Molten Fuel - Fuel circulates through the reactor, fission products get removed, for over 99% fuel use (vs. LWR ~3%). No long-term radioactive waste.
Salt Cooled - Coolant far below boiling point, reactor operates at atmospheric pressure. Fuel dissolved in stable salt (no water), no loss of coolant accident possible. No need for high-pressure safety systems.
High Inherent Safety - No water, no high pressure, nothing that could propel radioactive materials into the environment. Thermal expansion/contraction of molten fuel salt strongly regulates fission rate; MSR is a very stable reactor. Simple safety systems work even if no electricity or operators.
Easy Construction and Siting - Low pressure operation, so no high-pressure safety systems. No water, so no steam containment building. Reactor factory assembled, with modern quality control, sensors and communication.
Lower Cost - Even with exotic materials, construction costs will be dramatically lower than LWR — factory construction, minimal manual on-site preparation. No long-term radioactive waste, so no long-term storage.
High Temperature Operation - Heat to generate electricity, desalinate water, produce CO2-neutral vehicle fuel, etc.