What follows JET fusion?9 November 2022
The radiological challenge in decommissioning a fusion reactor is a fraction of that of a fission reactor, and repurposing the site is a more immediate challenge. JET is recruiting a team to take that on
Design of the UKAEA’S fusion tokamak Joint European Torus (JET) facility in Culham, Oxfordshire, began in 1973 and it started up operations in 1983. At the end of 2023 it will close and Carrie Leadbeater-Hart, Director of Decommissioning and Repurposing, is building a team that will celebrate the site’s anniversary by deciding how to replace it. At that time a decommissioning plan will be approved by the government. That is the challenge that has been taken on by Leadbeater-Hart.
She is keen to quickly build a team that can take it on. She says: “When I arrived the team was only 12 people and we are looking to build up to about 130 by the end of the year”. That big organisational build is one reason she wants to talk about the project – but as will become clear, nuclear engineers are far from being the only area she needs to recruit for new team members.
Managing radiological waste from fusion
There is radiological waste to manage in decommissioning JET but the quantity, when compared with a fission plant, is miniscule. Leadbeater-Hart says: “because of our magnetic confinement we don’t have so much contamination of the actual materials within the tokamak. There is some read across. But we don’t have any spent fuel, the waste that we have is much lower level and contamination is more easily manageable.”
There is no spent fuel to deal with but there is waste that corresponds with intermediate level waste (ILW) and low level waste (LLW) in fission reactors. On cost and safety grounds Leadbeater-Harts wants to see that reduced. She says: “One thing that I am driving the team towards is innovation. One of the drivers for that is reducing our waste legacy.” The project will produce about 200 tonnes of ILW – “about 150m3 depending on how we package it”. Leadbeater- Hart says that “in percentage terms that’s about 0 .1% of the waste that we will generate through the decommissioning”. Low-level waste is “about 1000m3, again depending on packing density,” which equates to about 0.9% of the total. “So the radioactive waste is only about one per cent of the total waste that we will produce in the decommissioning.”
It is not the same isotope mixture as in fission waste either: “The main concern is tritium and that is not really found in the fission community.” She explains: “It has a shorter half life [12 years] so it is much more manageable.” Leadbeater-Hart is pushing her team to reduce waste volumes as much as possible: “we will be heat-treating the intermediate level waste. As we pull the waste out of the tokamak, we will be size-reducing it, so it is small enough to go into a furnace.” The furnace will raise the packages to a temperature at which any tritium will be driven off as a gas. The tritium will be captured and the remaining waste can be categorised as low-level waste, “which is a huge positive”. Leadbeater-Hart says: “ The sort of percentages we are getting to is to reduce our ILW by 80%, so hopefully will end up with just a very small amount of residual ILW and that will be around exotic materials that we are struggling to de-tritiate.”
The materials include Inconel, carbon and stainless steel, where the de-tritiation process is proven, and tungsten and beryllium (used in the tokamak internals). For these materials, the process has yet to be proven but the team is working on that, using an on-site furnace to test the process.
With plans in place for the small amount of radiologically significant material, other decommissioning challenges are of a different nature.
Leadbeater-Hart says: “We are an operational site and that is a challenge in itself. In fission reactors the whole site is shut down, so you don’t have to balance operational works while decommissioning. There is a lot of interest in fusion so we have other companies interested in coming onto the site and building a future cluster.”
The department needs to support all any new-build and other operations on-site safely, while delivering the decommissioning “which can be quite a mucky business. We need to make sure that we are managing and controlling that decommissioning and repurposing” – that is part of her emphasis on the second part of her title, because throughout the decommissioning phase the team is looking at the buildings and assets to see how they can be best used in the future.
Discussing the decommissioning process, she says “We are lucky in that asbestos is not too much of an issue and we don’t have many other contaminants” apart from the tritium.
“The internals of the tokamak are going to be intermediate level waste, so they will be removed using remote handling technology”. JET has internal robotic arms which were used to place the internals, so the team knows they can be used to strip out the plasma-facing components. “Using remote handling will really reduce the amount of exposure any worker has to contaminated items,” she says.
The next phase is to remove what is called ‘phase two’ of the inside of the tokamak, which is the furniture that the tiles are hanging from. Cutting or laser cutting will be used to take it back to a smooth surface inside the vessel “and I am really pushing the team for innovation on how we can do that. I’ve asked them what are the possible solutions”.
All this waste will be removed through an existing fixed window in the Tokamak and into one of two new waste processing facilities – for ILW and LLW – that will reduce its volumes and treat it so it can be taken offsite.
Once that is done, it may be possible for operatives to work without suiting and with low radiological concerns, but that is not clear yet. Leadbeater-Hart says: “One of our projects is a characterisation study to see where the radiological hazards lie. Our current hypothesis is that once everything is pulled out of the Tokamak then we won’t need suited operations at all – it will be possible in respirators,” or possibly not even that.
A more positive plan
Currently the assumption – and government requirement – is that further demolition will leave the site entirely clear. But thinking about the ‘repurposing’ part of her brief Leadbeater-Hart says, “we have this amazing facility with bioshields and we have had a lot of interest from other commercial fusion companies that would like to come in and fill that space. So rather than raze it to the ground we are proposing to the government that they treat it as an asset rather than a liability and it be used as such.”
What might remain or be re-used depends on changes to the current ‘lifetime plan’.
Leadbeater-Harts is “still in the planning phase for the end of 2023, which is when the government will determine the strategy they want us to take forward.” The current lifetime plan would leave open space to be reused. Leadbeater-Hart’s proposal will be “to recycle and reuse a lot of what we have and then take things back to the bioshield. It would be an empty building where people could use our active drain, potentially use our cryoplants, use our grid connections.” The final form would depend on what a new company would want to use.
Leadbeater-Hart says, “We are really saying to the government that there is a massive opportunity and we should capitalise on it. It would be a shame to remove all the good stuff that we have, when the interest in fusion is increasing and it will be a significant part of our energy supply hopefully in years to come.” And, Leadbeater- Hart further emphasises that as her programme for decommissioning and repurposing is paid for by the taxpayer, any areas where she can pass an asset to new users will reduce the cost to the public purse.
Repurposing would add complexity to the process from a radiological health and safety perspective. It also makes dealing with conventional hazards more complex, “so I have to make sure the isolations are installed and controlled in a clear manner, so we don’t have any cable strikes and don’t crush any drains – particularly when we will have large machinery moving around, we need to be sure that we are protecting our assets,” she says.
The decommissioning process could take anything from 12 years to 17 years, says Leadbeater-Hart: “We are in the planning stages at the moment, so until we have our critical path plan approved by [government] they are just options”.
Whatever the timetable there is a site setup phase and the first big project is to design and build waste handling facilities, so that the second large project – removing internal ILW – has a destination. The site is congested but it does have space for these new builds “and we are coordinating closely with the campus development team”.
Before then, Leadbeater-Hart is pushing for innovation from her growing team to maximise de-tritiation. She says she is confident in the 80% reduction “and we really want to work on that 20%. Options are continuing with the heat treatment process and looking at whether we want to do any surface treatment on some of these exotic materials prior to heat treatment.” Leadbeater-Hart says that is “really reducing the hazardous stuff as early as possible.”
Building innovation in decommissioning
Leadbeater-Hart wants innovation across all aspects of the programme, so she is pushing as much for the team to find new ways to use buildings and site areas to support a ‘fusion hub’ on the site in future as to solve technical issues.
The programme as a whole falls into 17 major projects split into three programmes.
The first programme is decommissioning. That includes isolations and site clearance. Leadbeater-Hart says “in order to decommission effectively and safely we need to clear some space, for example for laydown areas. It is also the conventional clearance work.”
The team is working on a full inventory: “we have a good understanding of the radiological waste, but we want to build up a clearer inventory as regards the balance of plant. And make sure that we have that agreed with the regulator prior to decommissioning starting.”
The second programme of works is active buildings. A team is looking both in-vessel (the remote handling) and ex-vessel (there are some contaminated components in the active gas handling system). “Anything that has some active component is managed by that team.”
Finally there is new-build and repurposing. “One of the questions in my mind is what to believe as a positive legacy from decommissioning. Do we leave facilities that can then be leveraged and used in years to come and how do we give a ‘leg up’ to the next phase of fusion?,” she says.
Leadbeater-Hart wants to build up her team rapidly and is now recruiting a seven-person lead team, with heads of the three programmes plus heads of engineering, site construction, project management and finance.
She says: “the kind of skill sets that I try to encourage in decommissioning is slightly different to the skill sets that we have at the moment. You have the technical challenges of decommissioning, but really the challenge is organisational change. It is clearly understanding what the future will look like once operations are finished and building up a team that has the skills that we need – things like being comfortable that change will happen and really seeing it as an opportunity for innovation rather than something that is scary. One of my key roles is to try to build that decommissioning culture and to drive that positive working experience.”
She is determined that decommissioning be seen as a positive force and a focus for innovation and says “my way to a lot of that is diversity,” cross-fertilising with people from other high hazard industries.
Reflecting its relatively low radiological hazard – a fraction of that found at a nuclear fission site, even during operation – fusion is not regulated by the UK’s Office for Nuclear Regulation but instead by conventional regulators the Health and Safety Executive and the Environment Agency. The types of permit required will be planning permission for buildings to be put up or taken down. Although that will still involve regular engagement with the local community but Leadbeater-Hart says she is and indeed should be enthusiastic about that: “It’s not about what must we do but about how can we do this really well. And these are my nearest stakeholders, so I want them to be excited and their kids to be excited – I want them to come and work for me.”
Even at this early stage Leadbeater-Hart has advice on managing the full life cycle for the fusion plants that will follow. “We are working closely with ITER, in fact I chair an international forum on how we can help to build fusion facilities with the decommissioning in mind.” Her key takeaway so far: “It was massive foresight to put the remote handling capability in the JET tokamak, so we can decommission without getting humans involved. It was really amazing they had that foresight.”
Author: Janet Wood is an expert author on energy issues