Nuclear fusion may be closer to commercialization than previously thought, with private firms targeting operational reactors in the early 2030s. Major technical and economic hurdles remain, including net energy gain, plasma stability, materials durability, and fuel supply. Back in the last century, smart alecks said that commercial fusion would always be 50 years in the future. Now, energy consultant Wood Mackenzie has taken to discussing developments in nuclear fusion as if they might not be far off. A big change in view, considering that even recently, experts figured that harnessing nuclear fusion for commercial purposes was at least fifteen years away. In fact, the best-known international fusion effort, the ITER project based in France, projects an in-service date for its fusion reactor in the early 2040s (fifteen years from now). However, the three fusion development firms mentioned in the Wood Mackenzie report promised a working, commercially viable fusion reactor, or prototype, within five years. That's 2031 or 2032. This means they will be competing head-to-head with the first generation of new, small modular reactors (SMRs). The principal engineering challenge stems from the fact that a fusion reaction occurs at temperatures of about 100 million degrees Celsius (about ten times hotter than the center of the sun). First, the energy inputs are enormous. The ITER tokamak reactor, for example, is estimated to require about 100 MW of generation to power its systems. That's why there's a concern with net energy gain. Or stated differently, can the reactor produce more energy than it consumes? A bare minimum requirement for any technology to be considered commercial. Second is the challenge of maintaining a so-called stable plasma confinement. Not so easy with gases heated to 100 million degrees operating temperatures. The reactor's plasma consists of superheated gases (deuterium and tritium) whose nuclei collide and release large amounts of energy. Any sudden cooling of the plasma (from contact with the tokamak walls, for example) causes the chain reaction to stop, and reactor run times are currently measured in seconds. And third, there is the challenge of developing reactor materials that can avoid embrittlement due to the constant, intense neutron radiation, an issue they share with conventional atomic reactors. Tritium (H 3 ) supply, though, should not be taken for granted. Tritium is rarely encountered in nature here on earth and is generally produced as a by-product of nuclear reactions, in a limited number of facilities, some of which are scheduled to close down. Deuterium (H 2 ) is more abundant and can be extracted from water. Three US companies have made aggressive statements with respect to their progress in commercializing fusion technology. Commonwealth Fusion Systems, based in Boston (MIT connections), made two claims: that they will have a "commercially relevant" fusion plant online next year and a 400 MW grid-scale fusion plant in Chesterfield County, Virginia by the early 2030s. Commonwealth is designing a tokamak. Inertia Enterprises, which emerged mainly from the Lawrence Livermore National Laboratory in California, has asserted that its cost to produce electricity will be competitive with the lowest cost fossil generation and that it will break ground on a grid-scale fusion project by 2030. If the first claim about price is even remotely close to being true, then the company's proposed laser-based, fusion reactors will absolutely destroy prospective SMRs on a price basis. In a related note, Inertia raised $450 million in financing in February. Lastly comes Helion, which is partnered with Microsoft, and claims that it will deploy a fusion plant in 2028. From the perspective of SMRs, these announcements regarding fusion could not have come at a worse time. No one in a commodity-based business looks forward to a lower-cost competitor. But there are still four variables that could accelerate or slow progress in the field. The first is access to capital to finance these new facilities. The US federal government supports the fusion industry via ARPA-E grants of about $140 million this year. In China, the comparable annual figure is estimated to be about $3 billion. (However, much US fusion research is still privately financed.) Second is the ultimate cost and capital expenditure involved with these new facilities. Can they be built on time and within budget? And who cares what the first units cost if the Nth units are much cheaper. Good supply chains and long-term financial commitments are important here. Third are the technology assumptions, and which designs will be commercialized and most likely to be adopted as part of a large fleet? Lastly, fusion reactors have a much lower emissions profile than conventional nuclear reactors, which produce highly radioactive waste necessitating complex, long-lived storage plans. Fusion reactors emit non-toxic helium gas, although the reactor componen