A history of fusion research and development Part 3

Matteo Barbarino, a Nuclear Plasma Fusion Specialist from the International Atomic Energy Agency (IAEA) highlights key papers from the IAEA Fusion Energy Conference (FEC) 2018

This five-part article series, that opened with the first article and continued with the second article, presents and places into historical context a selection of leading papers from the 27th International Atomic Energy Agency (IAEA) Fusion Energy Conference (FEC), which took place in 2018 in India. These papers were highlighted by the conference’s programme committee as they present important advancements from the world’s leading fusion research facilities.

International collaboration and exchange are central ingredients of the FEC and having a paper selected by the programme committee is very prestigious.

The 28th Fusion Energy Conference (FEC 2020) will take place in Nice, France, next year. Meanwhile, let’s glance through some of the core papers from the FEC 2018 and learn about how they relate to historic developments in fusion energy research. 

Progress of JT-60SA Project (OV/3-1)

 The EU and Japan are jointly building a powerful tokamak called

JT-60SA in Naka, Japan, as a complement to ITER on a partnership called the Broader Approach Activities. JT-60SA was partially developed on the previous infrastructure of JT-60U, and it is designed to support ITER in the key areas of fusion plasma development necessary to decide construction design and plasma control schemes for DEMO – the demonstration fusion power reactor that will represent the final step before the construction of a commercial fusion power plant.

This paper highlighted the recent progress of the manufacturing and assembly of the JT-60SA with first experiments scheduled for September 2020. 

In 1996, the IAEA “Conference on Plasma Physics and Controlled Nuclear Fusion Research” changed its title to “Fusion Energy Conference”. This change was highlighted by the highest fusion triple product of any device to date achieved in JT-60U, which symbolized the state of readiness on the path to prototype fusion reactors. These results, obtained with D-D fuel, would have been equivalent to breakeven with a 50-50 mix of D and T:

USHIGUSA, K., JT-60 TEAM, “Steady state operation research in JT-60U”, Fusion Energy Conference (Proc. 16th Int. Conf. Montreal, 1996, Paper No. CN-64/O1-3) IAEA, Vienna (1997) 37.

Progress of the CFETR Design (OV/3-2)

As the next-step device in the roadmap for the realization of fusion energy in China, China Fusion Engineering Test Reactor (CFETR) proposes to breed its own necessary Tritium, generate steady-state burning plasmas, and ultimately produce 200–1000 MW of fusion power.

In future fusion power plants, the high-energy neutrons generated from the Deuterium-Tritium (D-T) fusion reactions will be absorbed in blankets surrounding the core for the ultimate goals of fuelling the reactor (by interacting with Lithium and breeding the necessary Tritium) and producing electricity (by capturing their energy and producing steam). If insufficient Tritium is produced, some supplementary source must be employed, creating additional difficulties such as handling, storage and transport.

This paper presented the engineering design of CFETR and the on-going R&D activities.

CFETR activities were unveiled at the FEC 2016:

WAN, Y.X., et al., “Overview of the present progress and activities on the CFETR”, Fusion Energy Conference (Conf. Material 26th Int. Conf. Kyoto, 2016, Paper No. CN-234/OV/3-4) IAEA, Vienna (2017) 140. 

Overview of the Validation Activities of IFMIF/EVEDA: LIPAc, the Linear IFMIF Prototype Accelerator and LiFus6, the Lithium Corrosion Induced Facility (OV/3-3)

 Although the energy of the neutrons produced from D-T reactions is crucial for the ultimate goals of fuelling the reactor and producing electricity, these highly energetic neutrons also carry the potential to cause material defects and transmutation, which brings into consideration other aspects such as radiation damage, biological shielding, remote handling and safety.

For future fusion power plants components, it is indispensable to develop a material that is strong at high temperatures and does not degrade to the point where it could be overheated and fail under operational conditions. Therefore, an International Fusion Materials Irradiation Facility (IFMIF) that operates in parallel with ITER will be critical for testing and selecting those materials that can withstand the extreme conditions produced by high-energy fusion neutrons.

The mission of the Engineering Validation and Engineering Design Activities for the IFMIF (IFMIF/EVEDA) project – which is part of the Broader Approach Activities jointly conducted by EU and Japan – is to provide the detailed engineering design of the IFMIF plant and to validate the technological challenges on an accelerator-based neutron source to generate a D-T fusion reactor relevant neutron flux for fusion material development and testing.

This paper presented the latest results of the validation activities of the IFMIF/EVEDA project.

The Broader Approach Agreement was signed jointly by Europe and Japan in 2007, and first IFMIF engineering studies were presented at the FEC 2008:

GARIN, P., SUGIMOTO, M., “The IFMIF/EVEDA Project: Outcome of the firs engineering studies”, Fusion Energy Conference (Proc. 22nd Int. Conf. Geneva, 2008, Paper No. CN-165/FT/1-2) IAEA, Vienna (2009).

The Strategy of Fusion DEMO In-Vessel Structural Material Development (OV/3-4)

D-T fusion is the easiest to achieve because the reaction rate peaks at a lower temperature and at a higher value than other reactions. However, the energy of the fusion-generated neutrons presents significant challenges regarding structural materials of the fusion reactor vacuum vessel.

Future fusion power plant will need to operate within limited parameters outside which sudden losses of energy confinement (disruptions) can occur, causing major thermal and mechanical stresses to the structure and walls. Therefore, some of the most significant technical challenges are to develop and qualify materials for a fusion DEMO reactor vessel, and the lack of facilities where materials can be tested under D-T fusion in-vessel conditions is a real drawback.

Currently, scientists and engineers use the knowledge and data acquired by fission neutron irradiation and various simulation irradiation experiments to develop and verify a framework of DEMO reactor design criteria for in-vessel components. 

This paper highlighted the design methodology based on probabilistic approaches for in-vessel structural material development toward a fusion DEMO reactor.

Featuring ‘Reactor Systems’ for the very first time, Session K at the FEC 1971 brought the attention to the challenges associated with structural material development: Plasma Physics and Controlled Nuclear Fusion Research (Proc. 4th Int. Conf. Madison, 1971, Session K) IAEA, Vienna (1971) 315–487.