  Basing on experimental data on irradiation-induced deformation of graphite we
introduced a concept of diffuse domain structure developed in reactor graphite
produced by extrusion. Such domains are considered as random continuous
deviations of local graphite texture from the global one. We elucidate the
origin of domain structure and estimate the size and the degree of
orientational ordering of its domains. Using this concept we explain the well
known radiation-induced size effect observed in reactor graphite. We also
propose a method for converting the experimental data on shape-change of
finite-size samples to bulk graphite. This method gives a more accurate
evaluation of corresponding data used in estimations of reactor graphite
components lifetime under irradiation.
