| Plate-type fuel assembly is a kind of nuclear reactor assembly composed of several dispersive fuel plates,which has the advantages of compact design,low fuel core temperature,large heat exchange area,high heat exchange efficiency and deep burn up,etc.,and has been widely used in small modular reactors or experimental research reactors.Because of the large number of each component in the fuel plate and adjacent plate space narrowing,external foreign bodies fall into the reactor core by expansion occurred after radiation exposure,or their own materials could lead to a coolant passage clogging,and cause the fuel plate local loss of coolant and temperature rise,which will cause the evaporation of the coolant and the disintegration of the fuel casing,resulting in leakage of radioactive material,posing a serious threat to the safety of the core operation.In this context,this paper based on COMSOL Multiphysics multi-field coupling program,using the Computational Fluid Dynamics(CFD)method,Taking the core standard fuel assembly of the International Atomic Energy Agency(IAEA)10 MW Material Test Reactor(MTR)as the research object,Numerical modeling and analysis are carried out for local blockage accident of fuel assembly.The results show that the temperature field characteristics under normal operating conditions are in good agreement with the reference value,which verifies the reliability of the model.Through the establishment of the slab fuel assembly local blocking flow of 2 d and 3 d space under steady state model and transient model,respectively to study the coolant inflow rate,single channel share access roads,the side block and center congestion,blockage in the different axial position on the influence of accident consequence,focuses on the single port completely jams component temperature distribution.On the basis of the steady-state calculation results of normal operation,the transient calculation and analysis of the two accident conditions of the occurrence of complete blockage of single flow channel and the occurrence of complete blockage of two adjacent flow channels are carried out,and the transient changes of temperature field after the occurrence of blockage condition are studied.The above research shows that the coolant inflow velocity is too small,which directly leads to insufficient cooling of the components and causes overheating of the core components.The blockage of a single coolant channel with different share will affect the flow velocity distribution and temperature field distribution of the channel coolant.The larger the blockage area proportion is,the larger the area of the vortex under the blockage surface will be,and the more obvious the temperature rise in the blocked channel will be.When the blockage is complete,the temperature will be the highest.Different boundary conditions were used to simulate the blockage surface in the modeling process,which also had an impact on the results.Compared with the complete blockage with the upstream flow isolated completely,the temperature change program caused by the complete blockage with the upstream flow isolated completely was significantly different from that of the incomplete blockage.When the blockage accident occurs,the temperature of the fuel plate connected with the blocked channel in the module responds quickly to the accident,while the time required for the coolant temperature to reach the stable state is relatively slow.When two adjacent flow channels are blocked at the same time,it is conservatively believed that the accident will cause the temperature of the intermediate fuel plate to rise to the point of melting the cladding material in a short time. |
PDF Full Text Request