U-Mo alloys are the most promising materials fulfilling the requirements of using low enriched uranium (LEU) fuel in research reactors. From a fundamental standpoint, it is of interest to determine the basic thermodynamic properties ofthe cubic y-phase U-Mo alloys. the authors focus the attention on the use of Mo doping together with ultrafast cooling (with high cooling rates or = 10 exponent 6 Ks-1), which helps to maintain the cubic gamma-phase in U-Mo system to low temperatures and on determination of the low-temperature properties of these gamma-U alloys. Using a splat cooling method it has been possible to maintain some fraction of the high-temperature y-phase at room temperature in pure uranium. U-13 at. percent Mo splat clearly exhibits the pure y-phase structure. All the splats become superconducting with Tc in the range from 1.24 K (pure V splat) to 2.11 K (U-IS at. percent Mo). The y-phase in U-Mo alloys undergoes eutectoid decomposition to form equilibrium phases of orthorhombic a-uranium and tetragonal gamma -phase upon annealing at 500°C, while annealing at 800°C has stabilized the initial y phase. The a-U easily absorbs a large amount of hydrogen (VH3 hydride), while the cubic bee phase does not absorb any detectable amount of hydrogen at pressures below 1 bar and at room temperature. At 80 bar, the V-IS at. percent Mo splat becomes powder consisting of elongated particles of 1-2 mm, revealing amorphous state.