Dry Recycling of Off-Grade Uranium Oxide Powder for Improving Sinterability

Abstract

Nuclear Fuel for Pressurized Heavy Water Reactor (PHWR) is produced through the conventional powder-pellet route using ex-Ammonium di-Uranate (ADU) as the starting material. In order to meet the requirement of the narrow band of process parameters for obtaining high quality finished UO₂ pellet, the quality of the starting powder UO₂ has to be consistently maintained within the given specification. The Specific Surface Area (SSA), particle size, Oxygen to Uranium ratio (O/U), bulk density and chemical purity of the UO₂ powder, as well as high recovery in sinterability test are key criteria for acceptance of powder lots.

The powder lots rejected in the sinterability test, if any, has so far been recycled by wet chemical route involving HNO₃ dissolution and consumption of large quantities of chemicals which in turn results in the generation of effluents.

An alternate process of recycle by 'dry route' has been developed, which not only eliminates the above disadvantages but also contributes to improvement of productivity. The 'dry-recycle' route (DRR) has paved the way for >95% acceptability of the powder lots in sinterability tests.

The present paper describes the important aspects of DRR developed at Nuclear Fuel Complex, on an industrial scale.