In recent years AFIT has built expertise and resources dedicated to the growth and characterization of actinide oxides. The primary purpose of this research was to integrate positron spectroscopy ? with which AFIT also has a long history ? into this actinide research. The main objectives were to construct a Positron Annihilation Lifetime Spectroscopy system, including a new positron source, and to characterize a number of hydrothermally grown ThO2 and U:ThO2 crystals. Lifetime measurements were conducted on nine crystal samples and the spectra analyzed to determine the purity and quality of the crystals. In addition, analysis and fitting of the experimental data allowed estimates of contribution percentages to be made; the samples themselves account for less than 30% of the sample counts in all cases. Overall, the low resolution and large number of non-sample counts indicates that the system was not sufficient to characterize the crystals. A strong foundation for actinide PALS studies was laid, but further work is required to build a more effective system.