In February 2021, I posted the article “The Fork in the Road to Electric Power From Fusion,” with links to a set of supporting articles that provide details on 18 fusion power reactor development projects, mostly at private firms.
In March 2023, the United States Government Accountability Office issued their report GAO-23-105813, “Technology Assessment – Fusion Energy – Potentially Transformative Technology Still Faces Fundamental Challenge.” This GAO report provides a comprehensive overview of the current status of several different fusion energy concepts being developed worldwide. You can download a copy of this GAO report here: https://www.gao.gov/assets/gao-23-105813.pdf
ANS summarized GAO’s finding: “Despite decades of research and recent promising developments, the report notes, fusion science has still not achieved net energy gain.”
To illustrate this point, GAO commented on the recent high-profile announcement that a net fusion energy gain had been achieved during a test at the National Ignition Facility (NIF). GAO graphically showed how this claim is only true from the perspective of the small fusion reaction chamber (the Hohlraum) at the heart of NIF. As shown in the following GAO diagram, which appropriately treats the whole NIF as a “black box,” a total of 300 Megajoules (MJ) were input to the facility and only 3.15 MJ were generated by fusion reactions in the Hohlraum. That fusion power was absorbed by the Hohlraum and adjacent NIF structures and systems. No “net power” left the NIF “black box,” but then, NIF wasn’t designed to be a power plant.
As future claims of net energy gain are made by the various fusion power reactor development teams, think of each of their fusion facilities as a black box. The future of fusion-generated electricity depends first and foremost on being able to get much more energy out of the black box than went into it.
This article provides a brief overview of the “mainstream” international plans to deliver the first large tokamak commercial fusion power plant prototype in the 2060 to 2070 timeframe. Then we’ll take a look at alternate plans that could lead to smaller and less expensive commercial fusion power plants being deployed much sooner, perhaps in the 2030s. These alternate plans are enabled by recent technical advances and a combination of public and private funding for many creative teams that are developing and testing a diverse range of fusion machines that may be developed in the near-term into compact, relatively low-cost fusion power plants.
1. Plodding down the long road to controlled nuclear fusion with ITER
Mainstream fusion development is focused on the construction of the International Thermonuclear Experimental Reactor (ITER), which is a very large magnetic confinement fusion machine. The 35-nation ITER program describes their reactor as follows: “Conceived as the last experimental step to prove the feasibility of fusion as a large-scale and carbon-free source of energy, ITER will be the world’s largest tokamak, with ten times the plasma volume of the largest tokamak operating today.” ITER is intended “to advance fusion science and technology to the point where demonstration fusion power plants can be designed.”
ITER is intended to be the first fusion experiment to produce a net energy gain (“Q”) from fusion. Energy gain is the ratio of the amount of fusion energy produced (Pfusion) to the amount of input energy needed to create the fusion reaction (Pinput). In its simplest form, “breakeven” occurs when Pfusion = Pinput and Q = 1.0. The highest value of Q achieved to date is 0.67, by the Joint European Torus (JET) tokamak in 1997.The ITER program was formally started with the ITER Agreement, which was signed on 21 November 2006.
Nations contributing to the manufacture of major ITER components. Source: SciTechDaily (28 Jul 2020)
The official start of the “assembly phase” of the ITER reactor began on 28 July 2020. The target date of “first plasma” currently is in Q4, 2025. At that time, the reactor will be only partially complete. During the following ten years, construction of the reactor internals and other systems will be completed along with a comprehensive testing and commissioning program. The current goal is to start experiments with deuterium / deuterium-tritium (D/D-T) plasmas in December 2035.
After initial experiments in early 2036, there will be a gradual transition to fusion power production over the next 12 – 15 months. By mid-2037, ITER may be ready to conduct initial high-power demonstrations, operating at several hundred megawatts of D-T fusion power for several tens of seconds. This milestone will be reached more than 30 years after the ITER Agreement was signed.
Subsequent experimental campaigns will be planned on a two-yearly cycle. The principal scientific mission goals of the ITER project are:
Produce 500 MW of energy from fusion while using only 50 MW of energy for input heating, yielding Q ≥ 10
Demonstrate Q ≥ 10 for burn durations of 300 – 500 seconds (5.0 – 8.3 minutes)
Demonstrate long-pulse, non-inductive operation with Q ~ 5 for periods of up to 3,000 seconds (50 minutes).
All that energy will get absorbed in reactor structures, with some of it being carried off in cooling systems. However, ITER will not generate any electric power from fusion.
The total cost of the ITER program currently is estimated to be about $22.5 billion. In 2018, Reuters reported that the US had given about $1 billion to ITER so far, and was planning to contribute an additional $500 million through 2025. In Fiscal Year 2018 alone, the US contributed $122 million to the ITER project.
You’ll find more information on the ITER website, including a detailed timeline, at the following link: https://www.iter.org
The ITER site in 2020, being built next to the Cadarache facility in Saint-Paul-lès-Durance, in Provence, southern France. Source: Macskelek via Wikipedia
2. Timeline for a commercial fusion power plant based on ITER
In December 2018, a National Academy of Sciences, Engineering & Medicine (NASEM) committee issued a report that included the following overview of timelines for fusion power deployment based on previously studied pathways for developing fusion power plants derived from ITER. The timelines for the USA, South Korea, Europe, Japan and China are shown below.
Source: “A Strategic Plan for U.S. Burning Plasma Research” (NASEM, 2019)
All of the pathways include plans for a DEMO fusion power plant (i.e., a prototype with a power conversion system) that would start operation between 2050 and 2060. Based on experience with DEMO, the first commercial fusion power plants would be built a decade or more later. You can see that, in most cases, the first commercial fusion power plant is not projected to begin operation until the 2060 to 2070 timeframe.
3. DOE is helping to build a fork in the road
Fortunately, a large magnetic confinement tokamak like ITER is not the only route to commercial fusion power. However, ITER currently is consuming a great deal of available resources while the promise of fusion power from an ITER-derived power plant remains an elusive 30 years or more away, and likely at a cost that will not be commercially viable.
Since the commitment was made in the early 2000s to build ITER, there have been tremendous advances in power electronics and advanced magnet technologies, particularly in a class of high temperature superconducting (HTS) magnets known as rare-earth barium copper oxide (REBCO) magnets that can operate at about 90 °K (-297 °F), which is above the temperature of liquid nitrogen (77 °K; −320 °F). These technical advances contribute to making ITER obsolete as a path to fusion power generation.
A 2019 paper by Martin Greenwald describes the relationship of constant fusion gain (Q = Pfusion / Pinput) to the magnetic field strength (B) and the plasma radius (R) of a tokamak device. As it turns out, Q is proportional to the product of B and R, so, for a constant gain, there is a tradeoff between the magnetic field strength and the size of the fusion device. This can be seen in the comparison between the relative field strengths and sizes of ITER and ARC (a tokomak being designed now), which are drawn to scale in the following chart.
Contours of constant fusion gain (Q) plotted against magnetic field strength (T, Tesla) and device size (plasma radius in meters): Source: Greenwald (2019)
ITER has lower field strength conventional superconducting magnets and is much larger than ARC, which has much higher field strength HTS magnets that enable its compact design. Greenwald explains, “With conventional superconductors, the region of the figure above 6T was inaccessible; thus, ITER, with its older magnet technology, is as small as it could be.” So, ITER will be a big white elephant, useful for scientific research, but likely much less useful on the path to fusion power generation than anyone expected when they signed the ITER Agreement in 2006.
For the past decade, there has been increasing interest in, and funding for, developing lower cost, compact fusion power plants using any fusion technology that can deliver a useful power generation capability at an commercially viable cost. Department of Energy’s (DOE) Advanced Research Project Agency – Energy (ARPA-E) has recommended the following cost targets for such a commercial fusion power plant:
Overnight capital cost of < US $2 billion and < $5/W
At $5/W, the upper limit would be a 400 MWe fusion power plant.
Since 2014, DOE has created a series of funding programs for fusion R&D projects to support development of a broad range of compact, low-cost fusion power plant design concepts. This was a significant change for the DOE fusion program, which has been contributing to ITER and a whole range of other fusion-related projects, but without a sense of urgency for delivering the technology needed to develop and operate commercial fusion power plants any time soon. Now, a small part of the DOE fusion budget is focused on resolving some of the technical challenges and de-risking the path forward sooner rather than later, and thereby improving the investment climate to the point that investors become willing to contribute to the development of small, low-cost fusion power plants that may be able to produce electrical power within the next decade or two.
These DOE R&D programs are administered ARPA-E and the Office of Science, Fusion Energy Sciences (FES).
ARPA-E advances high-potential, high-impact energy technologies that are too early for private-sector investment. The ARPA-E fusion R&D programs are named ALPHA, IDEAS, BETHE, TINA and GAMOW. ARPA-E jointly funds the GAMOW fusion R&D program and part of the BETHE program with FES. In addition, the ARPA-E OPEN program makes R&D investments in the entire spectrum of energy technologies, including fusion.
FES is the largest US federal government supporter of research that is addressing the remaining obstacles to commercial fusion power. The FES fusion R&D program is named INFUSE. In addition FES jointly funds GAMOW and part of BETHE with ARPA-E.
Here’s an overview of these DOE programs.
DOE ARPA-E ALPHA program (2015 – 2020)
In 2015, ARPA-E initiated a five-year, $30 million research program into lower-cost approaches to producing electric power from fusion. This was known as the ALPHA program (Accelerating Low-Cost Plasma Heating and Assembly). The goal was to expand the range of potential technical solutions for generating power from fusion, focusing on small, low-cost, pulsed magneto-inertial fusion (MIF) devices.
There were nine program participants in the ALPHA program. Helion Energy ($3.97 million) and MIFTI ($4.60 million) were among the private fusion reactor firms receiving ALPHA awards. Los Alamos National Laboratory (LANL) received $6.63 million to fund the Plasma Liner Experiment (PLX-α) team, which included the private firm HyperV Technologies Corp.
In 2018, ARPA-E asked JASON to assess its accomplishments on the ALPHA program and the potential of further investments in this field. Among their findings, JASON reported that MIF is a physically plausible approach to controlled fusion and, in spite of very modest funding to date, some particular approaches are within a factor of 10 of scientific break-even. JASON also recommended supporting all promising approaches, while giving near-term priority to achieving breakeven (Q ≥ 1) in a system that can be scaled up to be commercial power plant. You can read the November 2018 JASON report here: https://fas.org/irp/agency/dod/jason/fusiondev.pdf
DOE ARPA-E IDEAS program (2017 – 2019)
The ARPA-E IDEAS program (Innovative Development in Energy-Related Applied Science) provides support of early-stage applied research to explore pioneering new concepts with the potential for transformational and disruptive changes in any energy technology. IDEAS awards are restricted to a maximum of $500,000 in funding. There have been 59 IDEAS awards for a broad range of energy-related technologies, largely to national laboratories and universities.
There was one fusion-related IDEAS award to the University of Washington ($482 k).
DOE ARPA-E OPEN program (2018)
In 2018, ARPA-E issued its fourth OPEN funding opportunity designed to catalyze transformational breakthroughs across the entire spectrum of energy technologies, including fusion. OPEN 2018 is a $199 million program funding 77 projects.
Four fusion-related projects were funded for a total of about $12 million. ZAP Energy ($6.77 million), CTFusion ($3.0 million) and Princeton Fusion Systems ($1.1 million) were among the private fusion reactor firms receiving OPEN 2018 awards.
DOE ARPA-E TINA Fusion Diagnostics program (2019 – 2021)
The TINA program established diagnostic “capability teams” to support state-of-the-art diagnostic system construction/deployment and data analysis/interpretation on ARPA-E-supported fusion experiments. This program awarded $7.5 million to eight teams, primarily from national laboratories and universities.
DOE ARPA-E BETHE program (2020 – 2024)
DOE’s ARPA-E also runs the BETHE program (Breakthroughs Enabling THermonuclear-fusion Energy), which is a $40 million program that aims to deliver a large number of lower-cost fusion concepts at higher performance levels. BETHE R&D is focused in the following areas:
Concept development to advance the performance of inherently lower cost but less mature fusion concepts.
Component technology development that could significantly reduce the capital cost of higher cost, more mature fusion concepts.
Capability teams to improve/adapt and apply existing capabilities (e.g., theory/modeling, machine learning, or engineering design/fabrication) to accelerate the development of multiple concepts.
ZAP Energy ($1 million) and Commonwealth Fusion Systems ($2.39 million) were among the private fusion reactor firms directly receiving BETHE awards.
The following awards were made to universities or national laboratories working with teams that include a significant role for a private fusion reactor firm:
University of Washington received $1.5 million for improving IDCD plasma control, which is applicable to their collaborative work with CTFusion on the Dynomak fusion reactor concept.
LANL received $4.62 million to fund the Plasma Liner Experiment (PLX-α) team, which includes HyperJet
DOE ARPA-E / FES GAMOW program (2020 – 2024)
Yet another DOE funding program for fusion research is named GAMOW (Galvanizing Advances in Market-Aligned Fusion for an Overabundance of Watts), which is a $29 million program announced in February 2020. GAMOW is jointly funded and overseen by ARPA-E and FES. GAMOW program focuses on the following three areas:
Technologies and subsystems between the fusion plasma and balance of plant.
Princeton Fusion Systems ($1.1 million) was among the private fusion reactor firms receiving GAMOW awards.
DOE FES INFUSE program (2020 – present)
The DOE FES INFUSE program (Innovation Network for Fusion Energy) was created to “accelerate fusion energy development in the private sector by reducing impediments to collaboration involving the expertise and unique resources available at DOE laboratories.” ….”DOE-FES will accept basic research applications focused on innovation that support production and utilization of fusion energy (e.g., for generation of electricity, supply of process heat, etc.)….”
In Fiscal Years 2020 and 2021, the INFUSE program annual budget was $4 million. INFUSE is a cost sharing program with DOE-FES funding 80% of a project’s cost and the award recipient funding the remaining 20%. The DOE-FES INFUSE program home page is here: https://infuse.ornl.gov
So far, there have been three rounds of INFUSE awards. I think you will find that it is much more difficult to find detailed information on the DOE FES INFUSE awards, which are administered by Oak Ridge National Laboratory (ORNL), than it is to find information on any of the DOE ARPA-E program. Here’s a brief INFUSE summary.
1st round FY 2020: On 15 October 2019, DOE announced the first INFUSE awards, which provided funding for 12 projects with representation from six private companies partnering with six national laboratories. The six private firms included: Commonwealth Fusion Systems (4 awards) and TAE Technologies, Inc. (3 awards)
2nd round FY 2020: On 3 September 2020, DOE announced funding for 10 projects. The private firms included: Commonwealth Fusion Systems (3 awards), TAE Technologies, Inc. (1 award), Tokamak Energy, Inc. (UK, 3 awards), and General Fusion Corp. (Canada, 1 award).
1st round FY 2021: On 3 December 2020, DOE announced funding 10 projects in a second round of FY 2021 INFUSE awards. The private firms receiving awards included: Commonwealth Fusion Systems (1 award), General Fusion Corp. (Canada, 1 award), MIFTI (1 award), Princeton Fusion Systems (1 award), TAE Technologies, Inc. (2 awards), Tokamak Energy, Inc. (UK, 2 awards).
DOE-FES has issued a call for new proposals for FY 2021 INFUSE awards. The closing date for submissions is 26 February 2021.
So far, these ARPA-E and FES programs have committed about $127 million in public funds to 77 different projects between 2014 and 2021. While some of the awards are sizeable ($5 – 6 million), many are very modest awards. The DOE total for all small (non-mainstream) fusion projects over a seven year period is about the same amount as the annual US contribution to the ITER program, which isn’t going lead to a fusion power plant in my lifetime, if ever.
While DOE has been kind enough to create the fork in the road, they do not have the deployable financial resources to push on to the next step of actually building prototypes of commercial fusion power plants in the near term.
4. A roadmap for achieving commercial fusion sooner
In 2019 and 2021, the National Academies and DOE-FES, respectively, published the recommendations of committees that were charged with defining the path(s) forward for the US to achieve commercial fusion power. In both cases, the committee recommended continued support for ITER while urging the US to proceed with a separate national program that encourages and supports public-private partnerships to build compact power plants that produce electricity from fusion at the lowest possible capital cost. These committee reports are briefly summarized below.
National Academies: “Final Report of the Committee on a Strategic Plan for U.S. Burning Plasma Research” (2019)
In December 2018, a National Academy of Sciences, Engineering & Medicine (NASEM) committee issued a report entitled, “A Strategic Plan for U.S. Burning Plasma Research.”
As noted previously, the NASEM report described the current path forward based on power plants derived largely from ITER technology. On this path, the first commercial fusion power plant is not projected to begin operation until the 2060 to 2070 timeframe.
The NASEM committee report is very important because it defines an alternate pathway (i.e., the fork in the road) that could deliver fusion power considerably sooner and at much lower capital cost.
The committee offered the following recommendations:
The US should remain an ITER partner. This is the most cost-effective way to gain experience with burning plasma at the scale of a power plant. However:
Significant R&D is required in addition to ITER to produce electricity from this type of fusion reactor.
ITER is too large and expensive to be economically competitive in the US market when compared to other carbon-neutral energy technologies.
The US should start a national program of accompanying research and technology leading to the construction of a compact pilot power plant that produces electricity from fusion at the lowest possible capital cost.
Effective application of US near-term R&D investments is critical, as other nations continue to invest in new fusion facilities that advance their own approaches.
DOE FES: “Powering the Future – Fusion & Plasmas” (2021)
In January 2021, DOE FES published a draft report from their Fusion Energy Sciences Advisory Committee (FESAC) entitled “Powering the Future – Fusion & Plasmas.” This draft report supports the NASEM committee recommendations and concluded that there are two viable paths to commercial fusion power:
Partnership in the ITER fusion project is essential for US fusion energy development, as is supporting the continued growth of the private sector fusion energy industry.
Public-private partnerships have the potential to reduce the time required to achieve commercially viable fusion energy.
The fusion pilot plant goal requires “a pivot toward research and development of fusion materials and other needed technology.” Several new experimental facilities were recommended.
As of late January 2021, the FESAC final report was in preparation. When available, it will be posted here: http://usfusionandplasmas.org
Funding at the fork in the road
At the fork in the road, the US will be hedging its bets and taking both paths, continuing to support ITER at the current level (about $125 million/year) while building new fusion experimental facilities and trying to place a stronger emphasis on timely development of compact fusion power plants through public-private partnerships as well as infusions of private capital.
In the years ahead, the DOE FES fusion budget is expected to be essentially flat, with growth at just a modest rate of 2%/year being among the likely range of budget scenarios. At the same time, FES will attempt to launch several new major fusion R&D facilities and related programs, as recommended by FESAC.
Without a significantly bigger budget authorization from Congress, the FES budget becomes a zero sum game. To create the budget for any of these new R&D facilities and programs, other part of the FES budget have to lose. In this constrained budget environment, I think FES funding for compact fusion power plant development will find stiff competition and will not be on a growth path.
Recall that ARPA-E’s role is to advance high-potential, high-impact energy technologies that are too early for private-sector investment. When major risk issues for a particular fusion reactor concept have been resolved to an appropriate level, funding from ARPA-E may be redirected to other higher risk matters waiting to be addressed.
While the NASEM and FESAC reports support public-private partnerships, the sheer magnitude of the funds required (many billions of dollars) to develop several small prototype fusion power plant designs in parallel exceeds DOE’s ability to fund the deals at the same level as the current 80% (DOE) / 20% (private) partnership deals. The FES annual budget for the past three years has been quite modest: $564 million (FY2019 enacted), $671 million (FY2020 enacted) and $425 million (FY2021 requested).
Making real progress toward deployment of operational fusion power plants will depend on billions of dollars in private / institutional capital being invested in the firms that will design and build the first small commercial fusion power plants.
I think DOE and the commercial fusion power industry are in a similar position to NASA and the commercial spaceflight industry two decades ago when Blue Origin (Jeff Bezos, 2000) and SpaceX (Elon Musk, 2002) were founded. At that time, the traditional route to space was via NASA. Two decades later, it’s clear that many commercial firms and their investors have contributed to building a robust low Earth orbit spaceflight industry that could never have been developed in that short time frame with NASA’s limited budget. In the next two decades, I think the same type of transition needs to occur in the relationship between DOE and the private sector fusion industry if we expect to reap the benefits of clean fusion power soon. It’s time for FES and the commercial fusion industry to confirm that they share a vision and a common aggressive timeline for bringing small commercial fusion power plants to the market. That point doesn’t come across in the FESAC report.
Private and institutional investors already making major investments in the emerging fusion energy market. As you might expect, some fusion firms have been much more successful than others in raising funds. You’ll find a summary of publically available funding information on the Fusion Energy Base website here: https://www.fusionenergybase.com/organization/commonwealth-fusion-systems
5. The US Navy also may be building a fork in the road
The Navy has been quietly developing its own concepts for compact fusion power plants. We’ll take a look at three recent designs. Could the Navy wind up being an important contributor to the development and deployment of commercial fusion power plants?
6. The race is on to beat ITER with smaller, lower-cost fusion
In this section, we’ll take a look at the status of the following small fusion power plant development efforts, mostly by private companies.
Collectively, they are applying a diverse range of technologies to the challenge of generating useful electric power from fusion at a fraction of the cost of ITER. Based on claims from the development teams, it appears that some of the compact fusion reactor designs are quite advanced and probably will be able to demonstrate a net energy gain (Q > 1.0) in the 2020s, well before ITER.
You’ll find details on these 18 organizations and their fusion reactor concepts in my separate articles at the following links:
There certainly are many different technical approaches being developed for small, lower-cost fusion power plants. Several teams are reporting encouraging performance gains that suggest that their particular solutions are on credible paths toward a fusion power plant. However, as of January 2021, none of the operating fusion machines have achieved breakeven, with Q = 1.0, or better. It appears that goal remains at least a few years in the future, even for the most advanced contenders.
The rise of private funding and public-private partnerships is rapidly improving the resources available to many of the contenders. Good funding should spur progress for many of the teams. However, don’t be surprised if one or more teams wind up at a technical or economic dead end that would not lead to a commercially viable fusion power plant. Yes, I think ITER is heading down one of those dead ends right now.
So, where does that leave us? The promise for success with a small, lower-cost fusion power plant is out there, and such power plants should win the race by a decade or more over an ITER-derived fusion power plant. While there are many contenders, which ones are the leading contenders for deploying a commercially viable fusion power plant?
To give some perspective, it’s worth taking a moment to recall the earliest history of the US commercial nuclear power industry, which is recounted in detail for the period from 1946 – 1963 by Wendy Allen in a 1977 RAND report and summarized in the following table.
US fission demonstration power plants. Source: RAND R-2116-NSF
The main points to recognize from the RAND report are:
Eight different types of fission reactors were built as demonstration plants and tested. All of the early reactors were quite small in comparison to later nuclear power plants.
Some were built on Atomic Energy Commission (AEC, now DOE) national laboratory sites and operated as government-owned proof-of-principle reactors. The others were licensed by the AEC (now the Nuclear Regulatory Commission, NRC) and operated by commercial electric power utility companies. These reactors were important for building the national nuclear regulatory framework and the technical competencies in the commercial nuclear power and electric utility industries.
In the long run, only two reactor designs survived the commercial test of time and proved their long-term financial viability: the pressurized water reactor (PWR) and the boiling water reactor (BWR), which are the most common types of fission power reactors operating in the world today.
With the great variety of candidate fusion power plant concepts being developed today, we simply don’t know which ones will be the winners in a long-term competition, except to say that an ITER-derived power plant will not be among the winners. What we need is a national demonstration plant program for small fusion reactors. This means we need the resources to build and operate several different fusion power reactor designs soon and expect that the early operating experience will quickly drive the evolution of the leading contenders toward mature designs that may be successful in the emerging worldwide market for fusion power. The early fission reactor history shows that we should expect that some of the early fusion power plant designs won’t survive in the long-term fusion power market, for a variety of reasons.
Matthew Moynihan, in his 2019 article, “Selling Fusion in Washington DC,” on The Fusion Podcast website, offered the following approach, borrowed from the biotech industry, to build a pipeline of credible projects while driving bigger investments into the more mature and more promising programs. Applying this approach to the current hodgepodge of DOE fusion spending would yield more focused spending of public money toward the goal of delivering small fusion power plants as soon as practical. The actual dollar amounts in the following chart can be worked out, but I think the basic principle is solid.
Source: The Fusion Podcast, 12 January 2019
With this kind of focus from DOE, the many contenders in the race to build a small fusion power plant could be systematically ranked on several parameters that would make their respective technical and financial risks more understandable to everyone, especially potential investors. With an unbiased validation of relative risks from DOE, the leading candidates in the US fusion power industry should be able to raise the billions of dollars that will be needed to develop their designs into the first wave of demonstration fusion power plants, like the US fission power industry did 60 to 70 years ago.
Perhaps Carly Anderson had the right idea when she suggested Fantasy Fusion as a way to introduce some fun into the uncertain world of commercial fusion power development and investment. You can read her September 2020 article here: https://medium.com/prime-movers-lab/fantasy-fusion-77621cc901e2
If you believe we’re coming into the home stretch, it’s not too late to place a real bet by actually investing in your favorite fusion team(s). It is risky, but the commercial fusion power trophy will be quite a prize! I’m sure it will come with some pretty big bragging rights.
C. L. Nehi, et al., “Retrospective of the ARPA-E ALPHA Fusion Program,” Journal of Fusion Energy, 38_506 – 521, 2019: https://www.osti.gov/biblio/1572943
Fusion reactions in our Sun are predominately proton – proton reactions that lead to the production of the light elements helium, lithium, beryllium and boron. The next step up on the periodic table of elements is carbon.
Carbon is formed in our Sun by the “triple alpha” process shown in the following diagram. First, two helium-4 nuclei (4He, an alpha particles) fuse, emit a gamma ray and form an atom of unstable beryllium-8 (8Be), which can fuse with another helium nucleus, emit another gamma ray and form an atom of stable carbon-12 (12C). Timing is everything, because that fusion reaction must occur during the very short period of time before the unstable beryllium-8 atom decays (half life is about 8.2 x 10-17 seconds).
Stellar process for producing carbon-12. Source: Borb via Wikipedia
Stellar process for producing carbon-12. Source: Borb via Wikipedia
The carbon produced by the above reaction chain is the starting point for the carbon-nitrogen-oxygen (CNO) fusion cycle, which accounts for about 1% of the fusion reactions in a relatively small star the size of our Sun. In larger stars, the CNO cycle becomes the dominant fusion cycle.
The In the following diagram, the CNO cycle starts at the top-center:
First, an atom of stable carbon-12 (12C) captures a proton (1H) and emits a gamma ray (γ), producing an atom of nitrogen-13 (13N), which has a half-life of almost 10 minutes.
The cycle continues when the atom of nitrogen-13 decays into an atom of stable carbon-13 (13C) and emits a neutrino (ν) and a positron (β+).
When the carbon-13 atom captures of a proton, it emits a gamma ray and produces an atom of stable nitrogen-14 (14N).
When the nitrogen-14 atom captures a proton, it emits a gamma ray and produces an atom of oxygen-15 (15O), which has a half-life of almost 71 seconds.
The cycle continues when the atom of oxygen-15 decays into an atom of stable nitrogen-15 (15N) and emits a neutrino (ν) and a positron (β+).
After one more proton capture, the nitrogen-15 atom splits into a helium nucleus (4He) and an atom of stable carbon-12, which is indistinguishable from the carbon-12 atom that started the cycle.
The carbon-nitrogen-oxygen (CNO) cycle. Source: Borb via Wikipedia
As shown in the previous diagram, the CNO cycle generates characteristic emissions of gamma rays, positrons and neutrinos. With a neutrino detector, scientists would search for the neutrinos emissions from the nitrogen-13 and oxyger-15 decay steps in the CNO cycle.
The Borexino experimental facility is located at the INFN’s Gran Sasso National Laboratories in the Apennine Mountains, about 65 miles (105 km) northeast of Rome. The official website of the Borexino Experiment is here: http://borex.lngs.infn.it
The Borexino neutrino detector is in a underground laboratory hall deep in the mountain, which protects the detector from cosmic radiation, with the exception of neutrinos that pass through Earth undisturbed. Even with the huge Borexino detector in this very special, protected laboratory environment, the research team reported that detecting CNO neutrinos has been very difficult. Only about seven neutrinos with the characteristic energy of the CNO cycle are spotted in a day.
The Borexino neutrino detector is shown in the following diagram.
Source: INFN
INFN reported, “Previously Borexino had already studied in detail the main mechanism of energy production in the Sun, the proton-proton chain, through the individual detection of all neutrino fluxes that originate from it.”
For more information:
The Borexino Collaboration., Agostini, M., Altenmüller, K. et al. “Experimental evidence of neutrinos produced in the CNO fusion cycle in the Sun,” Nature, 587, 577–582, 25 November 2020: https://doi.org/10.1038/s41586-020-2934-0
The I. V. Kurchatov Institute of Atomic Energy in Moscow was founded 75 years ago, in 1943, and is named for its founder, Soviet nuclear physicist Igor Vasilyevich Kurchatov. Until 1955, the Institute was a secret organization known only as “Laboratory No. 2 of the USSR Academy of Sciences.” The initial focus of the Institute was the development of nuclear weapons.
Kurchatov Institute 75thanniversary on Russian commemorative postage stamp. https://en.wikipedia.org/
I. V. Kurchatov and the team of scientists and engineers at the Institute led or supported many important historical Soviet nuclear milestones, including:
25 December 1946: USSR’s F-1 (Physics-1) reactor achieved initial criticality at Kurchatov Institute. This was the 1st reactor built and operated outside the US.
10 June 1948: USSR’s 1st plutonium production reactor achieved initial criticality (Unit A at Chelyabinak-65). The reactor was designed under the leadership of N. A. Dollezhal.
29 August 1949: USSR’s 1st nuclear device, First Lightning [aka RDS-1, Izdeliye 501 (device 501) and Joe 1], was detonated at the Semipalatinsk test site in what is now Kazakhstan. This was the 1st nuclear test other than by the US.
27 June 1954: World’s 1st nuclear power plant, AM-1 (aka APS-1), was commissioned and connected to the electrical grid, delivering power in Obninsk. AM-1 was designed under the leadership of N. A. Dollezhal.
22 November 1955: USSR’s 1st thermonuclear device (RDS-37, a two-stage device) was detonated at the Semipalatinsk test site. This also was the world’s 1stair-dropped thermonuclear device.
5 December 1957: USSR’s 1st nuclear-powered icebreaker, Lenin, was launched. This also was the world’s 1st nuclear-powered surface ship.
4 July 1958: USSR’s 1st nuclear-powered submarine, Project 627 SSN K-3, Leninskiy Komsomol, made its 1st underway on nuclear power.
1958: World’s 1st Tokamak, T-1, initial operation at Kurchatov Institute.
I. V. Kurchatov and F-1 reactor on Russian commemorative postage stamp. Source: Wikimedia Commons
I. V. Kurchatov served as the Institute’s director until his death in 1960 and was awarded Hero of Socialist Labor three times and Order of Lenin five times during his lifetime.
After I. V. Kurchatov’s death in 1960, the noted academician Anatoly P. Aleksandrov was appointed as the director of the Institute and continued in that role until 1989. Aleksandrov already had a key role at the Institute, having been appointed by Stalin in September 1952 as the scientific supervisor for developing the USSR’s first nuclear-powered submarine and its nuclear power unit.
A. P. Aleksandrov and OK-150 reactor on Russian commemorative postage stamp. Source: Wikimedia Commons
Until 1991, the Soviet Ministry of Atomic Energy oversaw the administration of Kurchatov Institute. After the formation of the Russian Federation at the end of 1991, the Institute became a State Scientific Center reporting directly to the Russian Government. Today, the President of Kurchatov Institute is appointed by the Russian Prime Minister, based on recommendations from Rosatom (the Russian State Energy Corporation), which was formed in 2007.
You’ll find a comprehensive history of Kurchatov Institute in a 2013 (70thanniversary) special issue of the Russian version of Scientific American magazine, which you can download here:
The evolution of Kurchatov Institute capabilities from its initial roles on the Soviet nuclear weapons program is shown in the following diagram.
Source: Special issue 2013, www.scientificrussia.ru
Modern roles for Kurchatov Institute are shown in the following graphic.
Source: Special issue 2013, www.scientificrussia.ru
In the past 75 years, the Kurchatov Institute has performed many major roles in the Soviet / Russian nuclear industry and, with a national security focus, continues to be a driving force in that industry sector.
Now, lets take a look at a few of the pioneering nuclear projects led or supported by Kurchatov Institute:
F-1 (Physics-1) reactor
Plutonium production reactors
Obninsk nuclear power plant AM-1
T-1 Tokamak
F-1 (Physics-1) reactor
The F-1 reactor designed by the Kurchatov Institute was a graphite-moderated, air-cooled, natural uranium fueled reactor with a spherical core about 19 feet (5.8 meters) in diameter. F-1 was the first reactor to be built and operated outside of the US. It was a bit more compact than the first US reactor, the Chicago Pile, CP-1, which had an ellipsoidal core with a maximum diameter of about 24.2 feet (7.4 meters) and a height of 19 feet (5.8 meters).
The F-1 achieved initial criticality on 25 December 1946 and initially was operated at a power level of 10 watts. Later, F-1 was able to operate at a maximum power level of 24 kW to support a wide range of research activities. In a 2006 report on the reactor’s 60thanniversary by RT News (www.rt.com), Oleg Vorontsov, Deputy Chief of the Nuclear Security Department reported, “Layers of lead as they are heated by uranium literally make F1 a self-controlling nuclear reactor. And the process inside is called – the safe-developing chain reaction of uranium depletion. If the temperature rises to 70 degrees Celsius (158° Fahrenheit), it slows down by its own! So it simply won’t let itself get out of control.”
F-1 was never refueled prior to its permanent shutdown in November 2016, after 70 years of operation.
Top of the F-1 reactor core. Source: http://nuclearweaponarchive.org/
F-1 reactor facility cross-section diagram. The F-1 reactor is the igloo-shaped structure located in the open pit. Source: http://nuclearweaponarchive.org/
Graphite stacks of the F-1 reactor. Source: Kurchatov Institute
Plutonium production reactors
The first generation of Soviet plutonium production reactors were graphite-moderated, natural uranium fueled reactors designed under the leadership of N.A. Dollezhal while he was at the Institute of Chemical Machinery in Moscow. The Kurchatov Institute had a support role in the development of these reactors.The five early production reactors at Chelyabinsk-65 (later known as the Mayak Production Association) operated with a once-through primary cooling water system that discharged into open water ponds.
Simplified cross-section of a Russian graphite-moderated, water-cooled plutonium production reactor. Source: PNL-9982
Four of the five later graphite-moderated production reactors at Tomsk had closed primary cooling systems that enabled them to also generate electric power and provide district heating (hot water) for the surrounding region. You’ll find a good synopsis of the Soviet plutonium production reactors in the 2011 paper by Anatoli Diakov, “The History of Plutonium Production in Russia,” here:
Additional details on the design of the production reactors is contained in the 1994 Pacific Northwest Laboratory report PNL-9982, “Summary of Near-term Options for Russian Plutonium Production Reactors,” by Newman, Gesh, Love and Harms. This report is available on the OSTI website here:
Obninsk nuclear power plant AM-1 (Atom Mirny or “Peaceful Atom”)
AM-1 nuclear power plant exterior view. Source: tass.ruPanoramic view of the AM-1 power plant control room. Source: www.chistoprudov.ru via https://reactor.space/news_en/
Obninsk was the site of the world’s first nuclear power plant (NPP). This NPP had a single graphite-moderated, water-cooled reactor fueled with low-enriched uranium fuel. The reactor had a maximum power rating of 30 MWt. AM-1 was designed by N.A. Dollezhal and the Research and Development Institute of Power Engineering (RDIPE / NIKIET) in Moscow, as an evolution of an earlier Dollezhal design of a small graphite-moderated reactor for ship propulsion. The Kurchatov Institute had a support role in the development of AM-1.
The basic AM-1 reactor layout is shown in the following diagram.
Source: Directory of Nuclear Reactors, Vol. IV, Power Reactors, International Atomic Energy Agency, 1962
The closed-loop primary cooling system delivered heat via steam generators to the secondary-side steam system, which drove a steam turbine generator that delivered 5 MWe (net) to the external power grid. Following is a basic process flow diagram for the reactor cooling loops.
Source: Directory of Nuclear Reactors, Vol. IV, Power Reactors, International Atomic Energy Agency, 1962
Construction on AM-1 broke ground on 31 December 1950 at the Physics and Power Engineering Institute (PEI) in Obninsk, about 110 km southwest of Moscow. Other early milestone dates were:
Initial criticality: 5 May 1954
Commissioning and first grid connection: 26 June 1954
Commercial operation: 30 November 1954
In addition to its power generation role, AM-1 had 17 test loops installed in the reactor to support a variety of experimental studies. After 48 years of operation, AM-1 was permanently shutdown on 28 April 2002.
You can read more details on AM-1 in the following two articles: “Obninsk: Number One,” by Lev Kotchetkov on the Nuclear Engineering International website here:
The AM-1 nuclear power plant design was developed further by NIKIET into the much larger scale RBMK (Reaktor Bolshoy Moshchnosti Kanalnyy, “High Power Channel-type Reactor”) NPPs. The four reactors at the Chernobyl NPP were RBMK-1000 reactors.
The T-1 Tokamak
Research on plasma confinement is a toroidal magnetic field began in Russia in 1951, leading to the construction of the first experimental toroidal magnetic confinement system, known as a tokamak, at Kurchatov Institute. T-1 began operation in 1958.
Early operation of T-1 and successive models revealed many problems that limited the plasma confinement capabilities of tokamaks. Solving these problems led to a better understanding of plasma physics and significant improvements in the design of tokamak machines. You’ll find a historical overview of early Soviet / Russian work on Tokamaks in a 2010 IAEA paper by V. P. Smirnov, ”Tokamak Foundation in USSR/Russia 1950–1990,” which you can read here:
The basic tokamak design for magnetic plasma confinement has been widely implemented in many international fusion research machines, winning out over other magnetic confinement concepts, including the Stellarator machine championed in the US by Dr. Lyman Spitzer (see my 30 August 2017 post on Stellarators). Major international tokamak projects include the Joint European Torus (JET) at the Culham Center for Fusion Energy in Oxfordshire, UK, the Tokamak Fusion Test Reactor (TFTR) at Princeton Plasma Physics Laboratory in the US, the JT-60 at the Japan Atomic Energy Agency’s Naka Fusion Institute, and most recently the International Thermonuclear Experimental Reactor (ITER) being built now at the Saclay Nuclear Center in southern France.
Dr. Lyman Spitzer invented the stellarator in 1951 and built several versions of this magnetic plasma confinement machine at Princeton University during the 1950s and 1960s, establishing the world famous Princeton Plasma Physics Laboratory (PPPL) in the process. Dr. Spitzer’s earliest Stellarators were figure-eight devices as shown in the following photo.
Example of an early stellarator at the 1958 Atoms for Peace Conference, Geneva
In these first-generation stellarators, field coils wrapped around the figure-eight vacuum vessel provided the basic plasma confinement field. The physical twist in the stellarator’s structure twisted the internal magnetic confinement field and cancelled the effects of plasma ion drift during each full circuit around the device. You can download Dr. Spitzer’s historic 1958 IAEA conference paper, “The Stellarator Concept,” at the following link:
The next generation of stellarators adopted a simpler torus shape and created the twist in the magnetic confinement field with helical field coils outside the vacuum vessel.
While stellarators achieved many important milestones in magnetic confinement, by the late 1960s, the attention of the fusion community was shifting toward a different type of magnetic confinement machine: the tokamak. Since then, this basic design concept has been employed in many of the world’s major fusion devices, including the Alcator-C Mod (MIT, USA), Doublet III-D (DIII-D at General Atomics, USA), Tokamak Fusion Test Reactor (TFTR at PPPL, USA), Joint European Torus (JET, UK), National Spherical Torus Experiment Upgrade (NSTX-U at PPPL, USA) and the International Thermonuclear Experimental Reactor (ITER, France).
Now, almost 50 years later, there is significant renewed interest in stellarators. The newest device, the Wendelstein 7-X stellarator, became operational in 2016. It may help determine if modern technology has succeeded in making the stellarator a more promising path to fusion power than the tokamak.
Comparison of Tokamaks and Stellarators
Modern tokamaks and stellarators both implement plasma confinement within a (more or less) toroidal vacuum vessel that operates at very high vacuum conditions, on the order of 10-7 torr. Both types of machines use the combined effects of two or more magnetic fields to create and control helical field lines (HFL) that enable plasma confinement and reduce particle drift in the circulating plasma.
In the following description, the simple “classical” tokamak configuration shown below will be the point of reference.
Source: Hans-Jürgen Hartfuß, Thomas Geist, “Fusion Plasma Diagnostics With mm-Waves: An Introduction”
The main features of a tokamak are summarized below.
The vacuum vessel in a modern tokamak typically is an azimuthally-symmetric torus of revolution (donut-shaped), typically with a vertically elongated, D-shaped cross section. Modern “spherical” tokomaks maintain the D-shaped cross section, but minimize the diameter of the hole in the center of the torus.
Plasma confinement within the vacuum vessel is accomplished by the combined effects of a toroidal magnetic field and an induced poloidal magnetic field. Together, these fields create the helical field lines for plasma confinement. In the following diagram, the toroidal field is represented by the blue arrow and the poloidal field is represented by the red arrow.
By Dave Burke – Own work, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=1169843
The toroidal field (blue) is generated by a set of external toroidal field coils (TFCs) that surround the vacuum vessel.
The poloidal field (red) is generated by a strong induced plasma current (Iplasma), on the order of 106 amperes, flowing within the plasma inside the vacuum vessel. An external coil in the center of the tokamak serves as the primary coil of a transformer and the circulating plasma serves as the secondary coil of the transformer. To create the poloidal field, the transformer primary coil is charged at a controlled rate (i.e. to yield the desired rate of flux increase), thereby inducing a current in the plasma and heating the plasma by ohmic heating. When the primary coil reaches maximum flux, current is no longer induced in the plasma and the tokamak “pulse” is over.
A pair of vertical field coils (VFC), one above and one below the plane of the torus, provide the ability to radially position the plasma within the vacuum vessel.
Divertors inside the vacuum vessel define the maximum extent of the magnetically confined plasma, remove impurities from the edge of the plasma, and help minimize plasma-wall interactions.
The high current in the plasma can falter unexpectedly, resulting in a “disruption”, which is a sudden losses of plasma confinement that can unleash magnetic forces powerful enough to damage the machine.
A tokamak is mechanically simpler than a stellarator.
The physics characteristics of a tokamak typically yield better confinement capabilities than a stellarator.
While the “pulse” in a modern tokamak can last several tens of minutes, a pulsed mode of operation may not be suitable for a commercial fusion reactor.
Pulsed magnetic and thermal loads create mechanical fatigue issues that must be accommodated in the design of tokamak structures.
The simple “classical” stellarator configuration shown below will be the point of reference for the following discussion.
Source: Hans-Jürgen Hartfuß, Thomas Geist, “Fusion Plasma Diagnostics With mm-Waves: An Introduction”
The main features of a stellarator are summarized below.
There are many variants of devices called stellarators, with names such as Torsatron, Heliotron, Heliac, and Helias. All create the plasma confinement field with external magnet systems in various configurations and none depend on the existence of a toroidal plasma current.
In the classical stellarator in the above diagram, the plasma confinement field is created by a set of planar (flat) TFCs and external pairs (1, 2 or 3) of twisting helical field coils (HFC) with opposite currents in each conductor in the pair.
A stellarator is mechanically more complex and more difficult to manufacture than a tokamak.
Stellarators may use a divertor or a simpler “limiter” to define the outer extent of the plasma.
While a stellarator has no induced plasma current, other small currents, known as “pressure-driven” or “bootstrap” currents, exist. These small currents do not cause plasma disruptions as may occur in a tokamak, but complicate plasma confinement.
A stellarator is intrinsically capable of steady-state operation.
For a variety of reasons, a classical stellarator tends to lose energy at a higher rate than a tokamak. Advanced, modular stellarators are making progress in improving confinement performance.
You’ll find more comparative information in the July 2016 paper by Y. XU, “A general comparison between tokamak and stellarator plasmas,” which is available at the following link:
In the last two decades, dramatic improvements in computer power and 3-dimensional modeling capabilities have enabled researchers and designers to accurately model a stellarator’s complex magnetic fields, plasma behavior, and mechanical components (i.e., vacuum vessel, magnet systems and other structures). This has enabled implementation of a “plasma first” design process in which the initial design focus is on optimizing plasma equilibrium based on selected physics conditions. Key goals of this optimization process are to define plasma equilibrium conditions that reduce heat transport and particle loss from the plasma. As you might suspect, there are different technical bases for approaching the plasma optimization process. The stellarator’s magnet systems are designed to produce the confinement field needed for the specified, optimized plasma design.
This class of modern, optimized stellarators is characterized by complex, twisting plasma shapes and non-planar, modular toroidal coils that are individually designed, built and assembled. The net result is a stellarator with significantly better confinement performance that earlier stellarator designs. In this post, we’ll look in more detail at the following three advanced stellarators:
Wendelstein 7-AS [Max Planck Institute for Plasma Physics (IPP), Garching, Germany]
Helically Symmetric eXperiment (HSX, University of Wisconsin – Madison, USA)
Wendelstein 7-X [Max Planck Institute for Plasma Physics (IPP), Griefswald, Germany]
Wendelstein 7-AS Stellarator (1988 – 2002)
The Wendelstein 7-AS (W7-AS) was the first modular, advanced stellarator and was the first stellarator equipped with a divertor. It was used to test and validate basic elements of stellarator optimization. Basic physical parameters of W7-AS are:
Major radius 2 m
Minor radius 0.2 m
Magnetic field 2.5 – 3 T
The physical layout and scale of the W7-AS machine is shown in the first diagram, below, with more details on the magnet system in the following diagram.
Above & below: Wendelstein 7-AS. Source: Max Planck IPP, I. Weber
The W7-AS operated from 1988 to 2002. The IPP reported the following results:
Demonstrated that the innovative modular magnet coil system can be manufactured to exacting specifications.
Demonstrated improved plasma equilibrium and transport behavior because of the improved magnetic field structure.
Confirmed the effectiveness of the optimization criteria.
Demonstrated the effectiveness of a divertor on a stellarator (a common feature in tokamaks).
You’ll find more details on the W7-AS on the IPP website at the following link:
HSX is a small modular coil advanced stellarator that began operation in 1999 at the Electrical and Computer Engineering Department at the University of Wisconsin-Madison. HSX basic design parameters are:
Major radius 1.2 m
Minor radius 0.15 m
Magnetic field 1T
The physical arrangement of HSX is shown in the following diagram.
HSX physical configuration. Source: University of Wisconsin – Madison
The HSX was the first stellarator to be optimized to deliver a “quasi-symmetric” magnetic field. While the magnetic field strength is usually a two-dimensional function on the magnetic surfaces traced out by the field lines, quasi-symmetry is achieved by making it one-dimensional in so-called “magnetic coordinates” (Boozer coordinates).
Author Masayuki Yokoyama’s paper, “Quasi-symmetry Concepts in Helical Systems,” provides a description of quasi-symmetry.
“A key point of quasi-symmetry is that the drift trajectories of charged particles depend on the absolute value of the magnetic field (B) expressed in terms of magnetic field coordinates (Boozer coordinates). The plasma can be optimized in terms of the Boozer coordinates instead of the vector components of the field.”
You can read Yokoyama’s complete paper at the following link:
The HSX main magnetic field is generated by a set of 48 non-planar, modular coils, arranged in four field periods, yielding the twisting flux shape shown below.
HSX plasma configuration. Source: University of Wisconsin – Madison
The HSX team reported that “this is the first demonstration that quasi-symmetry works, and you can actually measure the reduction in transport that you get.”
The home page for this project is at the following link:
The Wendelstein 7-X (W7-X) is a Helias (helical advanced stellarator) and is the first large-scale optimized stellarator; significantly larger than Wendelstein 7-AS and HSX. The complete W7-X machine weighs about 750 tons, with about 425 tons operating under cryogenic conditions. The superconducting magnet system is designed for steady-state, high-power operation; nominally 30 minutes of plasma operation at 10 MW power. W7-X basic design parameters are:
The W7-X is drift optimized for improved thermal and fast ion confinement by: (a) implementing quasi-symmetry to reduce transport losses, (b) minimizing plasma currents (Pfirsch-Schluter & bootstrap currents) to improve equilibrium, and (c) designing a large magnetic well in the plasma cross-section to avoid plasma pressure instabilities.
The primary purpose of the Wendelstein 7-X is to investigate the new stellarator’s suitability for extrapolation to a fusion power plant design. The IPP website provides the following clarification:
“It is expected that plasma equilibrium and confinement will be of a quality comparable to that of a tokamak of the same size. But it will avoid the disadvantages of a large current flowing in a tokamak plasma: With plasma discharges lasting up to 30 minutes, Wendelstein 7-X is to demonstrate the essential stellarator property, viz. continuous operation.”
The main assembly of Wendelstein 7-X was completed in 2014. An IPP presentation on the manufacturing and assembly of W7-X is at the following link:
You’ll also find a good video, “Wendelstein 7-X — from concept to reality,” which provides an overview of the design and construction of the W7-X stellarator and the associated research facility, at the following link:
After engineering tests, the first plasma was produced at W7-X on 10 December 2015. A November 2016 article in Nature summarized on the results of initial operation of W7-X. The article, entitled, “Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000,” confirmed that the W7-X is producing the intended confinement field. This article includes the following 3-D rendering and description of the complex magnetic coil sets that establish the twisting plasma confinement fields in the W7-X.
“Some representative nested magnetic surfaces are shown in different colors in this computer-aided design (CAD) rendering, together with a magnetic field line that lies on the green surface. The coil sets that create the magnetic surfaces are also shown, planar coils in brown, non-planar coils in grey. Some coils are left out of the rendering, allowing for a view of the nested surfaces (left) and a Poincaré section of the shown surfaces (right). Four out of the five external trim coils are shown in yellow. The fifth coil, which is not shown, would appear at the front of the rendering.”
You can read the complete article at the following link:
A more detailed mechanical view of the W7-X, with a scale (gold) human figure is shown in the following diagram:
Source: IPP presentation, “Stellarators difficult to build? The construction of Wendelstein 7-X”
The large scale of the W7-X vacuum vessel is even more apparent in the following photo.
A segment of W7-X vacuum vessel. Source: adapted from IPP by C. Bickel and A. Cuadra/Science
Most of the wall protection components are uncooled. Operational limits on the W7-X (i.e., pulse duration, various temperatures) help protect the integrity of wall components.
The status of the W7-X as of February 2017 is outlined in a presentation by the W7-X team to the Fusion Energy Science Advisory Committee (FESAC), entitled “Recent results and near-term plans for Wendelstein 7-X,” which is available at the following link:
Update 19 March 2020: Proof of principal and a new upgrade campaign
In February 2020, Princeton Plasma Physics Laboratory (PPPL) reported on the SciTechDaily website that W7-X operation through the end of 2018 had successfully demonstrated the expected capability to moderate plasma leakage and improve plasma confinement. W7-X operation had achieved hundred-second pulses with heating powers of two megawatts and plasma energies of 200 megajoules. PPPL physicist Novimir Pablant stated, “This research validates predictions for how well the optimized design of the W7-X reduces neoclassical transport….,” and, “The research marks the first step in showing that high-performance stellarator designs such as W-7X are an attractive way to produce a clean and safe fusion reactor.”
Wide angle view of the interior of the Wendelstein 7-X plasma vessel, showing the different armor materials designed to take up the heat from the plasma. The surface contour of the wall follows the shape of the plasma. On average, the radius of the plasma is 55 cm. Credit: Bernhard Ludewig, Max Planck Institute of Plasma Physics
At the end of 2018, operation of the W7-X ceased and a new round of modifications was started. Key upgrades being implemented now for the W7-X are:
Installation of new water-cooled inner cladding on large sections of the plasma vessel to enable the W7-X to handle higher heating loads and longer plasma pulses, up to 30 minutes.
Installation of ten double strip, water-cooled divertor plates on the inner wall of the plasma vessel. Divertors are the parts of the new cladding system used to regulate the interaction between plasma and the inner wall of the plasma vessel. Without water cooling, the heat-resistant divertor tiles made of carbon-fiber-reinforced carbon could not withstand the heat load for the intended 30-minute plasma pulses.
In ten curved double strips, the divertor plates (brown) follow the shape of the twisted plasma (yellow). Source: IPP
IPP reports that this upgrade work is expected to continue until the end of 2021. You’ll find more details on the upgrade work, including the design of the divertors, on the IPP website at the following link: https://www.ipp.mpg.de/4828222/01_20
Conclusion
Following the success of two Wendelstein 7-X experimental campaigns from March 2016 to October 2018, a promising path forward is being pursued by the Max Planck Institute for Plasma Physics. Nonetheless, I believe my previous conclusion (below, from the original post in 2017) still stands. We’ll know a lot more after the W7-X upgrade work is completed and operations resume in late 2021.
So the jury is still out on the ability of advanced, optimized stellarators to take the lead over tokamaks in the long, hard journey toward the goal of delivering usable power from a fusion machine. Hopefully, the advanced stellarators will move the fusion community closer to that goal. No doubt, we still have a very long way to go before fusion power becomes a reality.
For more background information on stellarators:
A summary of Dr. Spitzer’s pioneering work at PPPL is documented in the following presentation:
Beidler, C.D., et al., “Stellarator Fusion Reactors – an Overview”, Max-Planck Institute for Plasma Physics, 2001, at the following link: http://fire.pppl.gov/itc12_wobig_paper.pdf
In June 2016, the International Atomic Energy Agency (IAEA) published a report by the Director General entitled, “Nuclear Technology Review 2016,” which highlights notable developments in 2015 in the following segments of the worldwide nuclear industry.
Power applications
Generation
Fuel cycle
Safety
Advanced fission
Gen III large water cooled reactors
Fast reactors
Gas-cooled reactors
Small & medium size reactors (SMRs)
Gen IV advanced reactors
Fusion
Accelerator and research reactor applications
Other applications
Emerging industrial applications of radiation technologies
Advances in medical imaging technology
Use of radiation in connection with managing mosquito disease vectors
Use of isotopic techniques for soil management
The following chart from the IAEA report shows the age distribution (years of operation) of the worldwide fleet of 441 operating power reactors. The median age of this fleet is about 26 years, and you can see a bow wave of aging nuclear power plants, followed by far fewer younger plants already in operation.
The following chart from the IAEA report shows the number of new plants under construction by region. As of the end of 2015, a total of 68 nuclear power plants were in various stages of their decade-long construction cycles. This chart clearly shows that Western Europe and the Americas are minor players in the construction of new reactors. Most of the new power reactor construction is occurring in Asia and Central / Eastern Europe.
IAEA reported that, in 2015, worldwide nuclear power generation reached 381.7 GWe. Projections for the future growth of nuclear power generation thru 2050 were given for two cases:
Low case: In this case, new plants just make up for the generating capacity lost from retiring plants. Projected 2050 worldwide generation: 371 GWe.
High case: This is a much more optimistic case, yielding about 964 GWe worldwide generation by 2050.
IAEA noted that, “The 21st Conference of the Parties to the United Nations Framework Convention on Climate Change (COP21) resulted in the Paris Agreement that neither identifies nor excludes any particular form of energy.” The Paris Agreement does not discriminate against nuclear power as a means for reaching lower carbon emission goals. In contrast, the U.S. Environmental Protection Agency’s (EPA) euphemistically named “Clean Power Plan” fails to give appropriate credit to nuclear power as a means for utilities and states to reduce the carbon emissions from their portfolio of power plants. (See my 3 July 2015 and 27 November 2015 posts for more on CPP).
IAEA further noted the contribution of nuclear power to meeting lower carbon emission goals:
“Nuclear power has significantly contributed to climate change mitigation by avoiding nearly 2 billion tonnes (metric tons) of carbon dioxide per year. For nuclear power to help limit global warming to 2o C by 2100, its capacity would need to match the high projection to avoid nearly 6.5 billion tonnes of greenhouse gas emissions by 2050.”
Among the small and medium size reactors (SMRs), IAEA noted that the following three were under construction in 2015: Argentina’s CAREM-25, Russia’s KLT-40S, and China’s HTR-PM. Another dozen SMRs were considered to be in the advanced design stage and potentially deployable in the near-term.
IAEA maintains its Advanced Reactors Information System (ARIS), as I reported in my 13 February 2015 post. This is a very comprehensive source of information on all types of advanced reactors. You can directly access ARIS at the following link:
The “Nuclear Technology Review 2016” provides a useful overview of worldwide nuclear fuel cycle activities:
Worldwide uranium mining in more than 15 countries produced about 57,000 tonnes of Uranium (U) in 2015. Kazakhstan is the leading producer, followed by Canada.
Worldwide annual capacity for conversion of U to UF6 was about 60,000 tonnes in 2015, approximately matching annual demand. Canada, China, France, Russia, UK and U.S. operate conversion facilities.
Worldwide annual enriched light water reactor (LWR) fuel fabrication capacity is about 13,500 tonnes vs. an annual demand of about 7,000 tonnes. In addition, the fuel fabrication capacity for natural uranium fuel for pressurized heavy water reactors (PHWRs) is about 4,000 tonnes vs. a demand of 3,000 tonnes. Thirteen nations produce LWR fuel, and five produce PHWR fuel.
Spent fuel reprocessing is being carried out in 5 nations: China, France, India, Russia and UK; with France and Russia offering reprocessing services to international customers. France and UK have the greatest capacity, reprocessing about 1,000 t HM/year.
IAEA reported that, “by the end of 2015, (worldwide) spent fuel in storage amounted to around 266,000 tonnes of heavy metal (t HM) and is accumulating at a rate of around 7,000 t HM/year.
Several nations are planning or developing their own geologic disposal facilities for spent nuclear fuel
There’s a lot more information in the IAEA report, including information on fusion, accelerators, research reactors, and industrial and medical applications of nuclear technologies. You can download this IAEA report at the following link:
Wide angle view of the interior of the Wendelstein 7-X plasma vessel, showing the different armor materials designed to take up the heat from the plasma. The surface contour of the wall follows the shape of the plasma. On average, the radius of the plasma is 55 cm. Credit: Bernhard Ludewig, Max Planck Institute of Plasma Physics
