Statistical fluctuations and dislocation climb during irradiation

Most models proposed for radiation creep invoke means whereby a 'mismatch' exists in the fluxes of vacancies and interstitials arriving at a dislocation, thus effecting a net climb rate. Gittus has proposed a means of obtaining radiation creep even when vacancies and interstitials reach a dislocation in equal numbers. This model involves random climb due to statistical fluctuations in the arrival of point defects followed by glide of the dislocation when a critical climb height (up or down) is reached. A corrected analysis of this model is presented, using his variance approach. Also presented is a simpler analysis assigning a diffusivity to an individual dislocation segment and treating it as a random-walker. A more general discussion is included of the viable possibilities for the required mismatch in point defect fluxes during radiation creep. (author)