Modeling of sink-induced irradiation growth of single-crystal and polycrystal zirconiums in nuclear reactors

The objective of this study is irradiation growth modeling of polycrystal zirconium using the advanced mean-field rate theory (MFRT) and growth equation. Since the 1960s, irradiation growth of zirconium has been among the most important phenomena in nuclear reactors. However, there is no general irradiation growth model that can explain changes in both the microstructure morphology and growth strain in polycrystal zirconium owing to lack of knowledge of the relevant atomistic information and MFRT. Although two groups have developed a single-crystal zirconium irradiation growth model, a general polycrystal zirconium model has not been developed. In this study, therefore, the defect flux was calculated using the MFRT, and the dislocation loop density was calculated from the defect flux. Moreover, the bias factor for each sink (dislocation lines, loops, and grain boundaries) was adopted in the MFRT. In addition, dislocation line and grain boundary effects were examined in polycrystal zirconiums. Finally, irradiation growth equation was established and growth strain was calculated using the average strain factor and anisotropy factor considering grain-interaction. For single-crystal zirconium and cold-worked polycrystal zirconium, irradiation growth strain results show good agreement with the experimental results. For annealed polycrystal zirconium, the results deviate from the experimental results.