13 ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 The U.S. target for energy transition to non-carbon emitting power sources by 2050 has sparked the formation of commercial ventures to develop fusion energy as a potential source of baseload power. Utility executives working with the National Academies of Science, Engineering, and Mathematics (NASEM) committee wrote a report entitled “Bringing Fusion to the U.S. Grid,” and indicated that there is a window for fusion energy to help with plant replacements in the 2050 timeframe[1]. At the same time, researchers have recently demonstrated significant improvements in key technologies for fusion such as high temperature superconducting (HTS) magnets. Improvements in the magnets have been projected to allow a 50× reduction in the volume of a fusion reactor. This would make fusion vessels more compact than the ITER project, an international collaboration to demonstrate key magnetic confinement fusion energy (MFE) technologies[2,3]. In addition, inertial confinement fusion energy (IFE) has become more pro- mising due to recent experiments at the National Ignition Facility (NIF) that achieved a target gain (fusion out / laser in) greater than 1[4]. OPPORTUNITIES AND CHALLENGES The commercial opportunity for fusion in the 2050s as well as the advances in fusion technologies have generated significant interest from private investors. Private investment in the fusion industry is now over $6 billion and companies are already starting to build pre-pilot plant testing facilities to demonstrate different aspects of their fusion technologies[4]. Private investors are taking a portfolio approach to fusion investments and are funding a variety of different fusion energy technologies including multiple MFE concepts (tokamaks, stellarators, axis-symmetric mirrors, Z-pinches), multiple IFE concepts in terms of driver and target types (laser indirect drive, laser direct drive, laser fast ignition, pulsed power, shock-driven), as well as hybrid concepts between MFE and IFE such as MagLIF. Most of the companies have aggressive timelines to get to a fusion pilot plant (FPP) by the mid 2030s[4]. The U.S. Department of Energy (DOE) has recently announced a fixedprice milestone payment program based on the NASA Commercial Orbital Transportation Services (COTS) program to help encourage commercial space flight, which included companies such as SpaceX. The goal of the DOE Milestone-Based Fusion Development Program is to create public-private partnerships to support fusion energy commercialization[5]. The Milestone Program will support companies as they solve the technical challenges on the way to commercializing fusion and will support collaborations with universities and national labs. Technology advancements in several materials science topics are needed in to achieve economic viability of fusion. Many of the reviews on materials science for fusion focus on plasma-facing materials and structural materials for a fusion device that can withstand the high temperatures and withstand high fluxes of displacive damage from 14 MeV neutrons in a D-T device[6-9]. This is still a very important area of research, but as the challenge for fusion has expanded to designing and constructing an entire FPP, the materials science challenges also increase in the areas needed to create an entire support system for the fusion device such as the breeding blanket, fuel cycle, target synthesis, power cycle, and remote maintenance. Each of these parts of an FPP will have unique challenges that will require novel solutions in reduced activation alloys, materials durability in molten metals or molten halides, low-defect and high throughput polymer target synthesis, tritium effects on materials, welding and joining, adsorbents, catalysis, and many other areas. This article provides an overview of the materials science and technology challenges that will need to be addressed in the process of getting to an FPP with a focus on the mechanically “soft” materials such as polymers that will serve functional needs in a fusion pilot plant. There are excellent recent high-level reviews on fusion materials research that are focused on first wall materials and structural materials that experience high temperatures and high amounts of radiation[10], but there are many polymeric materials that will be critical to enable fusion energy that Fig. 1 — Experimentally inferred Lawson parameters for fusion experiments. Reproduced from Ref. 15.
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