Vibrocompaction electrodynamique de nodules frittes d'oxyde d'uranium

Vibrocompaction of sintered UO₂ nodules and powders was studied on an installation equipped with an electrodynamic vibrator. The influence of the dimensions of the coarse fraction on the average fuel density was examined both theoretically and experimentally. This study has shown that certain dimensions are advantageous and that the diameter of the nodules must therefore be chosen between 20 and 30% of the inner diameter of the cladding tube. The role of the other 2 fractions is mentioned. Experiments have been carried out with different percentages of these fractions in order to establish a 'ternary' diagram, which gives the compositions to be used as a function of the finally desired density. Fabrication parameters, such as time and vibration power are also discussed. Examinations of the vibrocompacted rods containing nodules proved the good quality of these pins. Densification of the rods is rather quick and easy: a judicious choice of the initial load makes it possible to obtain a density of 87.9% T.D. The density fluctuations are ±1.3% as a maximum and very often below 1%. The different fabrication steps are also very reproducible and the technique is very versatile.