Reduction of the open porosity of UO2 pellets through pore structure control

A powder mixture was prepared by mixing uranium-dioxide (UO2) powder ex-AUG with its milled powder and was pressed into compacts. The UO2 pellets were sintered under hydrogen. The compact density increased with the content of milled powder, since the particles of the milled powder might fill the interstices between the particles of the UO2 powder ex-AUG during pressing. A mechanism for the formation of flake-like pores was proposed on the basis of the microstructures of the powder, the compact, a partially sintered pellet and a final pellet. The open porosity of a sintered pellet decreased with increasing content of the milled powder, and the reduction of open porosity could be mainly attributed to the decrease in the number of flake-like pores whose shapes deviate greatly from roundness. (C) 2000 Elsevier Science B.V. All rights reserved.