Silicate stabilisation of colloidal UO2 produced by uranium metal corrosion

JOURNAL OF NUCLEAR MATERIALS

卷:526

Article

Neill, Thomas S.^1,2  Morris, Katherine^1,2  Pearce, Carolyn, I^1,2,3  Abrahamsen-Mills, Liam⁴  Kovarik, Libor³  Kellet, Simon⁵  Rigby, Bruce⁵  Vitova, Tonya⁶  Schacherl, Bianca⁶  Shaw, Samuel^1,2 

[1] Univ Manchester, Res Ctr Radwaste Disposal, Sch Earth & Environm Sci, Oxford Rd, Manchester M13 9PL, Lancs, England

[2] Univ Manchester, Williamson Res Ctr, Sch Earth & Environm Sci, Oxford Rd, Manchester M13 9PL, Lancs, England

[3] Pacific Northwest Natl Lab, Richland, WA 99354 USA

[4] Natl Nucl Lab, Chadwick House,Warrington Rd,Birchwood Pk, Warrington WA3 6AE, Cheshire, England

[5] Sellafield Ltd, Hinton House,Birchwood Pk Ave, Warrington WA3 6GR, Cheshire, England

[6] Karlsruhe Inst Technol, Inst Nucl Waste Disposal INE, PO 3640, D-76021 Karlsruhe, Germany

关键词: Uranium;    Silicate;    Corrosion;    Colloid;    Coffinite;   

DOI  :  10.1016/j.jnucmat.2019.151751

来源: Elsevier

【 摘 要 】

U(IV) mobility can be significantly enhanced by colloids in both engineered and natural environments. This is particularly relevant in decommissioning and clean-up of nuclear facilities, such as legacy fuel ponds and silos at the Sellafield site, UK, and in long-term radioactive waste geodisposal. In this study, the product of metallic uranium (U) corrosion under anaerobic, alkaline conditions was characterised, and the interaction of this product with silicate solutions was investigated. The U metal corrosion product consisted of crystalline UO2 nanoparticles (5-10 nm) that aggregated to form clusters larger than 20 nm. Sequential ultrafiltration indicated that a small fraction of the U metal corrosion product was colloidal. When the uranium corrosion product was reacted with silicate solutions under anaerobic conditions, ultrafiltration indicated a stable colloidal uranium fraction was formed. Extended X-ray absorption fine structure (EXAFS) spectroscopy and high resolution TEM confirmed that the majority of U was still present as UO2 after several months of exposure to silicate solutions, but an amorphous silica coating was present on the UO2 surface. This silica coating is believed to be responsible for formation of the UO2 colloid fraction. Atomic-resolution scanning TEM (STEM) indicated some migration of U into the silica-coating of the UO2 particles as non-crystalline U(IV)-silicate, suggesting alteration of UO2 at the UO2-silica interface had occurred. This alteration at the UO2-silica interface is a potential pathway to the formation of U-silicates (e.g. coffinite, USiO4). (C) 2019 The Authors. Published by Elsevier B.V.

【 授权许可】

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