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Surface Site Densities of Uranium Oxides: UO2, U3O8

Published online by Cambridge University Press:  01 February 2011

F. Clarens ,
J. de Pablo ,
I. Casas ,
J. Giménez  and
M. Rovira
F. Clarens
Affiliation:
Chemical Engineering Department. Universitat Politècnica de Catalunya. 08028 Barcelona., Spain
J. de Pablo
Affiliation:
Chemical Engineering Department. Universitat Politècnica de Catalunya. 08028 Barcelona., Spain
I. Casas
Affiliation:
Chemical Engineering Department. Universitat Politècnica de Catalunya. 08028 Barcelona., Spain
J. Giménez
Affiliation:
Chemical Engineering Department. Universitat Politècnica de Catalunya. 08028 Barcelona., Spain
M. Rovira
Affiliation:
Chemical Engineering Department. Universitat Politècnica de Catalunya. 08028 Barcelona., Spain
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Abstract

The estimation of the surface site density for UO2 (main component of the SF matrix) is an important aspect to take into account in the development of radiolytical models for the dissolution of the spent nuclear fuel (SF). Also, other oxides can be formed on the SF surface due to the effect of radiolytically-formed oxidizing species. Due to the lack or reliable data in literature we have studied the surface site densities of two uranium oxides: UO2 and U3O8.

For this determination, the knowledge of both the reactive surface area and the surface charge of the solid are necessary. In this work the reactive surface area of the two solids was determined by the BET method while the surface charge was determined by potentiometric acid-base titrations of suspensions of the solids at different ionic strengths (0.001, 0.01, and 0.1 mol·dm−3) under N2 atmosphere.

The amount of adsorbed protons was calculated by subtracting blank titration from thesolid suspension titration. The single-site nonelectrostatic model (NEM) was used to describe titration data. Uranium speciation in solution was included in the model as well.

The surface area values obtained were 0.15 ± 0.01 m2·g−1 for UO2 and 0.77 ± 0.02 m2·g−1 for U3O8, while the surface acidic site densities were determined to be 165 ± 10 sites·nm−2 and 48 ± 3 sites·nm−2 for UO2 and U3O8, respectively.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 807: Symposium Scientific Basis for Nuclear Waste Management XXVII , 2003 , 71
Copyright
Copyright © Materials Research Society 2004

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References

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