Division of Nuclear Fuel Research, Japan Atomic Energy Research Institute, Tokai-mura, Ibaraki-ken, 319-11, Japan
Abstract:
Compressive creep tests of uranium dicarbide (UC2) have been conducted. The general equation best describing the creep rate over the temperature range 1200–1400°C and over the stress range 2000–15000 psi is represented by the sum of two exponential terms ge =A(σ/E)0.9 exp(−39.6 ± 1.0/RT) + B(σ/E)4.5 exp(−120.6 ± 1.7/RT), where pre-exponential factors are A(σ/E)0.9 = 12.3/h at low stress region (3000 psi) and B(σ/E)4.5 = 3.17 × 1013/h at high stress region (9000 psi), and the activation energy is given in kcal/mol. Each term of this experimental equation indicates that important processes occurring during the steady state creep are grain-boundary diffusion of the Coble model at low stress region and the Weertman dislocation climb model at high stress region. Both mechanisms are related to migration of uranium vacancies.