Surface alteration evidence for a mechanism of anoxic dissolution of UO2


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Type
Article
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Authors
Popel, AJ 
Beng Thye, Tan 
Thomas, Gouder 
Giulio, Lampronti 
Jason, Day 
Abstract

A secondary phase has been observed to nucleate on the surface of UO2 in a solution with uranium concentration values of ~10-9 mol/l. The UO2 was in the form of a 100 nm single crystalline film of UO2 epitaxially deposited on the (001) surface of a single crystalline silicon substrate. An extended (140 days) dissolution experiment with UO2 in contact with a solution in deoxygenated, deionised water, under an Ar atmosphere (~0.1 O2 ppm) at ambient temperature (~25 °C) suggests that uranium dioxide should dissolve and precipitate while remaining in the U4+ oxidation state to enable nucleation of a low solubility secondary phase. A mechanism for the anoxic dissolution of UO2 in deionised water is proposed that involves U4+ dissolution at defect sites that subsequently nucleate and precipitate in a less defective form.

Description
Keywords
UO2, Anoxic dissolution, Secondary phases, Nucleation, Thin film, Geological disposal
Journal Title
Applied Surface Science
Conference Name
Journal ISSN
0169-4332
1873-5584
Volume Title
464
Publisher
Elsevier
Sponsorship
Engineering and Physical Sciences Research Council (EP/I036400/1)
EPSRC (via University of Leeds) (EP/S011935/1)
B.T. Tan acknowledges funding from the Singapore Nuclear and Research Safety Initiative (SNRSI).