Thermal Characteristics Analysis For S-CO₂ Cooled Pebble Bed Reactor

In order to meet the growing market demand for nuclear energy,reactors with multi-application,miniaturization,modularization and other similar and significant features are favored by many countries in the world.In such a background,this work puts forward a new concept of supercritical carbon dioxide(S-CO2)cooled pebble bed reactor(SC-MPBR)that has the advantages of small size and high degree of modularity,as well as high thermal efficiency.For SC-MPBR,this work has done the thermodynamic design of supercritical carbon dioxide Brayton cycle,gives a reasonable scheme of direct cycle and the cycle's thermodynamic parameters were determined.The preliminary thermal design of reactor was also conducted to provide thermal parameters for the subsequent CFD analysis.In the CFD analysis of local structure of pebble bed,the mesh generation technology of pebble bed structure was introduced,and the influence of different contact point processing methods were compared.Through analyzing the different number and position of contact points caused effect on the flow and heat transfer mechanism in different pebble fuel arrangements,the way of improving temperature distribution on the surface of a single spherical fuel was proposed.Comparing the CFD calculation data with the KTA calculated values,KTA is claimed conservative in the thermal design of SC-MPBR.Finally,this work introduced the temperature distribution calculation method for the macroscopic scale,meso-scale,and the micro-scale.Besides,the two temperature method was improved and the coefficients calculation models were put forward to obtain more accurate temperature distribution on the surface of spherical fuel theoretically.The CFD modeling method for spherical fuel was introduced,and the calculation values of CFD model are used for the verification of TTM,results show that has a high accuracy and a wide application range.