The migration behavior of cesium during plasma gasification melting process of spent radioactive resins by thermodynamic calculation

Abstract

Plasma gasification melting is an effective method of spent radioactive resin disposal. However, the equilibrium distribution and migration of Cs during the plasma gasification melting process is still unclear. In this study, the volatilization behavior of Cs during the plasma gasification melting process of spent resins was investigated by thermodynamic model. The composition of the stable phase and the release of Cs from the stable phase in the three systems of Cs-C-O, Cs-S-O and Cs-N-O were calculated by HSC Chemistry. The possible composition of Cs during the plasma gasification melting process of spent resins was determined. At the same time, the thermodynamic simulation of spent resins in the temperature range of 300–1800 °C was carried out, and the morphological distribution of Cs during the plasma gasification melting process of spent resins was calculated and analyzed, which will provide theoretical guidance for subsequent experimental research. The results showed that Cs2CO3, Cs2SO4 and Cs2O were identified as the stable phases of each system at 1200 °C in air atmosphere. The existent forms of Cs in the three stages of plasma pyrolysis, gasification and melting are different. In the plasma pyrolysis and melting stage, Cs mainly enters the gas phase in the form of gaseous Cs and CsOH. In the plasma gasification stage, Cs mainly enters the gas phase in the form of gaseous Cs and Cs2SO4. By comparing with the results of some literature, the accuracy of thermodynamic calculation is proved. The migration and transformation law of Cs during the plasma gasification melting process of spent radioactive resins is revealed.