Analysis of flow path blockage accident in cased assembly

Highlights: ► The flow path blockage accident (FPBA) in a cased assembly is analyzed. ► The power distribution and blocked area are the main effect factors on the FPBA. ► The FPBA cannot change the positions of the maximum fuel temperature and MDNBR. ► If the reactor can be scrammed after FPBA, the fuel element will keep its integrity. - Abstract: The responses of the thermal-hydraulic parameters during flow path blockage accident (FPBA) in a cased assembly are different from those during FPBA in an assembly without case due to the different structures of these two fuel assemblies. The FPBA in a cased assembly is analyzed and simulated using RELAP5/MOD3.2. It is found that the reactor radial power distribution, axial power distribution and the blocked area are the main parameters which affect the processes and results of FPBA. When the reactor power is smaller than a certain value, the failure of fuel elements will not occur even when the flow path is blocked completely. The larger the reactor operating power, the higher the maximum fuel center temperature and the lower the water level in the reactor core. If the reactor can be scrammed after the flow path blockage, the circumambient fuel elements will be effectively cooled and keep their integrity. The results and conclusions are important to judge the integrity of fuel elements during FPBA in a cased assembly.