The distribution and selective decontamination of carbon-14 from nuclear graphite

Robert N. Worth; Alex Theodosiou; William Bodel; José David Arregui-Mena; Anthony J. Wickham; Abbie N. Jones; Paul M. Mummery

doi:10.1016/j.jnucmat.2021.153167

The distribution and selective decontamination of carbon-14 from nuclear graphite

Robert N. Worth, Alex Theodosiou, William Bodel, José David Arregui-Mena, Anthony J. Wickham, Abbie N. Jones, Paul M. Mummery

Applied Microanalysis and Thermophysics

Research output: Contribution to journal › Article › peer-review

9 Scopus citations

Abstract

This work investigates ¹⁴C release behaviour from UK Magnox reactor sourced irradiated graphite under relatively low temperature oxidation conditions: a 1% oxygen in argon atmosphere at temperatures ranging from 600°C to 700°C, and durations from 4 to 120 hours. A method is used for construction of a detailed ¹⁴C release profile with mass loss. The ¹⁴C release profile is predictable between samples, and an empirical release profile is derived to predict releases to higher mass losses than in this work. An accelerated ¹⁴C release rate at small mass losses is observed, indicative of a ¹⁴C-enriched surface region with a depleting concentration gradient into the material, and the source terms and complexities associated with predicting where the ¹⁴C arose from are discussed. Selective decontamination of a fraction of the ¹⁴C is possible, with the limitation of a reducing efficiency with mass loss and time. This work demonstrates a method for determining the distribution of ¹⁴C between near-surface regions and the bulk material in differing sources of irradiated graphite, and provides data in support of making an informed assessment for the adoption of low temperature thermal treatment and isotopic reduction of irradiated graphite wastes.

Original language	English
Article number	153167
Journal	Journal of Nuclear Materials
Volume	556
DOIs	https://doi.org/10.1016/j.jnucmat.2021.153167
State	Published - Dec 1 2021

Funding

This work was supported by the Engineering and Physical Sciences Research Council (EPSRC), studentship award number 1241249 and the EU FP7 CARBOWASTE project (FP7-211333). The authors would also like to acknowledge Greg Black and Lorraine McDermott, for contributions and guidance early in this programme of research, and to thank the National Nuclear Laboratory for performing the carbonaceous deposit analysis. Lastly, much of the inspiration and motivation for this work has stemmed from CARBOWASTE and the IAEA CRP for Treatment of Irradiated Graphite to Meet Acceptance Criteria for Waste Disposal (CRP T21026).

Keywords

Carbon-14
Nuclear graphite
Nuclear waste
Selective decontamination
Thermal oxidation

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10.1016/j.jnucmat.2021.153167

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title = "The distribution and selective decontamination of carbon-14 from nuclear graphite",

abstract = "This work investigates 14C release behaviour from UK Magnox reactor sourced irradiated graphite under relatively low temperature oxidation conditions: a 1\% oxygen in argon atmosphere at temperatures ranging from 600°C to 700°C, and durations from 4 to 120 hours. A method is used for construction of a detailed 14C release profile with mass loss. The 14C release profile is predictable between samples, and an empirical release profile is derived to predict releases to higher mass losses than in this work. An accelerated 14C release rate at small mass losses is observed, indicative of a 14C-enriched surface region with a depleting concentration gradient into the material, and the source terms and complexities associated with predicting where the 14C arose from are discussed. Selective decontamination of a fraction of the 14C is possible, with the limitation of a reducing efficiency with mass loss and time. This work demonstrates a method for determining the distribution of 14C between near-surface regions and the bulk material in differing sources of irradiated graphite, and provides data in support of making an informed assessment for the adoption of low temperature thermal treatment and isotopic reduction of irradiated graphite wastes.",

keywords = "Carbon-14, Nuclear graphite, Nuclear waste, Selective decontamination, Thermal oxidation",

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doi = "10.1016/j.jnucmat.2021.153167",

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AU - Theodosiou, Alex

AU - Bodel, William

AU - Arregui-Mena, José David

AU - Wickham, Anthony J.

AU - Jones, Abbie N.

AU - Mummery, Paul M.

PY - 2021/12/1

Y1 - 2021/12/1

N2 - This work investigates 14C release behaviour from UK Magnox reactor sourced irradiated graphite under relatively low temperature oxidation conditions: a 1% oxygen in argon atmosphere at temperatures ranging from 600°C to 700°C, and durations from 4 to 120 hours. A method is used for construction of a detailed 14C release profile with mass loss. The 14C release profile is predictable between samples, and an empirical release profile is derived to predict releases to higher mass losses than in this work. An accelerated 14C release rate at small mass losses is observed, indicative of a 14C-enriched surface region with a depleting concentration gradient into the material, and the source terms and complexities associated with predicting where the 14C arose from are discussed. Selective decontamination of a fraction of the 14C is possible, with the limitation of a reducing efficiency with mass loss and time. This work demonstrates a method for determining the distribution of 14C between near-surface regions and the bulk material in differing sources of irradiated graphite, and provides data in support of making an informed assessment for the adoption of low temperature thermal treatment and isotopic reduction of irradiated graphite wastes.

AB - This work investigates 14C release behaviour from UK Magnox reactor sourced irradiated graphite under relatively low temperature oxidation conditions: a 1% oxygen in argon atmosphere at temperatures ranging from 600°C to 700°C, and durations from 4 to 120 hours. A method is used for construction of a detailed 14C release profile with mass loss. The 14C release profile is predictable between samples, and an empirical release profile is derived to predict releases to higher mass losses than in this work. An accelerated 14C release rate at small mass losses is observed, indicative of a 14C-enriched surface region with a depleting concentration gradient into the material, and the source terms and complexities associated with predicting where the 14C arose from are discussed. Selective decontamination of a fraction of the 14C is possible, with the limitation of a reducing efficiency with mass loss and time. This work demonstrates a method for determining the distribution of 14C between near-surface regions and the bulk material in differing sources of irradiated graphite, and provides data in support of making an informed assessment for the adoption of low temperature thermal treatment and isotopic reduction of irradiated graphite wastes.

KW - Carbon-14

KW - Nuclear graphite

KW - Nuclear waste

KW - Selective decontamination

KW - Thermal oxidation

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The distribution and selective decontamination of carbon-14 from nuclear graphite

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Keywords

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