Using rate theory to better understand the stress effect of irradiation creep in iron and its based alloy

Abstract

Historically, rate theory is one of the most popular modeling methodologies used to simulate radiation effects on structural materials in nuclear reactors. However, the rate theory method has not been used to model the irradiation creep behavior of iron-based alloys exposed to a stress-applied environment. Therefore, this study is an attempt to compare the calculation results of the Brailsford method and our newly proposed method (modified Brailsford method). newly proposed method explains irradiation creep by the stress-enhanced diffusivity rather than modified formation energy which is adopted in Brailsford method. To verify newly proposed method, simulations were conducted at two different temperature conditions: 673 K and 873 K, which represent the minimum and maximum conditions in a fast breeder reactor; at 673 K, the original Brailsford method lacked the ability to consider the stress effect, whilst the newly proposed method showed relatively good agreement with the experimental data. At 873 K, both methods showed a high dependency on hoops stress. Moreover, molecular dynamic method is adopted and compared to newly proposed method at 873 K. One of the most distinguishing characteristics of the new method is that, depending on hoops stress, the creep rate shows the opposite behavior that of Brailsford method by dpa.