Radiation Damage in Nanoporous Nuclear Materials

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

Abstract

Materials in nuclear reactors are bombarded by neutrons. This can result in atoms being knocked off their lattice sites creating crystalline defects and in transmutation events which can create helium atoms. These processes can cause the physical properties of the material to deteriorate. In order to run a nuclear reactor safely it is vital to have materials which can perform under these extreme conditions. Furthermore, it is important to understand the physics behind the response of materials to radiation in order to predict how they will behave in-service and to develop new technologies.

One way to control the defects and helium which are created by neutron irradiation is to engineer a material with features which are designed to safely store them. The perfect such feature is a surface because it can never become saturated. Nanoporous materials have a structure like a nanoscale sponge and so have very high surface-area-to-volume ratios. Recently, nanoporous materials have been shown to have very good radiation tolerance and so have been proposed as candidates for use in nuclear applications. However, research so far has been limited to materials which are not suitable for use in nuclear reactors.

This research project will investigate nanoporous iron, nickel, zirconium, molybdenum, tungsten, silicon carbide and zirconium carbide. These materials all have properties which means they can be used in nuclear reactors. In order to explore the effects of irradiation, the Microscope and Ion Accelerator for Materials Investigations (MIAMI) facility at the University of Huddersfield will be used. The MIAMI facility incorporates a transmission electron microscope which allows materials to be observed on the nanoscale and an ion accelerator so the sample can be irradiated at the same time. The experiments will be combined with computer simulations to help explain the results in terms of the fundamental underlying atomistics.

The knowledge and understanding acquired from the experiments and the computer modelling will then allow nanoporous materials to be designed which are ideally suited for use in nuclear applications.

Planned Impact

Securing energy supplies is a key requirement for a prosperous economy. 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 as legislated in the Climate Change Act (2008). Looking beyond current and near-future nuclear reactor technologies, Generation IV fission reactors and magnetic-confinement fusion reactors will run at higher temperatures, with higher neutron fluxes and will develop lifetime damage levels up to ten times greater than those expected for current reactors. This poses significant challenges for the development of structural materials which can perform in these extreme environments. Performing the research and development on these materials whilst increasing the expertise base in the UK will allow that competitive advantage to be gained here.

Quality of life depends on many factors including a clean environment and access to energy. The aforementioned commitment of the UK Government to reductions in greenhouse gas emissions will require a shift away from our reliance on fossil fuels to power our lives. 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. Furthermore, policy makers such as Government and regulatory bodies such as the Office for Nuclear Regulations (ONR) must have good scientific evidence on which they can make sound decisions which are right for society. By improving our understanding of how materials respond to irradiation and developing what has the potential to be an important new nuclear-material technology, the proposed research project will support a safe move to a low-carbon future and provide a reliable basis on which decisions about our energy future can be based. Whilst nuclear power offers environmental benefits in terms of air pollution, it also presents challenges in terms of radioactive waste. The fuel cycles and fast-reactor designs of Generation IV offer the possibility of massively reducing the amount of radioactive waste requiring long-term storage whilst fusion has the potential to create no long-lived waste. By helping to overcome the materials challenges to the realisation of these technologies, the proposed research project will help protect society for millennia to come.

Maintaining human resources in terms of skills, knowledge and experience in nuclear areas is vital for academic research, nuclear energy generation, nuclear manufacturing and nuclear R&D in the UK. Due to low levels of spending on nuclear R&D in the UK over the last two decades, there have been relatively-few new entrants into the field resulting in a workforce with a demographic shifted towards retirement. The proposed research project will engage two postdoctoral researchers who will develop extensive expertise in the field of radiation damage in nuclear materials. At the end of the proposed research project they will be a vital asset to both academia and industry. Also, one the postdoctoral researchers will be trained in the operation of the MIAMI instrument which will increase the pool of operators of this significant facility built using EPSRC funding (EP/E017266/1). Transmission electron microscopy with in situ ion irradiation is a powerful technique for the exploration of the response of materials to radiation damage - however, it is a very specialised field and requires experienced scientists to design, execute and interpret the experiments. Increasing the pool of expertise in this area will enable the further application of this technique to help solve materials challenges in fields from nuclear to nanoscale manufacturing to semiconductor processing.
 
Description The accumulation of gases and crystalline defects in materials are important phenomena for nuclear materials. Nanoporous nuclear materials provide very large surface area at which such gases and defects can escape and annihilate. This project set out to explore these differences and their potential applications in developing novel advanced nuclear materials for next-generation energy systems.

In the course of this project, we have developed experimental techniques in which two forms of the same material (i.e. the nanostructured and the bulk) are investigated concurrently under the same conditions allowing direct comparison. This has allowed us to arrive at the key findings described below.

For example, experiments comparing nanoparticle and "bulk" tungsten samples have revealed significant differences between these two geometries in these regards with the former developing fewer (but larger) bubbles of gases and significantly lower levels of crystalline damage.

Furthermore, work on silicon carbide nanowhiskers has demonstrated lower rates of damage accumulation (which ultimately leads to the loss of crystal structure - amorphisation) again compared to the bulk counterpart.

Using observation of bubble evolution as a measure of swelling due to this phenomenon, measurably lower dimension changes are likely to occur in a nanoporous material of either tungsten or silicon carbide.

Irradiation which is able to displace atoms can cause a phenomenon known as sputtering in which atoms are ballistically removed individually or in clusters from a surface. In nanostructures with a high surface-area-to-volume ratio, an enhanced version of this process can result in enhanced ejection of large clusters of atoms. In this work, we have explored the significant effect which the crystallographic orientation of gold nanorods relative to incoming ion irradiation can have on the amount of resulting sputter. Channelling effects, which steer ions down open pathways in the crystalline structure thus avoiding collision, have been found to be likely responsible for the variations in the sputtering response of the different-orientated nanorods.
Exploitation Route This part of the project will be taken forward to explore the interaction of displacing irradiation with nanoparticles now that the effects of crystallographic orientation are better understood and can therefore be controlled for in the design of subsequent experiments. Understanding how the response to irradiation differs in nanostructured materials compared to their bulk counterparts can be put to use by others working on, for example, nanostructured materials and nanoparticles in nuclear environments, the ion beam processing of nanostructured semiconductor technologies, nanoparticles as sensitisers in particle-beam radiation therapies and nanomaterials in extraterrestrial environments.
Sectors Electronics,Energy,Healthcare,Manufacturing, including Industrial Biotechology

 
Title SICMod 
Description SICMod models a sphere at a diameter specified by the user. It then ensures that the TRIM collision calculations that take place outside of the calculated sphere are not taken into consideration when calculating the total damage. As part of this if an ion exits the volume of the sphere and then re-enters all subsequent collisions are discarded. SICMod modifies TRIMs config files so that the TRIM program runs with no user input and runs multiple times generating a new random seed number on each run. It does this in order to create multiple incident ions that are then calculated at different points on the calculated sphere. The reason for this is that an ion is highly unlikely to enter a particle at the same point multiple times and dependent upon where the particle enters the x value will differ resulting in a different number of collisions. The program then takes the output file generated by TRIM and creates graphical outputs showing the collision densities, implantation densities and the minimum distance to the surface. 
Type Of Material Technology assay or reagent 
Year Produced 2019 
Provided To Others? Yes  
Impact Helped to provide calculations for modelling nano-spheres. 
 
Description 13th European Conference on Accelerators in Applied Research and Technology (ECAART13) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact ECAART is the main conference for professionals working with accelerator-based research. The conference is held every 3 years and discusses the most recent research as well as future prospects for research with accelerators in fields such as material science, art, archaeology, life science, and environment. Areas of interest represented included: Simulation and fundamentals,Accelerator technology and development, Ion beam analysis, Ion beam modification of materials, Accelerator Mass Spectrometry, Synchrotron radiation, Applications to life science, Applications to art and archaeology, Radiation effects on electronics, Quantum technology applications.
Year(s) Of Engagement Activity 2019
URL https://www.ionbeamcenters.eu/ecaart13/
 
Description 21st 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 Gave a talk on enhanced sputtering effects in nanorods to world-leading researchers in the field on ion irradiation of materials.

IBMM (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 conference series started in Budapest, Hungary, in 1978. It is organized every other year. IBMM 2018, the 21st conference, will be held in San Antonio, Texas, USA. The scope of the conference ranges from fundamental radiation materials science to industry applications.
Year(s) Of Engagement Activity 2018
URL http://www.ibmm2018.com/
 
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 Invited talk at Electron Microscopy Society of India International Conference (EMSI 2018) - Bhudaneswar, India 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Invited talk titled "Sputtering of gold nanorods under ion irradiation observed using in-situ transmission electron microscopy"
Year(s) Of Engagement Activity 2019
 
Description Invited talk at Microscopy and Microanalysis 2019 - Portland, Oregon, USA 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Invited talk titled "Direct Comparison of Tungsten Nanoparticles and Foils under Helium Irradiation at High Temperatures Studied via In Situ Transmission Electron Microscopy"
Year(s) Of Engagement Activity 2019
 
Description The Conference on Application of Accelerators in Research and Industry (CAARI - 2018), 
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 Conference on Application of Accelerators in Research and Industry (CAARI - 2018), series brought together scientists, engineers, professors, physicians and students from all over the world who use particle accelerators in their research and industrial application. It was held in Grapevine, Texas USA from 12th to 17th August 2018. Each year the Topic Areas are reviewed and updated to reflect current research interests.I gave two talks one on enhanced radiation tolerance of tungsten nanoparticles and the second one on the Changes in the microstructure of SiC by He ion irradiation.
Year(s) Of Engagement Activity 2018
URL https://www.caari.com/home