Mechanical Properties of DU-xMo Alloys with x = 7 to 12 Weight Percent

Abstract

Mechanical properties of six depleted uranium-molybdenum (U-Mo) alloys have been obtained using microhardness, quasistatic tensile tests, and scanning electron microscopy (SEM) failure analysis. U-Mo alloy foils are currently under investigation for potential conversion of high power research reactors to low enriched uranium fuel. Although mechanical properties take on a secondary effect during irradiation, an understanding of the alloy behavior during fabrication and the effects of irradiation on the integrity of the fuel is essential. In general, the microhardness, yield strength, Young's modulus, and ultimate tensile strength improved with increasing Mo content. Microhardness measurements were very sensitive to local composition, while the failure mode was significantly controlled by the impurity concentration of the alloy, especially carbon. Values obtained from literature are also provided with reasonable agreement, even though processing conditions and applications were quite different in some instances.

Microstructural characteristics of DU–xMo alloys with x=7–12wt%

“…Electron microprobe analysis (EPMA) was not conducted on the alloys in this study. However, microindentation tests conducted on the alloys revealed that the DU-12Mo alloy had a microhardness value closer to that of a DU-14Mo alloy, and the DU-7Mo alloy had a microhardness value closer to that of a DU-8Mo alloy [13]. The microhardness measurements taken at the grain center in combination with the EPMA measurements suggests that the chemical bands that run across grains are Mo rich.…”

“…2 and 3), but rather a mixed recrystallized structure. However, mechanical tests performed on the same alloys showed that the DU-12Mo alloy failed via a ductile dimple rupture mode [13]. This failure mode was the result of small, closely spaced inclusions that created regions of localized strain discontinuity and nucleated microvoids that grew and coalesced as the deformation of the foil continued.…”

“…A phase analysis sample and chemical analysis samples were taken from the monoliths. The remainder of the foil was used to prepare tensile test specimens, results of which can be found in Burkes et al [13].…”

U-Mo Monolithic Fuel for Nuclear Research and Test Reactors

“…Dimensional stability of the fuel during reactor operation is extremely important. 12 Therefore, the high-temperature gamma (c) phase is desired, based on the isotropy that can be retained at room temperature and better resistance to thermal recycling and radiation damage. 13 In order to stabilize the high-temperature c phase, an alloying element is added, such as molybdenum (Mo) that has a high solid solubility in bcc c uranium.…”

“…14,15 The metallic fuel selected to replace the current HEU fuels is the LEU-10wt.% Mo alloy in the form of a thin sheet or foil encapsulated in AA6061 aluminum alloy with a zirconium interlayer. 12,16 The U-10Mo monolithic fuel can achieve the desired higher uranium density (15.6 g/cm 3 ). In order to effectively lead this investigation, new developments in processing and fabrication of the fuel elements have been initiated, along with a better understanding of material behavior before and after irradiation as a result of these new developments.…”