The Design Of Brayton Circle For S-CO₂ PBR And Reactor Core Thermodynamic Analysis

Improving the efficiency, reducing the cost of construction and operation of nuclear power plants is always desired as long as safety is maintained. From this point of view, the Brayton circle using supercritical carbon dioxide (S-CO2) as working medium has great advantages over traditional high temperature gas cooled reactors (e.g., the helium cooled reactor) because the required power of compressors is significantly reduced, which means higher efficiency can be realized with lower reactor outlet temperature. Moreover, the S-CO2 turbine and heat exchanger are much smaller than equipment using ideal gas. Theremore, the whole system of S-CO2 Brayton circle is much more compact.In this thesis, pebble bed reactors and S-CO2 Brayton circle are combined together to form a new S-CO2 direct cooled recompression Brayton circle system. To analyze the heat balance of this system, a program is established on mathematic software Matlab. Using this program, the effects of compressing ratio of compressors, the volume of recuperators and paramenters at inlet of compressors on thermal efficiency are investigated respectively. The results are used as evidence to optimize the designed system. To justify this investigation, the main heat transfer models used are compared with computational fluid dynamics (CFD) by the way of simulating the same models.Based on the parameters gotten from aforementioned research, the flow and heat transfer in BCC and FCC arranged pebble fuel assemble are carefully investigated. The results indicate obvious difference for the two arrangements whereas both of them can satisfy the requirements of the system since the maximum temperature in pebble fuel is significantly lower than the melting point of the fuel.