Radiation heterogeneous processes and hydrogen safet in nuclear reactors

In recent years, NPP built in different countries of the world occupy an important place among the growing environmental threats to humanity. There's a reason for that. Thus, the accident that occurred at the Chernobyl Nuclear Power Plant on April 26, 1986, and the breakdown of Japan's Fukushima Nuclear Power Plant as a result of a strong earthquake in 2010 proved once again that humanity is facing a great environmental threat. Therefore, there is almost no detailed information about the accidents at the NPP, as well as about the emergency modes in the water-cooled nuclear reactors. In recent years, revealing the mechanism and general regularities of processes both in normal and emergency modes in the contact of the heat separating element with heat carriers, the concentration of explosive hydrogen, and the radiation resistance of construction materials in the core of water- cooled nuclear reactors remain topical. The kinetic parameters of the formation of dangerous gas hydrogen as a result of radiation and radiation-thermal processes occuring in the contact of zirconium, stainless steel, zirconium alloy (Zr1%Nb), which are heat-separating element materials of water-cooled nuclear reactors, with water were determined. Research in this direction was carried out in the range of contact medium temperature in normal operation T=473-523 K and in emergency modes T≥873K. This process was carried out in the static mode of contact of special reactor materials with water at different pressures in the contact medium of the heat carrier. As a result of the conducted studies, it was determined that the yield of molecular hydrogen formed in the heat carrier of water-cooled nuclear reactors was consistent with the radiolytic decomposition process of pure water, but in real conditions it is very low. The yield of molecular hydrogen in the radiation-heterogeneous processes occurring in the contact of heat-seperating element materials with water was found to be 5-10 times higher than the homogeneous radiolysis processes of pure water. It was determined that this increase occurs under the influence of nuclear fission products within the heat-separating element and second electron beams emitted from metallic materials into the contact medium under the influence of gamma rays. By changing the contact time between the heat-separator and the heat carrier in a wide range, the processes occurring in hydrogen and metallic materials in the medium were studied, and it was found that oxidation processes occur on the surface of metallic materials as a result of the radiation and radiation-thermal processes occurring in this contact. At low temperatures T≤773K, these processes take place in two stages, first with the formation of a protective oxide layer, and then catostrophic oxidation processes on the surface of the metallic material. As the temperature rises T>773K, only catastrophic oxidation of metals in contact with water is observed. The mechanism of the processes was given based on studies conducted by Fourier-IR-spectroscopy (absorption and scattering), EPR, electrophysical, X-ray diffraction methods. Based on the obtained results, the concentration of hydrogen formed in the heat carrier in the normal and emergency modes of the reactor as a result of radiation-heterogeneous processes occurring in the contact of the heat-seperating element with heat carrier in the water-cooled nuclear reactors was determined. Corrosion process of construction materials in contact with water depending on temperature, steam pressure and intensity of gamma radiation was studied.