Molten Salt Reactor (MSR) Molten Salt Fast Reactor (MSFR) control Relative Gain Array (RGA) analysis a b s t r a c t The Molten Salt Fast Reactor (MSFR) has been recognised as a promising reactor concept and has been adopted as reference circulating-fuel MSR configuration in the framework of the Gen-IV International Forum. Up to now, a number of dynamic studies have been performed to investigate the transient response of the system and its stability, but no control-oriented analyses have been carried out yet. This work focuses on a preliminary evaluation of the MSFR controllability issues, assuming a decentral-ized feedback scheme of control. For this purpose, a simplified model of the reactor primary circuit has been set up adopting a point-kinetics description and a one-dimensional description of neutronics and thermal–hydraulics, respectively. First, the effect of all the possible input variables on different sets of output variables is investigated by means of the Relative Gain Array (RGA) analysis, providing a brief overview of the best input/output pairings with no restrictions on the number of control variables that can be used. Some control schemes are then selected and implemented in the model of the primary cir-cuit. The transient responses are analysed and compared, considering different control strategies. This work is thought to provide a first insight into some MSFR controllability issues as well as a preli-minary evaluation of possible control options.