The seismic analysis of the core structure in a pool-type material test reactor using 3-D finite difference method

The integrity of nuclear reactors under seismic conditions is one of the most important items of safety analyses. In order to keep the first barrier of radioactive materials and a safe emergency shutdown system under earthquake, the reactor components (particularly fuel elements) and the reactor control system must withstand against seismic loads without hazardous physical damage or failure. Among several qualification approaches of seismic analyses, the Finite Element Method (FEM) is the most common approach used in practical mechanical engineering problems. In this paper, a FEM is employed for detailed analyses; in which a 3-D homogenization model is chosen and used to study the overall static and dynamic behavior of Tehran Research reactor (TRR) core under seismic (level 2) excitations via 3-D visual effects of seismic stresses and damaged objects or displacement effects. Such visualization creates a unique sense of a realistic hazard. In this way, the ABAQUS software which is one of the leading applied FEM programs in the world are used for analyses. This software can easily and robustly solve dynamic, nonlinear, finite element models of structures. Two different kinds of seismic loading spectrum are used to cover and study a wide range of motivations and responses, conservatively. New safety assessment based on a 3-D accurate modeling and loading shows that the TRR core structures should be enhanced against severe seismic loads (particularly hard fast shocks recommended by the US NRC and IAEA) via dampers or any type of additional supports.