In-pile Xe diffusion coefficient derived from intragranular bubble growth

Experimental measurements of in-pile Xe diffusion are very limited. One of the rare observable that is directly related to it is the intragranular bubble radius. In this work we will determine the bubble distribution profile taking into account the evolution of the Xe concentration around the growing bubble, and assess its validity by comparison to experimental distribution profiles. Then the Xe diffusion coefficient can be deduced from experimental values of the bubble mean radius at different temperatures. The predicted activation energy is about 0.9 eV, well below the widely known value obtained from out-of-pile experiments (3.9 eV, Matzke, Rad. Eff. 53 (1980) 219) because of the presence of point defects created by the irradiation. Our value is, however, comparable, but still slightly lower, than the theoretically deduced value proposed by Turnbull et al. (~ 1.2 eV, J. Nucl. Mater. 107 (1982) 168) for the temperature range 800°C – 1400°C.