Process Development for the Immobilisation of Plutonium Containing Wastes and Residues



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tarix05.03.2018
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Process Development for the Immobilisation of Plutonium Containing Wastes and Residues
Project Supervisors: Dr Ewan Maddrell (Nexia Solutions) and Dr Neil Hyatt
Project aims and background

This project seeks aims to develop a processing method for fabrication of ceramic wasteforms for the immobilisation of plutonium containing wastes and residues. We have designed and developed several formulations for plutonium immobilisation by targeted solid solution of plutonium on suitable sites in different structure types. Our research to date indicates that the preferred ceramic formulation will be based on zirconolite (CaZrTi2O7) or pyrochlore (Gd2Zr2O7) materials. The conceptual ceramic processing route, to be developed in this project, will involve particle size reduction of the PuO2 feed, blending with the relevant precursor, granulation by roll compaction and consolidation to a fully dense monolith by sintering or hot isostatic pressing (HIPping). This project will use CeO2 as a PuO2 surrogate. The prospective Research Engineer will form part of the Nexia Solutions team working on the immobilisation project at the Sellafield site, with project placements at The University of Sheffield.



The key technical objectives of the project are:

1) To develop an understanding of the effect of key processing variables associated with:

- Size reduction and blending of the wasteform precursors by attrition milling to ensure the PuO2 simulant has the appropriate particle size to react to produce the intended wasteform phases

- Granulation of the blended wasteform precursors by roll compaction to ensure reliable and reproducible filling of HIP cans or pellet dies and production of a fully dense wasteform monolith.

2) Based on this understanding, to develop an over-arching quality control philosophy for the wasteform, such that if it can be demonstrated that certain critical process parameters have been met, then the quality of the final wasteform will be assured (to avoid sampling).

The project will involve the development of engineering scale processing equipment (attrition mill, granulator and HIP) and the application of materials characterisation techniques at the Sellafield site and in Sheffield laboratories (including, particle size analysis, X-ray diffraction, scanning and transmission electron microscopy coupled with energy dispersive spectroscopy and thermal analysis).


Research Engineer profile: the RE will have a background in Materials Science and Engineering, Chemistry, or a suitably related subject. The RE will be a member, or will apply for membership, of the Institute of Materials, Minerals and Mining and will work toward Chartered Engineer status.
Interested applicants should contact Dr Neil Hyatt in the first instance [mail to: n.c.hyatt@sheffield.ac.uk].
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