What the heck is nuclear fusion – and when will we harness it?

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Nuclear fusion is in the news again. This week, the US Department of Energy announced what it called a “major scientific breakthrough” in fusion energy research: For the first time, a fusion experiment had produced more energy than the energy needed to start the reaction . It’s not the first time we hear about the progress of fusion. There have been headlines for decades touting breakthroughs big and small, usually implying that we are closer than ever to generating all the clean energy we will ever need from fusion.

A “great scientific breakthrough” in fusion energy research

It’s a lot to take in, so The edge put together this fusion energy guide with the help of some experts. We’ve summarized it below scientists’ dreams of fusion, as well as the harsh realities facing the technology to bring the power of fusion from scientific ambition to commercial reality.

What is nuclear fusion?

Nuclear fusion has been an elusive energy dream for nearly a century. In theory it sounds quite simple. Stars, including our sun, create their own energy through a process called fusion, where atoms fuse together at high temperatures and pressures to make a heavier atom. Usually this concerns hydrogen atoms combine to form helium. The reaction releases a lot of energy, which is why scientists on Earth want to simulate it in a controlled way. (They’ve managed to do it in an uncontrolled way before. It’s called a hydrogen bomb.)

How does nuclear fusion differ from nuclear fission?

The nuclear power plants we have today generate electricity through fission, which is more or less the opposite of nuclear fusion. Nuclear fission releases energy by splitting atoms apart instead of fusing them together.

What are the benefits of nuclear fusion?

In theory, the possibilities are endless once humans figure out how to make nuclear fusion happen in a controlled manner. Hydrogen is the simplest and most abundant element in the universe. For example, you can get it from seawater. And if you do, a gallon of seawater can generate as much energy as 300 gallons of gasoline, according to the Department of Energy.

Today’s nuclear reactors have a big mess to clean up thanks to nuclear fission. By splitting heavily atoms, nuclear fission leaves radioactive waste. What to do with that nuclear waste for millions of years to come is an environmental nightmare the US still hasn’t figured out.

Fusion does not have these problems. Fusion builds new atoms – usually helium, like the stuff in balloons. It does not cause greenhouse gas emissions. In addition, this is a potentially unlimited source of energy that does not depend on the weather, which is still a challenge with renewable energy sources such as solar and wind.

Why haven’t we been able to make the ignition happen?

Well, it turns out to be very difficult to recreate a star in a lab. To initiate fusion, you need enormous amounts of pressure and heat. The environment in the heart of the sun naturally creates the extreme pressures necessary for fusion to take place. Here on Earth, scientists don’t just have that kind of pressure lying around and even have to hit the temperatures hotter than the sun to get the same response. Historically, that has taken more energy than scientists have actually been able to generate through fusion in a lab.

This also requires extraordinary amounts of money and highly specialized technology. With all that in mind, it’s amazing that we’ve made any scientific progress at all. Actually commercialize? That has a mountain of problems that we’ll talk about in a moment.

What is this new “breakthrough in nuclear fusion” that everyone is talking about?

At 01:03 on Monday, December 5, researchers at the Lawrence Livermore National Lab achieved “fusion ignition” for the first time on Earth.

Simply put, “They shot a bunch of lasers at a fuel pellet, and more energy was released from that fusion ignition than the energy of the lasers that went into it,” said Arati Prabhakar, director of the White House Office of Science and Technology Policy. , at a press conference. conference announcing the achievement on December 13.

A room filled with laser equipment

The target chamber of LLNL’s National Ignition Facility, where 192 laser beams delivered more than 2 million joules of ultraviolet energy to a small fuel pellet to create fusion ignition on December 5, 2022.
Image: Lawrence Livermore National Laboratory

Specifically, the experiment produced 3.15 megajoules of energy compared to the 2.05 megajoules the lasers used to initiate the fusion reaction. That’s about 1.5 gains in energy. It is modest, but achieving a net energy gain was nevertheless an important first for fusion research.

How did they do that?

Researchers used the world’s largest, highest energy laser system called the National Ignition Facility (NIF). NIF is the size of three football fields and can fire 192 powerful laser beams at a single target. To achieve fusion ignition, the energy of those 192 laser beams squeezes fuel into a diamond capsule about the size of a peppercorn and 100 times smoother than a mirror. The capsule contains hydrogen isotopes, some of which are “fused together” to generate energy. All in all, about 4 percent of that fuel was converted into energy.

Lasers are neat. Also tell me more about the diamonds.

“The fuel capsule is a BB point shell made of diamond that needs to be as perfect as possible,” said Michael Stadermann, Target Fabrication Program manager at Lawrence Livermore National Laboratory, at the Dec. 13 press conference. “As you can imagine, perfection is really hard, and so we’ve got to get there — we still have little flaws in our shells, smaller than bacteria.”

Symmetry plays a huge role in achieving ignition when it comes to both the target and its implosion. The lasers must be properly aligned and when it comes to the target you must maintain near perfect symmetry as you blast your target with intense pressure and heat. It’s like compressing a basketball to the size of a pea, experts say, all while maintaining a perfect spherical shape. If you deviate from that shape, you waste too much kinetic energy and you don’t get ignition.

Does this mean we are now getting nuclear fusion energy?

Not by a long shot. As the lab achieved “ignition,” they based their performance on a narrow definition of a “net energy gain” that focused only on the output of the laser. While the lasers fired 2.05 megajoules of energy at their target, they consumed a whopping 300 megajoules of the power grid. Taking this into account, a lot of energy was lost in this experiment.

To eventually have a fusion power plant, you need a much larger profit than 1.5 net energy profit. Instead, you need a profit of 50 to 100.

Where do we go from here?

There’s a lot of work to do. Researchers are constantly trying to make even more precise targets, centered on that perfectly symmetrical sphere. This is incredibly labor intensive. So much so that a single pellet target could cost about $100,000 today, according to University of Chicago theoretical physicist Robert Rosner. Rosner previously served on the NIF’s external advisory committee. That cost per pellet should drop to a few cents if fusion is to go commercial, Rosner says, because a fusion reactor might need as many as a million pellets per day.

And if you want to achieve ignition again using lasers, you need a setup that is more efficient and can work much faster. The NIF, as powerful as it is, is based on laser technology from the 1980s. There are more advanced lasers today, but the National Ignition Facility is a behemoth – construction began in 1997 and was not operational until 2009. Today, the NIF can fire its laser once every four to eight hours. A future fusion power plant should fire 10 times per second, according to Lawrence Livermore National Laboratory plasma physicist Tammy Ma.

“This is one detonator capsule, one time. To realize commercial fusion power, you have to do many things; you have to be able to produce a lot of fusion ignition events per minute,” Kim Budil, director of the Lawrence Livermore National Laboratory, said at the press conference. “There are very significant hurdles, not only in science but also in technology.”

Are there other ways to fuse atoms together?

Yes, lasers are certainly not the only strategy used to trigger inflammation. The other main strategy is to use magnetic fields to constrain plasma fuel using a device called a tokamak. A tokamak can be much cheaper to build than the NIF. Even private companies have built tokamaks, so more research has been done in this area.

A tokamak has yet to ignite. But the magnets it uses have the potential to sustain a fusion reaction over a longer period of time. (At NIF, fusion reactions take place within a fraction of a nanosecond.) Ultimately, breakthroughs in both areas of research could help bring fusion energy closer.

So what does achieving “inflammation” actually accomplish?

“We’ve reached the top of the hill,” said Gianluca Sarri, a physics professor at Queen’s University Belfast. The edge. He says establishing ignition was essentially the “hardest step” in fusion energy research, and it’s essentially “downhill” from here, even though there’s still a long way to go.

That said, achieving ignition is more of a scientific breakthrough than one with practical application to our energy system – at least not for many years to come.

However, when it comes to nuclear defense and non-proliferation, achieving ignition can have a more direct impact.

Wait, what is this about nuclear weapons?

NIF was originally developed to conduct experiments that would help the US maintain its stockpile of nuclear weapons without actually blowing them up. The 1996 Comprehensive Nuclear Test Ban Treaty banned all nuclear explosions on Earth and ended underground test explosions. NIF broke ground the following year. The nuclear ignition it was finally able to achieve in its Dec. 5 experiment essentially mimics the uncontrolled fusion that happens when a nuclear bomb explodes. The hope is that achieving ignition in a controlled manner in a lab will allow researchers to validate the computer models they’ve developed to replace live test explosions.

Cut to the chase. When will we get nuclear fusion power plants?

The most optimistic experts The edge expressed the hope that we would have the first fusion power station within ten years. But most experts, while still excited about the future of fusion power, think we’re probably decades away.

Will this solve climate change?

As long as it takes, we can’t afford to wait a decade or more for fusion power to remove pollution from our energy system. To prevent global warming from reaching a point where humanity would struggle to adapt, research shows that the world needs to reduce greenhouse gas emissions to net zero by around 2050. By 2030, carbon dioxide emissions from fossil fuels about half. That’s much faster real-world progress than fusion research has ever been able to achieve.

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