The reactor dynamics code DYN3D – models, validation and applications

•Overview on models and methods of the reactor dynamics code DYN3D.•Neutronic solvers for various fuel assembly geometries, diffusion and SP3 transport.•Code couplings to thermo-hydraulics system codes, fuel performance code and CFD.•Overview on verification and validation, examples for applications to challenging transient analyses.•Code versions for innovative reactors.

The article provides an overview of the reactor dynamics code DYN3D. The code comprises various 3D neutron kinetics solvers, a thermal-hydraulics reactor core model and a thermo-mechanical fuel rod model. The implemented models and methods and the capabilities and features of the code are described. Latest developments of models and methods are delineated. An overview on the status of verification and validation is given. Code applications for selected safety analyses are described. Furthermore, multi-physics code couplings to thermal-hydraulic system codes, CFD and sub-channel codes as well as to the fuel performance code TRANSURANUS are outlined. Developments for innovative reactor concepts, in particular Molten Salt Reactor, High Temperature Gas-cooled Reactor and Sodium Fast Reactor are delineated. The management of code maintenance is briefly described. An outlook on further code development is given.