Will Fusion Fizzle?

Following up on our previous post.

As is always the case with technologies that are still on the horizon, reasonable estimates of timelines and economics vary widely with fusion power. Unfortunately, the dominant voices in the discussion—the people journalists are most eager to cite and treat as authoritative—are some of the least trustworthy people you'll find, operating under some of the largest conflicts of interest imaginable. Pitchmen vying for billions of dollars in venture capital are treated as reliable and independent experts on the subject, telling their stories to journalists who never saw a gee-whiz, the-future-is-now story that they didn't rush to print. Take Hellion which basically pulled an operational date of 2028 out of its ass. In case you're curious, orifice-derived estimates will get you around $1.5 billion in today's market.

On top of that, we need to remember that the push for fusion startups is tied in with a highly representative example of the techno-optimist narrative, right down to the shaky economics and the tendency to substitute a fascination with postwar pulp sci-fi for actual engineering and economic analysis.

In terms of the engineering, if you look at experts not on the payroll of these companies and independent of the larger AI/robotics bubble, you'll find few who predict viable fusion reactors five years from now and many who think we are looking at 20 or 30 years in the future.

In terms of the economics, it is far from certain that fusion power will be cheaper than fission—remember, the majority of the cost of nuclear power today is on the operating side, not the fuel—and based on most estimates, it is likely to be more expensive than renewables such as solar and wind. This isn't to say the technology isn't promising and worth pursuing, but the stories we are being told about it are largely fantastic, and the surge of VC capital flowing into the sector makes no sense.

There is one more factor to take into account. The most powerful men in tech—Musk, Altman, Zuckerberg, et al.—are currently sitting on top of a multitrillion-dollar AI bubble that requires ever-increasing data center construction. According to some analysts, we are building far more capacity than we need, but if growth levels off, it threatens to deflate the entire bouncy house. One of the consequences of this unprecedented infrastructure expenditure has been a tremendous strain on our power grid and a huge surge in greenhouse gas emissions. Promising that a still-nonexistent technology will emerge in the next five or six years to solve the problem is extremely convenient for these people. It is also right on brand.

From "Notes on the Recent Hype about Imminence of Commercial Fusion Energy"

by John P. Holdren (who is kind of a big deal in the field) of the Belfer Center for Science and International Affairs

Originally published in June 2024 and updated in January 2026.

The best performances in fusion experiments to date—both in a tokamak and in the NIF―have been achieved using the deuterium-tritium (D-T) reaction. Getting a true energy gain from this reaction—more fusion energy out than the energy input to the system―is inherently much easier than achieving that with any other known fusion reaction; but it is nonetheless so difficult that nearly seventy years of research on controlled fusion worldwide, at a cost of many tens of billions of dollars, have not yet led to reaching this threshold of so-called “scientific feasibility.”

As I will explain, working with tritium poses big challenges for reactor design, for maintenance, for worker safety, and for public radiation exposures, but the difficulty of achieving even bare energy breakeven with any fusion reaction other than D-T is so great that most fusion scientists believe that success with reactions that avoid tritium will come much later if it comes at all. In what follows, I first address the challenges in making a practical magnetic-confinement fusion reactor using the D-T reaction, then the even bigger challenges of doing so with a laser-driven system using D-T....Bombardment by the 14-MeV neutrons produced by D-T fusion weakens most structural materials in short order, as well as turning steel, molybdenum, titanium, and most other metals intensely radioactive. The first problem could require frequent replacement of structural components exposed to fusion neutrons (quite possibly so frequent as to make the whole operation uneconomic) and the second problem greatly complicates all maintenance around the reactor innards (further threatening economic viability). How many of the today’s fusion optimists have thought about the stresses that operating continuously will impose on equipment working at the boundaries of conditions that today can be tolerated only briefly…or about how this challenge could be surmounted? Tritium—the radioactive isotope of hydrogen—is almost nonexistent in nature. It is produced for today’s uses by neutron bombardment of lithium inserts in fission reactors. The large quantities needed for D-T fusion-reactor operation would need to be “bred” in the reactor by bombardment of lithium in the reactor blanket by the 14-MeV neutrons. Tritium’s radiation is less penetrating than that of the main activation products of concern, but as an isotope of hydrogen it is comparably volatile, and the quantities stored and flowing in and around a D-T fusion reactor would represent a significant additional radiological hazard. The degree of tritium control needed to stay within current guidelines for public radiation exposure at a nuclear plant boundary would be extremely challenging to achieve in a tritium system as complex as that in a fusion reactor. The significant environmental/safety issues posed by tritium and activation products (which, by the way, will likely require long-term management as radioactive waste) have been ignored by practically all of the recent commentators, most of whom insist in passing that fusion is "clean."... But the factors by which the repetition rate and pellet cost in the NIF fall short of what would be required in a reactor are far larger. Today, with a large crew of highly trained specialists in full-time attendance, the NIF is lucky if it can get off two shots per day. A practical laser fusion reactor would require something like ten shots per second. As for the cost of the pellets that the laser beams irradiate, when last I looked they cost in the range of $10,000 each. For a practical fusion reactor, that cost would need to be no more than a few cents apiece. The enormous challenges posed by the use of tritium in magnetic-fusion reactors would not be less, and might be even larger, for inertial-confinement reactors. I think it’s fair to say that the scientific and technological problems that must be solved on the road to a practical fusion reactor—beyond energy breakeven in sustained operation—are not much easier than the breakeven problem itself, which is still unsolved after 70 years of costly international effort. Furthermore, there is no guarantee that, if all the technical challenges for either the magnetic or the inertial-confinement approach could be surmounted, the result would be economically competitive with other relatively clean energy options available in the same timeframe. The frequently heard claims about fusion being “cheap” take no account of the cost of building the reactor itself. The raw fuel for fusion would be cheap, as it is for fission reactors today. But the cost of the energy from fission is dominated by the cost of building and maintaining the reactor and associated facilities, not by fuel cost, and the same will be true of fusion. The studies of the likely economics of hypothetical fusion reactors in which I’ve been involved all indicated that it will be a great challenge to make electricity from fusion less expensive that that from fission. ... Nobody has a clear crystal ball when it comes to the characteristics of future technologies, and I am further handicapped by not having followed fusion science and technology particularly closely since leaving the White House in January 2017. Still, if I were a betting person and if I expected to be alive to collect, I’d bet we won’t see a successful commercial fusion reactor before 2050.