Blackburn, L., Crawford, R., Walling, S. et al. (9 more authors) (2021) Influence of accessory phases and surrogate type on accelerated leaching of zirconolite wasteforms. npj Materials Degradation, 5. 24. ISSN 2397-2106
Abstract
A fraction of the UK Pu inventory may be immobilised in a zirconolite ceramic matrix prior to disposal. Two zirconolite compositions, targeting CaZr0.80Ce0.20Ti2O7 and CaZr0.80U0.20Ti2O7, were fabricated by hot isostatic pressing, alongside a reformulated composition, nominally Ca0.80Zr0.90Ce0.30Ti1.60Al0.40O7, with an excess of Ti and Zr added to preclude the formation of an accessory perovskite phase. Materials were subjected to accelerated leaching in a variety of acidic and alkaline media at 90 °C, over a cumulative period of 14 d. The greatest Ce release was measured from CaZr0.80Ce0.20Ti2.00O7 exposed to 1 M H2SO4, for which 14.7 ± 0.2% of the original Ce inventory was released from the wasteform into solution. The extent of Ce leaching into the solution was correlated with the quantity of perovskite present in the wasteform, and associated with the incorporation and preferential dissolution of Ce3+. CaZr0.80U0.20Ti2.00O7 exhibited improved leach resistance relative to CaZr0.80Ce0.20Ti2.00O7, attributed to the decreased proportion of accessory perovskite, with 7.1 ± 0.1% U released to in 8 M HNO3 after 7 d. The Ca0.80Zr0.90Ce0.30Ti1.60Al0.40O7 composition, with no accessory perovskite phase, presented significantly improved leaching characteristics, with < 0.4%Ce released in both 8 M HNO3 and 1 M H2SO4. These data demonstrate the need for careful compositional design for zirconolite wasteforms with regard to accessory phase formation and surrogate choice.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © The Author(s) 2021. Open Access: This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. |
Keywords: | zirconolite; ceramic; leaching; polytype; perovskite; uranium; cerium; plutonium; HIP |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Materials Science and Engineering (Sheffield) |
Funding Information: | Funder Grant number ENGINEERING AND PHYSICAL SCIENCE RESEARCH COUNCIL EP/N017870/1 ENGINEERING AND PHYSICAL SCIENCE RESEARCH COUNCIL EP/N017374/1 RADIOACTIVE WASTE MANAGEMENT LTD RMW234 NUCLEAR DECOMMISSIONING AUTHORITY nan ENGINEERING AND PHYSICAL SCIENCE RESEARCH COUNCIL (EPSRC) UNSPECIFIED ENGINEERING AND PHYSICAL SCIENCE RESEARCH COUNCIL nan Engineering and Physical Sciences Research Council EP/S01019X/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 16 Apr 2021 14:58 |
Last Modified: | 03 Jun 2021 09:45 |
Status: | Published |
Publisher: | Nature Research (part of Springer Nature) |
Refereed: | Yes |
Identification Number: | 10.1038/s41529-021-00171-8 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:173147 |