The larger nuclei again needs less energy to hold it together — so energy is released. This is what happens in the Sun and stars, and research on how to harness fusion energy on Earth is being carried out in devices such as tokamaks and stellarators. While it might seem confusing that energy can be generated by both fusion and fission , as they appear to be quite opposite processes, the explanation lies in the size of the nuclei.
Light elements, such as hydrogen and helium, have small nuclei that release lots of energy when they fuse together.
Bigot was successful in establishing a professional project culture, and construction is now two-thirds complete. ITER will have many capabilities that go well beyond current tokamaks.
It will be the first device that can generate a burning plasma and explore the fundamentals of how a tokamak contains the fusion reaction and the process of self-heating.
This cutaway schematic of the ITER facility shows the tokamak in the center with a simulation of the fusion plasma inside the tokamak. The entire device is about five stories tall. ITER will be by far the largest and highest magnetic field tokamak in the world, and it will be powered by a central solenoid that will be the most powerful pulsed superconducting magnet ever constructed Figure 5.
Fabricated from 36 km of superconducting cable, this 1,ton magnet will drive 15 million amperes of current through the plasma, far more than anything that has been possible before.
The first of six modules that will comprise the central solenoid has finished testing and is being shipped to France this summer. In addition, ITER will serve as a test bed for a number of critical fusion technologies, including tritium breeding, plasma control, advanced diagnostics, and disruption mitigation.
Though it will not operate as a power plant, ITER will test safety features that future fusion power plants will require. As a first-of-a-kind research and demonstration project, ITER is naturally quite expensive. As large as that figure may seem, it is spread across a coalition of 35 nations, all of which will share in the technology ITER develops.
Short summaries of some of the efforts are given below. Courtesy: TAE Technologies. TAE Technologies. Though this is a more difficult reaction to achieve—requiring temperatures at least an order of magnitude higher—it has the advantage of not producing the highly energetic neutrons that complicate DT fusion.
FRC is a magnetic confinement method forming a toroidal plasma, but without a toroidal magnetic field Figure 6.
TAE is based in Irvine, California. It is hoped this will allow for smaller, more efficient, and less expensive magnets. General Fusion. This Vancouver, British Columbia—based company is pursuing one of the more revolutionary approaches, which it calls magnetized target fusion MTS. The MTS concept uses a sphere filled with molten lead-lithium, which is then pumped to form a vortex.
A pulse of magnetically confined plasma fuel is injected into the vortex, and an array of pistons creates a shock wave in the liquid metal to compress the plasma to fusion conditions. Heat from the liquid metal will then be captured and used to generate electricity.
Tokamak Energy. A UK company, Tokamak Energy is working on magnetic confinement fusion, but employing a tokamak with a more spherical shape, based on a concept developed in the U.
This device, called ST40, has been commissioned and research on it is currently ongoing. Tokamak Energy claims to have achieved plasma temperatures of up to 15 million degrees Celsius. ITER is not the only undertaking generating excitement in the fusion community. At least a dozen private start-up companies have begun investigating alternative approaches to fusion energy over the past decade see sidebar. Some of them are working on slightly different magnetic confinement methods, others are pursuing truly innovative—if high-risk—methods that could produce dramatic breakthroughs.
All of them are looking for paths to fusion that are simpler and less expensive than ITER. What will come after ITER? The details are still to be determined, but a number of targets are in sight. If all goes well, the technology from ITER should enable electricity generation from fusion, and member nations are not waiting until the late s to begin planning.
Several follow-on devices that will be even higher performance than ITER are in development. Courtesy: China Institute of Plasma Physics. Its initial phase will demonstrate fusion operation at about MW fusion power, but it will eventually be upgraded to at least 2 GW fusion power and MW net generation.
Formal construction of the device is slated to begin in the s, but construction of supporting facilities and key prototype components has already begun at a location in Hefei. Courtesy: EUROfusion. In the U. Until recently, progress toward fusion energy in the U. Funding for the U. A report from the National Academies of Science in strongly recommended that the U. This plant would likely have net generation of about MW to MW. The preference for a smaller design reflects the economic realities of electricity generation in the U.
The study is expected to be completed later this year. When will we see fusion as a meaningful element of the power mix? In this, it is worth remembering that practical fission generation was first demonstrated in the s, yet it was not until the mids that commercial nuclear plant construction began on a large scale.
Several of the earliest fission plants were public-private partnerships between utilities and the Atomic Energy Commission. The first U.
This does suggest, however, that large-scale commercial fusion energy should not be expected before the s, roughly 20 years after ITER begins DT operations.
Much of how a fusion plant would be built and operated does not fit within existing NRC regulations, a fact the NRC itself has recognized. The fusion industry has begun engaging with the NRC on what such a regulatory approach would look like, but no official rulemaking has begun, nor is it likely to until the technology of fusion power plants is considerably clearer.
Both federal and state regulatory environments will need to be adapted for fusion, a process that is likely to be drawn out and subject to extensive litigation. Though this article has focused on scientific and engineering factors, the ultimate deciding factors will be social and economic.
Fusion power plants will be built when investors and public utility commissions begin viewing them as worthwhile investments. Exactly when that point will be reached is difficult to say. It is likely that electricity from the first fusion plants will be expensive compared to other options, though the same was once true about large-scale renewable generation.
Fusion generation is certainly amenable to economies of scale, but the U. The proposed approach of developing a compact fusion pilot plant thus represents a strategic way to develop the technology before scaling up once the investment community has gained confidence in the economics of larger plants.
This pressure, combined with temperatures up to 27 million degrees Fahrenheit , gets atoms to fuse together. We don't have the technology to recreate the Sun's massive pressures, so researchers have to make up for that by getting hydrogen atoms even hotter than the sun does — in the range of hundreds of millions of degrees Fahrenheit. They heat up the atoms using various tools, including particle beams, electromagnetic fields such as microwaves and radio waves, and lasers.
The temperatures needed are so hot that the hydrogen fuel becomes a plasma , a state of matter that exists when a gas's atoms split into positively and negatively charged particles. Stars and lightning are plasma, as is the luminous matter inside neon signs. Researchers have been producing controlled fusion reactions for decades. These days, the big goal that hasn't happened yet is to make a fusion reactor that produces more energy than it takes in.
Plasma, like lightning, is very difficult to control. Cold fusion is the theoretical fusion of atoms at room temperature.
No one has ever done cold fusion — although there have been many false claims over the years. Scientists researching fusion energy are more interested in hot fusion, which they have been doing the s — the challenge now is just how to turn it into useful energy.
There are many approaches. Here are the two most worth watching. Researchers often do this in a tokamak , a donut-shaped reactor the weird shape helps keep the plasma in place. In the s, the European tokamak JET achieved 16 million watts of fusion power for less than a second. On the whole, JET was able to produce 65 percent of the energy that went into the experiment.
More recently, an international group is building the world's largest fusion reactor. This is an even bigger tokamak called ITER.
The goal of ITER is to produce million watts of power — in the range of a real power plant — for seconds at a time. The researchers also want to produce ten times more energy than is used by the system.
See how tiny that person in blue is compared to this giant fusion reactor? The NIF fires the lasers at a tiny gold can, which vaporizes and gives off x-rays. Those x-rays then hit a spherical pellet of hydrogen fuel that's smaller than a peppercorn. The x-rays heat and compress the fuel, which turns into plasma.
Then a minuscule portion of that plasma fuses into helium, giving off energy and neutrons for a split second. In February, , researchers at NIF reported that the fuel pellet made more energy than it absorbed for the first time.
The method isn't yet useful for any practical real-world power needs: the experiment's lasers used about times more energy than the fuel pellet produced. Still, it was promising: the results were in line with NIF's computer predictions, a sign that physicists' understanding of plasma is improving.
If people had to pick one, most would put their money on ITER. That's because NIF only researches fusion power as a side project — its main task is performing studies that help maintain and test the US nuclear arsenal. However, there's also a good chance that no one will succeed in producing practical fusion power. What scientists are currently doing are research projects that won't be hooked up to the power grid.
And getting a machine to do fusion for a split second every once in a while is nothing compared with building an actual power plant that can withstand the trauma of doing fusion all the time. It's a major engineering challenge, and some say that making a commercial power plant will be even harder than getting fusion to work in the first place. One big reason is that it requires working with plasma , which is really tricky. Because plasmas aren't that common on Earth, scientists had very little experience with them until they started studying fusion.
Plasma is difficult to hold: The plasma used in fusion-energy research is hundreds of millions of degrees Fahrenheit. You can't hold it using a solid container, because the container would just melt. Instead, physicists have to corral it using electromagnetic fields or work with it so quickly in less than a billionth of a second that holding it isn't an issue. Plasma is difficult to compress: If you don't compress plasma from all sides perfectly evenly, it will squish out wherever it can.
Scientific American explained this well: "Imagine holding a large, squishy balloon. Now squeeze it down to as small as it will go. No matter how evenly you apply pressure, the balloon will always squirt out through a space between your fingers. The same problem applies to plasmas. Anytime scientists tried to clench them down into a tight enough ball to induce fusion, the plasma would find a way to squirt out the sides. The folks associated with ITER say that they'll have plasma in the reactor in and will be doing fusion by But the project has been dogged by delays, not to mention a very negative review of its management recently.
So take those dates with a giant grain of salt.
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