Evaluation of dynamical behavior of Thorium fueled SMART reactor using lumped parameter dynamic model

The point reactor dynamic model is based on the lumped parameter model and, unlike the traditional reactor kinetics model, takes into account the effects of the fuel and moderator temperature on the system reactivity. This model is a system of nonlinear and nonhomogeneous differential equations and is used in the transient analysis of an initially critical system subjected to any perturbation. In this study, transient analysis of the Th-fueled SMART reactor is performed by the point dynamics model. Initially, the reactor is kept critical using the reactivity control mechanisms such as control rods insertioın and soluble boron addition to the moderator. The required neutronic parameters such as precursors’ parameters, neutron generation time, and reactivity coefficients are calculated using the Serpent 2 Monte Carlo code. The moderator average temperature and system pressure are used as two distinct thermodynamic properties to determine thermal-hydraulic parameters such as heat capacity, conductivity coefficient, convection coefficient, and fuel thermal resistance. For different reactivity insertion scenarios, MATLAB ODE45 suite is used to solve the point dynamic equations. The validity of the provided code is also verified either through comparison with the analytically solvable form of the point dynamic model or by analyzing the asymptotic equilibrium values of the considered parameters. Finally, it is seen that when an initially critical reactor operating at a certain power level undergoes a perturbation, after a short time the system becomes again critical and operates at an almost stable power level different from the pre-perturbation power level. This, in turn, implies that the calculated neutronic and thermal-hydraulic parameters are physically meaningful.