Stability analysis of the Generation-IV nuclear reactors by means of the root locus criterion

The development of next-generation nuclear reactors requires a careful investigation of their stability characteristics and of their overall dynamical behavior. In the current work, a stability analysis is carried out from the perspective of linear systems for all the Gen-IV reactor concepts. Linear, zero-dimensional models of the reactors are developed in MATLAB® and the root locus criterion is applied to investigate the stability of the systems over their entire power range. The analysis is carried out for the stand-alone cores, assuming the inlet coolant temperature as a fixed parameter, and also considering the primary coolant circuit of each reactor, in order to evaluate the effect of out-of-core energy dynamics on the systems stability. All the reactors proved to be stable with a large margin over their nominal power. In the last part of the work, a comparison of the dynamic behavior of the Gen-IV reactors is presented, in order to point out the influence of the different geometrical features and of the different materials employed as coolant.