the load caused by high pressure and temperature in case of a loss of coolant accident. Satisfactory and safe performance of nuclear containment structures under seismic occurrence is necessary in nuclear power plants to avoid radioactive leakage from nuclear reactor and power supply equipment. To fulfill these requirements reactor containment structure should have high strength with respect to seismic and pressure loading higher, damping characteristics with respect to dynamic loads, a large degrees of freedom with respect to shape and wall thickness, and should have ability for appropriate layout and design. Soil-structure interaction is one of the main factors affecting the behavior of reactor containment structure under dynamic loading and thus has been for a long an active field for research. This dissertation presents the comparison of the dynamic response of reactor containment structure obtained from different analytical models incorporating effect of soil-structure interaction on the analysis. The analysis is carried out using finite element analysis package "ANSYS". Reactor structure is analyzed using beam model and 3D finite element model. Natural periods and acceleration response of structure are compared using modal analysis and time history analysis, respectively, for different soil conditions (soft, medium and hard). Finally, the stresses in the reactor containment shells for hard soil conditions for both the models are studied using response spectrum analysis for spectral acceleration given in IS: 1893 (2002) code. Analysis shows more correlation in between the results of beam and 3D finite element model for hard and medium soil embedment as compared to soft soil embedment. Further CQC method for modal combination gives much close values of stresses between beam and 3D model, than SRSS method.