Exploration of Hydrogen Gas Evolution from Radioactive Sludges
type: CreativeWork
description: The proposed final resting place for radioactive waste in the UK is a geological disposal facility that will be built at a location in the UK, which has yet to be chosen, at some unspecified time in the future. To safely commit a waste material into this facility requires knowledge about the long-term behaviour of the material in the disposal conditions. It is critical to consider what effect the ionising radiation introduced by contaminants will have. In the case of Magnox sludge, a complex material that exists in large quantities, it is known that hydrogen gas will be produced by radiolysis. It is clear that fundamental understanding of this process is required to build confidence in the proposed disposal plans. In this investigation, we start with a simple model of bulk brucite, the main component of the Magnox sludge. When a high-energy ionising particle interacts with matter, its initial passage leaves a cylindrical track where there will be a high density of ions and radical species created. This process will spawn many secondary electrons with a lower energy than the initial particle and these will create small secondary tracks, known as spurs, near the main track. Additional electrons will be created at successively lower energies, and this cascade will continue until the electrons can no longer induce ionisations. The end result is that the largest population of electrons contains those with low energies, around the ionisation potential of the material being irradiated. Thus, in our calculations, using density functional theory, the effects of two types of electronic structure defect were considered. The first is the addition of an excess electron into the system, representing one of these many low energy electrons. The second is the addition of an excess hole, which simulates an ionisation. Molecular dynamics simulations were used to give insight into the effects of the defects on the material at room temperature. Complexity was added to the model by the c…
abstract: The proposed final resting place for radioactive waste in the UK is a geological disposal facility that will be built at a location in the UK, which has yet to be chosen, at some unspecified time in the future. To safely commit a waste material into this facility requires knowledge about the long-term behaviour of the material in the disposal conditions. It is critical to consider what effect the ionising radiation introduced by contaminants will have. In the case of Magnox sludge, a complex material that exists in large quantities, it is known that hydrogen gas will be produced by radiolysis. It is clear that fundamental understanding of this process is required to build confidence in the proposed disposal plans. In this investigation, we start with a simple model of bulk brucite, the main component of the Magnox sludge. When a high-energy ionising particle interacts with matter, its initial passage leaves a cylindrical track where there will be a high density of ions and radical species created. This process will spawn many secondary electrons with a lower energy than the initial particle and these will create small secondary tracks, known as spurs, near the main track. Additional electrons will be created at successively lower energies, and this cascade will continue until the electrons can no longer induce ionisations. The end result is that the largest population of electrons contains those with low energies, around the ionisation potential of the material being irradiated. Thus, in our calculations, using density functional theory, the effects of two types of electronic structure defect were considered. The first is the addition of an excess electron into the system, representing one of these many low energy electrons. The second is the addition of an excess hole, which simulates an ionisation. Molecular dynamics simulations were used to give insight into the effects of the defects on the material at room temperature. Complexity was added to the model by the c…
author: Johnston, Conrad
language: eng
keywords: Radiation damage, Materials science, Condensed matter physics
date published: 2019-7
date modified: 2026-07-24T03:55:05Z
provider: Queen's University Belfast
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Queen's University Belfast