Modeling Of Fouling On Heat Transfer Tube In Steam Generators For Sodium-cooled Fast Reactor

With the development of technology and increasing of people’s living standard,the consumption of electricity has increased year by year.It is expected that electricity will exceed petroleum as the most important energy source by 2030.Nuclear power has been rapidly developed as a low-carbon,clean and economical energy source.However,nuclear power also faces problems such as safety,shortage of uranium resources and disposal of spent fuel.To this end,experts from various countries have proposed the joint development of a new generation of nuclear reactors.Sodium-cooled fast reactors have received widespread attention due to the intrinsic safety of sodium,ability to breed nuclear fuel and transmute long-lived radioactive waste.As a pressure boundary of the sodium-water circuit of the sodium-cooled fast reactor,the steam generator plays an important role in reactor safety.Once the heat transfer tube leaks due to fouling corrosion on the vapor-liquid two-phase side,serious sodium water reaction accidents will occur.In addition to safety factors,fouling can also reduce the thermal hydraulic performance of heat transfer tubes in steam generators.In this paper,the fouling mechanism of heat transfer tubes of steam generator in sodium-cooled fast reactor is studied,and the fouling model is established.Besides,the fouling simulation program is edited using Fortran language.The program includes thermal hydraulic module and scaling calculation module.The thermal parameters obtained from the thermal hydraulic module are used as input values to the fouling module to calculate the axial dirt thickness distribution on the heat transfer tube,and then the dirt thickness is fed back to the thermal hydraulic module for updating thermal parameters.The thermal hydraulic module was based on a subchannel analysis program.By adding sodium property module,sodium heat transfer model,and sodium friction pressure drop model were developed to achieve the simulation results of the primary flow path(media sodium)and the secondary flow path.The fouling calculation module mainly studies the particle scaling and crystallization scale.According to the mechanism of fouling,it is divided into single-phase liquid zone,small bubble flow zone,slug-annular flow zone,dry and liquid deficit zone and single phase steam zone.The bulk fluid temperature distribution,the wall temperature distribution,the heat flux distribution,the fouling thickness distribution and their variation with time both were predicted by program.In addition,the chemical parameters of the water were analyzed.The effect of work parameters and geometric parameters on the amount of fouling were studied.In Chapter 2 of this paper,the calculation methods of related thermal parameters and the calculation logic of thermal modules are introduced.In Chapter 3,the mechanism of scaling and the calculation method of scaling calculation module are introduced.In Chapter 4,the physical model of steam generator is established and used.The Basset and Turner experiment results were used to verify the feasibility of the scaling module calculation.In Chapter 5,the experimental parameters of the China Experimental Fast Reactor were used as input values and the heat transfer tube fouling simulation program was used to calculate the parameters.As a result,the fouling thickness increases and gradually becomes stable as the operating time becomes longer.The fouling in the dry boiling region on the heat transfer tube is the most serious.After running for 10 months,the fouling thickness can reach about 26 μm.The mainstream temperature gradually increases along the axial direction of the heat transfer tube,and the saturation temperature remains unchanged in the two-phase region;the single-phase liquid region and the single-phase vapor region increase firstly and then decrease with the operating time,and basically do not change with the operating time in the two-phase region.The wall temperature of the heat transfer tube varies along the axial direction which is similar to that of the main flow temperature,but it suddenly increases at the gas-liquid two-phase single-phase steam transition point.In the single-phase liquid area,it gradually increases with the operating time and then gradually decreases in the single-phase steam area.Small,basically unchanged in the two-phase area.The heat flux will fluctuate greatly along the axial direction of the heat transfer tube,and reaches a minimum at the single-phase water-gas-liquid two-phase transition point,and the vapor-liquid two-phase-single-phase vapor transition point will reach its maximum value and then decrease dramatically.The heat flux of the tube increases firstly and then decreases with the running time.This is because a small amount of fouling will increase the heat transfer area and the heat transfer capacity increases.In addition,the fouling rate increases with the increase of the concentration of the dirt particles,the diameter of the particles,the diameter of the heat transfer tube and the heat flux,and the fouling velocity decreases with the increasing of mass flow and denudation coefficient.