3D transient CFD simulation of an in-vessel Loss-Of-Coolant Accident in the EU DEMO fusion reactor

Abstract

Accidental transients in fusion reactors, such as the in-vessel Loss-of-Coolant Accident (LOCA) considered here, are generally analyzed using system-level codes. However, because of their lumped nature, such tools cannot predict local pressure and temperature values, which are instead of interest to assess the integrity of the Vacuum Vessel (VV) structures. It is then fundamental to prove that the system-level tools' predictions are at least conservative. In this work, we analyze the helium flow inside the VV following a LOCA in the helium-cooled blanket of the EU DEMO, using a 3D transient CFD model implemented in the commercial STAR-CCM+ code. In view of the large pressure ratio, a hypersonic flow regime (Ma > 5) develops, with the formation of shock fronts requiring a high time and space resolution. The model is applied to compute the evolution of the pressure distribution inside the VV and then to compare it with the information provided by the system-level GETTHEM model. The predictions by the two models of the intervention time of the VV pressure suppression system are compared, showing that the 0D model is conservative.

Highly underexpanded helium jet and its effect on dust resuspension under in-vessel loss of coolant accident of fusion reactor

“…Meanwhile, the comparison of different turbulence results shows that the velocity distribution in the range of 0-600 m s −1 and the Mach number distribution in the range of 0-3 simulated by the k-w SST turbulence model are more similar to the results simulated by Uchibori et al [14]. Thus, the applicability of the model applied in this study to the underexpanded jet is qualitatively As shown in figure 6, the changes in pressure on the jet center line of different turbulence models are simulated and compared with the results of Uchibori [14], Zappatore [10], and experimental data of Kuehner [15] and Woodmansee [16]. Figure 6 shows that the pressure on the jet center line decreases with underexpansion and increases sharply with the generation of shock waves at the Mach number disk, so all results show a trend of first decreasing and then increasing.…”

“…In order to verify the effectiveness of the above solution model in the underexpanded jet, the flow under the same conditions as those in [10,[14][15][16] was simulated by ANSYS Fluent code, and the simulation results were compared with them. Figure 3 shows the geometric model of the verification simulation, and the pressure difference between the inside and outside of the model is large.…”

“…Therefore, when the adhesion force is constant, the airflow force is the decisive factor, and the friction velocity of the airflow directly determines the airflow force, which is crucial for dust resuspension on the wall of the VV [22,23]. The friction velocity is defined in equation (10):…”

“…The results showed that the volume fraction of beryllium dust decreases with an increase in height. Zappatore et al [10] simulated the flow-field changes in high-pressure helium impacting the VV within 60 ms after an in-vessel LOCA occurred in a heliumcooled blanket of a European demonstration reactor through STAR-CCM+ code. In general, the existing research on dust resuspension in fusion reactors mainly focused on a LOVA of atmospheric air entering the VV.…”