Simulation of ACE and MACE experiments with a phase segregation model using the TOLBIAC code

The paper presents an interpretation of the ACE and MACE MCCI tests with the TOLBIAC code. The phase segregation approach has been introduced in this code. The main physical assumptions are described. Chemical reactions with Zr are believed to be achieved when the ablation of concrete begins. Mass losses from the melt due to melt splattering are taken into account, as well as formation of lateral crusts. The calculated evolution of melt temperature fits well with measurements. The model predicts well the effect of a power increase on the melt temperature; it is stated that the usual model (without phase segregation) approach for heat transfer is not able to reproduce this effect. Sensitivity calculations are performed. It is concluded that initial conditions, melt sparging and presence of lateral crusts have a significant effect on melt temperature; on the contrary, physical properties (viscosity, with reasonable variation range) and power split have a small effect on melt temperature. Finally, the points in favour of the phase segregation approach are summarised. Further development needs for TOLBIAC are also outlined. (orig.)