The UK plans to expand sharply its nuclear capability, in an effort to reduce its dependence on coal-based fossil fuels. The government aims to build up to eight new reactors in the coming decades, with a view to increasing power capacity from around 8 gigawatts (GW) today to 24 GW by 2050. This would meet around 25% of the UK’s forecast energy needs, compared to around 16% 2020.
As part of this plan to triple nuclear capacity, an investment of £ 210 million is also underway for Rolls-Royce to develop and produce a fleet of small modular reactors (SMR). SMR is cheaper and can be used in places that can not host traditional, larger reactors, so this will provide more options for future nuclear power plants.
New reactors will inevitably mean more radioactive waste. Decommissioning of nuclear waste, starting in 2019, was already estimated to cost British taxpayers £ 3 billion per year. The vast majority of our waste is stored in warehouses at or near ground level, mostly at Sellafield nuclear waste site in Cumbria, which is so large that it has the infrastructure of a small town.
But underground storage of nuclear power is not a viable long-term plan – governments, academics and scientists agree that permanent underground storage is the only long-term strategy that satisfies safety and environmental considerations. So what plans are underway and can they be delivered safely?
The way ahead
It has taken many decades of international cooperation between academic and scientific institutions and government regulators to identify a feasible path towards the final disposal of nuclear waste. Previous ideas have been to dispose of the extra waste in spacein the sea and below seabed where tectonic plates converge, but each has been hailed as too risky.
Now almost every nation plans to isolate radioactive waste from the environment in an underground, well-constructed structure called a geological final disposal facility (GDF). Some models see GDFs constructed at 1,000 meters underground, but 700 meters is more realistic. These facilities will receive low-, medium- or high-activity nuclear waste (classified as such according to radioactivity and half-life) and store it safely for up to hundreds of thousands of years.
The process of creating such a facility is not simple. The organization responsible for delivering GDF, which is in the UK Nuclear waste services (NWS), must not only overcome huge environmental and technical problems but also serve the support of the public.
Will all GDFs look the same?
Although generic design concepts exist, each GDF will have unique aspects based on the size and composition of the waste inventory and the geology in which it is installed. Each nation will tailor its GDF to its individual needs, under the control of regulators and the general public.
However, the basis for all GDFs will be what is called concept with several barriers. This combines artificial and natural barriers to isolate nuclear waste from the environment and allow it to decay steadily.
The system for preparing highly active waste for storage in such a system will start with the use of nuclear fuel rods from reactors. First, all uranium and plutonium that are still useful for future reactions will be recycled. The remaining waste will then be dried and dispersed in one host glass, which is used because glass is tough, durable in groundwater and resistant to radiation. The molten glass will then be poured into a metal container and solidified, leaving two layers of protection.
This packaged waste will then be surrounded by a backfill of clay or cement, which seals the excavated rock holes and underground tunnel structures. Hundreds of meters of rock in itself will serve as the last layer of containment.
How’s the UK program going?
The UK GDF program is at an early stage. The localization process is based on a so-called volunteering strategy, where communities can present themselves as potential places to host the facility. A working group is currently working (TheddlethorpeLincolnshire) and three community partnerships (Allerdale, Mid Copeland and Southern Copeland in Cumbria) has been formed. While working groups are in the early stages of the localization process, the next step for community partnerships is to begin more extensive geological surveys, followed by drilling boreholes to assess the underlying rock.
Public support is the basis of the entire GDF program. While some nations may take a heavier approach and choose a website regardless of public support, the UK GDF mission has community and commitment at its core.
Why would the residents volunteer? This is a 100+ year old project that will require many people working very closely. At the Community Partnership stage, an investment of up to £ 2.5 million per year, per community, is expected.
The British program is a bit behind some other nations. The world leader is Finland, which has almost finished the world’s first GDF at Onkaloseveral hundred kilometers west of Helsinki. Preferred sites for GDF has also been selected in the USA, Sweden and France.
The British government aims to identify a suitable site within the next 15-20 years, after which construction can begin. The time scale from placement to closure and sealing of the first British GDF is 100 years, making this the largest British infrastructure project ever. The technology for delivering GDF is complete; the only thing left is to find a willing society with a suitable geology.
Is there any other way?
There is a scientific consensus, internationally, that the GDF method is the most technically feasible way to permanently dispose of nuclear waste. Onkalo is an example to the world that scientific collaboration and open involvement with the public can make safe storage of nuclear waste possible.
The only other approach that has received any attraction is deep borehole storage (DBD) concept. At face value, this is not too different from a GDF strategy; drill boreholes much deeper than a GDF would be (up to several kilometers) and lay waste packages in the bottom. Countries like Norway are considering this approach.
Author: Lewis Blackburn – EPSRC Doctoral Prize Fellow in Materials Science, University of Sheffield
Source: sn.dk