[en] The inspection of the fuel rods manufactured at INB, for production of fuel assemblies, is based on a group of scintillators detectors in series scanning the products. These detectors capture the gamma rays emitted on the decay of uranium isotopes (passive measurement) and determine the enrichment level (²³⁵U weight percent) of the UO₂ pellets inside the fuel rods. During the inspection of fuel rods for Angra-1 21^st Reload, it was found that the 2.6% ²³⁵U and 4.15% ²³⁵U pellets stacks behave as 2.6% ²³⁵U only. The investigation of this event allowed to conclude that the measurement of enrichment may be affected by the loss of the secular equilibrium among uranium isotopes and their decay products caused by the AUC precipitation during the UO₂ powder and pellet fabrication. Therefore, the spectrum background created by Compton scattering, inside Rod Scanner detectors, from high energies of ²³⁸U products decay affect the ²³⁵U% measurement. After continuous measurements, the 2.6% ²³⁵U and 4.15% ²³⁵U pellets stacks became distinguished and the results were used to calculate an 'equilibrium factor'. It was concluded that after 35 days the UO₂ powder should reach approximately 60% of secular equilibrium reinstatement and the rods assembled with the pellets produced from this powder would be adequate for inspection on Rod Scanner. It was concluded that would be possible to achieve the equilibrium factor by blending a lot of UO₂ powder manufactured a long time ago (old powder) with another lot early manufactured (young powder) resulting in a lot which would provide pellets and, consequently, rods adequate for inspection by Rod Scanner. This work presents a study of an alternative method to perform the inspection of fuel rods with UO₂ pellets early manufactured aiming to provide quality assurance for the product. (author)