Nuclear fusion reactions are processes where atoms fuse together to form larger atoms. When light atoms such as hydrogen and helium fuse they release large amounts of energy - of the order of a million times more than is involved in chemical reactions. In the sun and similar stars the main reaction is hydrogen atoms fusing together via several intermediate steps to form helium atoms. However it is extremely challenging to create the conditions for these reactions in artificial fusion reactors and most work has been done on the deuterium-tritium reaction.
Many types of fusion reactions release neutrons which, by irradiating surrounding materials, transmute some of them into radioactive isotopes. However there are some aneutronic reactions which do not release neutrons and thus do not produce radioactive materials.
Cold fusion, now generally called Low Energy Nuclear Reactions, is an area in which a few workers have claimed successful results but either have not shared their methods with others or, where they have been shared, others have been unable to reproduce their results.
- 1 General
- 2 Drawbacks of Deuterium-Deuterium and Deuterium-Tritium
- 3 Tokamaks
- 4 Other designs
- 5 Wendelstein 7-X stellarator
- 6 EAST / China
- 7 Aneutronic fusion
- 8 3He-3He
- 9 Boron-Hydrogen
- 10 Cold fusion / LENR
Could nuclear fusion be sustainable? Robert Steinhaus; Quora; 29 May 2017
Deuterium fusion and its ultimate potential for worldwide sustainable energy generation
Discusses potential energy yield of D available on Earth compared to possible energy requirement over remaining lifetime of sun, and available fusion pathways.
Drawbacks of Deuterium-Deuterium and Deuterium-Tritium
Fusion reactors: Not what they’re cracked up to be Daniel Jassby; Bulletin of the Atomic Scientists; 19 Apr 2017
Fusion reactors have long been touted as the “perfect” energy source. Proponents claim that when useful commercial fusion reactors are developed, they would produce vast amounts of energy with little radioactive waste, forming little or no plutonium byproducts that could be used for nuclear weapons. These pro-fusion advocates also say that fusion reactors would be incapable of generating the dangerous runaway chain reactions that lead to a meltdown—all drawbacks to the current fission schemes in nuclear power plants.
And, like fission, a fusion-powered nuclear reactor would have the enormous benefit of producing energy without emitting any carbon to warm up our planet’s atmosphere.
But there is a hitch: While it is, relatively speaking, rather straightforward to split an atom to produce energy (which is what happens in fission), it is a “grand scientific challenge” to fuse two hydrogen nuclei together to create helium isotopes (as occurs in fusion). Our sun constantly does fusion reactions all the time, burning ordinary hydrogen at enormous densities and temperatures. But to replicate that process of fusion here on Earth—where we don’t have the intense pressure created by the gravity of the sun’s core—we would need a temperature of at least 100 million degrees Celsius, or about six times hotter than the sun. In experiments to date the energy input required to produce the temperatures and pressures that enable significant fusion reactions in hydrogen isotopes has far exceeded the fusion energy generated.
But through the use of promising fusion technologies such as magnetic confinement and laser-based inertial confinement, humanity is moving much closer to getting around that problem and achieving that breakthrough moment when the amount of energy coming out of a fusion reactor will sustainably exceed the amount going in, producing net energy. Collaborative, multinational physics project in this area include the International Thermonuclear Experimental Reactor (ITER) joint fusion experiment in France which broke ground for its first support structures in 2010, with the first experiments on its fusion machine, or tokamak, expected to begin in 2025.
As we move closer to our goal, however, it is time to ask: Is fusion really a “perfect” energy source? After having worked on nuclear fusion experiments for 25 years at the Princeton Plasma Physics Lab, I began to look at the fusion enterprise more dispassionately in my retirement. I concluded that a fusion reactor would be far from perfect, and in some ways close to the opposite.
Imagining Fusion Power Robert L. Hirsch; Energy Matters; 26 Sep 2016
- looks at cons of ITER
Fusion Research: Time to Set a New Path Robert L. Hirsch; Issues in Science and Technology; Summer 2015
The inherent limitations of the tokamak design for fusion power will prevent it from becoming commercially viable, but the lessons from this effort can inform future research.
Revamping Fusion Research Robert L. Hirsch; Journal of Fusion Energy; Apr 2016
A fundamental revamping of magnetic plasma fusion research is needed, because the current focus of world fusion research—the ITER-tokamak concept—is virtually certain to be a commercial failure. Towards that end, a number of technological considerations are described, believed important to successful fusion research. Beyond critical attention to plasma physics challenges, there must be a much sharper focus on electric utility acceptance criteria, which strongly reflect the public interest. While the ITER-tokamak experience has provided important understanding of a variety of technology issues, it is expensive and time-consuming. Engineers with commercial-world experience must become involved in future fusion research and must have a major influence on program decision-making and evaluation. Fusion engineers will have to be imaginative while being rooted in an understanding of fission reactor development, nuclear regulation, and electric utility realities, the proper consideration of which will impact fusion program success. Properly developed, fusion power holds great promise as an attractive electric power source for the long-term future.
MIT/Commonwealth Fusion Systems - SPARC
MIT Is Building The World's Most Powerful Superconducting Magnets For an Amazing Cause Michelle Starr; Science Alert; 12 Mar 2018
The most promising source of clean energy humans can ever hope for is still fusion power - and researchers at MIT have just received US$30 million in funding to help make it happen.
MIT has joined forces with a newly formed private company called Commonwealth Fusion Systems, and together they hope to have a pilot fusion power plant in 15 years' time.
Compact Nuclear Fusion Reactor Is ‘Very Likely to Work,’ Studies Suggest New York Times; Sept 2020
A series of research papers renews hope that the long-elusive goal of mimicking the way the sun produces energy might be achievable.
...in seven peer-reviewed papers published Tuesday in a special issue of The Journal of Plasma Physics, researchers laid out the evidence that Sparc would succeed and produce as much as 10 times the energy it consumes.
Tokamak Fusion - UK
Tokamak Energy turns on ST40 fusion reactor World Nuclear News; 28 April 2017
The UK's newest fusion reactor has been turned on for the first time and has officially achieved first plasma. The reactor aims to produce a record-breaking plasma temperature of 100 million degrees for a privately-funded venture. This is seven times hotter than the centre of the Sun and the temperature necessary for controlled fusion.
Oxford, England-based Tokamak Energy said today that with its ST40 reactor "up and running", the next steps are to complete the commissioning and installation of the full set of magnetic coils which are crucial to reaching the temperatures required for fusion. This will allow the ST40 to produce a plasma temperature of 15 million degrees - as hot as the centre of the Sun - in the autumn of this year.
The UK Just Switched on an Ambitious Fusion Reactor - And It Works FIONA MACDONALD; ScienceAlert; 1 MAY 2017
The UK's newest fusion reactor, ST40, was switched on last week, and has already managed to achieve 'first plasma' - successfully generating a scorching blob of electrically-charged gas (or plasma) within its core.
The aim is for the tokamak reactor to heat plasma up to 100 million degrees Celsius (180 million degrees Fahrenheit) by 2018 - seven times hotter than the centre of the Sun. For this reactor, that's the 'fusion' threshold, at which hydrogen atoms can begin to fuse into helium, unleashing near-limitless, clean energy in the process.
Atkins will help Tokamak Energy design the first nuclear fusion power plant Amit Katwala; Institution of Mechanical Engineers; 28 Sep 2017
Atkins will help Tokamak Energy to plan and design the UK’s first nuclear fusion power plant. The project, which was announced today, is the first stage of a partnership that will seek to develop the first ever fusion facility that generates more energy than it consumes. The global engineering firm will develop a timeline and strategy for the facility, as well as designs and cost estimates for the infrastructure around it.
The facility will be centred around a new tokamak – a device designed to contain and control a fusion reaction and generate power. Tokamak Energy’s current prototype, the ST40 is four metres tall and 2.5m in diameter. It contains the reaction using magnets within a donut-like shape, and next year it’s hoped it will be able to reach temperatures of 100 million degrees Celsius. The reactor in the new installation is expected to three or four times larger.
Apollo Fusion website
Former Google Vice President Starts a Company Promising Clean and Safe Nuclear Energy Brad Stone; Bloomberg Technology; 3 Apr 2017
Subcritical reactor wikipedia
- Accelerator Driven System
Nuclear fusion–fission hybrid wikipedia
Hybrid nuclear fusion–fission (hybrid nuclear power) is a proposed means of generating power by use of a combination of nuclear fusion and fission processes. The basic idea is to use high-energy fast neutrons from a fusion reactor to trigger fission in otherwise nonfissile fuels like U-238 or Th-232. Each neutron can trigger several fission events, multiplying the energy released by each fusion reaction hundreds of times. This would not only make fusion designs more economical in power terms, but also be able to burn fuels that were not suitable for use in conventional fission plants, even their nuclear waste.
Boeing nuclear engine
Boeing patents jet engine powered by lasers and nuclear explosions South China Morning Post; 26 Aug 2016
Laser engine may also be used to power rockets, missiles, and even spacecraft, according to patent
Boeing's new jet engine works by firing high-power lasers at radioactive material, such as deuterium and tritium.
The lasers vaporise the radioactive material and cause a fusion reaction — in effect a small thermonuclear explosion.
Hydrogen or helium are the exhaust byproducts, which exit the back of the engine under high pressure. Thrust is produced.
At the same time, the inside wall of the engine's thruster chamber — coated in uranium 238 — reacts with the high-energy neutrons produced by the nuclear reaction and generates immense heat.
The engine harnesses the heat by running coolant along the other side of the the uranium-coated combustion chamber.
This heat-energised coolant is sent through a turbine and generator that produces electricity to power the engine's lasers...."
General Fusion website
General Fusion’s Magnetized Target Fusion system uses a sphere filled with molten lead-lithium that is pumped to form a vortex. A pulse of magnetically-confined plasma fuel is then injected into the vortex. Around the sphere, an array of pistons drive a pressure wave into the centre of the sphere, compressing the plasma to fusion conditions. This process is then repeated, while the heat from the reaction is captured in the liquid metal and used to generate electricity via a steam turbine.
General Fusion - System Animation General Fusion Inc; YouTube; 1 Aug 2013
General Fusion's system uses a sphere, filled with molten lead-lithium that is pumped to form a vortex. On each pulse, magnetically-confined plasma is injected into the vortex. Around the sphere, an array of pistons impact and drive a pressure wave into the center of the sphere, compressing the plasma to fusion conditions.
Helion Energy website
Lockheed Martin's new Compact Fusion Reactor might change humanity forever Physics-Astronomy; Feb 2015
The crucial point in the Skunk Works arrangement is their tube-like design, which permits them to avoid one of the boundaries of usual fusion reactor designs, which are very restricted in the sum of plasma they can sustain, which makes them giant in size—like the gigantic International Thermonuclear Experimental Reactor. According to McGuire: “The traditional tokamak designs can only hold so much plasma, and we call that the beta limit. Their plasma ratio is 5% or so of the confining pressure. We should be able to go to 100% or beyond.” This design lets it to be 10 times smaller at the same power output of somewhat like the ITER, which is anticipated to produce 500 MW in the 2020s. This is essential for the use of fusion in all kind of uses, not only in huge, costly power plants. Skunk Works is committed that their structure—which will be only the size of a jet engine—will be capable enough to power almost everything, from spacecraft to airplanes to vessels—and obviously scale up to a much bigger size. McGuire also claims that at the size of the ITER, it will be able to produce 10 times more energy.
Polywell EMC2 electrostatic Wiffleball
Nextbigfuture has obtained the independent reviews of EMC2 Fusions work for the US Navy from 2012 and 2013. The reviews were obtained with a Freedom of Information Act request. In our July 5, 2013, report, the review committee stated, “The EMC2 team is finally at the threshold of success or failure with the Polywell / Wiffle Ball fusion power concept. The focus of EMC2 efforts has sharpened considerably and is now totally concentrated on experimentally producing a so-called Wiffle Ball (WB) plasma in a Polywell magnetic field configuration and diagnosing it in detail to verify its confinement properties, a step that is essential to the success of their fusion power concept.”
Laser-boron fusion now ‘leading contender’ for energy Wilson da Silva; University of New South Wales, Sydney, newsroom; 14 Dec 2017
A laser-driven technique for creating fusion that dispenses with the need for radioactive fuel elements and leaves no toxic radioactive waste is now within reach, say researchers.
Dramatic advances in powerful, high-intensity lasers are making it viable for scientists to pursue what was once thought impossible: creating fusion energy based on hydrogen-boron reactions. And an Australian physicist is in the lead, armed with a patented design and working with international collaborators on the remaining scientific challenges.
In a paper in the scientific journal Laser and Particle Beams, lead author Heinrich Hora from UNSW Sydney and international colleagues argue that the path to hydrogen-boron fusion is now viable, and may be closer to realisation than other approaches, such as the deuterium-tritium fusion approach being pursued by US National Ignition Facility (NIF) and the International Thermonuclear Experimental Reactor under construction in France.
Road map to clean energy using laser beam ignition of boron-hydrogen fusion H. Hora, S. Eliezer, G.J. Kirchhoff, N. Nissim, J.X. Wang, P. Lalousis, Y.X. Xu, G.H. Miley, J.M. Martinez-Val, W. McKenzie, J. Kirchhoff; Laser and Particle Beams; 12 Dec 2017
With the aim to overcome the problems of climatic changes and rising ocean levels, one option is to produce large-scale sustainable energy by nuclear fusion of hydrogen and other very light nuclei similar to the energy source of the sun. Sixty years of worldwide research for the ignition of the heavy hydrogen isotopes deuterium (D) and tritium (T) have come close to a breakthrough for ignition. The problem with the DT fusion is that generated neutrons are producing radioactive waste. One exception as the ideal clean fusion process – without neutron production – is the fusion of hydrogen (H) with the boron isotope 11B11 (B11). In this paper, we have mapped out our research based on recent experiments and simulations for a new energy source. We suggest how HB11 fusion for a reactor can be used instead of the DT option. We have mapped out our HB11 fusion in the following way: (i) The acceleration of a plasma block with a laser beam with the power and time duration of the order of 10 petawatts and one picosecond accordingly. (ii) A plasma confinement by a magnetic field of the order of a few kiloteslas created by a second laser beam with a pulse duration of a few nanoseconds (ns). (iii) The highly increased fusion of HB11 relative to present DT fusion is possible due to the alphas avalanche created in this process. (iv) The conversion of the output charged alpha particles directly to electricity. (v) To prove the above ideas, our simulations show for example that 14 milligram HB11 can produce 300 kWh energy if all achieved results are combined for the design of an absolutely clean power reactor producing low-cost energy.
Wendelstein 7-X stellarator
EAST / China
'Man-Made' Sun Produces Longest Pulse At 50 Million Degrees NDTV; 17 Mar 2016
The Experimental Advanced Superconducting Tokamak (EAST), an artificial sun experiment developed by Hefei Institute of Physical Science of the Chinese Academy of Science, realised a ultra-high temperature (UHT) long pulse plasma discharge for 102 seconds as of January.
Aneutronic fusion Wikipedia
Would nuclear fusion be radioactive? Robert Steinhaus; Quora; 17 Nov 2017
There is a advanced form of nuclear fusion that should produce NO radioactivity.
He3 + He3 -> He4 + 2protons + 12.9 MeV
He3-He3 fusion uses totally non-radioactive fuel and produces totally non-radioactive Helium as nuclear waste (and no neutrons - only easily shieldable protons that can be collected and directly produce electricity at very high efficiency exceeding the Carnot efficiency of any thermal power plant)
The combined requirements of He3-He3 ICF fusion is only about 40X the combined temperature, plasma pressure, and confinement time requirements of DT fusion. This not an impossibly high requirement and will be reached in future ICF fusion power plants.
Is it possible to build a portable sized nuclear reactor and use it to power a home or vehicle? Robert Steinhaus; Medium; 8 Jul 2019
Really small and efficient nuclear reactors are feasible. Nuclear fusion has significant advantages when building really small reactors. Inertial Confinement Fusion operates using by far the highest density fusion plasma and this is significant from the standpoint of building a small and economic power reactor. The power that can be drawn from a burning plasma at fusion conditions is proportional to the square of the density of the fusion plasma. The denser the fusion plasma, the more energy that can be extracted from it. Inertial Confinement Fusion power plants that employ He3-He3 fusion could be small if desired (both in physical size and in power output).
In April 2021 an article "This Nuclear Reactor Just Made Fusion Viable by 2030. Seriously." by Caroline Delbert in Popular Mechanics claimed:
TAE Technologies, the world’s largest private fusion company, has announced it will have a commercially viable nuclear fusion power plant by 2030, which puts it years—or even decades—ahead of other fusion technology companies.
Cold fusion / LENR
Rossi 1 Megawatt Energy Catalyzer is a failure after 3 years of testing by Industrial Heat Next Big Future; 8 Apr 2016
A lawsuit has been filed by Andrea Rossi and Leonardo Corporation against Industrial Heat. Industrial Heat rejects the claims in the suit. They are without merit and we are prepared to vigorously defend ourselves against this action. Industrial Heat has worked for over three years to substantiate the results claimed by Mr. Rossi from the E-Cat technology – all without success.