## 4 Conclusions  
The review of open-access research undertakings, performed in this work, shows that, according to the majority of authors, the gamma radiation dose rate, exceeding 300 Gy/h, is the threshold value for the acceleration of corrosion processes in steel elements. In this case, corrosion itself is caused by the process of radiolysis. However, the rate of anaerobic corrosion of carbon steel increases even at lower dose rate values of 11 Gy/h  
Figure 3: A change in the diameter of the reinforcement over time (the dashed black line shows the reinforcement located closer to the wall surface; the red line shows the reinforcement on the opposite face).  
in accelerated tests limited in time. The time of exposure to ionizing radiation has a great effect on corrosion processes in steel elements in different environments. Hence, steel corrosion accelerates in the presence of chlorides if the accumulated dose exceeds 150 kGy. Higher accumulated doses, exceeding 0.3 MGy at the radiation rate of about 15 Gy/h, show the effect on corrosion processes (its acceleration) in unalloyed steel in cement mortar. At an accumulated dose exceeding 1.8 MGy, the corrosion of reinforcement accelerates in concrete specimens in the air. In addition, accumulated doses of several MGy trigger microscopic changes in concrete (microcracks, larger pores, greater brittleness), which promote the penetration of gases from the environment deeper into concrete and accelerate corrosion processes.  
In general, the following factors are important for processes of reinforcement corrosion in reinforced concrete structures:  
* Operating environments, namely, the presence of chlorides, ions of magnesium and carbon; temperature and humidity characteristics (higher radiolytic damage and accelerated carbonization were observed in the RH range of 50 to 75%, and similarly corrosion processes accelerated in steel elements in concrete under the combined effect of temperature (including radiation heating).
* Conditions of oxygen supply to a structure.
* Presence of residual water (initial water-cement ratio).  
Operational conditions for steel reinforcement in concrete, subjected to gamma radiation, are characterized by the effect of various factors during the initial period of operation of structures and further (at a high accumulated dose of ionizing radiation). Hence, radiolysis and carbonization processes prevail in the initial period, while the subsequent period is characterized by their consequences, such as brittleness, the formation of microstructural changes, and reduction in external pore permeability.  
In this work, the authors took into account the above degradation changes occurring under the effect of gamma radiation in reinforced concrete structures by varying the corresponding resistance of concrete and diffusion of oxygen in different time periods.  
As a result, the retrospective numerical analysis performed in the COMSOL software package for 100 years of operation of the structure shows that the anticipated change in the diameter of the reinforcement (from 2.8 to 3.1 mm) is quite consistent with corrosion rates presented in the Oak Ridge National Laboratory (NRC U.S.) report [48]; they contradict the data provided in the IAEA report [19] and some results of studies that involved accelerated corrosion tests conducted under the effect of gamma radiation.  
It is obvious that the modeling of corrosion processes under the effect of gamma radiation is a truly challenging research task. Despite the fact that the authors substantiated the viability of using standard software in the numerical modeling of corrosion processes by means of replacing the effect of gamma radiation by (1) oxygen diffusion and (2) a change in the resistance of concrete, development of a comprehensive analytical model requires further experimental studies, taking into account all factors of corrosion and radiation-triggered degradation of reinforced concrete structures under the extended exposure to gamma radiation.