The effect of milling on synroc powder characteristics

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dc.contributor.authorAngel, PJen_AU
dc.contributor.authorBuykx, WJen_AU
dc.date.accessioned2025-08-05T06:22:40Zen_AU
dc.date.available2025-08-05T06:22:40Zen_AU
dc.date.issued1991-08en_AU
dc.date.statistics2025-08-01en_AU
dc.descriptionPhysical copy held by ANSTO Library at DDC: 620.14/9.en_AU
dc.description.abstractSynroc is a crystalline titanate ceramic designed for the immobilisation of high level waste resulting from the reprocessing of spent nuclear fuel. The waste elements are immobilised in solid solution within the mineral phases: zirconolite (CaZrTi2O7), hollandite (Ba1.2(AITi)8O16) and perovskite (CaTiO3). The basic Synroc process involves mixing 10-20 % of a high level waste (HLW) solution (real or simulated) with the Synroc precursor, drying, calcining in a reducing atmosphere for redox control, and hot-pressing to high density. The precursor is a mixture of the oxides of Ti, Zr, Al, Ba and Ca in the proportions required to form the mineral phases [1]. In the early stages of the Synroc project precursor powders were prepared by ball-milling ZrO2, TiO2, A120,, CaCO3, and BaCO, in water. This resulted in powders with surface areas of approximately 5 m2/g which required relatively high hot pressing temperatures (21250 °C) to achieve near-theoretical density [2]. The desire for a more reactive precursor led to the adoption of the Sandia process [3] which involved the hydrolysis of titanium tetra-isopropoxide and zirconium tetra-n-butoxide in a methanolic solution of NaOH with an acetone/water mixture. The resulting (Na,Ti,Zr) hydrolysate was recovered by filtration and then reacted with an aqueous solution of Al, Ba and Ca nitrates, during which the Na was ionexchanged for aluminium, barium and calcium. After washing out the Na, a Synroc precursor with a surface area of 400 ml/g and excellent hot pressing properties was obtained. Although it was an improvement over the oxide route, the process was both complicated and expensive, resulting in its abandonment in favour of the ‘hydroxide route’. In the hydroxide route a mixture of titanium isopropoxide, zirconium-n-butoxide and aluminium-secbutoxide dissolved in anhydrous ethanol is hydrolysed with water containing the required amounts of Ba(OH)2 and Ca(OI-I); in solution/suspension [4]. This simple process has been scaled up to the production of Synroc precursor in batches of up to 100 kg. The powders generally derived from the hydroxide route have a particle size of approximately 10 μm, each particle being an agglomerate of smaller spherical particles 0.5 μm in diameter (the so-called "raspberry structure"). This paper describes experiments to break down the agglomerate structure in hydroxide route Synroc, by ball milling, in order to lower the temperature required for hot-pressing to near-theoretical density.en_AU
dc.identifier.citationAngel, P. J., & Buykx, W. J. (1990). The effect of milling on Synroc powder characteristics. Paper presented to the International Ceramic Conference (AUSTCERAM 90: ceramics technology - sharing the knowledge), Perth, Western Australia, 26-31 August 1990. Key Engineering Materials, 48-50, 674-678.en_AU
dc.identifier.conferenceenddate1990-08-31en_AU
dc.identifier.conferencenameInternational Ceramic Conference (AUSTCERAM 90: ceramics technology - sharing the knowledge)en_AU
dc.identifier.conferenceplacePerth, Western Australiaen_AU
dc.identifier.conferencestartdate1990-08-26en_AU
dc.identifier.isbn0878496084en_AU
dc.identifier.journaltitleKey Engineering Materialsen_AU
dc.identifier.pagination674-668en_AU
dc.identifier.placeofpublicationAedermannsdorf, Switzerlanden_AU
dc.identifier.urihttps://apo.ansto.gov.au/handle/10238/16386en_AU
dc.identifier.volume48-50en_AU
dc.language.isoenen_AU
dc.publisherTrans Tech Publicationsen_AU
dc.subjectMillingen_AU
dc.subjectSynroc processen_AU
dc.subjectSynthetic rocksen_AU
dc.subjectTitanatesen_AU
dc.subjectCeramicsen_AU
dc.subjectHigh-level radioactive wastesen_AU
dc.subjectRadioactive waste disposalen_AU
dc.subjectRadioactive waste storageen_AU
dc.subjectRedox processen_AU
dc.subjectHot pressingen_AU
dc.subjectTemperature rangeen_AU
dc.subjectAluminiumen_AU
dc.subjectBariumen_AU
dc.subjectCalciumen_AU
dc.subjectHydroxidesen_AU
dc.titleThe effect of milling on synroc powder characteristicsen_AU
dc.typeConference Paperen_AU
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