First Walls and Breeder Blankets: IDTechEx Explores Materials for Fusion
Author: Noah El Alami, Technology Analyst, IDTechEx
Fusion energy has long been cited as an energy source of the future, yet for a long time has seemed like a far-off prospect. However, recent advances in the science and engineering of fusion have now brought commercial maturity to a near horizon, with over 50 startups involved in the commercial fusion industry and plans for pilot plants within the next decade. The different technologies and leading startups in the fusion industry are covered extensively in IDTechEx’s new report, “Fusion Energy Market 2025-2045: Technologies, Players, Timelines”.
Scaling fusion up from lab projects to energy-producing power plants will be an immense engineering challenge, with a large bill of materials and many specialized components required. This article will focus on two of the most crucial and technically challenging materials in a fusion power plant: the plasma facing (or ‘first wall’) materials and the lithium-rich breeder blankets.
Designs for fusion power plants face a staggering bill of specialized materials, some of which require a significant scale-up from the quantities produced today. Image source: IDTechEx.
The first wall problem
As the closest surface to the plasma of fusion fuel, which can exceed 100 million degrees Celsius in normal operational conditions, plasma facing materials (PFMs) are exposed to the most extreme conditions in a fusion device. These conditions include extreme heat loads and electromagnetic forces, high fluxes of neutron irradiation, and collisions with other high-energy particles ejected from the plasma. PFMs have multiple and sometimes contradictory requirements, leading to what is known as the “first wall problem”.
PFMs, also known as first wall materials, need to endure these harsh conditions with minimal wear over time to both reduce the maintenance amount and avoid contaminating the sensitive fusion plasma. At the same time, PFMs must also have low neutron activation and hydrogen retention to minimize the buildup of radioactive material in the fusion chamber.
A range of materials have been explored as PFMs, but the most popular choice is currently in tungsten-based materials. Tungsten has a high melting point, high thermal conductivity, and a low sputtering yield. However, its high atomic mass makes the atoms that get sputtered into the plasma very damaging to its performance. Therefore, the development of tungsten alloys, composites, and coatings is an active area of research and development to create the ideal PFM.
Currently, China alone is responsible for around 80% of annual tungsten production, with global use in mining equipment, automotive parts, robotics, solar panels, and significant use in defense. Chinese tungsten exports are starting to face controls and restrictions due to their dual-use nature for both civilian and military applications. As the ‘space race’ for fusion heats up, the supply of tungsten could be one area where China has a powerful bargaining chip.
The need for breeder blankets and lithium use in fusion
The most common choice of fuel for a fusion reactor is deuterium and tritium, two isotopes of hydrogen which have the lowest energy barrier to fusion of any combination. However, with a short half-life of ~12 years, tritium is extremely scarce, with only a few fission reactors producing tritium as a byproduct, which supplies less than 50kg of estimated global reserves.
Tucked just behind the first wall of a fusion reactor is the neutron-absorbing ‘breeder blanket’. The purpose of this material is not only to absorb the high-energy neutrons released during fusion, which could otherwise cause damage to the surrounding equipment and environment, but also to breed tritium. A high-energy neutron incident on a lithium atom can split it into tritium and helium, regenerating the tritium fuel used to initiate the fusion reaction.
However, not all lithium is created equal. The isotope lithium-6, which has an abundance of only ~7.5% in natural lithium, is far more efficient at producing tritium, and so many fusion plant designs seek to enrich the lithium-6 content for their breeder blankets. The process used conventionally for separating lithium isotopes requires large volumes of mercury, and this refinement further increases the raw lithium demand.
Therefore, the challenge for the fusion industry is to not only finalize and prove the effectiveness of breeder blankets but also to develop a safe and stable supply chain for lithium and its refinement. In the short term, the greatest challenge will be demonstrating the effectiveness of breeder blanket designs for a circular tritium economy, while in the long run, fusion plants deployed at scale could represent a lithium demand on the same order of magnitude as lithium battery and electric vehicle markets.
A fusion of interests in an age of uncertainty
The rapidly growing commercial fusion market faces a host of technical challenges and materials opportunities. Some critical raw materials for fusion, such as tungsten and lithium, will also be subject to geopolitical challenges in their supply and competition from other industries in their demand. Meanwhile, other materials such as reduced-activation ferritic-martensitic (RAFM) steel, mercury, and superconducting tapes will be required in industrial quantities rarely seen today.
Therefore, collaboration between fusion players and public-private partnerships to help fusion startups build supply chains and ecosystems is now more important than ever. International projects such as ITER have already made strides in advancing fusion technology development and building the precursors of supply chains.
The challenge of sourcing and processing materials and components for fusion is now arguably greater than any obstacle in plasma physics or engineering. Identifying and acting on these supply chain constraints now will be key to securing sufficient resources by the time fusion is ready to scale. IDTechEx’s “Fusion Energy Market 2025-2045: Technologies, Players, Timelines” report features detailed timelines for the fusion market, with a dedicated chapter to materials opportunities in fusion and key components for the industry.
For more information on this report, including downloadable sample pages, please visit www.IDTechEx.com/Fusion, or for the full portfolio of energy-related research available from IDTechEx, see www.IDTechEx.com/Research/Energy
