Dissolution and Precipitation Process after Loss of Coolant Accident (LOCA) in a Reactor and Its Thermodynamic Analysis

The chemical effects of the containment sump after a nuclear power plant accident were simulated using a self-developed experimental system, and the experimental research on the dissolution and precipitation behavior of materials inside the safety shell after the accident was conducted. The dissolution and release behavior of seven materials in boric acid solutions (pH4) at different temperatures (75-145 ℃) was studied, as well as the dissolution and release behavior of materials at different temperatures when sodium hydroxide (pH8, pH12) was sprayed from a spray system. The relationship between the dissolution concentrations of representative elements (Al, Zn, Fe, and Ca) and time, pH, and temperature was determined. Three different precipitation methods were used to study the possible formation of precipitates under LOCA scenarios. Based on the experimental results, the chemical reactions that would occur in the simulated environment after the accident were elucidated through thermodynamic calculations.