A preliminary approach to the MSFR control issues

• First insight into the control of the new MSFR concept.
• Input/output pairing of the variables of a MIMO system through an RGA-based criterion.
• RGA analysis of the interaction between control and controlled variables for a feedback scheme of control.
• Identification of possible control schemes and evaluation of the MSFR closed loop transient response.

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 decentralized 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 circuit. 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 preliminary evaluation of possible control options.