Chinese Experimental Fast Reactor Core In One Direction, The Level Of Seismic Analysis

China Experimental Fast Reactor (CEFR) is the first fast reactor in China. The assemblies in Fast Breeder Reactor (FBR) core are deformed and shock each other under the earthquake. At the same time the fuel will be relocated, which results in variation of core reactivity. It is necessary to carry out seismic analysis of CEFR core for fuel load license. Safety qualification of the core under the earthquake is very important. Structural integrity of the subassemblies should be secured and the scram capability be maintained against the design seismic load. Variation of reactivity during an earthquake should be assessed.A lot of seismic analysis and experiments on FBR core has been carried out in other countries, specially in France and Japan, while less analysis and experiment has been taken in our country. In this paper some study on the model and the method in FBR core seismic analysis has been carried out by using a nonlinear finite element code FINAS developed by Japan. The beam with variable cross section area and moment of inertia is used to simulate one single assembly. The equivalent spring is used to simulate the gap between the spike of the assembly and the diagrid. Virtual added mass is used to simulate the fluid-structural interaction between the sodium and the assemblies during the earthquake. After that dynamic characteristics analyses of all kinds of the assemblies of CEFR core in air and sodium have been finished. Meanwhile shock analysis between one single assembly and the rigid wall has been completed. The results of these preliminary analyses demonstrate that the model is valid and effective.Based on these preliminary analyses, seismic analyses of center row of CEFR core under one single horizontal OBE and SSE have been completed by direct time integration method, which have given some results, including the deformation of core, the displacements of the assemblies, shock forces between the assemblies, bending moments in the sections of the assemblies, etc.The seismic analysis on selected three center rows of assemblies in CEFR core under OBE has also been carried out. The similar results have been given to compare with those of one row model. We can draw some conclusions as follows: The shock between neighbor rows under one single horizontal seismic excitation is relatively remarkable weak to those between the assemblies in the same row. Generally speaking, we can replace the displacements and the shock forces for three row model, even for the full core, by those for the one row model. And this replacement is some conservative.In this paper sensitivity analysis of some parameters which have been set assumed values has been taken. And some relationship curves between the results and the parameters have been given. We can estimate the corresponding results to real values of these parameters after we obtain them by analysis or experiment.It is the first attempt to a complete seismic analysis on FBR core in our country. In this paper some improvement on the model has been made. A set of local coordinate systems instead of the global coordinate system in conventional model is applied when taking the shock between neighbor rows into account. Due to the application of the local coordinate systems, the number of nonlinear finite elements has been significantly reduced and the computational time greatly shortened. Moreover, it is very convenient for us to acquire the shock forces between neighbor rows directly. We do not need vector re-composition of shock force after decomposition in the global coordinate system.