Chlorination reaction behavior of Zircaloy-4 hulls: experimental and theoretical approaches

Chlorination reaction behavior of Zircaloy-4 (Zry-4) cladding hulls was demonstrated by using a quartz reactor system. By reacting at 380 °C for 3 h, mass of the Zry-4 hulls decreased by 65.8 wt% with Cl₂ utilization of 87.1 mol%. Composition of collected product was analyzed and it was revealed that concentration of Zr was higher than 99.97 wt%. The purity of Zr in the experimental result was higher than expectation when considering Sn (1.31 wt%) and Fe (0.25 wt%) contents which can produce gaseous SnCl₄ and FeCl₃ at the experimental condition. Theoretical calculations were performed to clarify the high purity of Zr by using the HSC code. The simulation results revealed that formation of ZrCl₄ is more preferred than SnCl₄, FeCl₃, and CrCl₃. The preference of chloride formation was confirmed by the theoretical calculation, and it was suggested that the major constituents of Zry-4 might react with Cl₂ to produce chlorides in an order of ZrCl₄ > CrCl₃ > SnCl₄ > FeCl₃. It was also suggested that continuous removal of ZrCl₄ and sufficient supply of Zr source during the chlorination reaction might have contributed to the high purity of Zr.