In recent years efforts have been spent in the development of innovative reactors capable of operating with flexible Conversion Ratio (CR). Fast Reactors (FR) are natural candidates since they allow to achieve high CR, as well as an efficient TRU (TRansUranics) burning through a low CR and the closure of the fuel cycle. Among the fast-spectrum systems, a peculiar role is played by the Molten Salt Fast Reactor. This reactor lacks the sound technological basis available for the solid-fuelled liquid-metal-cooled FRs, but it shows fuel cycle potential benefits: it uses Th, which features vast natural resources and mitigates waste management issues due to a low generation of TRUs; it can naturally operate with flexible CR without design modifications thanks to the online reprocessing system; it can achieve high CR, with doubling times of the order of 40 years or lower; it can achieve good TRU-burning rates and very high burning rates of minor actinides. However, such fuel cycle flexibility implies a wide variety of fuel salt compositions. Along with the variation of the fuel salt properties, concerns arise for the varying safety features of the core, especially when using the MSFR as TRU-burner. This work first summarizes results regarding the fuel cycle performances of the MSFR when used as breeder, isobreeder or burner reactor. Subsequently, safety parameters are computed for each fuel cycle option and a simple approach based on reactivity and energy balances is employed to predict the reactor steady-state after major accidental transient initiators, thus giving indications of its inherent safety features for different fuel cycle strategies.