The government hopes its “golden age” of nuclear will increase the proportion of low-carbon electricity in the grid, strengthen UK energy security and power its AI ambitions. But in doing so, the new projects will also contribute to a growing mass of nuclear waste. Nuclear Waste Services (NWS), part of the Nuclear Decommissioning Authority, is the organisation charged with safe disposal of that material, which is currently stored at more than 20 sites around the country.
“The UK has got a really long history with nuclear, dating back more than 80 years, and we’ve got a significant volume of waste,” Martin Walsh, head of engineering at NWS, tells Professional Engineering. “We pay a price for our involvement early in the nuclear age.”
Equivalent in volume to 10,000 double-decker buses, that waste is formed of ‘packages’, which come in a variety of shapes and sizes. Weighing up to 60-80 tonnes, package forms include 3-metre long concrete boxes and 500-litre drums. Different nuclear processes create different types of waste – magnox fuel has its casing shredded off, mixed into a cement aggregate and cast into containers, for example, while the fuel itself is vitrified into a glass-like product.
“About 90% of that package volume already exists,” says Walsh, who is a civil and structural engineer but has been involved in multi-discipline projects for more than a decade. “It’s waste from existing nuclear power facilities, from defence, medical and industrial uses, and that amounts to just under 770,000 cubic metres of packaged waste. And we need to do something with it because, from a sustainability perspective, storing it in facilities on the surface won’t see out the lifetime of the waste as it decays, so we need a facility that can isolate and contain that waste.”
If surface storage cannot do the job, there is only one logical direction to look: underground. That is what NWS is doing, searching for appropriate sites for a geological disposal facility (GDF) deep beneath the surface, starting a process that could last almost 200 years.
The site evaluation phase of the GDF programme has identified a 300km2 area off the coast of Cumbria that could house a facility 200-1,000 metres below the seabed. There, engineered barriers could work alongside the natural barrier of deep, stable rock, containing waste and preventing radiation from reaching the surface at levels that could do harm. Going so far underground should protect the waste from earthquakes and any future changes, from the near term (rising sea levels) to more speculative possibilities (a new ice age).
An area of 20-50km2 would be required for the disposal site, which would be connected to a surface facility. The areas of South Copeland and Mid Copeland – which includes the Sellafield former nuclear power station and decommissioning site, housing much of the UK’s nuclear waste – have been identified as potential homes, and are being evaluated for their engineering and transport capabilities. Community support is needed to go ahead, Walsh stresses.
The evaluation process involves exploring a variety of systems for both the underground and surface sites, and the links between the two, including different combinations of tunnels, lift shafts, rail and handling systems.
Some countries use vertical shafts to transport nuclear waste underground, for example, but a ‘drift access way’ – an underground transit system along a sloped tunnel, potentially using a funicular railway – offers another option, depending on how it affects material handling.
Other nuclear nations only have to deal with one type of package, Walsh says, as seen during a recent visit to Finland. “We don’t. We have many different types of packages to move, so we have to have a system that’s adaptable and flexible for that huge inventory that we’ve got to manage.”
Rail is the preferred option for transporting waste to the surface sites because of the size and shape of the containers, while shipping offers another potential route. Many of the sites are not connected to rail, Walsh says, so connections might have to be installed, along with utilities, water and communications.
None of this will come cheap. The National Infrastructure and Service Transformation Authority reportedly said that overall costs of £20-53bn would make the project “unaffordable” earlier this year, with considerable uncertainty about major aspects of the programme. The true figure could be even higher, according to a report in New Civil Engineer.
With the government set on its nuclear vision, however, ongoing support for the project seems likely: 13% of the waste inventory allows for the new nuclear build, including Hinkley Point C and the SMR programme, Walsh says.
Borehole investigations are expected to start around 2030, with construction only able to begin when a suitable site has been identified, all consents and permits are obtained, and a ‘host community’ has confirmed its willingness. Potential incentives include an estimated 4,000 new jobs in the first 25 years and thousands more over the lifetime of the project, which could last for 175 years.
NWS hopes a GDF will be available for intermediate-level waste from 2050 to 2060 and high-level waste and spent fuel from 2075. Construction will take place in sections, with construction, operation, filling and closing the facility due to run into the next century.
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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.