[en] The supraatomic structure of single crystals of synthetic quartz was studied by thermal neutron small-angle scattering in the initial state (dislocation densities 54 and 570 cm^-2) and after irradiation in the WWR-M reactor (Petersburg Nuclear Physics Institute) by fast neutrons with energies E_n > 0.1 MeV at fluences F_n = 0.2 x 10¹⁷ -5 x 10¹⁸ neutrons/cm². It is established that fast neutrons form point, linear, and volume defects in the lattice throughout the entire volume of a sample. Large-volume structures-amorphous-phase nuclei-reach sizes of ∼100 nm in quartz, while occupying a small total volume of ∼0.3% even at the maximum fluence 5 x 10¹⁸ neutrons/cm². The main fraction of the damaged volume (up to 5%) corresponds to point (with a radius of gyration of 1-2 nm) and linear defects, giving a comparable contribution (∼1-4%). The extended linear structures with a radius of 2 nm, even at a moderate fluence of 7.7 x 10¹⁷ neutrons/cm², have a significant total length per volume unit (∼10¹¹ cm/cm³) and can form a connected network with a cell ∼30 nm in size in the sample. Foreign atoms and molecules can migrate through channels of this network