Variability Of Dynamic Characteristics Of Nuclear Power Plant Structures PDF Download

This research is part of a large research project with the objective of developing a toolset to advance the state of performing the seismic probabilistic risk assessment (SPRA) of commercial nuclear power plant (NPP). The project involves development of a dynamic failure analysis module using the Multiphysics Object Oriented simulation Environment (MOOSE, 2015) platform. This thesis describes the first effort to develop structural models and perform dynamic analysis within the MOOSE framework. In order to perform SPRA of NPPs, seismic analysis of the structures, systems, and components (SSCs) of interest at a NPP must be conducted. The seismic analysis of SSCs requires the development of SSCs’ realistic computational models to accurately determine their responses. This thesis describes the modeling procedures and dynamic analysis of some of the selected critical NPP structures, including containment structure, auxiliary building, and condensate storage tank (CST). Three-dimensional (3D) detailed finite element (FE), distributed-mass stick, and lumped-mass stick models of the containment structure are developed. Modal and transient analyses are performed, and then responses from different models are compared. Three different auxiliary building models are developed to investigate the torsional effects, and to see whether simplified models can accurately represent the 3D response of the structure. A number of 3D FE and 2D simplified CST models are developed. Modal analyses of the 2D and 3D models are performed and the dynamic characteristics of the models are compared. Transient and buckling analyses of the 2D simplified CST models are performed to determine the maximum axial loads and base reactions that can be used to determine failure probabilities due to buckling and sliding of the CST. Although 3D detailed FE models are the most accurate for structural dynamic analyses, many simulations under multiple ground motions will be needed in order to determine the failure probabilities of SSCs. Therefore, the main research objective is to develop relatively accurate simplified models of the selected NPP’s critical structures. As compared to the 3D detailed FE models, simplified structural models of SSCs can quickly provide sufficiently accurate response under multiple grounds motions for SPRA.