DFT study on the electronic structure and chemical state of Americium in an (Am,U) mixed oxide

Suzuki, Chikashi; Nishi, Tsuyoshi; Nakada, Masami; Tsuru, Tomohito; Akabori, Mitsuo; Hirata, Masaru; Kaji, Yoshiyuki

doi:10.1016/j.jpcs.2013.07.006

Cited by 17 publications

(21 citation statements)

References 30 publications

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“…Furthermore, the charge distribution found in this study is consistent with very early results on uranium-americium mixed oxides obtained by XPS (X-ray photoelectron spectroscopy) [29] and more recent XANES data [30], both indicating the presence of only Am þ III , and suggesting the presence of uranium in a slightly oxidized state. These experimental results were also supported by recent DFT (density functional theory) calculations which led to the same charge distribution [31].…”

Section: Discussionsupporting

confidence: 83%

Comparative XRPD and XAS study of the impact of the synthesis process on the electronic and structural environments of uranium–americium mixed oxides

Prieur

Lebreton

Martin

et al. 2015

Journal of Solid State Chemistry

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Section: Discussionsupporting

confidence: 83%

Comparative XRPD and XAS study of the impact of the synthesis process on the electronic and structural environments of uranium–americium mixed oxides

Prieur

Lebreton

Martin

et al. 2015

Journal of Solid State Chemistry

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“…In the present study, we propose the doping of americium oxide to stabilize the cubic structure during reductive sintering in order to solve the different problems cited above. Fluorite structured materials are known to have a high tolerance to alpha damage. − Uranium shows a very peculiar behavior when mixed with different trivalent oxides, namely a charge compensation phenomenon as a result of which oxidation of uranium over the oxidation state IV occurs even during reductive sintering. − This phenomenon helps the stabilization of the cubic phase solid solution even at low uranium concentrations. , Uranium–americium mixed oxides have been extensively investigated in recent studies, − mainly due to their potential use as a minor actinide-bearing blanket fuel in nuclear reactors for americium transmutation. However, most of these studies focus on americium concentrations from 10 to 50% (metal base ratio).…”

Section: Introductionmentioning

confidence: 99%

Optimization of Uranium-Doped Americium Oxide Synthesis for Space Application

et al. 2018

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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.

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“…Adsorption energies of water on differently oriented uranium dioxide planes were calculated. 14, 15,16 The work on the study of the electronic structure of uranium and its alloys [17][18][19][20][21] and oxides UO 2+x (x≤0 and x≥0) employed theoretical calculation results, [22][23][24][25][26][27][28][29][30][31][32][33][34] photoelectron spectroscopy (PES) [35][36][37][38][39][40][41] and X-ray photoelectron spectroscopy (XPS) widely. 38,[42][43][44][45][46][47][48][49][50][51][52][53][54][55] These techniques were used to study films on various substrates.…”

Section: Introductionmentioning

confidence: 99%

“…The work on the study of the electronic structure of uranium and its alloys − and oxides UO 2+ x ( x ≤ 0 and x ≥ 0) employed theoretical calculation results, − photoelectron spectroscopy (PES), − and X-ray photoelectron spectroscopy (XPS) widely. ,− These techniques were used to study films on various substrates. − ,− …”

Section: Introductionmentioning

confidence: 99%

XPS Study of Ion Irradiated and Unirradiated UO₂ Thin Films

et al. 2016

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XPS determination of the oxygen coefficient k O =2+x and ionic (U 4+ , U 5+ and U 6+ ) composition of oxides UO 2+x formed on the surfaces of differently oriented (hkl) planes of thin UO 2 films on LSAT (Al 10 La 3 O 51 Sr 14 Ta 7 ) and YSZ (yttria-stabilized zirconia) substrates was performed. The U 4f and O 1s core-electron peak intensities as well as the U 5f relative intensity before and after the 129 Xe 23+ and 238 U 31+ irradiations were employed. It was found that the presence of uranium dioxide film in air results in formation of oxide UO 2+x on the surface with mean oxygen coefficients k O in the range 2.07-2.11 on LSAT and 2.17-2.23 on YSZ substrates. These oxygen coefficients depend on the substrate and weakly on the crystallographic orientation.On the basis of the spectral parameters it was established that uranium dioxide films AP2,3 on the LSAT substrates have the smallest k O values, and from the XRD and EBSD results it follows that these samples have a regular monocrystalline structure. The XRD and EBSD results indicate that samples AP5-7 on the YSZ substrates have monocrystalline structure, however, they have the highest k O values. The observed difference in the k O values, probably, caused by the different nature of the substrates: the YSZ substrates provide 6.4% compressive strain, whereas (001) LSAT substrates result only in 0.03% tensile strain in the UO 2 films.129 Xe 23+ irradiation (92 MeV, 4.8 × 10 15 ions/cm 2 ) of uranium dioxide films on the LSAT substrates was shown to destroy both long range ordering and uranium close environment, which results in increase of uranium oxidation state and regrouping of oxygen ions in uranium close environment. 238 U 31+ (110 MeV, 5 × 10 10 , 5 × 10 11 , 5 × 10 12 ions/cm 2 ) irradiations of uranium dioxide films on the YSZ substrates were shown to form the lattice damage only with partial destruction of the long range ordering.3

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DFT study on the electronic structure and chemical state of Americium in an (Am,U) mixed oxide

Cited by 17 publications

References 30 publications

Comparative XRPD and XAS study of the impact of the synthesis process on the electronic and structural environments of uranium–americium mixed oxides

Comparative XRPD and XAS study of the impact of the synthesis process on the electronic and structural environments of uranium–americium mixed oxides

Optimization of Uranium-Doped Americium Oxide Synthesis for Space Application

XPS Study of Ion Irradiated and Unirradiated UO₂ Thin Films

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DFT study on the electronic structure and chemical state of Americium in an (Am,U) mixed oxide

Cited by 17 publications

References 30 publications

Comparative XRPD and XAS study of the impact of the synthesis process on the electronic and structural environments of uranium–americium mixed oxides

Comparative XRPD and XAS study of the impact of the synthesis process on the electronic and structural environments of uranium–americium mixed oxides

Optimization of Uranium-Doped Americium Oxide Synthesis for Space Application

XPS Study of Ion Irradiated and Unirradiated UO2 Thin Films

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XPS Study of Ion Irradiated and Unirradiated UO₂ Thin Films