The fuel capsule at the US National Ignition Facility is compressed by lasers. Shutterstock/Lawrence Livermore National Laboratory
For only the second time ever, increased performance over the initial successful effort, a fusion experiment has yielded a net gain in energy. But there are some crucial limitations to remember before getting excited about the future era of infinite renewable energy.
Just what are the benefits of fusion energy?
Fission processes, in which atoms are blasted apart to liberate energy and smaller particles, constitute the basis for today’s nuclear power plants. In contrast, fusion involves compressing smaller particles together to form larger atoms, just like the sun does. Fusion can produce more energy with no radioactive waste, but it has proven to be a gigantic task for physicists and engineers to confine and regulate such a reaction.
Ignition: what happened and how did it start?
When scientists at California’s Lawrence Livermore National Laboratory (LLNL) managed to extract more energy from a fusion reaction than they put into it, they made history in December 2022. Fusion was achieved in the laboratory’s National Ignition Facility (NIF) fusion reactor by subjecting isotopes of hydrogen (deuterium and tritium) to high enough temperatures and pressures generated by lasers. These lasers have an output of 2.1 MJ, however the reactor generated about 2.5 MJ, an increase of about 20%. While those ratios are far from what would be required to run a commercial reactor, they did provide a crucial glimmer of hope that fusion reactors were a realistic possibility.
The lab has apparently improved upon these figures, with the reactor producing roughly 3.5 megajoules. An ignition is defined as a reaction that exceeds break-even. The Financial Times claims the experiment took place on July 30.
Since our initial demonstration of fusion ignition in December 2022 at the National Ignition Facility, we have been conducting tests to further our understanding of this fascinating new scientific regime. On July 30th, we performed a repeat ignition experiment at NIF. The data is currently being analysed. A representative from LLNL informed New Scientist that the organisation would follow its usual procedure and share the findings at upcoming scientific conferences and in peer-reviewed publications.
What does this signify for the future of fusion energy?
In a nutshell, no.
The output of the reactor is more than that of the lasers, but the lasers are very inefficient, which is an issue. They require more electricity than the entire United States grid can provide in order to generate 2.1 megajoules of energy. Making a reaction that is self-sustaining in terms of all the energy it takes to complete it, not just the final laser stage, is a major problem for the future.
Another concern is that the NIF reactor can only be turned on once, for a few billionths of a second, before its components must be cooled for several hours. A commercial reactor would need to have numerous ignitions every second, essentially round the clock.
Naturally, even after a reactor has been designed to run for extended durations and its genuine energy requirements have been countered by the lasers, it will still only be breaking even. To make the astronomical investment in fusion power plants economically viable, we need to extract a substantial amount of net energy.
What is the general consensus?
According to physicist Jeremy Chittenden of Imperial College London, the true milestone will be reached in 2021 when an experiment at LLNL proves that this form of reactor can work at all, independent of output.
For the first time ever, we exported more energy than we imported in December of last year, and that was the greater story. However, scientifically speaking, that was merely an expected result of their previous year’s demonstrations. In essence, he explains, this represents an even greater increase in the already record-breaking harvest.
According to Chittenden, recent progress has come from maintaining control of the reaction for longer periods of time, allowing for a greater amount of energy to be extracted. Only a small fraction of the fuel is actually used in the tests at LLNL.
The ability to “control and hold the plasma there for longer and get more energy out” has been demonstrated, he says. When using a match, “you have to light the head of the match, get the burn process working, and then basically just hold the match as long as you can before you burn your fingers.”
Do you think fusion will eventually be solved?
The future cannot be known with certainty since there may be insurmountable obstacles, yet there is more reason for hope now than ever before. In essence, the ignition benchmark verifies the validity of the science and shifts the focus from physics to engineering.
There are two primary lines of investigation that strive to produce practical nuclear fusion. Both methods involve containing a plasma, but one utilises magnetic fields and the other employs lasers. The second method, inertial confinement fusion, is what NIF employs; it entails heating and rapidly expanding a tiny capsule containing hydrogen fuel with lasers. However, there are many new companies developing novel ideas that could be successful. Through these tests, we are gaining insight into the nature of the issue and potential solutions.
Chittenden argues that although the LLNL reactor is likely to show significant efficiency improvements, fundamental adjustments are required to make such a system economical. As the author puts it, “it’s intrinsically inefficient because of this indirect approach, which is this conversion of lasers into X rays, means we have to heat up a lot more material up than we would, for example, if we just used the lasers to heat the fuel directly.”
One thing is certain, though: we cannot count on technology to solve the climate change dilemma. A fusion reactor that actually works is at least several decades away. Clean and abundant energy will have to come from renewable sources in the short and medium term, but fusion reactors will be the probably the greatest payoff ever gained from a coordinated research effort spanning more than a century.
FAQs
Q1: What is the basis of fusion energy?
A1: Fusion involves compressing smaller particles to create larger atoms, releasing energy in the process, unlike nuclear fission that breaks atoms apart.
Q2: How did the fusion experiment at LLNL succeed in achieving fusion?
A2: Scientists at LLNL achieved fusion by subjecting hydrogen isotopes to high temperatures and pressures using lasers, yielding more energy than was input.
Q3: What are the potential benefits of fusion energy?
A3: Fusion could offer a cleaner energy source with abundant fuel, minimal radioactive waste, and reduced environmental impact compared to fission-based nuclear power.
Q4: Has fusion achieved self-sustaining energy production?
A4: While progress has been made in achieving fusion, current methods are not yet self-sustaining in terms of energy input vs. output.
Q5: What challenges does fusion energy face?
A5: The inefficiency of current fusion methods, the need for precise control, and the requirement for sustained ignition pose significant challenges for practical fusion energy.
