A TGA study on the chlorination reaction kinetics of Zircaloy-4 cladding hulls

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

“…The modified TGA-HC system introduced in our previous work [9] was employed for this study. Briefly, a balance was put on the top of the system which is covered by an acryl box and connected to an argon inlet and computer system through an RS232C cable.…”

“…An average slope value of 1.06 was achieved from Fig. 2, which means that a contracting volume model (slope ¼ 1.07) is the most suitable one as the case of Zircaloy-4 [9]. The contracting volume model is expressed as:…”

“…This result suggests that the conditions of these experiments are under the influence of total flow rate, in other words, the experiments were performed in the starvation condition. In the present study, the total flow rate was fixed at 120 mL/min owing to limitations of the TGA system, and to compare the results with those of Zircaloy-4 shown in our previous work [9]. Thus, the Q term was not considered as a variable in the present study, but it should be noted that the reaction rate might increase with increasing Q.…”

“…One can determine the most suitable model 1) by comparing (da/dt) versus a graphs because each model has characteristic shape, 2) by fitting experimental results for all models, or 3) by using the SharpeHancock plot [20]. The third option was employed in the present study, because it was identified in our previous work on Zircaloy-4 that a change of reaction mechanism occurs during the reaction [9], and the SharpeHancock plot can clarify simultaneously both the most suitable reaction mechanism and a region where the mechanism is available. The SharpeHancock plot can be achieved using an equation of ln½Àlnð1 À aÞ ¼ lnðBÞ þ m lnðtÞ (4) where B is a constant and m is a slope of ln[Àln(1 À a)] versus ln(t) plot.…”

“…But the initial version of the TGA system for the hull chlorination (TGA-HC) exhibited a problem owing to the buoyancy effect. A modified version of the TGA-HC system was successfully demonstrated in our previous work, where the chlorination reaction kinetics of 3 cm long Zircaloy-4 tubes were achieved [9]. Here, it needs to be mentioned that Zircaloy-4 contains Sn, Fe, and Cr as major alloy elements, while ZIRLO has Sn, Nb, and Fe as its alloying constituents.…”