For decades, the narrative of the fusion community has been that a fusion reactor would be a safe, environmentally friendly, cost-effective and inexhaustible source of energy. Under the guise of initially only conducting highly attractive basic research in physics, fusion research has received considerable and ever-increasing government research funding in the leading industrialised countries and increasingly from the EU for more than half a century. In contrast, it has actually been physics-dominated, application-orientated research aiming at a reactor. However, far less attention was paid to the considerable, more technically dominated and other challenges for the reactor vision.

While there were still efforts in the 1980s and 1990s in the U.S. and Europe to occasionally pursue paths towards technology assessment and evaluation that made technical design challenges recognisable, this has largely come to a standstill in the 21st century. Significant differences between the main paths of fusion reactor research (magnetic confinement (MCF) and inertial confinement (ICF)) have at least become clear.

The fusion narrative is currently changing. On the basis of so-called breakthroughs in MCF and ICF experiments in recent years, the application orientation of research is now being emphasised. Nevertheless, it is still unclear whether the physical requirements for a fusion reactor (in particular sufficiently long burning of the fusion plasma in an MCF-based system or the need for an extremely high repetition rate in an ICF-based system as well as an energy gain factor of 20 or 100) could be achieved. Some influential politicians, official government bodies and representatives of a growing start-up scene not only emphasise the attractiveness of  fusion as part of an extended nuclear renaissance, but also promise the imminent realisation of prototype reactors, possibly in as little as ten years.

It is not easy to verify the extremely high promises, as no expertise independent of the fusion research community has been established, although this was already identified as a central political need for action in 2002 in a study by the Office of Technology Assessment at the German Bundestag.

A central point would be to analyse the considerable development risks on the way to a fusion reactor. These include development risks with regard to the tritium fuel (realisation of breeding processes, storage, retention, avoidance of radioactivity release, proliferation concerns) with regard to the reactor structure materials (extreme alternating thermal loads, neutron shielding, neutron activation, resulting radioactive waste, availability of critical resources) with regard to the economic boundary conditions (capital costs, repair requirements versus realistically achievable full load hours), with regard to many new reactor components (including breeding zones, ICF drivers etc.).

What does the physical progress achieved in expensive fusion reactor research actually tell us in view of the multiple challenges and development risks on the way to a reactor? Is the exuberant hope for fusion justified? Does it fit into the energy system of the future? Wouldn't it be the task of politicians and research funding organisations to ensure that clarifications are reached here independently of the fusion community?

How to cite: Liebert, W.: Fusion narratives, Third interdisciplinary research symposium on the safety of nuclear disposal practices, Berlin, Germany, 17–19 Sep 2025, safeND2025-163, https://doi.org/10.5194/safend2025-163, 2025.

Radioactive waste from fusion reactors is fundamentally different from that from fission systems, consisting primarily of tritium-containing waste forms and neutron-activated structural materials, with no high-level waste or transuranic elements. This presentation provides an overview of the applicability of national and international waste management frameworks to fusion-derived radioactive waste. It compares national and international regulatory approaches and standards with the German regulatory system and acceptance criteria for existing repositories. Emphasis is placed on the classification, interim storage and disposal pathways for low- and intermediate-level fusion waste. Based on some likely inventories and radiological characteristics, we present possible needs for fusion-specific adaptations to ensure consistency, safety and feasibility in future repository planning.

How to cite: Englert, M. and Kopp, A.: Nuclear Waste from Fusion Power Plants, Third interdisciplinary research symposium on the safety of nuclear disposal practices, Berlin, Germany, 17–19 Sep 2025, safeND2025-161, https://doi.org/10.5194/safend2025-161, 2025.

Since the Lawrence Livermore Laboratory’s National Ignition Lab’s supposed breakthrough in fusion energy utilization in December 2022, the promises of nuclear fusion as being a clean, cheap, reliable, and sustainable source of energy that can help mitigate climate change without the drawbacks of nuclear fission (i.e., most notably safety issues and highly active radioactive wastes), have been reiterated by media and policymakers alike (Wimmers et al. 2025). However, despite these claims, the establishment of nuclear fusion as an energy generation technology remains decades away as substantial technological challenges are yet to be overcome (Grünwald 2024). Historical institutional large-scale development projects like the ITER are being increasingly challenged by new entrants who, while each following different fusion reactor approaches, promise to have their first prototypes operational within the next decade (Wimmers et al. 2025). To determine whether these concepts might be feasible for commercialization in the coming years, a detailed assessment of their progress is necessary. Thus, this paper aims to analyze the techno-historic readiness levels of different reactor concepts based on the innovation chain proposed by Grubb (2004). We select several different new ventures, clustered by their varying technological approaches (albeit limiting the assessment to inertial and magnetic confinement fusion concepts), and determine their current development status on the innovation chain. We find that while most projects have moved on from the first stage, “Basic Research,” many remain several years away from reaching the critical level of “Demonstration,” in which a functioning device is shown to run reliably and consistently. In line with other literature (e.g., Takeda et al. (2023) or Lesch & (2024)), we conclude that currently projected development time frames of a few years until the provision of functioning prototypes is unrealistic and not to be expected from a techno-economic perspective. Moving along, potential funding should focus on a limited number of technologies so that future stages of commercialization and market diffusion that are, as of today, not to be expected in the coming decades, might be achievable in the future, and fusion avoids the “technology valley of death” (Grubb, Hourcade, and Neuhoff 2014).

References

Grubb, Michael. 2004. “Technology Innovation and Climate Change Policy: An Overview of Issues and Options.” Keio Economic Studies 41 (January):103–32.

Grubb, Michael, Jean-Charles Hourcade, and Karsten Neuhoff. 2014. Planetary Economics – Energy, Climate Change and the Three Domains of Sustainable Development. London, UK: Routledge.

Grünwald, Reinhard. 2024. “Auf dem Weg zu einem möglichen Kernfusionskraftwerk. Wissenslücken und Forschungsbedarfe aus Sicht der Technikfolgenabschätzung.” PDF. Büro für Technikfolgen-Abschätzung beim Deutschen Bundestag (TAB). https://doi.org/10.5445/IR/1000177720.

Kleidon, Axel, and Harald Lesch. 2024. “Kann Kernenergie zur Energiewende beitragen?: Zukünftige Energieversorgung in Deutschland.” Physik in unserer Zeit, July, piuz.202401718. https://doi.org/10.1002/piuz.202401718.

Takeda, Shutaro, Alexander Ryota Keeley, and Shunsuke Managi. 2023. “How Many Years Away Is Fusion Energy? A Review.” Journal of Fusion Energy 42 (1): 16, s10894-023-00361-z. https://doi.org/10.1007/s10894-023-00361-z.

Wimmers, Alexander, Fanny Böse, Alexander Buschner, Claudia Kemfert, Johanna Krauss, Julia Rechlitz, Björn Steigerwald, and Christian Von Hirschhausen. 2025. “Kommerzielle Energieerzeugung Mit Kernfusion Nicht Absehbar – Anwendungsforschung Entwickelt Sich Dynamisch.” DIW Wochenbericht 92:S. 195201. https://doi.org/10.18723/DIW_WB:2025-13-1.

How to cite: Wimmers, A., Dering, C., and von Hirschhausen, C.: Innovation Dynamics in Nuclear Fusion: A Unexpected Nuclear Renaissance in the Making?, Third interdisciplinary research symposium on the safety of nuclear disposal practices, Berlin, Germany, 17–19 Sep 2025, safeND2025-150, https://doi.org/10.5194/safend2025-150, 2025.