Response From Pietro Barabaschi, Director-General of ITER

May 2, 2023

Dear Mr. Krivit,

Thank you for your message. As I have noted already previously since I became ITER-DG in October 2022, I fully agree with you when you say that accuracy is important in scientific communication. This can be particularly challenging when communicating complex science and engineering in a simplified way to public audiences, including to journalists. At ITER, we are making it a priority to improve this accuracy.

Regarding the article you cite by the Australian Broadcasting Company (ABC),  the original interview was conducted in May 2022, in the form of a podcast; and the print article that came out in March 2023 excerpted some elements from that podcast, adding to the inaccuracies on several points:

1. It is frequently said that ITER and other fusion devices will recreate the fusion power that exists at the centre of the sun and stars. That is not strictly accurate: while ITER will seek to operate at very high temperatures (~150 million decrees, i.e. even hotter than in the sun’s core) , it will not be able to recreate the extreme density conditions (present in the sun due to its gravitational force) that enable proton-proton fusion at the sun’s core. Rather, fusion scientists and engineers seek to mimic the sun by using other atoms which are “easier” to fuse: in the case of ITER, the goal is to fuse deuterium (D) and tritium (T), two isotopes of hydrogen, using magnetic confinement of plasma at high temperatures but at densities which are achievable. Additionally, DT reactions will yield to a power density which is more amenable for power generation.
2. The ten-fold return on energy that is part of the ITER design – often referred to as Q>=10 – refers explicitly to the ratio of thermal energy output from the fusion reaction, contrasted to the thermal energy used to heat the plasma. This “ten-fold return”, which hence applies to the plasma part of ITER, is frequently misinterpreted, and since I joined we are working on additional measures to ensure clarity in our public communication. We also need to emphasize repeatedly that ITER, as an experimental device, will not produce electricity.
3. When we assert that fusion will not produce long-lived radioactive waste, we should be careful to characterize that as a goal, not a certainty; because we are still working to develop the materials that can sustain the extraordinary neutron flux that will impact the first wall (plasma-facing wall) of a tokamak.
4. When we speak about fusion power plants producing continuous energy, that is also a goal, especially for tokamaks. ITER’s design envisions 400-second pulses, and a steady-state Q of 5, but this goal has yet to be realized. Stellarator designs are better at achieving steady-state output, but are more difficult to build than tokamaks.
5. Lastly, I confirm that you are correct that ITER will install tritium-breeding blankets on only a small fraction of the tokamak walls. The goal for future tokamaks will be a closed fuel cycle (one tritium atom produced for one tritium atom consumed in the plasma), but this is not the goal of ITER. ITER is designed to breed tritium only on a small demonstration scale.

We will communicate these points to our ABC contacts for their consideration. We will also continue to work with our ITER team, especially with those who communicate with public audiences and journalists, to achieve greater accuracy.

The technical challenges that remain for magnetic confinement fusion to be feasible are well-known within the fusion community. Many experts are working to solve those challenges, both at ITER and in fusion projects around the world. If we can overcome those challenges, fusion energy will contribute for the future of our society.

There is no need to oversell that promise, nor to minimize the challenges that we are all committed to solve.

With kind regards,

Pietro

May 2, 2023

Dear Dr. Barabaschi,

Thank you for your letter. Your five bullet points go a long way toward communicating the objectives of the ITER project accurately. As one of your organization’s most prolific critics, I applaud your effort.

I have only one minor quibble. The goal for future tokamaks is not to produce one tritium atom for each tritium atom consumed in the plasma. That would be a tritium breeding ratio (TBR) of 1.0. Full-scale tritium breeding is not part of the ITER, but communicating this technical aspect more precisely to the public would be useful.

A fusion reactor must produce tritium at a higher rate than it consumes tritium in order to compensate for inefficiencies and downtime – that is, to be self-sufficient. Fischer et al. determined that a TBR of at least 1.05 is needed for the EU DEMO reactor to attain self-sufficiency.

However, Abdou et al. explained that an “analysis of current worldwide first wall/blanket concepts shows that achievable TBR for the most detailed blanket system designs available is no more than 1.15.” This is an extremely thin margin – so thin that these authors (one is an ITER Organization scientist) wrote that “a primary conclusion is that the physics and technology state-of-the-art will not enable [the EU] DEMO and future power plants to satisfy these principal requirements.”

I wish you success with your project.

Steven