A new random distribution method to simulate PBM type reactors with MCNP

The very complex geometry of PBM type reactors along with software limitations have made the simulation of this type of reactor very difficult, even in the case of such flexible code’s as MCNP. In this paper a new random distribution method is proposed for the pebbles inside the core. This method has the advantage of needing a limited number of surfaces and cells thus reducing computation time and making it usable in older versions of MCNP. Whilst keeping the geometry as simple as possible, as shown by our simulations, this new distribution method greatly enhances the results obtained in the criticality height benchmark.

► Definition of a new BCC based unit cell.
► New modeling method for the pebbles inside the PBM-type reactor core.
► Benchmarking of the proposed model for the HTR-10 B1 benchmark problem.
► Effect of the mean distance of the fuel pebbles from the outer reflector on the critical height.