Modelo de cinética inversa para o cálculo da reatividade de reatores a sal fundido

Abstract

Most molten salt reactor designs present a liquid fuel that, mixed with the coolant composed of molten salts, circulates through the reactor. This circulation introduces important phenomena in the study of reactor physics, thus requiring changes in the existing physical models applied in conventional reactors with solid fuel. One of the main influences of the fuel flow in the reactor is in the delayed neutron precursors’ concentration, which partially decay outside the core, not contributing to the fission chain reaction. In this thesis, we investigate the physical models used for this type of reactor, especially the neutron point kinetics, in order to develop an inverse kinetics model, which has practical applications such as core reactivity monitoring and control rod calibration. The developed model has analytical, semi-analytical and numerical solutions. After verifying this model through consistency tests, which demonstrate a satisfactory agreement between the inverse and the point kinetics, two applications in transients are proposed: a linear variation between power levels, and the determination of criticality regions of the reactor during a decrease in flow velocity. The results obtained show that the proposed inverse kinetics model is capable of accurately determine the reactivity both for the execution of power variation, in the first scenario, and to maintain the reactor subcriticality in case of accidents, in the second scenario.