Conceptual design studies for the liquid metal spallation target META:LIC

A re-evaluation of various target concepts was decided by the target station concept selection group during the design update phase of the European Spallation Source (ESS) in order to include new target concepts in their selection process. During this phase, the META:LIC (Megawatt Target: Lead bismuth Cooled) concept was invented and developed based on an analysis of existing and new liquid metal targets. Within two years of design and research activities, the META:LIC concept reached the level of proof of principle and was selected as comparative target solution for assessment purposes for ESS. Both a window target option for the start of operation and a windowless target option with extended lifetime are foreseen. The present work describes the META:LIC target concept that has LBE (lead-bismuth eutectic) as a spallation material and a primary coolant. Emphasis has been placed on the target module. Thermo-hydraulic simulations for both options are presented, as well as design measures to mitigate pulsed proton beam induced phenomena. For the window target option, adequate window cooling has been shown by thermo-hydraulic simulations without reaching flow corrosion relevant velocities. Furthermore, both the effects of propagating pressure waves and cavitation are of major concern for liquid metal window targets subjected to a pulsed proton beam. These are addressed for the META:LIC window option by design measures. Design measures include an expansion volume and result in internal free surfaces. The feasibility of internal free surfaces is proven by VOF (a volume of fluid approach) simulations. In addition, VOF simulations demonstrate that for the windowless target module a stable free surface flow can be established. In conclusion, the modular META:LIC concept represents an innovative target solution which fits the boundary conditions of ESS