Chemical states and reactions in multicomponent and multiphase systems containing different nuclide quantities

Abstract

Nuclear energy systems are typically multicomponent and multiphase, containing a wide range of nuclides in different quantities, including major, minor and micro elements. In the primary circuit of a nuclear reactor, the fission and activation products generally fall into the micro element category. Investigating the chemical states and reactions of these micro elements presents a significant challenge. In this study, we propose a systematic approach to determining the chemical states and reactions in multicomponent and multiphase systems with varying nuclide quantities, based on fundamental physical principles. To demonstrate the applicability of this method, we utilized the primary circuit of a 10-MW high-temperature gas-cooled experimental reactor (HTR-10). The dominant chemical states of iodine in the primary circuit of HTR-10 were identified as CsI(g), HI(g), and RbI(g). Nine fundamental chemical reactions involving iodine were also identified. Furthermore, the results indicate that the major elements influence both the pressure and chemical potential of minor and micro elements, while minor elements can affect the chemical potential of micro elements. Additionally, the 2-D projected phase diagram developed in this study provides more comprehensive information than traditional 2-D phase diagrams, particularly regarding the relative quantities of components in complex systems.