The supra-atomic structure of single crystals of synthetic quartz with a dislocation density of 54 cm(-2) in their initial state and after irradiation in a VVR-M reactor by fast neutrons with the energy, E (n) > 0.1 MeV, at fluences of 2.3 x 10(19) and 4.5 x 10(1)9 N/cm(2), has been studied by the method of small-angle thermal neutron scattering. It has been established that fast neutrons create point, linear, and bulk defects throughout the entire material. It has been shown that extended defects have a significant integral length per volume unit equal to similar to 3 x 10(11) cm/cm(3), and can form a consolidated network in the sample with a cell size of similar to 30 nm, through the channels of which the migration of impurity atoms and molecules is possible.