NSUF 24-4820: In-Situ TEM Characterization of Ion-Irradiated U-10Mo Alloys at Sub-Eutectoid Temperatures

U-Mo alloys have been of interest to the nuclear energy community as an efficient fuel with good resistance to adverse irradiation effects such as fuel swelling. The stability of U-Mo fuels arises from a high temperature γ-phase which can be stabilized at room temperatures under specific quenching conditions. At sub-eutectoid temperatures, U-Mo fuels demonstrate phase decomposition from γ→α+γ' when subjected to thermal ageing. These phases demonstrate poor irradiation behavior, and their formation is detrimental. Conversely, under irradiation, phase reversal driven from α+γ^'→γ occurs. These opposite phenomena are driven by thermal diffusion and radiation induced displacement spikes respectively. Hence, while the extent of phase decomposition increases with temperature, higher fission rates result in increased phase reversal. Hence, at every temperature, there is a critical fission rate above which phase reversal overpowers phase decomposition. Yet, recent investigations have demonstrated the occurrence of phase decomposition in U-10wt.%Mo alloys during neutron irradiation, the extent of which increases with the fluence. The authors hypothesize the involvement of a third, unknown mechanism that depends on the fluence itself. As the fraction of the γ-phase dictates the irradiation stability of the fuel, it is important to understand all the factors that affect phase transformations in this alloy and their respective mechanisms. To investigate this new mechanism, this research will employ in-situ TEM to characterize U-10wt.%Mo specimens that have been ion-irradiated at different temperatures and flux rates. The temperatures are chosen such that their critical fission rates are within the range of achievable flux rates at IVEM. The specimens to be used in this study are DU-10wt.%Mo TEM disks listed in the Fuels and Materials library under Experiment 10-242. Prior to irradiation, the specimens will be prepared using jet-polishing at INL, and then be shipped to ANL for IVEM characterization. At the IVEM-Tandem Facility at ANL, 1 MeV Xe ions will be used to irradiate the specimens at two temperatures (350°C and 375°C) and two flux rates (3×10^11 ions cm^(-1) s^(-1)and 1.3×10^12 ions cm^(-1) s^(-1)). Irradiation at two different flux rates will help verify the historical interpretation of phase reversal being driven by fission rates. Real-time bright and dark field TEM imaging, as well as selected area electron diffraction and energy dispersive spectroscopy will provide insights into the decomposition modes and detect potential decomposition favoring phenomena like radiation induced segregation. The sample preparation will take about one day, and, allocating two days for each specimen, the ion irradiation and characterization will take about eight days.

추가 정보

필드	값
Award Announced Date	2024-02-02T12:13:14.033
Awarded Institution	Purdue University
Facility Tech Lead	Alina Montrose, Wei-Ying Chen
Irradiation Facility
PI	Sukanya Majumder
PI Email	[email protected]
Project Type	RTE
RTE Number	None