05-16U

Basing on some phenomenological theories of the crack formation in solids, an analysis of the creation of microcracks (MC) inside lava-like fuel-containing materials has been performed. The considered Griffith model for the two-dimensional MC is modified taking into account the diffusion of particles on the crack surface. For this model the actvation energies, that define the times of the MC nucleation and growth, is calculated. This formalism is applied to the Frenkel model which assumes the interaction between the MC edges in the tip zone. The results for the MC profiles in plastic materials are also presented and the efficiency of the mentioned models are analyzed.