Alternative reactor types and the future of nuclear waste management: BASE in discussion with experts at the IAEA General Conference

BASE discussion at the IAEA on the challenges of novel reactor concepts, moderated by Jochen Ahlswede. Source: BASE

Molten salt reactors, gas-cooled fast reactors and small modular reactors (SMRs) – there has been growing international interest in so-called "novel" or "alternative" reactor concepts for several years now.

The Generation IV International Forum (GIF), where several countries are working together on the research and commercialisation of alternative reactor concepts, was founded in 2001. These countries include China, the United States and members of the European Union. In comparison to conventional light water reactors (LWRs), the promoters of such technologies are hoping for lower costs, greater safety and proliferation resistance as well as a reduced waste load.

However, alternative reactor concepts raise numerous questions, particularly with regard to waste management issues: What waste streams do these reactors generate? What are the associated challenges? And what can we learn from past experiences in nuclear waste management for dealing with alternative reactors in the future?

Discussion with experts alongside the IAEA General Conference

The expert panel on "New Reactor Types and the Future of Nuclear Waste Management: Opportunities, Challenges and Risk" focussed on a critical examination of the above questions. BASE had organised this event at this year's 67th General Conference of the International Atomic Energy Agency (IAEA). The General Conference, where delegates from all IAEA member states negotiate key issues of nuclear safety and security every year, provided an ideal setting. A science-based debate on waste management issues with regard to new reactor concepts was initiated with over 60 representatives from member states and the IAEA.

This goal was achieved primarily thanks to an expert panel of internationally recognised scientists who were keen to engage in discussion:

• Professor Allison Macfarlane from the University of British Columbia brought with her many years of research experience in the field of waste management safety. Furthermore, she also shared her political experience from her previous position as head of the US Nuclear Regulatory Commission.
• Professor MV Ramana, also from the University of British Columbia, contributed his extensive expertise on the economic aspects of new reactor types.
• The panel was completed by Dr Christoph Pistner from the Öko-Institut, who has already written several expert reports on safety issues relating to new reactor concepts.
• Jochen Ahlswede, Head of the Research/International Department at BASE, moderated the panel.

Findings from the discussion

The lively exchange produced some key findings:

1. Alternative reactor types increase the complexity of nuclear waste management.

Contrary to what is often claimed, alternative reactor types do not offer a simple solution to the nuclear waste problem. On the contrary: nuclear waste management will become even more complex if alternative concepts are used.

The reactor concepts currently being researched show fundamental differences with regard to the fuel types and coolants used. It is difficult to summarise their challenges in general terms. However, the variety of concepts will increase the number and type of waste streams in the future, which in turn will require untested forms of treatment. The emergence of more complex waste streams could also increase the risk of unauthorised persons gaining access to radioactive materials. Furthermore, despite various approaches to recycling spent fuel, none of the concepts offer a solution to the fundamental disposal problem. The need for a deep geological repository remains.

2. Many future risks cannot yet be assessed due to the early stage of development of the concepts.

Contrary to what the terms "novel" or "alternative" might suggest, many of the alternative concepts have already been pursued for decades. Research into molten salt reactors, for example, dates back to the 1960s. Nevertheless, the majority of concepts are still a long way from commercial application. Accordingly, there is still a great deal of uncertainty based on the current state of knowledge. It is difficult to say what additional challenges might arise for nuclear waste disposal in the future.

The continuing uncertainty renders the promises made by the promoters of these technologies, namely that alternative reactor concepts will reduce waste streams and thus facilitate disposal, all the more problematic.

3. There is no clear "best in class" among alternative reactor concepts at present.

It is hard to say which of the reactor concepts currently under development offers the most potential and should be promoted more strongly. None of the new concepts have yet demonstrated their worth in practice. The question of whether SMR concepts actually do have a lower waste load and higher safety compared to conventional LWRs thus remains unanswered.

This finding is also consistent with the conclusion of a report published by the US National Academies of Sciences, Engineering and Medicine in 2023, according to which alternative reactor concepts must first complete the design phase and prove themselves in actual operation. Before that, it is impossible to "understand the numerous trade-offs of the various design concepts and choose a 'best in class'" (NASEM 2022, p. 55).

4. SMRs do not offer developing countries a safe, low-threshold entry into nuclear energy.

Proponents often promote the argument that the supposedly low-cost, low-emission SMR concepts could secure the energy supply in developing countries in particular. However, it is currently much more promising for developing countries to invest in existing renewable energies rather than in unproven reactors.

Conclusion

To summarise, there was one main takeaway from the event held on the side-lines of the General Conference: As far as nuclear safety is concerned, alternative reactor concepts raise more questions than they provide answers.

This makes it all the more important to conduct a science-based dialogue at international level that also sheds light on the potential problems of these technologies.

SMRs and alternative reactor concepts are currently experiencing unprecedented popularity. This was also illustrated by the many themed side events at the General Conference, whose titles reflected the promise of these reactors: "SMART SMR Demonstration Project: Towards a Low-Carbon Future with Global Partners" or "Fast Future of Small and Medium Sized Reactors".

Against this background, the BASE expert panel succeeded in drawing a more complex picture. A technical basis was created for future debates on the disposal aspects of alternative reactor concepts.

Contact

If you have any questions or require further information, please contact

Dr Ingo Kock
Head of Department F4
Research on safety analysis and methodology
ingo.kock@base.bund.de