Studies for the Characteristics of Sintered Uranism Dioxide Fuel (Part I)

Abstract

Sintered UO2 pellets of high densities are used as fuel for water-cooled reactors. Relations between physical properties … such as bulk density, tap density, specific surface area, average particle size and compatibilities or sinterabilities of as-received, oxidation-reduction treated or ball-milled powders were examined. In these experiments, powders were compacted at 2-7 t/cm2 and were sintered for 1-10 hours at temperatures from 1400°C to 1650°C in an atmosphere of cracked ammonia.The results are summarized below :1) The specific surface areas of UO2 powders increased with increasing oxidation-reduction cycles ; however only small change was observed in the ball-milled UO2 powders.2) In contrast to the ball-milled UO2 powder, the green density of the oxidation-reduction treated UO2 decreased with increasing specific surface area. Ball-milling and oxidation-reduction treatment improved the sinterability.3) The activation energy of the densification of UO2 during sintering in cracked ammonia was calculated.4) It was found that the densification factors are proportional to the specific surface area of as-received or activation treated powders.