Optimization of Uranium-Doped Americium Oxide Synthesis for Space Application

Abstract

Americium 241 is a potential alternative to plutonium 238 as an energy source for missions into deep space or to the dark side of planetary bodies. In order to use the Am isotope for radioisotope thermoelectric generator or radioisotope heating unit (RHU) production, americium materials need to be developed. This study focuses on the stabilization of a cubic americium oxide phase using uranium as the dopant. After optimization of the material preparation, (AmUNpPu)O has been successfully synthesized to prepare a 2.96 g pellet containing 2.13 g of Am for fabrication of a small scale RHU prototype. Compared to the use of pure americium oxide, the use of uranium-doped americium oxide leads to a number of improvements from a material properties and safety point of view, such as good behavior under sintering conditions or under alpha self-irradiation. The mixed oxide is a good host for neptunium (i.e., theAm daughter element), and it has improved safety against radioactive material dispersion in the case of accidental conditions.

Determination of Mass Attenuation Coefficients of Th, U, Np, and Pu for Oxygen KαX-Rays Using an Electron Microprobe

“…Judging from the analytical total, however, the PENELOPE MACs provide a more satisfactory estimate of the oxygen content because of the closeness of the total to 100%. The formula of the analyzed uranium-doped americium oxide sample was written as (Am 0.80 U 0.12 Np 0.06 Pu 0.02 )O 1.8 and was found to be in good agreement with the thermogravimetric analysis reported by Vigier et al (2018).…”

“…The results obtained in the previous section have been used to improve the analysis of a uranium-doped americium oxide sample, which consisted of a large ceramic pellet prepared as a small-scale radioisotope heater unit prototype (Vigier et al, 2018). The Am used to prepare the sample had been aged for approximately 40 years, and therefore, it contained a significant amount of 237 Np due to α decay of 241 Am.…”

European Radioisotope Thermoelectric Generators (RTGs) and Radioisotope Heater Units (RHUs) for Space Science and Exploration

“…This is also highlighted by Sarsfield et al (2017) and Epifano et al (2017). Therefore, the focus for the ESA programme shifted to Am 2 O 3 (Watkinson et al 2017a) and more recently to a uranium-stabilised cubic americium oxide (Vigier et al 2018) to produce a consolidated fuel form.…”

“…For images of americium-based pellets and further details of the consolidation work carried out with americium oxides, the readers are referred to Sarsfield et al (2017Sarsfield et al ( , 2018 and Vigier et al (2018).…”

“…• The work by Vigier et al (2018) also suggests that the fuel form is likely to be a mixed oxide of americium and uranium-based fuels where the latter could comprise 15% of the total fuel mass. • The need to potentially accommodate more fuel mass while constraining the heat source volume.…”