Computational Design of Graphene-Based Materials for Challenging Nuclear Decommissioning Applications

The safe decommissioning of facilities used in the nuclear fuel cycle (nuclear fuel reprocessing, research and development and energy production) is a major socio-economic challenge facing the UK, with a predicted total cost of £120bn over the next 120 years. The decommissioning process will generate large volumes of water-based waste (effluent) which is radioactive and must be treated. As well as a number of specific challenges associated with the current materials and processes used to treat effluent, many new challenges are likely arise in the near future as decommissioning activity gathers pace. Overcoming these challenges is critical in the context of establishing public confidence in the management of radioactive waste as well as underpinning the UK's long-term energy strategy.

Graphene oxide, a derivative of graphene with a high oxygen content, has exceptional properties which have already been demonstrated in other fields (e.g. desalination), and may be able to overcome the limitations faced by the materials currently used in effluent treatment. Graphene oxide could be used to treat effluents in two separate ways. Firstly, graphene oxide flakes could be added to the effluent and used to directly bind radioactive species (adsorption). Alternatively, a semi-permeable membrane, fabricated from individual graphene oxide flakes, could be used to sieve out the radioactive species (filtration).

In this innovative and ambitious project, the science underpinning the use of graphene oxide in nuclear effluent treatment will be developed using a methodology led by computer simulation. Firstly, the development of new 'coarse-grained' models of graphene oxide will significantly extend the length and time scales accessible to simulation and open up the possibility of investigating the stability of graphene oxide membranes and dispersions. Using the new models, the efficacy of graphene oxide for the treatment of effluents containing some of the most problematic and dangerous radioactive species (e.g. uranium, plutonium, caesium and strontium) will be assessed, delivering the relevant physical and thermodynamic data required for the next stage of process development. The design and performance of graphene oxide will be optimised to improve decontamination factors for specific effluent treatment challenges. As a result, the project has the potential to revolutionise the techniques used in the treatment of radioactive effluent.

The most significant impact of this project will be in the nuclear decommissioning industry. Sellafield Ltd currently treat ~1 million cubic metres of effluent per year in the EARP and SIXEP effluent treatment plants. There is a legal requirement to use the best available techniques (BAT) to treat effluent and the adsorption or filtration of effluent using graphene oxide has the potential to achieve much higher decontamination factors than conventional techniques. In the near future, existing technologies may become redundant as the effluent composition changes during post-operational clean-out (POCO) and new technologies, such as graphene oxide, will be required. There is, therefore, potential for significant improvements in the cost, treatment time and effectiveness for both current and future effluent treatment applications. The availability of faster and more effective effluent treatment technologies could also reduce the total radiation dose to those who work within effluent treatment plants. One of the goals of the National Nuclear Laboratory (NNL), who are project partners, is to produce the technological solutions for decommissioning challenges, and the project clearly contributes to this goal. The Nuclear Decommissioning Authority (NDA), who are a public-body with responsibility for overseeing and monitoring all nuclear decommissioning activity, currently spend ~£3bn a year. Improvements in the efficacy of effluent treatment using graphene oxide may help to reduce this overall cost, which is ultimately a burden on the taxpayer.

Improving the technologies used for nuclear effluent treatment will help to underpin new nuclear energy generation, which will contribute to the UK achieving its greenhouse gas emission reduction target of 80% by 2050, mitigating anthropogenic climate change with benefits for all of society. The expansion of nuclear power in the UK (the government aims to have 16GW of new nuclear capacity by 2030, and providing ~30% of total demand by 2050) will ultimately lead to cheaper and more secure energy supplied to the end consumer, as well as the creation of thousands of jobs for construction workers (Hinckley Point C alone is expected to create 25,000 jobs during core construction and opportunities for local and international businesses). Radiation exposure to the public must be less than statutory dose limits and as low as reasonably achievable. The effective treatment of nuclear effluents using graphene oxide and safe subsequent disposal of radioactive species will also limit or prevent radioactive discharges into the environment, where they can potentially pose a risk to public health and damage to the environment. This will particularly benefit those living in close proximity to nuclear facilities (e.g. in the boroughs of Allerdale and Copeland).

In addition to the benefits to the nuclear industry and the public, there will be large number of academic beneficiaries across a wide range of disciplines.

All of the above groups will be engaged throughout the project. Impact will be delivered to:
1) Industry by establishing an industrial advisory panel for the project to meet annually (including representatives from NNL, Sellafield Ltd and NDA).
2) Industry by delivering a Multiscale Modelling Workshop for nuclear industry partners, to explain the underlying principles behind new modelling methodologies and provide hands-on experience of these techniques.
3) Public by establishing an accessible project website, social media and sharable content.
4) Public by attendance at science festivals, talks and debates.
5) Knowledge transfer by academic publications and conference presentations.
6) Knowledge transfer by organising a one-day symposium; "Multiscale Modelling of Graphene".