Chlorination Reaction Behavior of Zircaloy-4 Hulls: A Preliminary Study on the Effect of the Oxidation Process on the Reaction Rate

Abstract

The recovery of Zr from Zircaloy-4 (Zry-4) cladding hulls was demonstrated to investigate the effect of the oxidation process on the reaction rate of the chlorination reaction. In chlorination reaction experiments performed for 6 h, where reaction products were collected every 2 h, it was observed that a significant decrease in the reaction rate was caused by the oxidation process (500 o C, 10 h under an air atmosphere) within the reaction period of 0 -2 h. The amount of reaction residue increased from 0.95 to 1.65wt% of initial weights in the fresh and Zry-500-10 (Zry-4 hulls oxidized at 500 o C for 10 h under an air atmosphere) hulls, respectively. The purity of the recovered Zr was identical at 99.61wt% for the fresh Zry-4 and Zry-500-10 hulls. Quantitative analysis of the chlorination reaction rate was performed by varying the reaction time from 0.5 to 1.0, 2.0, and 4.0 h. The fitting results showed that the relationship between weight loss and reaction time can be interpreted by a linear line with a slope of 23.35wt%/h for the fresh Zry-4 case, while two linear lines were necessary to fit the results of Zry-500-10. In addition, the slope values were 17.12 and 27.16wt%/h for (0 -20) and (20 -100)wt% loss regions, respectively.

Surface Analysis Study on ZIRLO Cladding Hulls Oxidized at Low Temperatures

“…However, the chlorination reaction result of ZIRLO-500-24 (35.3% weight loss) shows that the chlorination reaction can proceed in the absence of ZrO when the thickness of the oxide layer is thin enough (about 3.22 μm). A gap in the reactivity between side walls and cutting edges should be considered, because the XPS results represent the oxidation status of side walls while the chlorination reaction prefers cutting edges [15]. The photograph of ZIRLO-500-24 shown in ref.…”

A thermo-gravimetric analysis study on the chlorination reaction of ZIRLO cladding hulls

“…First of all, the next work should be done for oxidized cladding hulls, because actual cladding hulls have micrometers thick oxide layers on their side walls. It was qualitatively identified that oxidized cladding hulls suffer from incubation time [5] or late reaction rate in an early stage of the chlorination reaction [7]. A quantitative analysis on the effect of oxide layer formation can be identified using the TGA-HC system, and the results will contribute to the design of a large scale cladding hull chlorination system.…”

“…At KAERI, fundamental approaches including reaction kinetics were mainly made to build a database for scale-up [7e9]. The first approaches were done using a quartz reactor by repeated experiments for various reaction periods [7]. In that study, a linear reaction rate equation was achieved for bare Zircaloy-4 cladding hulls, while delayed reaction rate was observed in oxidized Zircaloy-4 cladding hulls.…”