Characterization of pore networks in UO2-PuO2 fuel pellets

The open porosity in uranium-plutonium dioxide pellets can approximately be described as an arrangement of large spherical pores, which are interconnected through narrow cylindrical channels. Within this model properties depending on the porosity of pellets are well described by introducing two channel parameters for the average number k of channels, which interconnect at one pore (connectivity) and the average effective channel length ratio tau. Besides measurements by means of image analysis and mercury intrusion porosimetry studies of gas-effusion are necessary to obtain these network parameters. The result of this comprehensive pore structure characterization provides the possibility to interpret the gas exchange in fuel pellets in a quantitative manner. (Auth.)