The SPARC Fusion Reactor

There’s a lot of excitement about a new approach to fusion power:

• Henry Fountain, Compact nuclear fusion reactor is ‘very likely to work,’ studies suggest, The New York Times, 29 September 2020.

Scientists developing a compact version of a nuclear fusion reactor have shown in a series of research papers that it should work, renewing hopes that the long-elusive goal of mimicking the way the sun produces energy might be achieved and eventually contribute to the fight against climate change.

Construction of a reactor, called SPARC, which is being developed by researchers at the Massachusetts Institute of Technology and a spinoff company, Commonwealth Fusion Systems, is expected to begin next spring and take three or four years, the researchers and company officials said.

Although many significant challenges remain, the company said construction would be followed by testing and, if successful, building of a power plant that could use fusion energy to generate electricity, beginning in the next decade.

This ambitious timetable is far faster than that of the world’s largest fusion-power project, a multinational effort in Southern France called ITER, for International Thermonuclear Experimental Reactor. That reactor has been under construction since 2013 and, although it is not designed to generate electricity, is expected to produce a fusion reaction by 2035.

But fusion has been twenty years off since the 1950s. What’s the evidence that Sparc will work? I guess most of the evidence is here—a series of seven papers, which luckily are available open-access:

Status of the SPARC physics basics, Journal of Plasma Physics 86 (2020).

I have not read these! And even if I did, since I’m not an expert on fusion reactors—obviously a tricky subject—I’m not sure how much my impression would help.

Do you know any commentary on SPARC from other experts on fusion reactors? The more detailed, the better. All I’ve seen so far are very sketchy remarks from people who don’t seem to know what they’re talking about.

17 Responses to The SPARC Fusion Reactor

  1. Keith Harbaugh says:

    Is the ITER project taking so incredibly long because of funding constraints, or some other reason? Is there a good source for the answer? Thanks.

    • John Baez says:

      Here’s a story written in 2017:

      • Henry Fountain, A dream of clean energy at a very high price, The New York Times, 27 March 2017.

      A quote:

      First discussed in 1985 at a United States-Soviet Union summit, the multinational effort, in which the European Union has a 45 percent stake and the United States, Russia, China and three other partners 9 percent each, has long been cited as a crucial step toward a future of near-limitless electric power.

      ITER will produce heat, not electricity. But if it works — if it produces more energy than it consumes, which smaller fusion experiments so far have not been able to do — it could lead to plants that generate electricity without the climate-affecting carbon emissions of fossil-fuel plants or most of the hazards of existing nuclear reactors that split atoms rather than join them.

      Success, however, has always seemed just a few decades away for ITER. The project has progressed in fits and starts for years, plagued by design and management problems that have led to long delays and ballooning costs.

      ITER is moving ahead now, with a director-general, Bernard Bigot, who took over two years ago after an independent analysis that was highly critical of the project. Dr. Bigot, who previously ran France’s atomic energy agency, has earned high marks for resolving management problems and developing a realistic schedule based more on physics and engineering and less on politics.

      “I do believe we are moving at full speed and maybe accelerating,” Dr. Bigot said in an interview.


      “Fusion is very hard,” said Riccardo Betti, a researcher at the University of Rochester who has followed the ITER project for years. “Plasma is not your friend. It tries to do everything it can to really displease you.”

      Fusion is also very expensive. ITER estimates the cost of design and construction at about 20 billion euros (currently about $22 billion). But the actual cost of components may be higher in some of the participating countries, like the United States, because of high labor costs. The eventual total United States contribution, which includes an enormous central electromagnet capable, it is said, of lifting an aircraft carrier, has been estimated at about $4 billion.

      Despite the recent progress there are still plenty of doubts about ITER, especially in the United States, which left the project for five years at the turn of the century and where funding through the Energy Department has long been a political football.

      The department confirmed its support for ITER in a report last year and Congress approved $115 million for it. It is unclear, though, how the project will fare in the Trump administration, which has proposed a cut of roughly 20 percent to the department’s Office of Science, which funds basic research including ITER. (The department also funds another long-troubled fusion project, which uses lasers, at Lawrence Livermore National Laboratory in California.)

      Dr. Bigot met with the new energy secretary, Rick Perry, last week in Washington, and said he found Mr. Perry “very open to listening” about ITER and its long-term goals. “But he has to make some short-term choices” with his budget, Dr. Bigot said.

      I don’t know what’s happened since 2017.

  2. Robert Smart says:

    Another promising idea:

  3. Wyrd Smythe says:

    As a vaguely related aside, I was watching a series of interview clips the other day, and I believe it was the great Roger Penrose who commented that, while mathematicians usually move towards elegance, simplicity, and symmetry, fusion physicists shun it because an elegant, simple, symmetrical solution is guaranteed to be wrong. Fusion physics, apparently, is messy, complex, and intricate.

    Which, perhaps, is why it’s been “about 20 years away” for over 50 years. :)

  4. Anonymous says:

    I am not familiar with the SPARC approach or the MCF side of the fusion research; however, direction of the energy sector is increasingly clear with the current rise of renewables (LCoE of PV and wind @ ~$20/MWh, with PV learning curve aiming for ~$10/MWh in 2030s). In fact, it is likely that any thermal cycle power plant will find it extremely hard (if not impossible) to compete with renewables based on the capital expenditures on the turbine side itself with zero capital spent on the steam production side.

    In terms of ancillary services such as grid balancing or voltage/frequency control these can be solved much more cheaply via grid integration and demand-side measures (ERCOT in Texas already has some interesting demand-side measures) – this is documented by the research into smarter regulation and introduction of smart meters.

    • John Baez says:

      In terms of ancillary services such as grid balancing or voltage/frequency control these can be solved much more cheaply via grid integration and demand-side measures (ERCOT in Texas already has some interesting demand-side measures) – this is documented by the research into smarter regulation and introduction of smart meters.

      People who claim wind and solar aren’t enough often say the intermittent nature of these power sources requires us to keep nuclear power or other “on-demand” sources of power. Are you saying that can be minimized—or eliminated entirely?

      • Anonymous says:

        ‘Intermittent’ is not the right word (albeit commonly used by parties with vested interests in fossil conventional generation) – it is preferable to call these variable resources. Nowadays it is commonly more difficult to predict the energy demand than the energy supply from a PV solar panel.

        On the contrary, conventional generation such as CCGT / coal / nuclear power plants are intermittent in the sense that they can fail (and are indeed not generating about ~10% of the year due to maintenance / technical issues). Recent blackouts in California were blamed on the renewable supply – what should be noted is that California has overbuilt CCGT generation and much of the blackout was actually caused by two CCGT power stations turning off. PV rarely encounters technical issues that lead to sudden generation loss – the predictability of power from PV panels is actually astoundingly good. There are also renewable energy approaches that can store energy longer-term (thermal solar, hydro) – economics of these in the US are a different discussion.

        In terms of supply-demand matching conventional generation can only react in a matter ~15 minutes to any supply shortage. Increase in electromobility will lead to advent of ‘fast grid regulation’ whereas the charging cars can check the grid frequency as they are charging (in fact – they already do that) and if the frequency falls below 60Hz they can slow charging down / if the frequency rises above 60Hz they can preferably charge. Similarly, they can deploy energy to the grid at night when not in use. Incentive to do that is a matter of energy market regulation, but it is not particularly complicated. These systems also offer much faster frequency regulation (check virtual power stations) than other systems.

        If we are discussing the economics aspect of this entire issue – I recommend you look at the ‘2035 report’ published by Berkeley in June – it discusses an economically neutral pathway to 90% less CO2 emissions by 2035. Complete decarbonisation is quite possible by 2050.

        I would be happy to discuss this further – but I am absolutely knackered after an infinitely long session at the APS-DPP conference. I also want to say that I am a big fan of your blog and found your discussion of Noether’s theorem a few years back in London quite interesting.

        • Anonymous says:

          Actually, I will add that nuclear power is hardly ‘on-demand’ – it is always on unless you give it a few months notice to turn off, it’s refueling (every few years), or if it malfunctions. In the UK the government had to pay wind farms to disconnect during the COVID19 lockdown as the energy supply was far higher than the demand (it fell ~10-20% if I remember correctly). Nuclear could not just switch off their generation at a short notice. Energy over-supply causes much the same issues as energy under-supply – frequency of the grid rises, generators can disconnect, currents can flow in the wrong directions.

  5. Keith Harbaugh says:

    Latest (2021-01-19) information on how they are modelling what will happen in ITER:

    “To facilitate the design and operation of the ITER tokamak, scientists worldwide have been conducting what are known as nuclear analyses, which are aimed at theoretically examining its outcomes and potential.

    So far, nuclear analyses based on data gathered by the ITER reactor have relied on detailed but partial models that only represent specific parts of the tokamak.

    “Due to the computational limitations of a couple of decades ago, the ITER neutronics community worldwide, including ourselves (the TECF3IR research team at UNED), have so far been working using partial models of the ITER tokamak,” Rafael Juarez, one of the researchers who carried out the study, told “Since then, however, computer power has evolved significantly. Furthermore, in recent years, the computational codes that we use have undergone advances as well, some of them enabled by TECF3IR.” “

  6. Keith Harbaugh says:

    Am I am posting too much on this topic?
    If not, here is an article suggesting the ITER may have problems:

    “Potential design problems for ITER fusion device”

    “A key obstacle to such design is the performance during abnormal events including plasma disruptions and so-called edge-localized modes (ELMs). In these events, a massive and sudden release of energy occurs quickly, due to loss of full or partial plasma confinement, leading to very high transient power loads on the reactor surface boundaries. A successful reactor design should tolerate several of these transient events without serious damages such as melting and vaporization of the structure. This paper highlights, through comprehensive state-of-the-art computer simulation of the entire ITER interior design during such transient events, e.g., ELMs occurring at normal operation and disruptions during abnormal operation, potential serious problems with current plasma facing components (PFCs) design.”

  7. John Baez says:

    No, Keith, you’re not posting too much on this topic! It’s very interesting to me, and I don’t have enough time to research it myself. I sometimes get grumpy when people post comments about W, Y, and Z on an article about X, but you’re not doing that. At least in my mind, ITER is close enough to SPARC that anyone reading about SPARC would be interested in ITER’s triumphs or difficulties.

    So thanks.

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