Abstract:Nuclear-fuel-safety-rod-driving mechanism is an important part of the nuclear reactor and its seismic characteristic is a very critical parameter in safety evaluation.In the preliminary design stage,the simulation of the distribution of stress under seismic load is helpful to improve its seismic characteristic.To ensure that the nuclear fuel safety rod driving mechanism functions safely and reliably in the whole longevity,the seismic analysis was carried out at the level of preliminary design.First,the model of nuclear-fuel-safety-rod-driving mechanism was simplified based on the parameter settings.Second，the seismic response spectrum was ensured, referring to domestic and overseas seismic fortification criterion，and then the practical condition was analyzed and converted to boundary condition in finite element model.The stress distribution of the whole mechanism and the outer sleeve and the single internal structure were calculated and compared.And the influence of the outer sleeve on seismic characteristic was studied.The typical node paths were constructed based on the features of three models.The comparison of the extracted stress from the node paths showed the difference of stress distribution of three models.The results indicated that directly analyzing the stress distribution of the outer sleeve could evaluate the rationality of the whole mechanism.The outer sleeve can efficiently reduce the stress of internal structure under seismic load,the stress distribution of the outer sleeve is nearly the same with the whole internal structure,and the stress distribution of the single outer sleeve is nearly the same with the outer sleeve,which is a great reference to the engineering design.By this way,the efficiency of design would be enhanced and the risk would be reduced.