Analytical and Numerical Assessment of Thermally Induced Pressure Waves in the IFMIF-DONES Liquid-Lithium Target

Abstract

The intended steady-state operation conditions of the IFMIF-DONES target system are based on the D+ beam stationary running at full nominal power (5 MW). Nevertheless, critical situations can occur in case of unavoidable sudden events like beam trips. The instantaneous variation in the heating power deposited in the lithium when the beam is rapidly switched between-on and -off states leads to the thermal expansion, which is compensated by the compression of the target material, resulting in locally high pressures and a pressure wave propagating through the target towards the back wall. Besides tensile stress of the back wall structure caused by shock pressure waves, undesirable cavitation may occur, when pressure waves are reflected leading to negative pressures.For this purpose, analytical and numerical thermo-hydraulic analyses of the effects generated in the lithium during the beamon/beam-off switches are performed. The pressure wave development inside the Li-target has been analysed numerically with the CFD code Star-CCM+. The simulation of the thermal induced pressure in the Li-target shows that for normal operation conditions peak pressures of about 0,3 MPa can be reached. In both "beam-on" and "beam-off" cases a zone with a negative static pressure flow is forming in the Li-target. The results obtained from analytical and numerical analyses of the thermally induced pressure waves are discussed concerning potential cavitation and stability of the lithium free-surface flow. Simulation results served as input for the analysis of fatigue effects occurring in the target structure during sudden beamon/beam-off events.

Loss of Liquid Lithium Coolant in an Accident in a DONES Test Cell Facility

“…Considering thermal-hydraulic analyses performed within the DONES/IFMIF facilities context, most of the studies have focused on CFD modeling of liquid lithium target with a focus on correctly modeling phenomena such as liquid metal flow, free surface flow under vacuum [34][35][36][37] or specific effects resulting from beam/target interactions [38]. This is justified by the many requirements for facility operation relying on the specific conditions that the flowing liquid lithium film will stably achieve.…”

Assessment of Fatigue Effects Induced by Fast Beam Transients in the IFMIF-DONES Li Target

“…In order to perform the fatigue analysis of the BP, the time evolution of the pressure distribution on the component following a fast beam trip event is needed. To this purpose, a CFD calculation of the fluid dynamic conditions in the lithium during various type of beam transients have been preventively carried out by KIT [5] and then provided as input to the thermomechanical model for fatigue assessment. In particular, Fig.…”

“…Therefore, this latter case represents the worst one from the fatigue point of view as it presents the greatest pressure excursion during the transient. The sudden beam ON/OFF switch gives rise to much lower pressures and thus it is not relevant to thermomechanical aspects (it is however important for the study of potential cavitation issues, see [5]). The propagation of the pressure along the backplate in case of sudden switch OFF/ON of the beam is illustrated in Fig.…”