Critical remarks on the current TAB report on nuclear fusion
A study commissioned by the German Bundestag contains misleading and erroneous passages. We correct and classify statements.
On 9 January 2025, the Office of Technology Assessment at the German Bundestag (TAB) published a ‘TA-Kompakt-Studie’ (in German only) on nuclear fusion. The title: ‘Nuclear fusion: progress and challenges towards a possible power plant’.
The TAB report has caused consternation among scientists at the Max Planck Institute for Plasma Physics (IPP) because it contains errors, inaccuracies and inconsistencies. We would like to point out the following passages, which are either incorrect or could give a false impression:
- Page 15ff, Box 2.2: ‘PROTO is a prototype power plant following DEMO...’ it says. Later, the author writes about the steps ITER - DEMO - PROTO.
The fact is that PROTO has not been an issue for two decades. In the European roadmap, DEMO has long since represented the final step before the commercial power plant and has thus taken over the function of PROTO. This comment from us was sent to the Office of Technology Assessment prior to publication. The author merely added a clarification in footnote 11. The false impression remains in the main text that ITER needs two follow-up power plants to arrive at a commercial plant. - Page 26, 3.1.2: ‘In contrast, the neutrons produced during D-T fusion carry more than 100 million times more energy (14 MeV). The destructive effect on materials is correspondingly greater. This is usually expressed in dpa (displacements per atom), i.e. the number of impacts to which each atom in the solid body is exposed.’ This comparison is incorrect: A fission reactor can also have fast neutrons, in which case the energy is also in the MeV range. The dpa damage is similar for fission and fusion.
- Page 26, 3.1.2: ‘For DEMO, about 70 dpa can be expected over the lifetime of the facility (...). This leads to a significant change in the material properties (embrittlement, etc.).’ Correct: The 70 dpa only refer to the lifetime of the blanket (which can be replaced regularly) and not to the entire facility. For example, the vacuum vessel will only be exposed to approx. 3 dpa over the entire DEMO lifetime.
- Page 29, 3.1.3: This concerns the possible damage of high temperature superconductors (HTS) by neutrons: ‘It is known that these can already be degraded by much lower radiation damage (in the order of less than 10 dpa) than is to be expected in the plasma-near area of a power plant over its operating life (in the order of 100 dpa).’ Correct: The 100 dpa mentioned refer to the first wall. The coils are subjected to a load that is 100,000 to 1,000,000 times lower. Here, the blankets also fulfil the function of protecting the coils from the neutrons.
- Page 28ff, 3.1.3: In its discussion of HTS technology, the report does not mention the progress made by the US start-up Commonwealth Fusion Systems and the Chinese state project BEST (Burning Plasma Experimental Superconducting Tokamak). The use of HTS in these two new experiments guarantees the corresponding technology development.
- Page 36, Box 3.5: 'The European-Japanese JT-60 SA research project is currently the largest and most advanced tokamak in operation worldwide (until ITER is commissioned). In March 2021, a defect in the electrical insulation of the magnetic coils occurred during the start-up. (…) A similar incident, which would have to be repaired using robotic systems alone in the case of operation with tritium, could easily mean the commercial end for a power plant. The fact is that this was not an incident, but simply a design flaw that will not be repeated. The long repair time for JT-60 SA is due to the fact that a redesign was necessary.
Background: IPP received an advance version of the TAB report for the first time on 6 December 2024 – in connection with a media request from the Science Media Center (SMC). At that time, the report had already been accepted by the Bundestag Committee for Education, Research and Technology Assessment. The SMC forwarded our comments and corrections to the Office for Technology Assessment. The author only corrected one passage. For another, he added a footnote (see above).
Assessment by IPP Director Prof. Sibylle Günter
The Science Media Center also asked Prof. Dr. Sibylle Günter, Scientific Director of the Max Planck Institute for Plasma Physics, for an assessment in connection with the TAB report. We document the questions of the SMC and the answers of Prof. Günter here:
Question: At what point can we expect fusion power plants to start feeding net energy into the grid at the earliest? How can this time span be estimated and how large are the uncertainties?
Prof: Günter: ‘According to the European Union's roadmap, which our institute helped to develop, fusion energy should be available at the beginning of the second half of this century. The development is based on a phased plan in which smaller magnetic fusion plants will initially explore the material and physical principles for larger power plants. Milestones achieved, such as the energy record at the European tokamak JET, show the progress that has been made, although no magnetic fusion plant can currently achieve a positive energy balance – but this is the plan. ITER will be the first device to supply more energy than was supplied as heating energy, while its successor DEMO is to generate electricity for the grid. The development of a fusion power plant could be accelerated by doing more in parallel. With significantly higher funding and approval procedures tailored to fusion, a first power plant could go online as early as 20 years after the start of an ambitious programme.
And another comment on the Volumetric Neutron Source (VNS) discussed on page 38 of the TAB report: This refers to a small fusion device in which power plant-relevant components and their interaction can be tested and further developed. A VNS operated in parallel with the realisation of DEMO can be useful. We are currently discussing the topic. However, if a VNS were built before DEMO is realised, it could delay the use of nuclear fusion on the European roadmap by about 30 years.’
Question: According to the TAB report, fusion power plants cannot be easily integrated into an energy system dominated by renewable energies because they require power plants that can be quickly adjusted with low investment costs. Hydrogen production or heat applications could therefore be more suitable applications. To what extent do you agree? Where do you see potential for the use of fusion power plants?
Prof: Günter: ‘Fusion power plants can produce electricity, but they can also supply process heat for industry and provide energy for the production of synthetic fuels such as hydrogen. Furthermore, it is also conceivable, for example, to use the energy to capture CO2 from the air and to operate seawater desalination plants. We assume that these power plants will tend to run in continuous operation, so they are comparable to today's base load power plants.
Will power plants of this kind fit into a future energy system? To answer this question, we are working together with scientists who are competent in this field, for example with the Chair for Renewable and Sustainable Energy Systems at the Technical University of Munich. One result of the investigations: fusion power plants can interact very well and meaningfully with renewables in a future electricity market. Their output can be regulated as required. (1) If we assume that fusion power plants will both provide electricity when it is needed and produce chemical energy storage media such as hydrogen at other times, they will also fit well into a future energy system.
Furthermore, it is not possible to make a reliable prediction today about the energy situation in Germany or the world in the second half of the century. It's not just about electricity generation, but also about primary energy demand, three quarters of which is currently based on fossil sources in Germany and an even larger share worldwide. The forecast for energy demand is also uncertain. For example, technology companies are warning of the gigantic energy demand that will result from the use of artificial intelligence. And the war in Ukraine has just shown us how quickly energy policy certainties sometimes have to be abandoned.
So the question is: do we want to invest in fusion energy now, so that it will be available to us as a reliable energy source in the second half of the century, given the uncertain future of energy demand and supply?’
(1)
Larissa Breuning, Anđelka Kerekeš, Alexander von Müller, Julia Gawlick, Soner Candas, Hartmut Zohm, Thomas Hamacher:
Operational planning of magnetic confinement fusion power plants using a MIP unit-commitment model
In: Fusion Engineering and Design (submitted 2024) / 33rd Symposium on Fusion Technology (SOFT 2024)
Question: According to the TAB report, high-level radioactive waste can probably be avoided in fusion power plants, but the volume of lower-level radioactive waste is greater than in conventional nuclear power plants (p. 63). To what extent do you consider the waste produced by fusion reactors to be relevant and problematic?
Prof: Günter: ‘The radiation of fusion waste decreases significantly faster than that of highly radioactive waste from fission power plants. Scientists are researching materials for wall components that further reduce activation. Recycling technologies are needed that allow all activated components of a fusion reactor to be released after some time or reused in new power plants. It is currently assumed that recycling by remote handling could begin as early as one year after a fusion power plant is shut down. Unlike fission reactors, this should not require a final repository.’
Question: The report cites helium, beryllium and lithium as examples of resources needed for fusion energy that could be in short supply (p. 58). How do you assess their role? Are there any other resources that could become problematic if fusion power plants are widely deployed?
Prof: Günter: ‘In principle, we do not see any bottlenecks in the supply of lithium as a raw material. Fusion power plants will only require a small proportion of global production. Investment in technology development for the large-scale enrichment of lithium-6 from natural lithium is required.
Beryllium is currently the preferred material for the neutron multiplier in the breeding blanket. Should it be used in a large number of fusion power plants in the long term, increased use would have to be made of recycling methods. This is because only about 0.2 per cent of the beryllium is used in a blanket component during one year. (2) However, the fusion community has already recognised this problem and is working on alternative concepts that also use solid lead as a neutron multiplier (see, for example, (3)).
Helium is to be used as a coolant in the breeding blanket and in the superconductors. We do not expect a bottleneck for the first decades of fusion power plants. (4)
(2)
Bradshaw, A.; Hamacher, T.; Fischer, U. (2011):
Is nuclear fusion a sustainable energy form?
In: Fusion Engineering and Design 86
(3)
K. Jiang, Q. Wu, L. Chen, S. Liu (2023):
Conceptual design of solid-type PbxLiy eutectic alloy breeding blanket for CFETR
In: Nuclear Fusion 63.
(4)
Danilo Nicola Dongiovanni, Y. Melese, F. Gracceva, C. Bustreo, Alexander von Müller:
On the impact of nuclear fusion power plants deployment on selected critical materials consumption
In: Energy Strategy Reviews (submitted 2024)
Disclaimer: Prof. Dr. Klinger, Director at the Max Planck Institute for Plasma Physics in Greifswald, is named in the TAB report as one of the twelve experts who were available to the author for interviews. Apart from this interview, Prof. Klinger did not contribute to the preparation of the report.