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A GDF in rock deep below the seabed – yes, it could work

Blog posted by: , 25 February 2021 – Categories: Waste management.

Ship at sea trailing seismic sensors

Graphic shows a vessel trailing streamers used to carry out a seismic survey, one of many investigations needed to assess geological suitability of a potential site

We're willing to explore any areas identified

As we begin to discuss the prospect of hosting a deep geological facility with our first Working Groups and the wider communities around them, one of the interesting questions we’ve come across is whether it’s feasible to construct the underground part of a facility deep below the seabed.

The simple answer is ‘yes’ – if Working Groups ask us to look at this option, we’re very willing to explore any areas that are identified, either close to the coast or extending up to the 22km outer limit of UK territorial waters.

Image shows cut-away of GDF under the seabed

A GDF could be deep below the rocks of the seabed

It’s important to emphasise that we would need further, much more detailed investigations to understand whether any areas could be realistic possibilities, and we don’t expect to reach this position for a number of years.

Research down the years

Exploring the suitability of rocks deep below the seabed off our coast has been a consideration for many years. RWM is actively involved in research that would inform future decision-making if a sub-seabed location becomes of interest for a community.

Numerous wide-ranging studies have been carried out both in the UK and overseas, since scientists and engineers first looked into how best to deal with the radioactive waste that has been accumulating since research into atom-splitting technologies began to gather pace in the post-war years.

During the early decades of nuclear experimentation, the focus was on making the technology work safely and efficiently:  little attention was paid to future decommissioning or dealing with the radioactive waste products.

Numerous solutions were considered in the past, ranging from disposal in ice sheets, on the ocean floor, rock melting and firing the waste into outer space.

The right thing to do

Today, science and environmental standards have advanced and the internationally recognised solution for radioactive waste is geological disposal – because we know it’s is the right thing to do. This comprises a land-based surface facility connected to engineered vaults and tunnels that are deep underground. The underground part of the facility could be wholly or partially below the seabed.

Internationally, precedents already exist. Sweden has a disposal facility for Intermediate Level Waste (ILW) 60 metres below the floor of the Baltic Sea, which opened in the 1980s. The global oil and gas industry has been drilling deep below the seabed for decades. Think too of the Channel Tunnel or Boulby Mine on the east coast which is more than 1,000 metres below the seabed and extends to approximately 10 miles off the coast.

A GDF deep below the seabed

For the UK, a prospective GDF below the seabed off our coastline could definitely be worth investigating.

From a geological perspective, there is in fact little difference between a GDF constructed within rocks under land or within rocks under the seabed. A GDF exists to isolate the waste from the surface environment, and providing the correct geological environment is selected, it makes little difference what is going on in that surface environment – land or sea. In either scenario, the depths of rock above ensure protection for many thousands of years.

What's absolutely clear is that while a GDF could be built hundreds of metres below the seabed, we aren't going to dispose of waste on the seabed itself.

Compared to a land-based GDF, there are different challenges and considerations, such as avoiding disruption to marine environments during preliminary investigations and construction. We would also need to liaise with a different set of stakeholders, such as those in the fishing and maritime sectors.

But our priorities would remain the same:  safety and security, plus full compliance with all the regulatory criteria.

A GDF under the seabed is also likely to require infrastructure improvements on land, perhaps expanding an existing port or constructing a new one, which could have spin-off benefits for a local community.

Research and engagement with communities

The search areas, however, will be defined by the working groups and the eventual selection of a site, whether on land or below the seabed, will be very much influenced by the views and feedback expressed during local community discussions. And of course, a site would need to be comprehensively investigated and confirmed as geologically suitable.

Buildings on land next to the sea

Graphic showing a land-based site characterisation deep borehole compound for a possible GDF deep under the seabed

In the meantime, RWM is in the process of examining all the previous research relating to disposal under the seabed, and has commissioned further studies to understand in greater detail how to proceed with geological investigations, together with the design and construction of sub-seabed facility – if this is what we’re asked to explore.

These reports will add to the information already available and help to inform continued discussions about possible locations both on land and under the seabed. We look forward to the outcomes!

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Channel website: https://www.gov.uk/government/organisations/nuclear-decommissioning-authority

Original article link: https://nda.blog.gov.uk/2021/02/25/a-gdf-in-rock-deep-below-the-seabed-yes-it-could-work/

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