부산대학교 도서관

Radiolysis of the VVER coolant during the transition of hydrogen from the liquid phase into gas-vapor bubbles is calculated. It is found that the decrease in the concentration of hydrogen in the liquid phase occurs until the hydrogen flow into bubbles becomes comparable to the hydrogen production due to radiolysis. In this case, a jump in hydrogen concentration leads to a sharp restructuring of the entire pattern of time dependences of the concentrations of radiolysis products. This is especially true for the behavior of concentrations of O2 and H2O2, i.e., the main oxidants of the zirconium cladding of fuel elements. It is shown that the local oxygen concentration relative to the permissible value can increase by more than 1000 times when the reactor is operated at >50% Nnom power. Similar behavior is demonstrated by hydrogen peroxide H2O2. However, the increase in its relative concentration by the same time is slightly more than one order of magnitude. A significant local increase in the concentration of oxidizing products of the radiolysis of O2 and H2O2 in the coolant seems to be the main reason for the appearance of a white deposit on the cladding of VVER fuel elements near the 12th spacer grid. [ABSTRACT FROM AUTHOR]