Achievements of spray activities in nuclear reactor containments during the last decade

During the course of a severe accident in a nuclear power plants, spray systems are used in the containment in order to prevent overpressure and to wash-out fission products. Spray will also have an impact on the gas mixing in case of the presence of hydrogen. This paper presents the current achievements of spray activities during the last decade. Spray systems in nuclear reactors are described and an overview of the knowledge gained on these sprays during the last decade is given. During this period, more and more studies devoted to CFD simulations (Computational Fluid Dynamics) of real containment severe accident conditions have been published. In order to give confidence to such calculations, code validation is mandatory. As a result, experiments have been performed in order to validate the spray models. A review of experimental programs, in CARAIDAS, CALIST, TOSQAN (IRSN) and MISTRA (CEA) facilities is presented here. Spray models developed for the codes involved in the above mentioned simulations of these experimental programs are also discussed, as well as international benchmarking activities performed during the last decade. CFD calculations at real scale with well validated phenomena on separate-effect tests are recommended in order to bring some insights for different configurations typical for safety concerns.