Nuclear fusion has promised us a clean, powerful way of generating energy for decades. Where ‘normal’ nuclear reactors pick apart heavy atoms, a fusion reactor fuses lighter atoms together – a process that, it is predicted, will eventually produce tens of times more power than you put into it. While nuclear fusion, compared to standard nuclear energy, produces virtually no waste and uses atoms as ‘fuel’ that you can extract from water. On paper, a kilogram of atoms for fusion contains ten million times more energy than a kilogram of coal, oil or gas, proponents like to say. And that without emitting greenhouse gases.
On the way to that promised future, physicists have now taken ‘a very important step’, as physicist Egbert Westerhof, of the research institute Differ in Eindhoven involved in the experiments, describes it.
‘Happy Day’
Physicists take this step inside JET, a test reactor located in Culham, UK, near Oxford. Caught in powerful magnetic fields, a plasma was briefly created, the red-hot soup of charged particles in which nuclear fusion takes place. Because deuterium and tritium atoms fused together, two heavier variants of hydrogen, the plasma produced a total of 59 megajoules of energy for five seconds. The researchers more than doubled their previous record. The reactor set that record, of 22 megajoules, about a quarter of a century ago, in 1997.
Incidentally, the prevailing record for the most productive second was not broken, but that is less important: future nuclear fusion reactors must generate a reliable, constant amount of energy for a long time. A longer period with higher yields in total is better than a short-term high peak.
‘A happy day for nuclear fusion’, is how physicist Thomas Klinger (Max Planck Institute for Plasma Physics) describes the announcement of the result of his JET colleagues. He himself is working on a – subtly – different design for a future reactor, the Wendelstein 7-X in Germany, a so-called stellarator. ‘This result is good news for anyone involved in mergers. Most reactors will eventually work with this type of deuterium-tritium fuel.’
The most famous of these will be the ITER megaproject, a giant reactor costing approximately 27 billion euros that is currently being built in the French Provence. It will not be put into operation until around 2035 at the earliest, and in turn will serve as a preliminary study into the follow-up reactor DEMO, expected around 2050. This should then be the first fusion reactor that – if everything goes as desired – will actually go into service. act as a power plant. At the earliest, therefore, nuclear fusion will not be able to contribute significantly to our energy production until around 2060, experts believe. This makes it too late for the current energy transition, which should be completed by 2050.
On the rack
The plasma produced no net energy in the new experiments, because keeping the experiment running simply cost too much energy. At the same time, such a net result was not the intention at all. Energy gains require the economies of scale of a large reactor such as ITER. The British test reactor, a much smaller model, was built to test the underlying physics.
Since the record set in 1997, the reactor has been updated and our knowledge of nuclear fusion has greatly improved. The test reactor has therefore been given a new wall, among other things. ‘The behavior of your plasma depends on the wall you use,’ says Westerhof. Contaminants can enter the plasma from the wall and cause, for example, that plasma loses energy. The new wall is made of tungsten and beryllium, which disturb the plasma less than the carbon from the previous wall. ITER will therefore also use these materials in the future.
In addition, the test reactor was equipped with more powerful heating elements than before to heat the plasma, and decades of accumulated knowledge about the physics behind it were applied. This ensured, among other things, that the researchers now knew better when and where to heat the plasma.
The fact that they have set a new record with these techniques, the same ones that will be used in the large reactor in France from 2035, is confirmation that nuclear fusion is on the right track. ‘Scientifically this is of significant importance’, responds physicist Richard Hawryluk (Princeton University). “This result reinforces our confidence that ITER will complete its mission.”
‘Not finished yet’
Contrary to what is usual in science, the results of the research have not yet been published in a professional journal. In fact, a number of experiments are not yet ready at all. Nevertheless, the researchers involved wanted to get the good news about energy production out immediately. The more detailed, scientifically sound analysis will follow later.
‘We have carried out many other measurements with the reactor, which will further increase our knowledge of plasma’, says Westerhof. For example, the researchers tried out new heating methods, which they will soon be able to use in ITER.
‘I think in one or two years we will have published the most important results.’ And even after that, Westerhof expects physicists to make new discoveries from the current measurements. “We’re far from done with this.”