Radiation Damage in Nanoporous Nuclear Materials

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.

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.