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Title: Microstructures and corrosion of intermediate level wasteforms fabricated using novel thermal techniques
Author: Hutchison, Charles Allan
ISNI:       0000 0004 6496 9048
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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Simulant intermediate level waste materials received from Sellafield, 3 produced using Joule heating techniques, and 3 from plasma furnace methods, were characterised and subjected to leaching tests for up to 14 weeks to assess their potential as a waste matrix. Each wasteform was used to simulate a combination of waste surrogates such as plutonium contaminated material, site ion exchange plant waste, high metal content waste, Magnox sludge, asbestos, or pile fuel cladding. Five samples were characterised as glass composite materials, containing a crystalline and glassy portion, with the sixth being characterised as a glass. XRD and EDX analysis were used to identify the crystalline components, revealing a wide array of phases over the six samples such as pigeonite, anorthite, diopside, Cerium-Lanthanum silicate, proto and clino hypersthene, augite, and two glasses from liquid-liquid phase separation. ICP-OES analysis and pH were used to analyse the leachant, and SEM-EDX surface scans and depth profiles for analysis of the wasteform, post corrosion. Results revealed several of the wasteforms to be more than adequate for safe disposal, showing protective corrosion layers or durable crystalline components. However, not all wasteforms were suitable; in particular glass encapsulated metals should not be used as a waste matrix due to the susceptibility of the metal/metal oxide portion to chemical attack.
Supervisor: Lee, Bill ; Vandeperre, Luc Sponsor: Sellafield Ltd
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral