Details

Autor(en) / Beteiligte

• Andrello, C.
• Gouder, T.
• Favergeon, L.
• Desgranges, L.
• Tereshina-Chitrova, E.
• Havela, L.
• Konings, R.J.M.
• Eloirdi, R.

Titel

In-situ high resolution photoelectron spectroscopy study on interaction of sodium with UO2+x film (0 ≤ x ≤ 1)

Ist Teil von

• Journal of nuclear materials, 2021-03, Vol.545, p.152646, Article 152646

Ort / Verlag

Amsterdam: Elsevier B.V

Erscheinungsjahr

2021

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• •Interaction study of sodium with UO2+x (0 ≤ x ≤ 1) film using high-resolution XPS.•Sodium does not reduce UO2.•Sodium reduce UO2+x (0 < x ≤ 1) till UO2.•Interaction of sodium and UO3 at 673 to 773 K to form NaUO3.•Under UHV and along heat treatment, sodium stabilise U(V). We studied in-situ the interaction of sodium metal with UO2+x (0 ≤ x ≤ 1) using thin films prepared by sputter deposition on Au substrate. X-ray Photoelectron Spectroscopy (XPS) and Grazing Incidence X-Ray Diffraction (GIXRD) characterized films before and after interaction. The results show that sodium does not reduce stoichiometric UO2 at room temperature. Plasmon loss peaks, observed at the Na1s photoemission (PE) line, are characteristic of metallic sodium particles, and point to a weak interaction between sodium and UO2. The oxidation of the sodium at room temperature takes place only on hyper-stoichiometric uranium dioxide films. Indeed, sodium deposition on UO2+x (0 < x ≤ 1), eventually results in the complete reduction of U(VI) down to U(IV). Molecular and atomic oxygen affect differently the oxidation of uranium and sodium. The wetting of the gold by the sodium is much more important when sodium is oxidised by atomic oxygen. This leads to a shift of the Na1s core level peak, while molecular oxygen gives a peak broadening without shift. Atomic oxygen seems to play the same role as the interstitial oxygen present in the UO2+x film. The oxygen dissociation may be the limiting step of sodium oxidation on gold and on UO2. Heat treatment of sodium on UO3 at about 773 K leads to the formation of the NaUO3 film as demonstrated by a quantitative analysis by XPS and GIXRD. The results show also that once U(V) is formed, it stays stable up to at least 973 K, the temperature at which shrinkage of the film is observed. [Display omitted]