A research project is underway in Belgium that is expected to save a substantial waste management challenge in nuclear decommissioning by effectively sorting molten metals to extract the radioactive elements.

News that the European Commission has given the final go-ahead for the SMELD project opens the door to more efficient removal of radioactive elements from metals derived from decommissioned nuclear facilities and a major boost to the creation of a nuclear circular economy.

SMELD, State-of-the-art MEtal MElting Limiting waste during D&D, is a research project aimed at enabling larger quantities of metals from decommissioned nuclear power plants to be re-used. The goal is for the techniques developed to far exceed the performance of the current generation metal melting technologies. As Guido Mulier, Senior Business Developer D&D at SCK CEN, tells NEI: “The challenge today is that there are furnaces on the market which are used to melt nuclear metals. They do a good job and have done for many years, but they have their limits in the kind of material that they can melt and also in the level of radioactivity they can handle. It’s different depending on the radio nuclides in the metal. An example is cobalt 60, when the level of cobalt 60 is too high current smelters cannot accept those metals. In the United States, they accept a higher level of cobalt 60, but again there is a limit.”

Now a joint research project between Belgium’s nuclear research centre SCK CEN and the Liège-based research institution the Centre for Metallurgical Research (CRM Group) aims to change that and boost the opportunities for the circular economy in dismantling and decommissioning of nuclear sites by constructing a novel nuclear furnace. Mulier continues: “Where that limit available on the market today is reached, that is where we start with our SMELD project. That’s where we are looking to improve and to increase the possibilities so that more metals could have a second life.”

Above: SCK CEN/CRM research is focusing on how to coalesce radioactive materials in such a way that they can extract them from molten metal reasonably efficiently

Advancing metallurgical techniques

The intention is that SMELD will lead to an upgraded form of the technology able to capture most of the radioisotopes during melting and then subsequently separate them from the metal. By doing so the technology will enable a dramatic reduction in the quantity of radioactive waste while also increasing the volume of materials available for reuse. Some radioisotopes are difficult to ‘capture’ using the techniques currently available and this new approach is expected to improve performance their too.

The initial focus is on material that is too radioactive to be recycled immediately, but not radioactive enough to be disposed of as radioactive waste.

There are substantial volumes of such material in play, making such an endeavour a significant contributor to nuclear waste reduction. “Worldwide in operation at the moment, there are 437 reactors and around 70 reactors in construction in China and elsewhere. So you have market of roughly 500 reactors today in operation. When we look at Europe there are 167 in operation and most of them are from the seventies and eighties, so about 30 years and more old. From those 167 there are 40 of them that will pretty soon, over the next 10 years, come to a dismantling phase. Furthermore, in Europe you have 70 reactors at the moment that are already in decommissioning. That could be that actual dismantling has just started, but that gives an indication of the European market.”

Given these figures, there are roughly 100 reactors in Europe that are either being decommissioned or are set to enter a decommissioning phase soon. “Making a calculation roughly you can suggest about 500 tonnes of steel in each reactor that normally would be considered as waste, as a disposal issue with no future use. You can multiply now by hundred for Europe or multiply by 500 when looking at worldwide figures. We are looking at how can we improve this to benefit the circular economy by putting more metals into a second life,” explains Mulier.

Above: The project is about trying to create a circular economy in the nuclear decommissioning arena

Melting metals for recycling

Given existing approaches can’t easily separate some of the higher activity components, which thus means that the whole batch must be disposed of as waste, the SCK CEN/ CRM research is focusing on how to coalesce radioactive materials in such a way that they can extract them from molten metal reasonably efficiently.

“We aim to investigate first what the various nuclides are doing once the radioactive metal has been melted. What’s their behaviour, are they staying in the middle, going to the surface or are they sinking maybe to the bottom?” says Mulier, adding: “Once you understand the behaviour in relation to the various parameters like temperature, pressure and so on, then we would like to direct those radionuclides in a certain way.”

Above: Existing approaches can’t easily separate some of the higher activity components, which thus means that the whole batch must be disposed of as waste

Mulier explains that a better understanding of the system and the various parameters may also allowed those parameters to be steered better. He says: “For example, maybe you can take those cobalt 60 radio nuclides and bring them to the surface where you extract it, or maybe by adding additives they come together and sink to the bottom. That’s the research that we have to do and you may have 10, 20, or 30 different nuclides and with different levels of radiation or also the kinds of metals concerned. It could be a combination of certain metals welded together which cannot be treated. It means there are a lot of possibilities that we have to investigate.”

From theory to reality

This initial feasibility will be used to validate theoretical approaches and will use thermodynamic simulations to improve the performance of the furnace and to test the practical feasibility of the melting process. “We start with a feasibility study and there’s already been a lot done here and also by those smelters from around the world,” says Mulier, noting that the next phase is the development of a small laboratory furnace: “We will install a tabletop furnace where a few grammes of non-nuclear metals will be melted and will be analysed. We will observe the behaviour again and then once we have this tested and we understand the behaviour, then we go to a hot table furnace model where we will work with nuclear material.”

The initial part of that process is being carried out by CRM Group and will be followed with small-scale tests at SCK CEN using radioisotopes. These initial tests will enable researchers to identify potential optimisations and address any unexpected challenges, including the way in which the furnace operates and the materials processed, as well as the interaction with the radioactive metal itself, before the system becomes fully operational.

Mulier emphasises the importance of combining the two skill sets to forward the research programme: “CRM have knowledge on how to melt metals that are non-nuclear while SCK CEN are experts in the nuclear side. We bring those two businesses together and that’s unique bringing those two knowledge pillars together to find a solution for those metals.”

Having completed the research on radioactive materials in the tabletop model the goal is to scale up the design to develop a larger prototype furnace. Again, this will begin operations with non-radioactive materials. Says Mulier: “The next step is a large scale but still a prototype furnace and again in a cold, non-nuclear, way.”

So-called hot testing using nuclear materials will follow. “This is a bigger size furnace roughly five meters up to six meters wide and a height of five meters. That isn’t so big compared to the metal melting industry, in fact it is rather small. Then you have to install air ventilation, filters and so forth you also have to provide the logistics because you are working with nuclear material so that fits in a bigger building,” notes Mulier. The two project partner’s scaled up development of a genuine advanced processing furnace is set to be delivered in 2026.

Mulier though is already focused on the outcomes: “The most important goal is to have more metal that can have a second life and we believe that we can go up to 97% or 98% of the metals that we try to melt to give them this second life.”

Going commercial

Having established the feasibility at scale the goal is to build a commercial partnership with a company that can build the business while leaving the partners to continue their research programme and deliver further optimisations. “We will facilitate the way towards a third party, an industrial partner who will take the commercial side of this furnace where we still have the right to continue research. That’s the next step, to find this third party,” says Mulier.

The Belgian government has already committed €13.5m of funding for the project to develop the proof of concept and to build a furnace, but more will be needed to continue and to expand the innovative research after 2026. Scaling up to a five by five metre unit means attracting a commercial partner: “When it comes to the commercialisation and the industrial scale model, there it’s important that we speak with a third party,” says Mulier.

The SMELD project aims to develop a new technology with a global potential to significantly reduce waste volumes. Given the hundreds of reactors worldwide that will need to be decommissioned at some point and the legacy materials housed at sites like Sellafield in the UK, it is clear this kind of innovative engineering R&D is an opportunity to further reduce the ecological impact of nuclear power life cycle while adding thousands of tonnes of metals to the creation of a circular economy. As Mulier concludes: “That is what this project is all about, to create a circular economy in dismantling”.