Hydrothermal synthesis of ThO2, UxTh1-xO2, and UOx at temperatures between 670°C and 700°C has been demonstrated. Synthesis at these temperatures is 50-80°C below prior growth studies and represents a new lower bound of successful growth. ThO2 single crystals of dimensions 6.49mm x 4.89mm x 3.89 mm and weighing 0.633g have been synthesized at average growth rates near 0.125mm/week. Single crystal UxTh1-xO2 crystals with mole fractions up to x≈0.30 have also been grown. The largest alloyed crystal with mole fraction x≈0.23 has dimensions of 2.97mm x 3.23mm x ∼3mm and recorded average growth rates near 0.2mm/week. Four structures were solved from X-ray diffraction data and their crystallographic data reported here. Rocking curve analysis determined a dislocation density of 1.2×109 cm-2.