Formation of stable uranium(VI) colloidal nanoparticles in conditions relevant to radioactive waste disposal

Pieter Bots, Katherine Morris, Rosemary Hibberd, Gareth T.W. Law, J. Frederick W. Mosselmans, Andy P. Brown, James Doutch, Andrew J. Smith, Samuel Shaw

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

The favored pathway for disposal of higher activity radioactive wastes is via deep geological disposal. Many geological disposal facility designs include cement in their engineering design. Over the long term, interaction of groundwater with the cement and waste will form a plume of a hyperalkaline leachate (pH 10-13), and the behavior of radionuclides needs to be constrained under these extreme conditions to minimize the environmental hazard from the wastes. For uranium, a key component of many radioactive wastes, thermodynamic modeling predicts that, at high pH, U(VI) solubility will be very low (nM or lower) and controlled by equilibrium with solid phase alkali and alkaline-earth uranates. However, the formation of U(VI) colloids could potentially enhance the mobility of U(VI) under these conditions, and characterizing the potential for formation and medium-term stability of U(VI) colloids is important in underpinning our understanding of U behavior in waste disposal. Reflecting this, we applied conventional geochemical and microscopy techniques combined with synchrotron based in situ and ex situ X-ray techniques (small-angle X-ray scattering and X-ray adsorption spectroscopy (XAS)) to characterize colloidal U(VI) nanoparticles in a synthetic cement leachate (pH > 13) containing 4.2-252 μM U(VI). The results show that in cement leachates with 42 μM U(VI), colloids formed within hours and remained stable for several years. The colloids consisted of 1.5-1.8 nm nanoparticles with a proportion forming 20-60 nm aggregates. Using XAS and electron microscopy, we were able to determine that the colloidal nanoparticles had a clarkeite (sodium-uranate)-type crystallographic structure. The presented results have clear and hitherto unrecognized implications for the mobility of U(VI) in cementitious environments, in particular those associated with the geological disposal of nuclear waste. (Figure Presented). © 2014 American Chemical Society.
LanguageEnglish
Pages14396-14405
Number of pages10
JournalLangmuir
Volume30
Issue number48
Early online date23 Oct 2014
DOIs
Publication statusPublished - 9 Dec 2014

Fingerprint

Radioactive waste disposal
waste disposal
Uranium
disposal
radioactive wastes
Colloids
cements
Radioactive Waste
Waste disposal
uranium
colloids
Cements
Radioactive wastes
Nanoparticles
nanoparticles
X rays
x rays
Spectroscopy
Adsorption
Forms (concrete)

Keywords

  • uranium
  • hexavalent
  • colloids
  • nanoparticle
  • geological disposal
  • radioactive waste disposal
  • cement
  • nuclear waste

Cite this

Bots, P., Morris, K., Hibberd, R., Law, G. T. W., Mosselmans, J. F. W., Brown, A. P., ... Shaw, S. (2014). Formation of stable uranium(VI) colloidal nanoparticles in conditions relevant to radioactive waste disposal. Langmuir, 30(48), 14396-14405. https://doi.org/10.1021/la502832j
Bots, Pieter ; Morris, Katherine ; Hibberd, Rosemary ; Law, Gareth T.W. ; Mosselmans, J. Frederick W. ; Brown, Andy P. ; Doutch, James ; Smith, Andrew J. ; Shaw, Samuel. / Formation of stable uranium(VI) colloidal nanoparticles in conditions relevant to radioactive waste disposal. In: Langmuir. 2014 ; Vol. 30, No. 48. pp. 14396-14405.
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Bots, P, Morris, K, Hibberd, R, Law, GTW, Mosselmans, JFW, Brown, AP, Doutch, J, Smith, AJ & Shaw, S 2014, 'Formation of stable uranium(VI) colloidal nanoparticles in conditions relevant to radioactive waste disposal' Langmuir, vol. 30, no. 48, pp. 14396-14405. https://doi.org/10.1021/la502832j

Formation of stable uranium(VI) colloidal nanoparticles in conditions relevant to radioactive waste disposal. / Bots, Pieter; Morris, Katherine; Hibberd, Rosemary; Law, Gareth T.W.; Mosselmans, J. Frederick W.; Brown, Andy P.; Doutch, James; Smith, Andrew J.; Shaw, Samuel.

In: Langmuir, Vol. 30, No. 48, 09.12.2014, p. 14396-14405.

Research output: Contribution to journalArticle

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AU - Bots, Pieter

AU - Morris, Katherine

AU - Hibberd, Rosemary

AU - Law, Gareth T.W.

AU - Mosselmans, J. Frederick W.

AU - Brown, Andy P.

AU - Doutch, James

AU - Smith, Andrew J.

AU - Shaw, Samuel

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KW - uranium

KW - hexavalent

KW - colloids

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KW - geological disposal

KW - radioactive waste disposal

KW - cement

KW - nuclear waste

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