Managing our nuclear waste
01 June 2007
Regardless of future decisions on nuclear power, the UK has to deal with its nuclear waste legacy. The Government's recent decision to build a geological repository prompted the RSC to bring together UK experts to examine the scientific challenges this will involve.
The safest and most secure way to store radioactive waste is in a deep geological repository. This was the consensus at a scientific workshop on nuclear waste management held at Loughborough University last November and coorganised by the RSC. The workshop report, launched in February, concluded that there are no insurmountable scientific or technical barriers to such long-term storage in the UK.
The workshop 'UK Long-term nuclear waste management: next steps?' was organised in the wake of the 2006 public consultation on managing radioactive waste safely. The public consultation was carried out by the Committee on Radioactive Waste Management (CoRWM), which was established by Government in 2003. Its aim was to review the options and recommend a long-term solution that protects people and the environment.
The UK has a complex inventory of radioactive waste generated by nuclear power, military defence, medical applications and other applications (for example americium- 241 is used in smoke detectors as a source of ionising radiation to detect the smoke). Until very recently no long-term management method had been agreed for these wastes.
In July 2006 CoRWM recommended that geological disposal coupled with safe and secure interim storage is the way forward for storage of the UK's higher activity wastes. The Government accepted these recommendations in October and announced a timetable for the delivery of an interim storage and geological disposal programme.
Nuclear waste remains radioactive for many thousands of years. In a geological repository radioactive waste would be safely stored in a stable rock formation at a depth of between 300 - 1000 metres. The waste would be stored in an engineered containment system built to withstand radiation, heat (in the case of high active waste) and the external environment over very long timescales.
The 'next steps' workshop was sponsored by sixteen organisations, across all relevant scientific disciplines including the RSC. The workshop report, launched on 6 February 2007, highlighted a number of key technical questions that still need answering.
Can we build a UK repository?
Scientists at the workshop agreed that the tools, techniques and relevant experience needed to site and build a geological repository already exist in the UK. The process would involve detailed geological surveying to investigate the properties of potential sites followed by the design, construction and operation of the repository. There is already well established science for assessing the long-term engineered and natural containment of a repository.
But building such a repository is no small task and in the meantime, above ground facilities capable of storing radioactive materials are needed. CoRWM has recommended that such storage facilities will be needed for approximately 100 years, and will need similar design features to any geological repository in terms of its ability to provide secure storage.
Locating the repository
Broadly speaking, UK geology is well mapped out and we can identify potential host areas with desirable geological characteristics for the repository sites. Such characteristics include physical stability and predictable hydrogeology. It has been estimated that more than 30% of the UK has geological characteristics that would be suitable for a repository.
Geology aside, there are likely to be other issues not directly related to the geology such as transportation issues related to moving the waste to the site. To identify a suitable location for a UK repository the workshop agreed that government will need to apply rigorous criteria that are developed in close consultation with stakeholders.
If communities are to accept a repository, the workshop acknowledged the critical importance of transparent community engagement. In particular, scientists and engineers need to understand how the public and the media perceive risk and uncertainty, and accordingly be more forthcoming and sensitive when addressing these issues.
"scientists and engineers need to understand how the public and the media perceive risk and uncertainty"
Universities and learned and professional bodies could be among the main sources of trust in building relationships between local communities and technical experts.
Open or closed repository?
The decision as to whether the repository remains open or is closed immediately after it is filled will require balancing the public desire for monitoring waste in situ, allowing its retrieval, with the concerns that an open repository could compromise safety. The workshop acknowledged the significant engineering challenges that would be associated with retrieving waste.
How many repositories?
The number of repositories needed in the UK is still up for debate. It will depend on whether high-level, intermediate-level and low-level waste can be safely disposed of in a single facility. It's possible that geological segregation will be needed for different wastes, for example waste that is heat generating may need to be stored in different conditions.
A separate decision is also required as to whether spent nuclear fuel, civil and military plutonium and uranium, should be classified as a waste or reused as fuel. Both plutonium and uranium can be recycled and used as nuclear fuel.
If classified as waste then we need to develop stable encapsulation matrices, for example vitrified glass. This is particularly important for plutonium where no waste form currently exists. Management and disposal of such materials will be dependent on these factors.
Gaps in knowledge
The workshop acknowledged and discussed some of the knowledge gaps that require a substantial R&D programme. Firstly, the geological environments of repository sites and the requirements for interim storage must be well understood before we can design the most appropriate and stable waste forms.
The UK has several problematic radioactive waste streams, including noncompactable waste arising from building decommissioning, large volumes of contaminated land, poorly characterised historic waste, graphite and spent fuel. These all need further research so that the best waste form and disposal route is developed.
Research and development effort is essential to demonstrate the long term suitability and performance of all the parts of a waste management system Long-term safe containment will rely on the waste form, the repository containment barrier, the buffer and backfill and the surrounding host rock and overlying geology.
The understanding of how waste forms change long-term will require a deep understanding of the mobility of radionuclides. This knowledge is needed to minimise the risk of their escape.
Finally, although a deep geological repository is the best option at present, the workshop concluded that research into alternatives should continue. One such option is deep borehole disposal where waste canisters are stored a depths of up to 5 km in 1 metre wide boreholes.
Do we have the skilled personnel?
One of the most concerning areas highlighted at the 'next steps' workshop is the decline in the UK nuclear skills base. This has followed the significant decline in R&D funding in nuclear fission over the last 20 years, since the last nuclear power station was built and nuclear power fell out of favour.
We need a nuclear skills renaissance in order to provide the scientists and engineers of the future who will implement the construction and design of a nuclear waste repository. The RSC and other learned and professional societies have been lobbying on this issue for several years and will continue to do so.
"we need a nuclear skills renaissance in order to provide the scientists and engineers of the future"
The creation of several new research centres and initiatives are the first steps toward this renaissance. This includes the Manchester Dalton Nuclear Institute launched in July 2005, and the Nuclear Technology Education Consortium, a consortium of UK universities providing postgraduate education in nuclear science & technology.
In addition, in October 2006 Alistair Darling, Secretary of State for Trade and Industry announced the creation of a national nuclear laboratory based around the British Technology Centre in Sellafield, West Cumbria. This should provide additional momentum for a skills renewal.
The RSC's role
There is currently encouraging momentum from the Department for Environment, Food and Rural Affairs (Defra) in achieving radioactive waste management and it's important that this momentum is not lost. Whilst the technical challenges are significant, it's impossible to decouple them from the societal issues surrounding the location and public acceptability of a UK repository.
The construction of a repository is a long-term project which needs long term planning and protection from changes in the political environment. Learned and professional societies could have a role to play here in becoming the honest brokers between government and the public in community engagement programmes.
Contact and Further Information
Executive Director, Communications, Policy and Campaigns
Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 0WF
Tel: + 44 (0) 1223 432267