Simulation Strategy For Multi-body Structure Of Side Reflector In HTGR Ceramic Internals Subjected To Seismic Loading

Along with human beings'consciousness of sustainable development, nuclear power, which is often treated as a kind of clean energy with mature technology, attracts more and more attentions. In nuclear engineering, safety is one of the most vital focuses. Reactor structures must work safely under various complicated conditions and loads, especially when earthquake occurs.In the reactor core, stack structure composed of graphite bricks with simple connection components is the most popular structural form. Hence, it is a typical multi-body dynamic problem when the structure is excited by earthquake loadings. In order to reduce the difficulties in seismic analysis, such stack structure is often simplified as some 2D local systems composed of rigid bodies and spring-dashpot connectors. However, this strategy is rarely used in 3D simulation because the computational cost is unacceptable.The purpose of this dissertation is to find an efficient and correct simulation strategy for seismic analysis of the 3D multi-body structure of side reflector in HTGR ceramic internals, and implement a safety assessment for a real structure. The main contributions are as follows.Firstly, according to the characters of the reactor core structure, several simplification and modeling schemes are presented and compared. A kind of simplification model, which is composed completely by spring-dashpot connecters and with the lowest computational cost, is chosen for further studies.Secondly, according to the fundamental principle of the multi-body dynamic, some reasonable techniques are designed for obtaining equivalent damping and elastic coefficients of the connectors. Then, a verification procedure is carried out by comparing the results of the proposed connector model with the elastic/rigid contact model, which shows the validity and the efficiency of the proposed model.Thirdly, a parametric modeling scheme for above model is accomplished by compiling a scripting program based on ABAQUS platform. So, heavy work caused by manual operation for repeated modeling of a large amount of connectors can be avoided.Finally, a 3D simplification model of a real structure is established. By adopting above equivalent elastic and damping coefficients, the dynamic response is obtained through numerical analysis in ABAQUS. By means of post-processing techniques, the numerical results are analyzed in both time and frequency domains, and the strengths of some key structural components are also checked. Thus, the safety assessment of the real structure is achieved.