Fusion narratives

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?