Research Of LMFBR Core Assemblies Aseismic Model

Safety qualification of the core is a crucial issue in the seismic design of a LMFBR. Structural integrity of assemblies should be secured and the scram capability be maintained against the design seismic loads.Core dynamics of LMFBR is a new and difficulty topic. There are small gaps between the hundreds assemblies, and sometimes assemblies collide, which will bring non-linear contact problems. For these reasons, a nonlinear analysis with assembly collision is necessary to predict the seismic response in the cluster of assemblies. It is better to establish a relatively simple calculation model with little degrees of freedom and the limited element numbers where the collision phenomena cannot be mistaken.This paper presents series of experiments and theoretical researches of LMFBR, which have been done in France, Japan and Italy etc, introduces the research method in dynamics applied to the nuclear industry. Beam elements are used in the eigenvalue and free vibration analysis of single assembly. Two general-purpose codes ANSYS and CASTEM2000 are used, and the results are compared. It is used two methods (modal analysis and direction integration) to have a seismic analysis of single assemblies. Spring and gap element are employed to simulate impacts between assemblies. A horizontal seismic model of one-row assemblies is built, from which we can get the time history of the displacement, the acceleration and the impact forces. The agreement between the results of the analysis and SYMPHONY experiment is fairly good, (France and Japan have performed a collaborative experiment program named SYMPHONY), and further validated proposed FEM.Based on these results, a model of one-row assemblies in water and a core model will be made as the next step of the analysis.