Influence of accessory phases and surrogate type on accelerated leaching of zirconolite wasteforms

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 Ca0.80Zr0.90...

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Autores principales:	Lewis R. Blackburn, Rachel Crawford, Samuel A. Walling, Laura J. Gardner, Max R. Cole, Shi-Kuan Sun, Clémence Gausse, Amber R. Mason, Martin C. Stennett, Ewan R. Maddrell, Neil C. Hyatt, Claire L. Corkhill
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Materials of engineering and construction. Mechanics of materials TA401-492
Acceso en línea:	https://doaj.org/article/a10a21309bb64c589487c64af2f2391d
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spelling	oai:doaj.org-article:a10a21309bb64c589487c64af2f2391d2021-12-02T14:59:09ZInfluence of accessory phases and surrogate type on accelerated leaching of zirconolite wasteforms10.1038/s41529-021-00171-82397-2106https://doaj.org/article/a10a21309bb64c589487c64af2f2391d2021-05-01T00:00:00Zhttps://doi.org/10.1038/s41529-021-00171-8https://doaj.org/toc/2397-2106Abstract 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.Lewis R. BlackburnRachel CrawfordSamuel A. WallingLaura J. GardnerMax R. ColeShi-Kuan SunClémence GausseAmber R. MasonMartin C. StennettEwan R. MaddrellNeil C. HyattClaire L. CorkhillNature PortfolioarticleMaterials of engineering and construction. Mechanics of materialsTA401-492ENnpj Materials Degradation, Vol 5, Iss 1, Pp 1-11 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Materials of engineering and construction. Mechanics of materials TA401-492
spellingShingle	Materials of engineering and construction. Mechanics of materials TA401-492 Lewis R. Blackburn Rachel Crawford Samuel A. Walling Laura J. Gardner Max R. Cole Shi-Kuan Sun Clémence Gausse Amber R. Mason Martin C. Stennett Ewan R. Maddrell Neil C. Hyatt Claire L. Corkhill Influence of accessory phases and surrogate type on accelerated leaching of zirconolite wasteforms
description	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.
format	article
author	Lewis R. Blackburn Rachel Crawford Samuel A. Walling Laura J. Gardner Max R. Cole Shi-Kuan Sun Clémence Gausse Amber R. Mason Martin C. Stennett Ewan R. Maddrell Neil C. Hyatt Claire L. Corkhill
author_facet	Lewis R. Blackburn Rachel Crawford Samuel A. Walling Laura J. Gardner Max R. Cole Shi-Kuan Sun Clémence Gausse Amber R. Mason Martin C. Stennett Ewan R. Maddrell Neil C. Hyatt Claire L. Corkhill
author_sort	Lewis R. Blackburn
title	Influence of accessory phases and surrogate type on accelerated leaching of zirconolite wasteforms
title_short	Influence of accessory phases and surrogate type on accelerated leaching of zirconolite wasteforms
title_full	Influence of accessory phases and surrogate type on accelerated leaching of zirconolite wasteforms
title_fullStr	Influence of accessory phases and surrogate type on accelerated leaching of zirconolite wasteforms
title_full_unstemmed	Influence of accessory phases and surrogate type on accelerated leaching of zirconolite wasteforms
title_sort	influence of accessory phases and surrogate type on accelerated leaching of zirconolite wasteforms
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/a10a21309bb64c589487c64af2f2391d
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Influence of accessory phases and surrogate type on accelerated leaching of zirconolite wasteforms

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