Cascade damage in nickel: Production, saturation and recovery

• Published in: Journal of nuclear materials 1988-05, Vol.152 (2), p.204-211
• Main Authors: Birtcher, R.C., Blewitt, T.H.
• Format: Article
• Language: English
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/0022-3115(88)90328-5

Changes in the electrical resistivity and length were simultaneously measured during the bombardment of nickel at 70 K with 235U fission fragments and during a subsequent isothermal annealing program. The resistivity changes and length changes were linearly related during the damage production for damage concentrations less than 80% of the defect saturation limit. The initial ratio of the length change to the resistivity change was 8.4 × 10 4/Ω m . At high damage concentrations, the length change increased at a slightly higher rate than the resistivity change. During isothermal annealing of the near-saturation defect concentration, the resistivity and the length changes had identical recoveries through stage I and most of stage II. During stage III annealing, the ratio of the length change to the resistivity change showed a small increase. At temperatures above 475 K, this ratio showed a marked increase as the resistivity change exhibited recovery without a corresponding recovery of the length change. These differences, which are attributed to the direct formation and growth of three-dimensional vacancy agglomerates, and results of transmission electron microscopy suggest that the sign of the third derivative of the resistivity with respect to fast-neutron fluence (the sense of curvature in the damage rate) is positive for materials in which cascades collapse to loops, and negative for materials in which three-dimensional vacancy agglomerates are stable.