Nuclear fusion has made a major breakthrough, according to US scientists.
If an experiment goes well, it could pave the way for lots of clean energy in the future, but there are still big problems to solve.
After more than 50 years of research into nuclear fusion, scientists have confirmed that a big step forward has been made that could lead to a lot of clean energy in the future.
Researchers at the US National Ignition Facility in California said that fusion experiments had given off more energy than was put in by the lab’s huge, high-powered lasers. This is called “ignition” or “energy gain,” and it is a big deal.
Scientists praised the breakthrough as proof that the power of the stars can be used on Earth. However, the technology is still not ready to be used in power plants, and it won’t solve the climate crisis any time soon.
The policy director at the White House Office of Science and Technology, Dr. Arati Prabhakar, said, “Last week, they fired a bunch of lasers at a pellet of fuel, and the fusion reaction gave off more energy than the lasers put in. This is a great example of what can be done when you keep trying.
Fusion energy makes clean energy more likely because the reactions don’t make greenhouse gases or radioactive waste. Fusion fuel is made of heavy forms of hydrogen called deuterium and tritium. One kilogram of fusion fuel gives as much energy as 10 million kilograms of fossil fuel. But 70 years have passed to get to this point.
Jill Hruby of the National Nuclear Security Administration (NNSA) said at the announcement on Tuesday that the US had “taken the first tentative step toward a clean energy source that could change the world.”
At the Lawrence Livermore National Laboratory, near San Jose, there is a huge complex called the National Ignition Facility. It was built so that short, small-scale experiments could be done to re-create what happens inside nuclear bombs. This way, the US could keep its nuclear warheads in good shape without having to do nuclear tests.
But the experiments are also steps toward clean fusion power. For the reactions to happen, scientists fire up to 192 huge lasers into a hohlraum, which is a centimeter-long gold cylinder. The intense energy heats the container to more than 3 million degrees Celsius, which is hotter than the sun’s surface, and bathes a fuel pellet the size of a peppercorn in X-rays.
The X-rays remove the pellet’s surface and set off a rocket-like implosion, which raises the temperature and pressure to levels only seen inside stars, giant planets, and nuclear explosions. The implosion goes at 400 km/s, which causes the deuterium and tritium to join together.
Einstein’s equation E=mc2 says that when two hydrogen nuclei join together, they make a lighter helium nucleus and a burst of energy. Deuterium is easy to get from seawater, while lithium, which is found in the Earth’s crust, can be used to make tritium.
In the most recent experiment, scientists put in 2.05 megajoules of laser energy and got 3.15 megajoules back. This is a gain of about 50% and shows that fusion reactions in the pellet were driving more fusion reactions. Dr. Marvin Adams at the NNSA said, “The energy was made in less time than it takes light to travel one inch.”
Still, the search for fusion power plants has a long way to go. Even though the pellet gave off more energy than the lasers put in, the calculation doesn’t take into account the 300 megajoules or so that were needed to power up the lasers. About once a day, the NIF lasers fire, but a power plant would have to heat targets 10 times per second. The cost of the goals is another issue. The ones used in the US experiment cost tens of thousands of dollars, but they would only need to cost pennies for a power plant to work. Another question is how to get the heat from the energy.
The head of the Lawrence Livermore National Laboratory, Dr. Kim Budil, said that “a few decades of research could put us in a position to build a power plant” if enough money was spent on it. She also said that an alternative power plant based on technology used at the Joint European Torus (JET) in Oxfordshire could be ready sooner.
Justin Wark, a professor of physics at the University of Oxford and the director of the Oxford Centre for High Energy Density Science, said, “In some ways, everything changes, and in other ways, nothing changes.” “This result proves what most physicists have always thought: that fusion is possible in the lab. But the problems that need to be solved to make something that looks like a commercial reactor are huge and shouldn’t be taken lightly.
He said that asking how long it might take to solve the problems was like asking the Wright brothers, right after their first flight, how long it would take to build a plane that could fly across the Atlantic. “I know that everyone wants to see this as the best way out of the energy crisis. It’s not, and anyone who says it is with confidence is lying. Fusion isn’t likely to have an effect soon enough to help with the climate change crisis we’re facing right now, so we can’t let up on our efforts in this area. The most recent results also show that the basic science works. The laws of physics don’t stop us from reaching the goal; the problems are technical and economic. The Nobel Prize-winning atomic physicist Niels Bohr once said, “It’s hard to predict the future, especially when you don’t know what will happen.”
Dr. Mark Wenman, a reader in nuclear materials at Imperial College London, called it “a fantastic scientific breakthrough—something we haven’t done in 70 years of trying.” But he said, “There are still problems with how to get the energy out of the system, how to keep it going long enough to be useful, how to increase the amount of energy, and whether it can be cheap enough to compete with other sources.”