Validation and verification of the coupled neutron kinetic/thermal hydraulic system code DYN3D/ATHLET

The results of DYN3D/ATHLET simulations were assessed both against available measured data and calculations performed with similar multi-physics codes. The paper includes an overview of the simulated problems and the most representative results of DYN3D/ATHLET validation/verification for all coupling modes. The obtained experience of code validation provides a better understanding of reactor transients with a strong interaction between neutron kinetics and thermal hydraulics, helping to improve computation models. This experience is also useful for the present and further activities in coupling of DYN3D with other best estimate codes, like CFX, TRANSURANUS, etc.