Advances in the development of the code FRENETIC for the coupled dynamics of lead-cooled reactors

The simulation of the dynamic behavior of lead-cooled fast reactors (LFRs) is a key step in the development of this innovative nuclear technology. To this aim, computational tools for the coupled neutronic/thermal-hydraulic description of the reactor core need to be developed. This task can be carried out at different levels of complication. Some codes are characterized by a highly detailed description of the system components, but they also require a high computational cost. At Politecnico di Torino, the research group of nuclear engineering is developing the FRENETIC code for the dynamic simulation of LFR cores with closed hexagonal fuel elements at a reduced computational cost, suitable for parametric evaluations and simulations of safety-related transients. The code separately solves the neutronic and thermal-hydraulic model equations, with neutronic/thermal-hydraulic feedback introduced through a coupling procedure. The work carried out during this year activity is focused on the following topics: • further development and validation of the thermal-hydraulic module by introducing additional models for the treatment of hexagonal fuel assemblies of a specific geometry (the so-called "box-in-the-box" configuration) and the radial conduction in the fuel pin; • development of the neutronic module by introducing a new decay-heat model; • first coupled neutronic/thermal-hydraulic validation of the code against the shutdown heat removal tests performed on the Experimental Breeder Reactor II of Argonne National Laboratory.