High-Fidelity Depletion-Pebble-Flow Coupling Simulation of Pebble Bed Reactor HTR-PM

Abstract The high-fidelity depletion and pebble-flow coupling simulation of pebble bed reactor is realized based on Monte Carlo (MC) and Discrete Element Method (DEM). An HTR-PM full scale model with 420,000 fuel pebbles is built using the open-source MC code OpenMC, and the pebble trails are obtained with the open-source DEM code LAMMPS. The OpenMC code is modified so that the model geometry can change from one depletion step to another, and thus can be coupled with pebble-flow calculation. To obtain the high-fidelity results, each fuel pebble is specified to be a single burnup-zone. The pebble-wise power distribution and nuclide composition results are obtained and agree with the physical expectations. The model is depleted for 39 steps with each step representing 2 days. The time-consumption is 2.5 hours per step with a neutron history of 50,000,000 and a parallel scale of 40 MPI processes and 28 OpenMP threads per process. The memory-consumption is 40 GB per process.