*3.2. Effects of Nickel Ion Irradiation*

formed by irradiation).

Figure 8a,b shows the microstructure after Ni3+ ion irradiation at room temperature. After the irradiation (up to 3.0 dpa), high-density dislocation loops (approximately 4.1 <sup>×</sup> <sup>10</sup><sup>20</sup> <sup>m</sup>−<sup>3</sup> ) were detected. In the Zr alloys, interstitial-type dislocation loops (a-loops) and vacancy-type dislocation loops (c-loops) are known to form. Nakamichi et al. investigated the formation and growth process of a-loops in Zry-2 under electron irradiation using a high voltage electron irradiation (HVEM) [20]. Estimated migration energy for interstitial and vacancy were 0.17 eV and 1.0 eV, respectively. These dislocations formed in this study were identified as a-loops because of vacancy mobility at room temperature. A-loop formation was already saturated, and the loops were connected. Figure 9a,b shows the desorption spectrum before and after the 3.2 MeV Ni3+ ion irradiation at room temperature, respectively. A new stage appeared in the position close to Peak A because of the Ni3+ ion irradiation (up to 3.0 dpa).
