Various Bypass Flow Paths and Bypass Flow Ratios in HTR-PM

In HTR-PM, gaps between graphite and carbon blocks are widely distributed in the reactor core. The cold helium flows may be bypassed and not completely heated, therefore, the accurate prediction of bypass flows is a key problem related to the reactor safety. The flow network method was employed to represent interconnected bypass flow paths and calculate the bypass flow rates. Bypass paths in irregular shapes were simulated by CFD to get local and friction resistances. Typical bypass flow paths, included flow through sealing ring to the pebble discharge tube, flow through small holes to the control rod channels and flow through vertical gaps to the hot plenum, were modeled to calculate corresponding bypass flow rates. Large gaps, where might induce high flow rates at two ends of the bypass paths, should receive more concerns.