Formation and build-up of corrosion products in fuel elements of A water-moderated/water-cooled power reactor

Abstract

We consider the kinetics of the build-up of activity in the loop of the VVER-440 reactor on the basis of data concerning the variation of the /sup 59/Fe activity on the surface of fuel elements since the fraction of iron corrosion products in the deposits on the fuel elements is usually more than 90%. The approximating mathematical model is constructed on the basis of the following assumptions: the concentration of the active and inactive iron in the coolant is constant over the entire loop; the controlling processes of mass and radioactive exchange on the surface of fuel elements are determined by the rate constants of deposition and wash-off, which are assumed to be the same for active and inactive iron; the iron nuclides are activated mainly by thermal neutrons; and iron atoms do not diffuse into the layer of oxide deposits.