Irradiation-growth in annealed Zr-2.5 wt% Nb at 353 K

Zr-2.5 wt% Nb growth specimens have been irradiated at 353 K to a fast neutron dose of approximately 4.0 X 1025n/m2. Specimens were taken from the longitudinal and transverse directions of a nominally annealed, seam-welded tube and irradiated in both the stress-relieved and fully annealed conditions. Growth in these specimens is characterised by large positive and negative strains in the longitudinal and transverse directions respectively, dimensional changes in weld material exhibiting intermediate growth behaviour. The results are compared with growth data on both annealed and cold-worked zircaloy-2 at 353 K and discussed in terms of the effect of texture, grain size, and cold work on irradiation growth. It is concluded that the continuation of growth to high doses in annealed Zr-2.5 wt% Nb at 353 K results from interstitial-induced dislocation climb, with vacancies diffusing to grain boundaries. (Auth.)