Development of a subchannel code for blockage accidents of LMFRs based on the 3D fuel rod model

To predict the thermal-hydraulic (T/H) parameters of the reactor core for liquid-metal-cooled fast reactors (LMFRs), especially under flow blockage accidents, we developed a subchannel code called KMC-FB. This code uses a time-dependent, four-equation, single-phase flow model together with a 3D heat conduction model for the fuel rods, which is solved by numerical methods based on the finite difference method with a staggered mesh. Owing to the local effect of the blockage on the flow field, low axial flow, increased forced crossflow, and backflow occur. To more accurately simulate this problem, we implemented a robust and novel solution method. We verified the code with a low-flow (similar to 0.01 m/s) and large-scale blockage case. For the preliminary validation, we compared our results with the experimental data of the NACIE-UP BFPS blockage test and the KIT 19ROD blockage test. The results revealed that KMC-FB has sufficient solution accuracy and can be used in future flow blockage analyses for LMFRs.