A method of semiempirical prediction of corrosion of cladding zirconium alloys as a function of the operating conditions and composition is presented. The laws of thermodynamics and chemical kinetics of the oxidation reactions of a multicomponent zirconium alloy form the physicochemical basis of the computational method. The method is based on a model developed at the All-Russia Research and Design Institute of Integrated Power Technology for the corrosion of commercial and experimental zirconium alloys in water media under autoclave and reactor conditions taking account of the composition of the alloy and the water chemistry. The model is verified on the basis of independent tests performed on a series of zirconium alloys under autoclave and reactor conditions. The method developed makes it possible to predict the corrosion of fuel-element cladding made from zirconium alloys with fuel burnup to 80 MW·days/kg under the conditions of one-and two-phase VVER and RBMK coolant.To validate any alloy for use as fuel-element cladding, it is necessary to know the properties of the alloy including its corrosion resistance. The alloy can be chosen in three ways: reactor tests, extra-reactor studies, and verification of the computational models on the basis of experimental data. When studying the corrosion of zirconium alloys, a large number of factors must be taken into account, including the properties of the coolant and the cladding material as well as the operating parameters.The empirical models of the corrosion of zirconium alloys treat oxidation as a thermally activated process. The models are limited to the systems for which the corrosion rate is determined mainly by the corrosion aggressiveness of one participant in the reaction -water, i.e., the models are developed for strictly determined operating conditions and one chosen alloy [1,2].The objective of the present work was to develop a single methodological approach to predicting the corrosion of commercial and experimental zirconium alloys in water media under autoclave and reactor conditions.The present work proposes a method of predicting corrosion of cladding zirconium alloys as a function of their composition and service conditions. The physical-chemical basis of the method is based on the laws of thermodynamics and chemical kinetics of the oxidation reactions of a multicomponent zirconium alloy.
Model of Corrosion of Zirconium AlloysEffect of Water Chemistry. A model giving a unified description of the corrosion mechanism for cladding zirconium alloys for nuclear power plants with RBMK and VVER throughout the entire operating cycle of fuel assemblies -in the core at high temperature and during storage of spent nuclear in water at low temperature -has been developed at the All-Russia Research and Design Institute of Integrated Power Technology (VNIPIET) on the basis of an analysis of operating and exper-