CFD simulation of the control rod system test at the Complot experimental loop

In the framework of the MAXSIMA project, we simulate the dynamics of the control Rod (CR) system of the MYRHHA reactor, in the COMPLOT experimental facility, under development at SCK•CEN. We simulate by CFD means the transient behavior of the full scale control rod in a flowing Liquid Bismuth Eutectic (LBE) environment. The insertion must be performed in 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. The original geometry of the fluid path is modeled with high fidelity, while some simplifications are made for the moving component. 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. We develop moving mesh techniques and implement strategies for the conservation of a good quality mesh, paying particular attention 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 re-meshing 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 method is applied to reproduce the CR motion as in the COMPLOT experiment, with several preliminary simplifications and gradual increased geometrical accuracy. At first, the displacement is imposed, according to SCK•CEN theoretical calculations; then we intend to infer the displacement by Newton law from the force balance on the CR. The numerical methodology and the results will be validated against the experimental results and will be used further to support the MYRRHA design.

@TechReport{PM14b,
  author       = {Profir, M. and Moreau, V.},
  title        = {CFD simulation of the control rod system test at the Complot experimental loop},
  institution  = {CRS4},
  month        = {december},
  year         = {2014},
  type         = {Deliverable D3.8},
  keywords     = {MYRRHA, liquid lead, safety rod systems, dynamic mesh},
  url          = {https://publications.crs4.it/pubdocs/2014/PM14b},
}