Seismic Analyses Of Lead-Bismuth-Cooled Fast Reactor Vessel

With the development of nuclear industry, the U.S. Department of Energy and the international nuclear experts put forward the concept of Generation-IV nuclear reactor systems. Lead-Bismuth-Cooled fast reactor is one of the six most promising advanced reactor systems for Gen-IV. The use of lead-bismuth coolant can improve some economics and safety. Reactor vessel is the key equipment of the whole nuclear power plant. It is one of three radioactive protection barriers. It is very important to ensure the structural integrity and functionality of the reactor vessel. So the seismic analysis of the reactor vessel is an important issue in lead-bismuth-coo led fast reactor design.An example of storage tank problem with both numerical and experimental solutions is chosen in this paper to ensure the validity of analyzing fluid-structure interaction systems by means of AN SYS. Then this paper focus on the vessel of lead-bismuth cooled reactor CLEAR (China LEad Alloy cooled Reactor), builds up the vibration models of fluid-structure interaction systems for both a top support type and a bottom support type. The time history response analyses are carried out to calculate the dynamic responses of reactor vessel under gravity, hydrodynamie, axial load and SL-2 seismic load. It is found that the bottom support type of CLEAR vessel is prior in terms of anti-seismic designs.The bellows are modeled by the equivalent spring elements which are uniformly added to the top of cylinder part of the vessel to accomplish the mechanical seals and elastic connection between the reactor vessel and the guard vessel. Meanwhile the effects of this elastic connection on structural seismic performance are analyzed. It is found that the maximum stress intensity at the end of the lower skirt support decreases with increasing equivalent spring stiffness.Finally a sensitivity analysis of spring stiffness which has been set assumed value is studied. At the last part of this paper the calculation and evaluation for reactor vessel stress intensity are given which consider the primary stress and secondary stress. Based on the ASME codes and the nuclear power plant earthquake code etc., it is found that the stress intensity of the CLEAR vessel is qualified.