| Abstract |
| The permeation behavior of hydrogen through the oxide layer on the modified Zircaloy-4 (Zry-4) alloy was investigated. The modified Zry-4 was prepared by changing the chemical composition of standard Zry-4. The tin content of Zry-4 (1.5 wt%) reduced to 0.5 wt% and alloying elements such as Si, 0, and Nb were newly added from 0.01 wt% to 0.2 wt%. The oxide layers were grown in a static autoclave at 360℃ under the pressure of 2660 psi for 150 days. Permeation behaviors were characterized by measuring the time lag (t_L) of hydrogen permeation in the oxide. After the steady state of permeation flux, Fick`s law was used to calculate the diffusivity of hydrogen in the modified Zry-4 specimens. The diffusivity of hydrogen in 0.5Sn-0.1Nb-0.1Fe-0.2Cr-0.2O-Zr specimen (1.26×10^-8 ㎠/s) turned out to be lower than that in 1.5Sn-0.2Fe-0.1Cr-0.1O-0.01Si-Zr and Zry-4 specimens. It was shown from the oxide structural investigation that the hydrogen diffusivity is dependant on the amount of tetragonal phase in the zirconium oxide; the phase transition of the oxide from tetragonal to monoclinic was found in 150 days exposure and the 0.5Sn-0.1Nb-0.1Fe-0.2Cr-0.2O-Zr specimen showed higher amount of tetragonal phase than the 1.5Sn-0.2Fe0.1Cr-0.1O-0.01Si-Zr specimen and Zry-4. In addition to the oxide structural study, effects of the microstructure of zirconium alloy such as precipitates and grain boundaries on the diffusivity and solubility of hydrogen were studied. |
|
|
| Key Words |
| Modified Zircaloy - 4 , Hydrogen behavior , Oxide layer , Diffusivity , Solubility , Tetragonal phase , Grain size |
|
|
 |
|
