Explainer: Nuclear fusion breakthrough achieved – what does it mean?

A technician reviews an optic inside the preamplifier support structure at the Lawrence Livermore National Laboratory in Livermore, Calif., in 2012. (Image Credit: Damien Jemison/Lawrence Livermore National Laboratory)

American scientists have achieved “ignition” —  a nuclear fusion reaction that produced more energy than it took to create. This was described as a “major scientific breakthrough” and a key step forward in the pursuit of a near-limitless source of clean energy.

“We have taken the first tentative steps toward a clean energy source,” said Jill Hruby, the U.S. Energy Department’s National Nuclear Security Administration. The fusion record was achieved at the National Ignition Facility at California’s Lawrence Livermore National Laboratory (LLNL). U.S. Secretary of Energy Jennifer Granholm said the breakthrough was “one of the most impressive scientific feats of the 21st century.”

What is the new breakthrough?

The US$3.5 billion National Ignition Facility (NIF), which has the world’s highest-energy laser system, used its set of 192 lasers to deliver 2.05 megajoules (MJ) of energy onto a pea-sized gold cylinder containing a frozen pellet of the hydrogen isotopes deuterium and tritium. It then produced 3.15 MJ of fusion energy output — roughly 54% more than the energy that went into the reaction.

Simply put, the scientists “shot a bunch of lasers at a pellet of fuel, and more energy was released from that fusion ignition than the energy of the lasers going in,” White House Office of Science and Technology Policy Director Arati Prabhakar explained on December 13.

Why is it important?

For more than 60 years, scientists have pursued one of the toughest challenges ever conceived: harnessing nuclear fusion and replicating the phenomenon that powers the Sun. With the latest experiment, the researchers achieved a milestone as for the first time the fusion reactor produced more energy than was used to trigger the reaction.

“Ignition allows us to replicate for the first time certain conditions that are found only in the stars and the sun,″ said U.S. Energy Secretary Jennifer Granholm. “This milestone moves us one significant step closer” to having zero-carbon fusion energy “powering our society.”

What is nuclear fusion?

Nuclear fusion is the process that powers the sun and other stars. The reaction occurs when nuclei of two atoms collide under extreme temperatures, causing a reaction that can generate tremendous amounts of energy with few environmental costs. Fusion works by pressing hydrogen atoms into each other with such force that they combine into helium, releasing enormous amounts of energy and heat without creating radioactive waste.

Fusion vs fission: The main difference is that fission is the splitting of an atom into two or more smaller ones while fusion is the fusing of two or more smaller atoms into a larger one.

To create fusion ignition, the National Ignition Facility’s laser energy is converted into X-rays inside the hohlraum, which then compress a fuel capsule until it implodes, creating a high-temperature, high-pressure plasma. (Image Credit: NIF)

How breakthrough will lead to clean renewable energy?

Unlike oil, coal, natural gas, and other fossil fuel sources, nuclear fusion does not produce greenhouse gas emissions or radioactive waste. Its major by-product is the non-toxic gas helium. The core materials of nuclear fusion — deuterium and tritium — are available in seawater. Deuterium can be extracted from water and tritium from lithium. 

The latest experiment aims to harness nuclear fusion to provide near-limitless clean energy on Earth. But there’s still a long way to go before this goal becomes a reality.

How and when can we harness clean energy?

The current achievement does not mean that fusion is now a viable carbon-free power source but there is significant progress. Kim Budil, director of the Livermore Lab, said that advances in recent years mean the technology is likely to be widely used in “a few decades” rather than 50 or 60 years as previously expected.

The experiment offers the possibility of “basically unlimited” fuel if the technology can be made commercially viable, says Daniel Kammen, a professor of energy and society at the University of California at Berkeley. 

Professor Riccardo Betti, an expert in laser fusion, says there’s a long road ahead before the net energy gain leads to sustainable electricity. One of the major hurdles to commercial use is scaling up the energy output. “This is one igniting capsule, one time. To realize commercial fusion energy, you have to do many things. You have to be able to produce many, many fusion ignition events per minute,” according to Kim Budil, Lawrence Livermore National Laboratory director. “There are very significant hurdles, not just in the science but in technology” that require concerted efforts and investment to build a power plant.

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