Study On Thermal Hydraulics Of Helical Tube Steam Generator For Small Modular Reactor

The research and development of small modular reactor(SMR)is a new trend of international nuclear energy application development,and it becomes an important way to seek the market of nuclear energy application.Comparing to other energy and largescale reactors,the international atomic energy agency(IAEA)think that the SMR has significant advantages on security,economy,nuclear non-proliferation and non-field loading capacity.The construction of SMR is flexible,simple and widely used,and it can effectively solve the power transmission problem in power-deficient areas and is considered as a “turning point for the nuclear energy industry”.SMR has received close attention from all countries in the world,especially developing countries.Because of its unique advantages of compact structure and high heat transfer efficiency,the helical coiled once through steam generators(HOTSG)have been widely used in the steam generator research and development design of SMR.Because the steam generator is a device with a relatively high incidence of accidents in the reactor operation,HOTSG has completely different structural characteristics from other types of steam generators,so studying the characteristics of HOTSG is very important for SMR design and construction.In order to accurately analyze the steady-state operating characteristics of HOTSG in SMR,the structural characteristics of HOTSG were analyzed,and the appropriate structural calculation principle was determined.The two-fluid model was used as a mathematical model to calculate the secondary-side vapor-liquid two-phase flow,and the vapor-liquid two-phase relationship was established.In the thermal phase transition model,the secondary heat transfer region is divided into a single-phase liquid region,a low-cooled superheated boiling region,a saturated nuclear boiling region,a transition boiling region,a membrane boiling region,and a superheated steam region.The heat transfer and pressure drop calculation model suitable for HOTSG was selected by comparison.The discrete format of the control equations was determined,the underrelaxation method was used to control the time steps,the staggered grid and the SIMPLIC algorithm were used to calculate the flow field,and the Successive Over Relaxation(SOR)iteration method was used to solve the equations.In this study,the simulation program of HOTSG was compiled with FORTRAN language.The MRX reactor in Japan and the SMART reactor in Korea were used as reference for program verification.Comparing with the ONCESG developed by the Korea Atomic Energy Research Institute,the simulation results agree well.The MRX reactor was then used as the basic study object to carry out the steady-state heat transfer analysis for the SMR.The effects of the secondary side flow rate,inlet water temperature,and the primary side flow rate on the heat transfer of the steam generator were studied.Results shows that the length of the boiling region gradually decreases when the secondary side flow rate decreases.As the water temperature increases,the total heat transferred from the primary side coolant to the secondary side working medium decreases;the primary side coolant flow has a significant influence on the length proportional distribution of each heat transfer area and the water vapor outlet temperature.The flow controls the outlet temperature of the steam.This study provided some guidance for engineering design and construction of HOTSG through steady-state characteristics analysis and lay a foundation for the future studies of flow instability and transient research.