The theoretical investigation for the role of nonlinear couplings between elements of damage structure of irradiated crystal in its self-organization and influence of external fluctuations of defect generation rate on this process is developed. It is shown that nonlinear couplings determine kind and parameters of the arising structure or terminal behavior namely concentration decomposition in alloys, oxygen impurity redistribution and its nonhomogeneous precipitation in silicon, breaks on curves of the creep-rate dependence on temperature and dose, creep and swelling rate oscillations. Parameters of the arising structures and conditions of its development are obtained. It is determined that the fluctuations of irradiation conditions are most strongly apparent in dynamic behavior of system. As a result new unstable regions and new dynamic behavior that do not have deterministic analog appear. The cause of it is strong interaction between fluctuations that is accompanied by their essential increase. Fluctuations in irradiated materials are substantially nonequilibrium, since the main cause for generation of defects, i.e. irradiation, is an external factor. Unlike the equilibrium internal fluctuations, they are not inversely proportional to a certain power of the characteristic size of the system. On the contrary, significant deviations of the density of point defects from its average in the process of irradiation are quite common. Especially great is the role of random external disturbances in systems with nonlinear links, in processes of radiation-induced transformations, which have a threshold nature and exhibit branching points, where qualitatively different ways of evolution are possible. On the one hand, the stochastic nature of defects is related to the fluctuations of the flux of impinging particles (neutrons, ions, etc.). On the other hand, the formation of defects in real crystal correlates with the disposition of various imperfections in it, such as dislocation, grain boundaries, precipitates, etc., which are distributed in the crystal randomly.