Multiphase modelling of 1D and 2D pressure wave propagation in a liquid metal using compressibleInterFoam

This study explores the use of OpenFOAM compressibleInterFoam solver to model pressure transients during loss-of-coolant accidents (LOCAs) in liquid metal breeding blankets (LM-BBs) of fusion reactors. In LM-BBs that adopt the separately-cooled architecture, the lead-lithium eutectic alloy (PbLi) serves as a tritium breeder and carrier and neutron multiplier, while the coolant is a secondary fluid such as helium or water. Under LOCA conditions, high-pressure coolant injection into PbLi can trigger complex two-phase flows and pressure shocks, posing significant risks to blanket integrity. The presence of reactive coolants, such as water, further complicates this scenario through exothermic reactions that amplify transient pressures and produce hydrogen, challenging current modelling tools ability to capture these coupled phenomena accurately. Given these constraints, we assess OpenFOAM capability to simulate representative LOCA transients in two-dimensional (2D) geometries. Validating against analytical benchmarks, we simulate helium or steam jets entering a stagnant, low-pressure PbLi pool, examining configurations with both a gas plenum and a fully liquid metal setup. A mesh sensitivity analysis highlights the significant effect of grid resolution on wave propagation, with coarser meshes dampening wave amplitude and delaying shock transmission. The results indicate that OpenFOAM can capture the primary dynamics of two-phase interactions and pressure transients within these prototypical setups. The findings underscore OpenFOAM potential as a flexible, extensible framework for fusion safety studies, though further development is necessary to incorporate critical LOCA phenomena like phase change, solid–fluid interactions, and magnetohydrodynamic effects. This work thus lays the foundation for advancing OpenFOAM-based tools capable of informing future experimental designs and enhancing safety assessments for fusion reactor LM-BBs.