| It is necessary to consider the fluid-solid coupling effect due to the interaction between coolant and core assembly when analyzing the seismic performance of the fuel assemblies submerged in coolant used in a fast reactor. The effect of coolant for the core assembly can be seen as a kind of damping. Most of the researchers usually take added mass method to consider this effect. Meanwhile the added mass and damping were treated as the constants in the previous researches. In fact, the effect on assemblies from the coolant was the variables strongly dependent on the gap between the core assemblies. According to Wilson’s theory predicts, the added fluid mass is inversely proportional to the width of gap, while the added damping is inversely proportional to the cubic width of gap. In order to more accurately simulate the vibration of the core assembly, the methodology for the seismic analysis of FBR core assemblies using variable added damping have been studied. First, based on the formula derived by Liu Aiguo about added damping relationship with the gap, discrete added damping value is achieved according to the different gap. software ANSYS is applied in numerical simulation, by extracting every moment of the gap value in the simulation process to change the fluid added damping value, then calculated the next step. In this way, the simulation of variable added damping was achieved.In this paper, seismic analysis model of single row (5) core assembly of FBR was established. By comparing the two kinds of added damping models, the result show that the seismic analysis of the core assembly with variable added damping is feasible and correct. Meanwhile, Comparing with the added mass method used before, the simulation method used in this paper can get a more precise vibration of the core assembly. This also helps to reduce the conservative of the structural design and it is meaningful in engineering application as well. |
