Development and validation of the multi-physics DRACCAR code

•Recent advances in the development and validation of the DRACCAR code are presented.•Experimental programs dealing with reflooding of an intact or ballooned bundle are simulated.•Ways of improvement have been identified and are in progress such as a new reflooding model and a 6 equation version of the thermal–hydraulics code.•Spent-fuel-pool draining accidents are addressed and the modeling flexibility of the DRACCAR code to model non axis-symmetric systems is emphasized. To meet the simulation needs of its LOCA R&D program, the IRSN is developing a multi-rod computational tool named DRACCAR. In order to realistically describe the behavior of the reactor core during a Loss Of Coolant Accident (LOCA), modeling has to take into account many coupled phenomena such as thermics (heat generation, radiation, convection and conduction), hydraulics (multi dimensional 1–3 phase flow, shrinkage), mechanics (thermal dilatation, creep, embrittlement) and chemistry (oxidation, oxygen diffusion, hydriding,...). This paper presents several aspects of the DRACCAR code abilities: first to handle thermal–hydraulics during reflooding of an intact and of a partially ballooned bundle and secondly the simulation of the OECD SFP phase II experiment dealing with the instantaneous draining of a spent fuel pool.