  In a fusion or advanced fission reactor, high energy neutrons induce the
formation of extended defect clusters in structural component materials,
degrading their properties over time. Such damage can be partially recovered
via a thermal annealing treatment. Therefore, for the design and operation of
fusion and advanced fission nuclear energy systems it is critical to estimate
and predict the annealing timescales for arbitrary configurations of defect
clusters. In our earlier paper [I. Rovelli, S. L. Dudarev, and A. P. Sutton, J.
Mech. Phys. Solids 103, 121 (2017)] we extended the Green function formulation
by Gu, Xiang et al. [Y. Gu, Y. Xiang, S. S. Quek, and D. J. Srolovitz, J. Mech.
Phys. Solids 83, 319 (2015)] for the climb of curved dislocations, to include
the evaporation and growth of cavities and vacancy clusters, and take into
account the effect of free surfaces. In this work, we further develop this
model to include the effect of radiation defects that are below the
experimental detection limit, via a mean field approach coupled with an
explicit treatment of the evolution of discrete defect clusters distributed in
real space. We show that randomly distributed small defects screen diffusive
interactions between larger discrete clusters. The evolution of the coupled
system is modelled self-consistently. We also simulate the evolution of defects
in an infinite laterally extended thin film, using the Ewald summation of
screened Yukawa-type diffusive propagators.
