A Study of the Combined Effects of Displacement Damage and Helium Accumulation in Model Nuclear Materials

Lead Research Organisation: University of Huddersfield
Department Name: Sch of Computing and Engineering

Abstract

Nuclear power is arguably the only option for large-scale baseload electricity generation that is compatible with the UK Government's commitment to an 80% reduction in greenhouse gas emissions by 2050. The safe operation of current and future generations of nuclear reactors requires the development and refinement of materials to be used in the construction of reactors and in materials (glass and glass-ceramic wasteforms) to be used for the long-term safe disposal of radioactive wastes. The inevitable irradiation of such materials with energetic particles such as neutrons and alpha particles can have extremely deleterious effects on their structural strength and even their physical dimensions. Ballistic effects cause atoms to be knocked off their normal positions creating vacant sites (vacancies) and displaced atoms (interstitials). Nuclear reactions induced by neutron irradiation can create alpha particles (which are just helium nuclei) causing a build-up of helium gas in these materials. Helium has very little solubility in most materials and will generally combine with vacancies (or accumulate in other regions of lower than average electron-density) to form bubbles. These can have very significant unwanted effects on the properties of the materials by, for instance, building up at the boundaries between grains in polycrystalline materials and making them much more brittle and likely to fracture. Bubbles will also result in highly undesirable changes to the physical dimensions of components. The high temperatures at which reactors operate, and to which wasteforms will be subjected for the first 500 years-or-so of storage, can greatly exacerbate these problems, particularly in the reactor materials by enabling the vacancies, interstitials and helium atoms to combine in different ways and form extended defects such as voids, dislocations and stacking faults.

This project aims to explore systematically the effects that varying the amount of displacement damage, the helium concentration and the temperature has on the damage that develops in a range of structural materials and wasteforms. Different combinations of these parameters pertain to different types of material (both structural and wasteforms), different reactors and even different locations within a reactor. In addition, aspects of the waste glasses, such as alkali content and the presence of glass ceramic interfaces will also be varied in order to determine their role in the development of bubbles and other defects. The project exploits the unique attributes of the MIAMI facility (constructed with EPSRC funding) that permit the ion irradiation of thin foils of materials in-situ within a transmission electron microscope. By varying the ion energy, the ratio of injected helium to the amount of displacement damage can be varied over the range of values relevant to reactor and wasteform materials without the necessity of using two separate ion beams. The ability to irradiate at a range of temperatures from -150 to +1000 degrees Celsius means the that the entire relevant parameter space (helium content, damage and temperature) can be explored.

In this way, transmission electron microscopy (and also electron energy-loss spectroscopy for the nuclear glasses) will be used to build up a comprehensive dataset of the form and structure of defects (defect morphologies) resulting from the various combinations of these parameters. The main aim is then to develop a phenomenological picture of the processes occurring. For the structural materials, the dataset will be calibrated and validated by comparisons with neutron-irradiated materials which will give the dataset greater power to predict defect morphologies likely to result under reactor conditions.

Finally, through collaboration with computer modellers, we will seek to obtain a fundamental understanding of the underlying physical processes which drive the behaviour of these materials under irradiation.

Planned Impact

Securing energy supplies is a key requirement for a prosperous economy. Electricity from nuclear power is an essential component of the energy mix for baseload generation in the UK. This is set to expand with the UK Government in 2008 approving eight sites for the development of new nuclear power stations and the announcement in 2013 of the development of the first of these with two new European Pressurised Reactors (EPRs) at Hinkley Point in Somerset.

This research project will generate scientific results and understanding which will enable the nuclear industry to safely operate the UK's fleet of nuclear power stations. Understanding how materials perform under the extreme conditions found in a nuclear reactor core over, for example, the 60 year operational lifetime of an EPR, will allow the industry and Office for Nuclear Regulation (ONR) to make informed decisions based on scientific evidence. This will support the safe generation of electricity in the UK from a secure low-carbon source and therefore will ensure the reliable supply of energy to power the rest of the economy.

As well as the structural materials used in the reactors, it is also vital that the materials which can be used to safely contain nuclear waste be developed and understood. Therefore a significant component of the project will focus on nuclear glasses and glass-ceramic composites to support regulators and industry in planning disposal which will be safe for centuries to millennia.

The UK has been a leader in nuclear energy for 60 years. In order for this world-class industrial sector to flourish it is vital to maintain the expertise and to continue to develop cutting edge nuclear technologies in the UK. Looking beyond the new nuclear power stations to be built in the UK over the next decade, Generation IV reactor concepts offer even greater gains in safety and cost. This research project will support the contribution of the UK to these emergent technologies laying the foundations for the domestic nuclear industry to develop these advanced reactor designs and thus concentrate economic activity in the UK. Similarly, the UK has been a pioneer in the development of fusion power through projects such as the Joint European Torus (JET) at the Culham Centre for Fusion Energy. As the global effort to realise this technology shifts focus to the International Thermonuclear Experimental Reactor (ITER) in France, maintaining the contribution of the UK to the fundamental science will keep the UK as a centre of excellence in this field and will enable UK businesses to exploit fusion when it becomes a practical source of energy. Finally, overcoming the materials challenges to ensure the safe storage of nuclear waste will benefit the economy not only in the short term as these solutions are implemented but also in the much longer term as potentially disastrous financial and environmental costs are avoided.

As described above, wealth will be generated in the UK through support for both UK nuclear energy electricity generation and the development of new nuclear technologies. With world demand for energy continually increasing, producing energy in the UK cheaply and sustainably will create wealth both in the generation sector and in all other sectors of the economy which depend on a reliable affordable energy supply. Furthermore, the creation of intellectual property and the manufacture of components for nuclear power stations can flourish if the research, development and exploitation of these technologies are supported in the UK.

Our quality of life is dependent on many factors including a clean environment and access to energy. The UK is committed to an 80% reduction in greenhouse gases by 2050 and this will require a shift away from our reliance on fossil fuels. Nuclear energy will be a vital component of this change but it is important that we continue to develop our understanding and technologies in order to facilitate a safe expansion in this area.

Publications

10 25 50
 
Description We have been investigating the build-up of helium in tungsten simulation nuclear reactor conditions using ion beams which irradiate think foil specimens in a transmission electron microscope. We are building up a data-set of extended defects occurring as we vary the parameters displacement damage, helium content and temperature.

We have discovered that superlattices of helium bubbles develop under these conditions and that the lattice constant of this superlattice decreases with increasing helium concentration.
Exploitation Route When the full datasets are available on defect structures in various materials as a function of He content, displacement damage and temperature, these will be used as reference data by other researchers.
Sectors Education,Energy

 
Description Ion Beam Irradiation for High Level Nuclear Waste Form Development (INWARD)
Amount € 4,500 (EUR)
Funding ID F11022 , CRP 2183 (https://www.iaea.org/projects/crp/f11022) 
Organisation International Atomic Energy Agency 
Sector Public
Country Austria
Start 10/2018 
End 10/2022
 
Description W and W-Ta alloy proton irradiations 
Organisation University of Manchester
Department School of Materials Manchester
Country United Kingdom 
Sector Academic/University 
PI Contribution Provided access to the MIAMI facilities and performed irradiation and annealing experiments for the collaborators at the University of Manchester with detailed electron microscopy analysis
Collaborator Contribution Performed analysis and comparison with their other work at other irradiation facilities thus, exchanging of knowledge between separate work performed on this grant and their work, leading to validation of corroboration of results and output of research
Impact Two articles have been published as a result of this collaboration in highly relevant journals to the work.
Start Year 2016
 
Description 23rd International Conference on Ion Beam Modification of Materials 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact International Conference on Ion Beam Modification of Materials is the world's leading platform for ion beam experts and educators to exchange and report their most recent significant findings in the ion beam community. The scope of the conference ranges from fundamental radiation materials science to industry applications.
Year(s) Of Engagement Activity 2018
URL https://10times.com/ibmm-texas
 
Description 5th International 5th Workshop On TEM With In Situ Irradiation 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The event was the three-day 5th Workshop On TEM With In Situ Irradiation, known as WOTWISI-5. It was attended by scientists from nine countries, including the USA, Japan, China, Australia and Finland. They are specialists in a technique that allows the minute observation of radiation damage in a wide range of materials whilst the irradiation is being induced with ion and/or electron beams. The nuclear industry is a key sector for this research.

Previous gatherings have taken place in Japan, France and the USA and the inaugural WOTWISI was in 2010, in Salford, where it was launched by Professor Stephen Donnelly and Dr Jonathan Hinks as part of the EPSRC-funded project "Worldwide network of in-situ TEM/ion accelerator facilities ( EP/F012853/1).
Year(s) Of Engagement Activity 2018
URL https://www.hud.ac.uk/news/2018/april/unihostswotwisi-5/
 
Description 5th Workshop On TEM With In Situ Irradiation (WOTWISI) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The event was the three-day 5th Workshop On TEM With In Situ Irradiation, known as WOTWISI-5. It was attended by scientists from nine countries, including the USA, Japan, China, Australia and Finland. They are specialists in a technique that allows the minute observation of radiation damage in a wide range of materials whilst the irradiation is being induced with ion and/or electron beams. The nuclear industry is a key sector for this research. Previous gatherings have taken place in Japan, France and the USA and the inaugural WOTWISI was in 2010, in Salford, where it was launched by Professor Stephen Donnelly and Dr Jonathan Hinks as part of the EPSRC-funded project "Worldwide network of in-situ TEM/ion accelerator facilities (EP/F012853/1).
Year(s) Of Engagement Activity 2018
URL https://www.hud.ac.uk/news/2018/april/unihostswotwisi-5/
 
Description Conference: Ion Beam Modification of Materials 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited talk at International conference.
Year(s) Of Engagement Activity 2016
URL https://www.gns.cri.nz/Home/News-and-Events/Events/IBMM-2016
 
Description Conference: Ion Beam Modification of Materials 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited talk on: "TEM with in situ Ion Irradiation of Nuclear Materials under "In-Service" Conditions"
Invited talk at Microscopy and Microanalysis, Columbus, OH, USA on Thursday 28th July 2016 by Dr J A Hinks, CI on project. the talk led to questions, discussion and potential future collaborations.
Year(s) Of Engagement Activity 2016
URL http://www.microscopy.org/mandm/2016/
 
Description European Microscopy Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Dr Graeme Greaves presented a paper on the MIAMI facilities at the European Microscopy Congress in Lyon in 2016 (EMC2016) leading to questions and discussion and possible new collaborators and/or users of our facilities.

EMC2016 gathered around 2500 visitors from 51 countries all over the World. Along with an international and multidisciplinary high quality conference, EMC2016 hosted Europe's largest exhibition dedicated to microscopy. The congress also offered a large number of training and scientific activities.
Year(s) Of Engagement Activity 2015,2016
URL http://www.emc2016.fr/en/
 
Description International Workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Joint ICTP-IAEA Workshop on Radiation Effects in Nuclear Waste Forms and their Consequences for Storage and Disposal (12 - 16 September 2016)

PURPOSE The Workshop aims to gain awareness on the most recent findings of research into radiation effects in nuclear waste forms and their role for waste storage and disposal. It aims to contribute to the transfer of specific knowledge to Member States towards their capacity building efforts and competence in nuclear waste immobilisation and disposal. FOCUS The workshop will focus mainly on experts on radiation effects in materials to explore the potential of both experimental and theoretical/computational approaches aiming to understand the consequences of irradiation of materials under extreme conditions, particularly focusing on long-term irradiation conditions envisaged for nuclear waste forms containing long lived fission products and actinides.
Year(s) Of Engagement Activity 2016
URL http://indico.ictp.it/event/7633/
 
Description International Workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The 4th international workshop on Transmission Electron Microscopy with in-situ irradiation is organized in Orsay, France, from the 16th March to the 18th of March, 2016.

The workshop focused on the combination of TEM with in situ ion and electron irradiation. Representatives of such facilities were present (UK, France, US). Areas for discussion included advances in electron microscopy and ion irradiation techniques as well as current and future research. Various scientific fields utilizing the technique were covered including: nuclear materials, radiation effects in semiconductors, nanostructural modification, single and multi ion effects, J A Hinks, R W Harrison and S E Donnelly participated and all gave presentations.
Year(s) Of Engagement Activity 2016
URL http://wotwisi4.in2p3.fr/
 
Description MRS Spring Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presentation by Dr R W Harrison (PDRA on this project) at annual spring meeting of the Materials Research Society, MRS 2016, Phoenix, Arizona, USA, March 2016
Year(s) Of Engagement Activity 2016
URL http://www.mrs.org/spring2016
 
Description TMS Annual Meeting 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact R W Harrison, one of the PDRA on this project presented his work at the TMS annual conference 2017, San Diego, California, USA, Feb 2017. His paper led questions and discussion afterwards and enquiries about access to MIAMI Facilities.
Year(s) Of Engagement Activity 2017
URL http://www.tms.org/meetings/annual-17/AM17home.aspx
 
Description Visit to French nuclear laboratory 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact This was a visit by PI, CI and PDRA on project to the major French nuclear laboratory CEA Marcoule. The purpose was for discussion regarding common interests and possible further collaborations with staff at Marcoule. We gave presentations on our work and facilities. Note that this laboratory is one of the supporters on this grant.
Year(s) Of Engagement Activity 2017
URL http://www.cea.fr/Pages/le-cea/les-centres-cea/marcoule.aspx
 
Description Workshop on Microscopy of Irradiation Damage 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact A small workshop-style meeting on "Microscopy of Irradiation Damage" in Oxford, 21st - 23rd March 2018.The theme of the meeting was to discuss the different radiation induced defects that can be studied by various microscopy techniques, particularly by TEM, STEM and APT. It encouraged participation from active research students and postdocs. Included ample discussions centred around a small number of keynote lectures and two substantial poster sessions.

See https://mffp.materials.ox.ac.uk/content/microscopy-irradiation-damage-21-23-march-2018
Year(s) Of Engagement Activity 2018
URL https://mffp.materials.ox.ac.uk/content/microscopy-irradiation-damage-21-23-march-2018