Study On Fluid-Solid Thermal Coupling Characteristics Of Center Measuring Column In Fast Reactor Under Thermal Shock

The central measuring column of the fast reactor is a key component of the important equipment cock in the fast reactor.It is responsible for providing the lifting rods for the control rods,shielding the thermal oscillation and thermal shock of the core outlet to protect the internal penetrating structure.It is very important for the safe operation of the reactor.important.The shutdown temperature of the sodium-cooled fast reactor core is much lower than the operating temperature of the core.Under the fast reactor accident conditions,the sodium temperature at the core outlet will undergo a rapid transition from high temperature to low temperature,with a maximum temperature difference of 140 degrees Celsius.Right and left,the temperature drop rate is up to 14 degrees Celsius per second,and the central measurement column will withstand the thermal shock to the structure caused by the drastic drop in sodium temperature at the core outlet.The thermal stress caused by large thermal shock may exceed the yield limit of the material itself,cause thermal fatigue and thermal aging of the central measurement column,and even cause the central measurement column to fail,which directly affects the safe operation of the reactor.Due to the relatively low operating experience of sodium-cooled fast reactors,there is less research on thermal stress and fatigue life under thermal shock at the center measurement column of fast reactors at home and abroad.Therefore,the center measurement column of fast reactors is subject to thermal shock during the emergency shutdown process.The analysis of thermal stress and fatigue life is of great significance.This paper analyzes the stress field and fatigue evaluation of the central measurement column based on the fluid-solid coupling method.First,the uncladding structure is modeled.The fluid-solid coupling module in ANSYS Workbench is used to calculate the central measurement column under accident conditions.In the absence of a cladding,thermal stress due to thermal shock,and fatigue analysis according to the method provided by the ASME design code,found that the cladding-free structure will fail within the design life.For the selection of the temperature load on the wall of the center measurement column,this article adopts the method of using the overall temperature of the wall of the center measurement column as the temperature load.Domestic scholars choose the temperature of the path where the temperature of the center measurement column changes most sharply in the height direction as the entire center measurement column The thermal stress on the wall surface is calculated by thermal stress.The thermal stress value obtained by this calculation method may be too conservative.It is necessary to compare the results obtained by the two temperature load selection methods and analyze the effect of the two temperature loading methods on the calculation results..As the uncladding structure cannot meet the design life requirements,the cladding structure is modeled,and the same temperature load is applied to the cladding structure for stress calculation and fatigue life analysis.It is concluded that the cladding structure can meet the design life.Requirements,and compare the calculation results with the calculation results of the uncladding structure,analyze the fatigue damage of the central measurement column during the design life,and the shielding effect of the cladding on thermal shock.