Formation and evolution of radiation defects are determined by the irradiation conditions. Some of these conditions do not get sufficient attention. In particular, this is true for the gamma-annealing process whose role in radiation-induced effects have not been considered in detail previously. Reactor experiments have shown that volume expansion of diamond and silicon carbide depends on the γ-radiation flux value: the higher the gamma-flux, the lower is the expansion. Radiation γ-annealing was also discovered in reactor grade graphite. Analysis has shown that this phenomenon is probably operating in reactor pressure vessel materials. This phenomenon opens a new perspective of radiation effects mitigation and reactor materials life cycle management using neutron and gamma-ray intensity control.