There are more “salts” than common table salt which contains sodium as a component. Mostly research reactors used “metallic” sodium as the primary loop coolant-—also found in hollow exhaust valves for some engines-—valued for enhanced heat conduction.
The salt in molten salt reactors is often a mixture of lithium fluoride and beryllium fluoride with a uranium compound dissolved as the fuel component.
So a molten sodium thorium reactor wouldn’t be a significant fire safety issue within the engine compartment of an ocean going vessel?
What could go wrong?
www.webelements.com/sodium/chemistry.html
Sodium metal reacts rapidly with water to form a colourless solution of sodium ... the sodium metal may well become so hot that it catches fire and burns intensely.