Research on Fuel Element Positioning Structure and Heat Transfer Characteristics of The Lead-Bismuth Cooled Fast Reactor

After the new crown pneumonia outbreak, climate catastrophe will be the next crisis facing humanity. Stopping global warming requires a halt to the emission of greenhouse gases into the atmosphere. Among the "zero carbon" power sources, solar and wind are both intermittent resources, with high power volatility and low power density (5-50w/m²). Nuclear power is the main force to promote the " grid decarbonization" action. The Lead (lead or lead-bismuth eutectic alloy) cooled fast reactor is one of the generation IV fast reactors for further development. The lead or lead-bismuth alloy possesses good performances, such as high boiling point, high density and low chemical activity. Like the sodium cooled fast reactor, it allows the closure of the fast reactor fuel cycle and therefore enhances the utilization ration of U resources. It can also incinerate and transmute the long lived high radioactive waste and therefore reduce the radioactive waste volume. And a new balance of economics and safety has been established that will make nuclear power both safe and economical, making it possible to downgrade the green premium of "zero carbon" power. Fuel assembly is the key element in the reactor, the positioning design of which is one of the key technologies. A reasonable positioning structure should be designed which can maintain appropriate rod-to-rod spacing, limit the maximum amplitude of the fuel elements and provide a suitable channel for the coolant. For the grid spacer, wire-wrap or rib, whichever positioning structure is used in the fuel assembly, it must participate in the important coolant flow process, and has obvious influence on heat transfer. Therefore, on the basis of considering the core factors such as material selection and structural form, the design of positioning structure also needs to focus on the thermohydraulic process that it participates in and influences. In this paper, according to the design requirements of the fuel assembly of the Lead-Bismuth Engineering Test Reactor, the research and selection of fuel assembly positioning structure are carried out, and the influence of different positioning structure and parameters on the heat transfer of coolant flow in the assembly is analyzed, which provides design reference for the optimization of fuel assembly positioning structure of the Lead-Bismuth Cooled Reactor.