Thermal Oxidation of Nuclear Graphite: A Large Scale Waste Treatment Option

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Abstract

This study has investigated the laboratory scale thermal oxidation of nuclear graphite, as a proof-of-concept for the treatment and decommissioning of reactor cores on a larger industrial scale. If showed to be effective, this technology could have promising international significance with a considerable impact on the nuclear waste management problem currently facing many countries worldwide. The use of thermal treatment of such graphite waste is seen as advantageous since it will decouple the need for an operational Geological Disposal Facility (GDF). Particulate samples of Magnox Reactor Pile Grade-A (PGA) graphite, were oxidised in both air and 60% O2, over the temperature range 400 -1200 ⁰C. Oxidation rates were found to increase with temperature, with a particular rise between 700 - 800 ⁰C, suggesting a change in oxidation mechanism. A second increase in oxidation rate was observed between 1000 - 1200 ⁰C and was found to correspond to a large increase in the CO/CO2 ratio, as confirmed through gas analysis. Increasing the oxidant flow rate gave a linear increase in oxidation rate, up to a certain point, and maximum rates of 23.3 and 69.6 mg / min for air and 60% O2 respectively were achieved at a flow of 250 ml / min and temperature of 1000 ⁰C. These promising results show that large-scale thermal treatment could be a potential option for the decommissioning of graphite cores, although the design of the plant would need careful consideration in order to achieve optimum efficiency and throughput.

Bibliographical metadata

Original languageEnglish
JournalPLoS ONE
DOIs
Publication statusPublished - 9 Aug 2017

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