The results are presented of experiments on annealing in reactor and furnace the diamond pre-irradiated with reactor neutrons. It is established that annealing in a reactor proceeds more intensively than thermal annealing provided the γ-flux was lower in primary irradiation than in the secondary one. The γ-flux ratio varied due to the use of absorbing or amplifying screens and also by varying the reactor types or sample position. The experiment is described on electron annealing of a damaged diamond (electron energy 200 KeV). The volume of an elementary cell (expansion) with the constant measured radiographically was used in all experiments as the standard of defects present. The conclusion is that the contribution of γ-radiation always associated with the reactor neutron radiation to the formation of defect structure in materials is quite significant.