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Immobilisation of caesium in magnesium phosphate-based blends

Yue, Y; Zhou, Q; Bai, Y; Li, L; Song, J; You, C; Qian, J; ... Deng, M; + view all (2016) Immobilisation of caesium in magnesium phosphate-based blends. In: Proceedings of the 36th Cement and Concrete Science Conference. The Institute of Materials, Minerals and Mining: London, UK. Green open access

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Abstract

Disposal of Caesium (Cs) by incorporating it into host matrices has been proved as a promising concept. Even though Portland cement (PC) based systems can be used to encapsulate low (LLW) or intermediate level waste (ILW), they are not efficient for immobilising Cs due to the very high water-solubility of Cs. Magnesium phosphate cement (MPC), a chemically bonded ceramic consists of struvite families produced by the acid based reactions between dead-burnt magnesium oxide (MgO) and phosphates (e.g., KH2PO4), can be a potential candidate for hosting Cs, since it has been reported that Cs can be incorporated in the Kstruvite structures by substituting potassium (K) to form (K,Cs)-struvite. However, the acid-based reaction to form MPC under ambient temperature between magnesium oxide (MgO) and phosphates (e.g., KH2PO4) is violent and exothermic, which raises concerns about industrial application of MPC in real world. In this work, ground-granulated blast-furnace slag (GGBS) and pulverised fuel ash were used to replace MPC in order to reduce the heat released. The feasibility of MPC, as well as MPC-based blends, i.e. GGBS-MPC or PFAMPC matrices, for immobilising Cs was assessed by their leaching behaviour at the ages of 3d, 7d and 28d. In addition, two typical PC based systems currently used in nuclear waste immobilisation, i.e., pure PC and PC-GGBS (1:9) mixes, were also produced and tested as controls. The results indicated that all the MPC mixes, including pure MPC, GGBS-MPC and PFA-MPC, demonstrated superb capability for immobilising Cs, with the immobilisation rates achieved more than 99.5% at all curing age investigated. Compared to the traditional PC and PC/GGBS mixes, the MPC mixes nearly doubled the Cs immobilisation rate, which is rather encouraging.

Type: Proceedings paper
Title: Immobilisation of caesium in magnesium phosphate-based blends
Event: 36th Cement and Concrete Science Conference
Location: Cardiff, UK
Dates: 05 September 2016 - 06 September 2016
Open access status: An open access version is available from UCL Discovery
Publisher version: http://www.iom3.org/cementitious-materials-group/
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Civil, Environ and Geomatic Eng
URI: https://discovery.ucl.ac.uk/id/eprint/1523325
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