Axial and Azimuthal Asymmetry of RBMK-1000 Fuel-Element Cladding Oxidation

Abstract

The particularities of the axial and azimuthal asymmetry of nodular corrosion of RBMK-1000 fuel-element cladding operating in FA at power 1.7–2.2 MW are examined. The measured thickness of the oxides is compared with the concentration of the oxidative products of radiolysis in the coolant and the computed distribution of the thermophysical parameters in a fuel channel of the reactor. It is shown that the axial asymmetry of the oxidation of the fuel elements could be due to the temperature distribution in cladding and the non-uniform content of radiolytic oxygen and the radicals HO₂ and \( {\mathrm{O}}_2^{-} \) over height in FA and the azimuthal distribution is due to the radial distribution of the fast and thermal neutron fluxes. The results of studies attesting the possibility of the appearance in the RBMK-1000 fuel channel of conditions where the corrosion rate of the cladding on the sections between the spacer grills is comparable to the oxidation rates of VVER-1000 fuel elements are presented.