White Rose University Consortium logo
University of Leeds logo University of Sheffield logo York University logo

The Development of Calcium Aluminate Phosphate Cement for Radioactive Waste Encapsulation

Swift, Paul David (2013) The Development of Calcium Aluminate Phosphate Cement for Radioactive Waste Encapsulation. PhD thesis, University of Sheffield.

[img]
Preview
Text
Paul Swift - Thesis - The Development of Calcium Aluminate Phosphate Cement for Radioactive Waste Encapsulation - Final.pdf
Available under License Creative Commons Attribution-Noncommercial-No Derivative Works 2.0 UK: England & Wales.

Download (19Mb) | Preview

Abstract

Reactive metals such as aluminium metal make up a significant proportion of the UK’s legacy radioactive waste. Current treatment methods – encapsulation in PC-based cementitious systems – do not perform optimally when applied to reactive metals. Corrosion of encapsulated aluminium, caused by the availability of free-water and highly alkaline pore solution, results in expansive corrosion products and the generation of significant quantities of hydrogen gas, which compromises the long-term performance of waste packages. Calcium Aluminate Phosphate cements (CAP), formed from acid-base reaction between Calcium Aluminate Cements (CAC) and an acidic phosphate-based solution, were identified as alternative encapsulants that provide different internal chemistry i.e. pore solution of lower pH which may be advantageous when applied to the encapsulation of reactive metals. Various types of phosphates, monophosphates and polyphosphates, were assessed to identify suitable pre-cursor materials for producing a cementitious matrix when mixed with CAC, and a CAP formulation envelope suitable for the industry-defined processing and operational property requirements, was identified. The corrosion behaviour of aluminium encapsulated in the CAP system was characterised by a dormant period, during which the corrosion and gas generation rates were very low, and a significant increase after the dormant period. The phase evolution of the CAP system altered not only the physico-mechanical properties of the system in longer-term but was also responsible for the latent corrosion behaviour of aluminium encapsulated in the CAP system.

Item Type: Thesis (PhD)
Keywords: Radioactive Waste, Encapsulation, Immobilisation, Calcium Aluminate Phosphate Cement, Calcium Phosphate Cement, Aluminium, Corrosion
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Materials Science and Engineering (Sheffield)
Identification Number/EthosID: uk.bl.ethos.605260
Depositing User: Mr Paul David Swift
Date Deposited: 30 Apr 2014 09:51
Last Modified: 03 Oct 2016 11:16
URI: http://etheses.whiterose.ac.uk/id/eprint/5782

You do not need to contact us to get a copy of this thesis. Please use the 'Download' link(s) above to get a copy.
You can contact us about this thesis. If you need to make a general enquiry, please see the Contact us page.

Actions (repository staff only: login required)