Variations in the size of zirconium alloy components for nuclear reactors

Considered are the data on the nature and absolute values of dimensional changes in parts of fuel assemblies made of zirconium alloys, obtained in the process of CANDU, SGHWR, PWR and BWR reactor operation. Discussed are the main mechanisms, causing the change of fuel assembly linear dimensions under irradiation. The operation of tubes (technological channel) in CANDU and SGHWR reactors has shown, that dimensional instability is observed in the gradual increase of the diameter and length. The tube length increases proportionally to energy release. But absolute values of elongation noticeably depend on the production technology. The tubes, made with the greatest stretching during pressing and cold deformation of rolling have the maximal elongation, while minimal elongation (0.19%) is observed at the shortest stretching and cold deformation values. Changes in dimensions of fuel element shells come in most cases to the reduction of diameter, growth of ovality, bending and elongation. The shell diameter in PWR reactors decreases more, than in BWR. It is noted, that creating the preliminary pressure in KWV reactor fuel elements promotes the decrease of their elongation. It is underlined, that the model, suggested for describing the changes of tube dimensions of CANDU reactor technological channels, according to which deformation by each of the main three directions (axial, radial and tangental) is comprised of the radiation growth and creep, permits to forecast the dimensional change, to evaluate the contribution of creep and radiation growth, to understand the effect of different technology