Applications to Phebus and Quench experiments

Boron carbide is used in many designs of nuclear power plants like BWR, VVER, some PWR, and EPR as a neutron absorber material. It is important, therefore, to assess its effects on the main core degradation phenomena, as well as the gas release, and the impact on the fission products behaviour during severe accidents. This paper is focused on the progress on the B4C control rod modelling in Severe Accident codes (SA), like ATHLET-CD, ICARE2, ASTEC MELCOR and MAAP, performed in the frame of the Network of Excellence SARNET during the five year activity of the Work Package 9.2, following on from the previous European Union 5th Framework COLOSS project. Starting from basic modelling derived from available tests reported in literature, large improvements of the correlation for B4C oxidation were gained from analytical experiments performed at FzK (Germany) and IRSN (France), mainly at higher temperature. The modelling has been applied to the analysis of experiments involving a B4C control rod in a small fuel rod assembly, such as Phebus FPT3 in pile experiment, as well as out of pile experiments Quench 07 and 09, aimed at studying the course of severe accidents. Regarding the hydrogen generation, the results given by different code simulations ar