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The immobilisation of Caesium and Strontium from nuclear waste captured by IONSIV

Day, George (2018)
Ph.D. thesis, University of Birmingham.

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Abstract

A previous study revealed Cs\(_2\)TiNb\(_6\)O\(_1\)\(_8\) to be the major Cs-containing phase after hot isostatic pressing Cs-loaded IONSIV (a commercial exchanger) which demonstrated excellent wasteform properties. Both experimental and theoretical studies have been carried out in order to assess if Cs\(_2\)TiNb\(_6\)O\(_1\)\(_8\) is able to retain \(^1\)\(^3\)\(^7\)Ba\(^2\)\(^+\), the transmutation product of \(^1\)\(^3\)\(^7\)Cs\(^+\). A series of samples with different charge compensation mechanisms have been synthesised including Cs\(_2\)\(_-\)\(_x\)Ba\(_x\)Ti\(^(\)\(^4\)\(^+\)\(^)\)\(_1\)\(_+\)\(_x\)Nb\(^(\)\(^5\)\(^+\)\(^)\)\(_6\)\(_-\)\(_x\)O\(_1\)\(_8\), Cs\(_2\)\(_-\)\(_x\)Ba\(_x\)Ti\(^(\)\(^3\)\(^+\)\(^)\)\(_x\)Ti\(^(\)\(^4\)\(^+\)\(^)\)\(_1\)\(_-\)\(_x\)Nb\(_6\)O\(_1\)\(_8\) and Cs\(_2\)\(_-\)\(_x\)Ba\(_x\)TiNb\(^(\)\(^4\)\(^+\)\(^)\)\(_x\)Nb\(^(\)\(^5\)\(^+\)\(^)\)\(_6\)\(_-\)\(_x\)O\(_1\)\(_8\). Analysis suggested that Ba incorporation was not successful because of the identification of Ba impurities in the X-ray diffraction patterns. A series of atomistic simulations have also been performed to support the experimental work, using the General Utility Lattice Program code which suggested that Ba incorporation is not energetically favourable.

Sr-loaded IOSNIV has also been thermally converted via calcination (in air) and hot isostatic pressing. The removal and immobilisation of Sr is an important process on account of \(^9\)\(^0\)Sr being one of the more problematic radionuclides produced from the fission process. Both thermal conversion methods produced crystalline phase assembles which were analysed by X-ray diffraction, X-ray fluorescence and microscopy studies. The HIPed materials performed well in aqueous durability tests, suggesting these wasteforms will be suitable for final disposal in a geological disposal facility.

Type of Work:Ph.D. thesis.
Supervisor(s):Hriljac, Joseph A.
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Chemistry
Subjects:TA Engineering (General). Civil engineering (General)
TP Chemical technology
Institution:University of Birmingham
ID Code:8206
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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