When is a fusion device a reactor?

Reports on scientific events should use the right words to describe what is going on. That means not describing a plasma device as a reactor.

A flurry of media coverage heralded the arrival of the Wendelstein 7-X “fusion device”. (The quotes are there for a reason that will become clear.) Unfortunately, even writers who should know better have mistakenly attached the “reactor” tag to this interesting German experiment. It is no such thing. In reality, it is a plasma physics machine that stops a long way short of a fusion reactor. Nor does it claim to be a reactor.

The first sign of confusion was when, within days of the “switch on” – more on that later – an anonymous editor “improved” the Wikipedia page on fusion power. The contributor claimed that the machine “performed fusion and sustained it for several seconds”. Oh no it didn’t.

In reality, it wasn't even a plasma experiment that sparked off this example of Wikipedia’s ability to publish scientifically misleading cobblers. The event on 10th December 2015 at the Max Planck Institute for Plasma Physics (IPP) in Greifswald, Germany, was one of those “flick the switch to see if it works” steps on the path towards doing proper science on Wendelstein 7-X. It was another month before the device produced a hydrogen plasma, the sort that you need if you want to research nuclear fusion.

The official announcement of that initial event described it as “the first helium plasma”. (Helium shots, as they are known on fusion devices, help to clean up the machine’s innards.) There was no fuel in there to perform, let alone sustain, fusion reactions.

Helium (He) is the “ash” that you get when you use the traditional fusion fuels, deuterium (D) and tritium (T). Bang these together under the right conditions and you get He and a neutron (n+ in the equations). Catch the neutron and you can recover its energy.

Energy free

There’s another clue as to the new machine’s role in that first announcement: it revealed that “Wendelstein 7-X, the world's largest stellarator-type fusion device, will not produce energy.”

While it is disappointing when even Wikipedia gets this sort of thing wrong – it is, after all, the first website that many people will visit when researching a subject – it is more frustrating when reputable sources get it wrong, or at least mislead their readers.

For example, that otherwise reliable magazine The Engineer would have us believe that Wendelstein “is set to bring the concept of nuclear fusion to fruition”. Not a hope. Even the enormous, and enormously expensive, International Thermonuclear Experimental Reactor (ITER) isn’t likely to do that. And ITER really will have deuterium and tritium in its plasma.

That otherwise reputable scientific journal Nature also made the reactor mistake. You can, just about, forgive misleading headlines, such Nature’s Reactor roars into life, but the short item beneath that headline also gushed that “The fusion reactor’s design differs from that of the other most-promising fusion facility, ITER, being built near Cadarache, France.”

Nature managed to repeat the blunder when it reported in the same issue “German Chancellor Angela Merkel this week kicked off real fusion research on the country’’s new reactor Wendelstein 7-X by flicking the switch to fill the reactor with hydrogen plasma.” (As an aside, it is inelegant writing to use the ‘reactor’ word twice in one sentence.)

The next example of misidentification appeared in Materials World. This billed the machine as “the world's largest stellarator fusion reactor”. The magazine then goes on to explain that Wendelstein 7-X won’t enter reactor territory when it says “IPP currently has no plans for a deuterium-tritium mix test with the W7-X”. No reactor then.

The only mention of reactors in IPP’s own material is when it refers to ITER as the “international test reactor”. By no coincidence, IPP is also involved in ITER, it is developing the all important plasma control system.

For a much more realistic and accurate description of Wendelstein 7-X read Dan Clery in Science. Clery, a long term observer of the fusion scene and author of a book on the subject, A Piece of the Sun, clearly knows his reactors from his elbow. (Sadly, Clery could not prevent an editor at Science from headlining Wendelstein 7-X as a reactor in an earlier story, but we all know that journalists don’t write their own headlines.) As Clery says, the real value of Wendelstein is as a plasma device, it is a stellarator, a different arrangement of the magnetic fields that it takes to hold a hot plasma in place while fusion happens.

Stellarator is an interesting alternative to the Tokamak configurations that have dominated fusion research since around 1970. As IPP’s material puts it: “The goal is to put the quality of the plasma confinement on a par with that of a tokamak for the very first time.”

Finger on the button

There was also a reasonable and reasoned account of Wendelstein 7-X on The Wire. The only reason for mentioning that, apart from welcoming its detailed assessment, is to mention another ripple in reality.

The piece told us that "German Chancellor Angela Merkel pressed a button that switched the Wendelstein 7-X on". Well, up to a point, but the piece was only quoting an official announcement.

An unnamed technician “switched the Wendelstein 7-X on” in December, when the original press release went out, although even that is stretching the notion of switching on. These machines are a complicated combination of all sorts of bits and pieces that get switched on at different times. (That's sort of implied in the piece.)

If you read that official announcement you will see that the IPP team is careful to explain what did happen when Merkel waved her finger. “At the push of a button by Federal Chancellor Angela Merkel, a 2-megawatt pulse of microwave heating transformed a tiny quantity of hydrogen gas into an extremely hot low-density hydrogen plasma.”

In defence of The Wire, dragging in someone famous to press a fake button is a part of the game that science has to play to get funds and to persuade people that it is spending that money wisely. As such, it is a harmless conceit. It is certainly more interesting that cutting ribbons or smashing bottles of champagne, or whatever Germans do instead of that wasteful practice.

Does it matter when publications attach the reactor label to what the people who built it describe as a “fusion device”? Apart from  favouring scientific accuracy, it is also important to give readers the right impression. What will they make in five years time when Wendelstein has been through its original research programme without a fusion reaction in sight?

For decades the fusion community has mis-sold its machines. Once upon a time the US operated a fusion device that it sold as the Tokamak Fusion Test Reactor, a short-lived, misguided and failed attempt to upstage Europe’s Joint European Torus (JET). It no way was it a reactor. And unlike JET, it didn’t do much, if any, fusion.

One day, faced with another request for a pile of money to build yet another “reactor”, the people who pay for them may finally throw up their hands and abandon the whole venture. That would be a pity. It may be a century before the likes of EDF start building fusion reactors, but when it does these machines will be a bit more reliable than wind turbines and solar panels.