CFD simulations of MYRRHA Control Rod system in COMPLOT facility

In the framework of the MAXSIMA project we simulate the buoyancy driven control rod system of the MYRRHA reactor, in the COMPLOT experimental facility. We simulate by CFD means the transient behavior of the full scale Control Rod (CR) in a flowing Liquid Bismuth Eutectic (LBE) environment. The insertion is performed in a quite small time lapse (less than 1s), under the buoyancy influence and is slowed down by means of a damper which forces the fluid through a series of discharge slots. Globally, the original geometry is modeled with high fidelity, keeping a reasonable balance between computational power and physical behavior. The fluid path is modeled in full detail, while for the moving component some simplifications are made. Given the complexity both of the geometrical model and of the physics, the work has been split in two distinct steps. The preliminary stage regards half of the movement of the absorber pins bundle. In this stage, we familiarize with the geometry, we develop moving meshes techniques and implement strategies for the conservation of a good quality mesh. Particular attention is paid to the solution independence with respect to the re-meshing operations. Suitable boundary conditions, compatible with the displacement, are determined. The second step would have been to reproduce the second part of the CR movement in a much stiffer configuration, facing the limitation of the technique. However, in the meantime, the overset mesh methodology implemented in STAR-CCM+ reached sufficient maturity, allowing the entire CR displacement to be simulated in one shot. The background domain and a volume enclosing the moving component are separated overlapping regions, each with its own mesh. An interface is created in order to couple the solutions on the two overlapping grids. The main advantage is that there is no need for re-meshing. The method is explained and is applied to reproduce the CR insertion as in the COMPLOT experiment, with an imposed displacement.

@Misc{PM14d,
  author       = {Profir, M. and Moreau, V.},
  title        = {CFD simulations of MYRRHA Control Rod system in COMPLOT facility},
  year         = {2014},
  keywords     = {MYRRHA, liquid lead, safety rod systems, dynamic mesh},
  url          = {https://publications.crs4.it/pubdocs/2014/PM14d},
}