The objective of this work was firstly to categorize the data on dimensional change of the VVER fuel rods and to identify the primary variables influencing performance, and secondly to benchmark the irradiation-thermal creep model for Zr-1% Nb alloy cladding tubes against the VVER fuel rod dimensional changes data. The creep model was developed using the results of in-pile and out-of-pile tests of tube specimens.
Data arrays on the change of fuel rod diameter and length were obtained during examination of eight VVER-440 fuel assemblies and 16 VVER-1000 fuel assemblies. Qualitative analysis was performed of the measurement results presented as dependencies of averaged axial strain on burnup.
Similar calculated dependencies were obtained using the creep model considering the irradiation growth strain. The quantitative analysis showed that differences between the calculated and actual dimensional changes of the fuel rods did not exceed 3–5 % for VVER-440 and 7 % for VVER-1000.