Modelling Uranium Corrosion by Hydrogen and Formation of Uranium Hydride
Lead Research Organisation:
University of Huddersfield
Department Name: Sch of Applied Sciences
Abstract
Long-term storage of nuclear fuel requires specialist storage conditions, for both human and environmental safety. Some waste-streams containing uranium metal, e.g. Magnox fuel held at Sellafield, undergo long-term storage before spent fuel reprocessing. During the storage of the metal, the formation of uranium hydride is a recognized hazard, with many potential issues, including the formation of the pyrophoric material and the mechanical stress introduced by the metal-hydride interfaces. The hydride can form whether or not the outer layer of the uranium metal has been oxidized to uranium oxide, as hydrogen percolates through the oxide layer.
Understanding the long-term ageing of the nuclear fuel is of vital importance and although the control over the corrosion of the metal by hydrogen and the structure and properties of the resulting hydride are fundamental to addressing the safety concerns of long-term storage, experimental investigation of such systems is hindered by the radioactivity of the samples, making modelling techniques invaluable tools for studying the metal-hydride interface.
We will investigate the structure and properties of the interface between uranium metal and hydride using a holistic modelling approach that combines calculations over differing length scales. In order to enhance the safety of the spent fuel during storage by defining the structural details of the metal-hydride interface and its relationship with the mechanical stress and reactivity at the interface. We aim to provide (1) an atomistic model of the early stages of formation of the hydride on the metal, (2) the percolation of hydrogen through the oxide layer formed due to metal corrosion by oxygen, and (3) the defect chemistry at the metal-hydride and metal-oxide interface.
Understanding the long-term ageing of the nuclear fuel is of vital importance and although the control over the corrosion of the metal by hydrogen and the structure and properties of the resulting hydride are fundamental to addressing the safety concerns of long-term storage, experimental investigation of such systems is hindered by the radioactivity of the samples, making modelling techniques invaluable tools for studying the metal-hydride interface.
We will investigate the structure and properties of the interface between uranium metal and hydride using a holistic modelling approach that combines calculations over differing length scales. In order to enhance the safety of the spent fuel during storage by defining the structural details of the metal-hydride interface and its relationship with the mechanical stress and reactivity at the interface. We aim to provide (1) an atomistic model of the early stages of formation of the hydride on the metal, (2) the percolation of hydrogen through the oxide layer formed due to metal corrosion by oxygen, and (3) the defect chemistry at the metal-hydride and metal-oxide interface.
Organisations
People |
ORCID iD |
| David Cooke (Primary Supervisor) | |
| Thomas Smith (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/R513234/1 | 01/10/2018 | 30/09/2023 | |||
| 2282308 | Studentship | EP/R513234/1 | 01/10/2019 | 30/09/2022 | Thomas Smith |
| Description | The formation of cubic plutonium hydrides (PuH2 and PuH3) during long-term storage of nuclear materials is of interest due to their pyrophoric nature and ability to catalyse the oxidation reaction which can induce mechanical stress on the storage vessel. There is disagreement in the experimental literature on the magnetism of PuH2, with ferromagnetic and antiferromagnetic order both determined. Using a density function theory (DFT) methodology we investigate the magnetic order of PuH2 and PuH3 along with their structure and electronic properties. Furthermore, the presence of defects within the fluorite structure impact the materials thermal conductivity. We study the intrinsic Frenkel and Schottky defects in the fluorite system and their impact on the structural dynamics and thermal properties. Water is also present in the sealed storage vessel in storage conditions. We study the interactions of water on different PuH2 surfaces to produce morphology phase diagrams. Our computational findings offer insight into a difficult and challenging area for experimental study due to the materials toxicity and radioactivity. This work is therefore of interest and will inform future experimental research and industrial processes. |
| Exploitation Route | The methodology used in this work can be used by other researchers. Complex parameters were used in these calculations such as Hubbard U, spin-orbit coupling and non-collinear magnetism. Findings on the properties of plutonium hydrides and the interactions of water on plutonium dihydride surfaces will guide future experimental studies. The methods used to obtain morphology phase diagrams and phonon dispersions of defective models can be applied to other materials. |
| Sectors | Energy,Environment |
| Description | Conferences |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Postgraduate students |
| Results and Impact | Attendance at international and national conferences were oral and poster presentations were performed to an audience consisting of industry professionals, academics and postgraduate students. These conferences provided the opportunity to network and discuss research with peers. Below is a list of conferences attended in chronologic order: (1) Smith Thomas, Poster Presentation, "Simulations of Ce Containing Materials using Density Functional Theory Calculations", 39th Christmas Meeting of the RSC Solid State Chemistry Group, Liverpool, 16-17th December 2019 (2) Smith Thomas, Poster Presentation, "Modelling Ce-Based Materials using ab initio Calculations", New Horizons in Materials Modelling 2020, York, 10th January 2020, (3) Smith Thomas, Oral Presentation, "Magnetic properties of cubic plutonium hydrides: A density functional theory study", ACS Spring 2021, San Antonio Texas USA (Virtual), April 5-16th 2021 (4) Smith Thomas, Poster Presentation, "First-principles study of plutonium hydrides", CCP5 Summer School 2021, Durham, 11-22nd July 2021, (5) Smith Thomas, Oral Presentation, "An ab initio investigation of the impact of intrinsic defects on the thermal properties of CeO2", MCC 4th Conference, Daresbury Laboratory 6-8th July 2022 (6) Smith Thomas, Oral Presentation, "A first-principles study of the impact of intrinsic defects on the thermal properties of ceria", CPP5 AGM 2022, University of Huddersfield, September 5-7th 2022 (7) Smith Thomas, Poster Presentation, "The magnetic properties of cubic PuH2 and PuH3: a first-principles investigation", CPP5 AGM 2022, University of Huddersfield, September 5-7th 2022 |
| Year(s) Of Engagement Activity | 2019,2020,2021,2022 |