The Molten Salt Reactor (MSR) is considered a game-changer in the field of nuclear energy and a strong asset in the combat against climate change. The expanding R&D programmes in China, EU, Russia, and the USA, lead to a vibrant atmosphere with many bright students entering the scene and new start-up companies eager to commercialize this technology. The MSR typically consists of a reactor core with a liquid fuel salt, and an integrated treatment unit to clean and control the fuel salt composition. Due to the liquid fuel, the MSR excels on safety and can operate as a breeder with thorium or uranium, or as a burner of spent fuel actinides. However, to make these promises reality, R&D is needed to demonstrate the inherent safety of the reactor, the feasibility of the fuel cycle facilities, and the path towards licensing and deployment. This will take time during which the safety requirements will become more stringent. This proposal aims to develop and demonstrate new safety barriers and a more controlled behaviour in severe accidents, based on new simulation models and assessment tools validated with experiments. Our proposal cover the modelling, analysis, and design improvements on: • Prevention and control of reactivity induced accidents • Redistribution of the fuel salt via natural circulation and draining by gravity • Freezing and re-melting of the fuel salt during draining • Temperature control of the salt via decay heat transfer to the environment • Thermo-chemical control of the salt to enhance the radionuclide retention • Nuclide extraction processes, such as helium bubbling, fluorination, and others • Redistribution of the source term in the fuel treatment unit • Assessment and reduction of radionuclide mobility • Barriers against severe accidents, such as fail-safe freeze plugs, emergency drain tanks, and gas hold-up tanks The grand objective is to ensure that the MSR can comply with all expected safety requirements in a few decades from now.