The prediction of dynamic behavior of neutron distribution is essential for both design and safety analysis. In the present article, we have attempted to summarize various models for the analysis of time-dependent behavior of the thermal reactor systems currently under design. The underlying equations and various computer codes developed have also been presented. An overview has been presented on the current status of the reactor kinetics capabilities for thermal reactor design and analysis. As the new reactor concepts are being proposed, it has become essential to extend the design and safety analysis to multi-physics modeling. The recent work on the development of coupled neutronic–thermal–hydraulic capabilities for modern reactor designs such as AHWR, HTRs, and MSRs has also been presented.