Drones, robots and digital twins are being developed to add value and accelerate the strategy for the UK’s reactor decommissioning programme as the nuclear sector steps up efforts to collaborate with construction. Denise Chevin reports
Irrespective of whether any, or how many, or what type, of new nuclear power stations get the go-ahead in future, capital spending in the UK nuclear power sector will be many tens of billions of pounds. Part of this spend is the substantial cost of dismantling older reactors and, in the near term, investing in interim waste management and storage facilities near to or on the existing licensed sites to enable the various decommissioning programmes to progress.
As the nuclear sector makes plans for this most technically challenging assignment, it is turning to BIM, digital twins, robotics and drones.
Digital technology is being accelerated in the sector as part of the need to meet the requirements in the Nuclear Sector Deal, which was struck in June 2018. Like the Construction Sector Deal, the Nuclear Sector Deal sees innovation investment in return for improvements in delivery. This includes reducing the cost of new build projects by 30% by 2030 and saving 20% in the cost of decommissioning compared with current estimates by 2030.
Digitalisation is also being employed to help implement a completely new decommissioning strategy. One of the most advanced uses of digital technology being rolled out is for the dismantling of the Magnox nuclear power stations, with Magnox planning to go to the market in 2021 to look for partners to develop the tools.
“We have a Nuclear Sector Deal with substantial cost reduction targets, and we see digital as a key enabler,” says Alastair Laird, director of reactor deconstruction & transfer at EDF (UK) and trustee of the professional body, the Nuclear Institute (NI).
“Looking ahead, we all need to embrace the digital revolution, embrace the opportunity to use new technologies and embrace BIM and better data platforms to optimise our decision making and replication process. Some of the early UK decommissioning programmes have not been good at this. As with any sector that has world experts and professional engineers/scientists, we can sometimes over-debate and internalise things rather than implement new solutions,” he adds.
Joining the UK BIM Alliance
The announcement earlier in November that the NI has joined the UK BIM Alliance affiliate programme is a clear sign how determined it is to share and collaborate.
The NI is the professional body for the nuclear industry and represents almost 3,000 professionals at all levels across the sector, from new build and operations to decommissioning.
Says Laird: “The NI wanted to start to align opportunities for collaboration around those two sector deals for nuclear and construction, and to leverage the initiatives that are taking place, particularly in construction around BIM and digital information management. That’s why we joined the BIM Alliance.”
The NI wants to encourage digital into three key areas of the nuclear sector, explains Laird.
The first is new nuclear build – Hinkley C and Sizewell C – as well as the small modular reactors now in development.
“Second, we also want to bring it into decommissioning, because there’s £100bn decommissioning programme for the legacy sites under the Nuclear Decommissioing Authority (NDA), and there’s another emerging decommissioning programme for the Advanced Gas Cooled Reactors (AGRs).
“And the third area is waste management. A key enabler here is how we retrieve, package, and dispose of the radioactive waste. So, we’ve got to get our decision making focused around scenarios, options and timely use of digital information and replication opportunities,” Laird says.
Magnox and digital dismantling
One of the most advanced uses of digital technology being rolled out is for the dismantling of 26 Magnox nuclear reactors, which are spread over 11 sites, 22 of which are owned by Magnox Ltd, a subsidiary of the NDA. These graphite core reactors were built in the 1950s, 60s and 70s and have all completed their operational phase. Wylfa in Anglesey, the last one in operation, shut down five years ago.
Originally, the plan had been to leave these reactors for about 80 years, let the radioactive components decay and then decommission them, explains John Norton, head of technical strategy, at Magnox Ltd: “The assumption was that we would be able to do more manual decommissioning in 80 years – but the feeling now is that we would still have to use remote handling techniques, so why not do it now.”
To decommission the reactors safely, the team is adopting a high-tech approach. The optimium way of dismantling the reactors will be modelled after building a suitably detailed digital twin, developed with help from drone-mounted laser scanning equipment and point cloud surveys, combined with the original drawings. Once a digital twin has been built, it can be used to devise cutting and dismantling tools and routes for removing/processing the waste.
Enter the robots
The decommissioning will then be carried out by specially built robotic tools, which Magnox is looking to the supply chain to develop. This approach, similar to that deployed on a Windscale AGR research reactor many years ago, is again being deployed on the Magnox Steam Generating Heavy Water Reactor that is currently being decommissioned at Winfrith in Dorset.
“A big challenge digitally is converting paper drawings into digital – particularly as they might not be the same as the ‘as built’ structures,” says Norton. “Also, it’s key to establish the right level of detail in the right areas of the digital twin. We could take a labour-intensive approach, for example, of modelling each fuel channel in the reactor. But this may be wasted effort if the channel configuration has no bearing on the way it will be dismantled.
“For Magnox, it’s more like a reverse of BIM. Traditionally, the BIM model starts with a blank page and builds up information in levels of detail. The challenge here is that we have large complex structures and we need to be able to take parts away without them falling over. We can’t be spending lots of time and effort modelling detailed elements that aren’t important.”
Norton says that the Magnox team, working with the supply chain, have proven to themselves – and to the regulator – that they can design the tools and techniques to be able to do this, and that decommissioning the reactors allows them to close the nuclear life cycle; in the UK, we have designed, built and operated commercial reactors, and now we are taking them apart. And that erodes one of the main arguments used against nuclear new build, that we don’t know how to take them down.
Norton expects the Magnox programme of graphite core reactors alone to amount to £20bn over the next 40 years. As each reactor site in the Magnox portfolio was designed slightly differently, each will need its own bespoke digital twin and dismantling tools. Many new facilities will be designed as well, for waste retrieval, processing and interim storage; and each of them will have their own BIM models.
Gwynedd site goes first
The first commercial reactor site where Magnox hopes to apply its new strategy is Trawsfynydd in Gwynedd, Snowdonia. It has begun cleaning up the site in preparation for the physical dismantling to begin in around 2025.
Says Norton: “Before then, we will have to do characterisation of the core components and design the tools and techniques to cut through the concrete bio-shield, gaining access to the reactor core and retrieve the materials. Where possible, through the detailed characterisation, Magnox expects to be able to potentially reuse and recycle some of the materials, therefore diverting it away from costly disposal.”
If Magnox has its business case approved to commence reactor decommissioning work, it will engage with the supply chain to develop this new digital environment for design, operational modelling, waste assessments, safety case development, and operator training.
Norton estimates that it will take circa 15 years to dismantle, including five years building the new facilities and five to six years for waste retrieval – which amounts to about 7,000 cu m of radioactive waste alone, nearly the same volume as three Olympic-size swimming pools.
Soon after starting at the Trawsfynydd reactor site, Magnox intends to move on to the Dungeness reactor site in Kent, and then its site at Hunterston, west of Glasgow.
Main image: Magnox's Trawsfynydd reactor site in Gwynedd; 54931224 © Rory Trappe | Dreamstime.com
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