The following is a ttransscription from CBCradio/the current (feb 10 2022)
Scientists hail a step forward in harnessing nuclear fusion
Guest: Dennis Whyte
MG: Hi, I'm Matt Galloway, you're listening to The Current.
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MG: It's not your radio acting up. The signal is fine. You're listening to nuclear fusion. The thing that powers the sun and the moon shot that could one day provide limitless clean energy. This week, scientists at the Joint European Tourist Lab announced a breakthrough. They created a mini star that burned for about five seconds, creating nuclear fusion a huge step forward. They're saying in that field. Dennis Whyte is the director of Plasma Science and Fusion Centre at MIT in Boston. Dennis. Good morning.
DENNIS WHYTE: Good morning.
MG: This has been kind of like a holy grail when it comes to power generation for a long time. The joke is that that fusion is just 30 years away, but people have been saying that for 30 years. We'll talk about what these scientists did, but why do you think this is being framed as such a step forward?
DENNIS WHYTE: Right. So what the scientists did was recreate the conditions, which are very similar to those that occur in the centre of stars and our own sun. And when you achieve these very high temperatures, the hydrogen fuel which is contained within it, start to produce fusion reactions. And this produces energy. And of course, this has been, as you stated, the holy grail of the idea of this is to bring the power of the stars down to Earth and to be able to recreate those conditions in such a way that it makes a significant amount of energy. And so what our colleagues at the jet lab produced was a very exciting more than doubling of the previous record for energy output from from fusion reactions. So this is why we're excited.
MG: So walk us through in language that we can understand what was happening in the machine that would produce that energy.
DENNIS WHYTE: Right. So we cannot directly recreate the conditions of a star because it takes something as large as a star. So on Earth. What we do is we create a containment system made with very strong magnetic fields. It's in the shape of a doughnut for four science reasons. So we create this magnetic cage, if you like, isolated from the the plasma fuel away from any terrestrial contact or heat it. And then the fusion reactions start to occur. And what the scientists did here in particular, was they were able to sustain those conditions for on the order of five to six seconds. And they were producing large amounts of fusion energy such that it was a record year, 60 million jewels of energy was created in around five to six seconds.
MG: That is enough, we're told, to boil a 60 kettles of water. It may not sound like a lot, but why is that a big deal?
DENNIS WHYTE: Yes. So the total amount of energy at this point is still, you know, not enough to obviously operate a standard commercial power plant. What was special about this is, of course, the fact that it was being done from fusion reactions and in the end, fusion is an energy source. So the more energy that you produce, the more viable it is becoming that it also has to do with the fact of how much how much energy was being produced per unit time, which is the power. And the fact that this was at around 10 million watts of power means that this is getting closer to the scales that you would imagine for a commercial uses of fusion, for example, that was directly converted into electricity that would be enough for about 10000 people. So you can see what that's significant.
MG: So in some ways, this is proof of concept.
DENNIS WHYTE: Yes. And so we've had our handle for for a while on the physical conditions needed and the science of what would make fusion reactions occur. Because also, the exciting thing about what's happened to the jet was that their improvement on the previous record came through innovations and improvements in the underlying technology, which are themselves going to be key to providing practical power plants.
MG: Should we be concerned with how much energy the machine needs to put in in order to generate that energy?
DENNIS WHYTE: Right, so right. So this is the next step in this. And so this is an extremely affirming aspect of the science of fusion and moving forward and using this particular figuration of the magnetic cage that we call a tokamak. The next step will be in fact, producing more energy than the heat, which is required to keep it hot. So right now, the the experiments suggest that they reported that while they were producing large amounts of fusion power, they're actually using more heat than than that fusion power to keep it hot. So the next step, which is coming in two experiments one of them here in Boston and one in the south of France will seek to in fact go past that threshold, which is which is which will be a key for net energy production and obviously for commercial fusion.
MG: The thing with the holy grail is that it's very difficult to get your hands on the holy grail. Why has it been so difficult to harness this energy source?
DENNIS WHYTE: Right. So first of all, was the need for a the science understanding of how you recreate the these extraordinary temperatures and in confinement on Earth. So this is non-trivial. This is these temperatures are on the order of 100 million degrees Celsius. So that was gained over decades of hard fought, you know, research around the world. And what this result shows is that it largely this the science is in hand. The other challenge has been the scale and the expense of creating these devices, which would be able to reproduce these conditions. This is also where there's very exciting news and is that around the world and including here in our own effort at MIT with ah, with a commercial start up, we have actually saltiness even advancing the technology such that the size, complexity and cost of the objects that are are required to recreate these conditions are decreasing. So it's sort of good news on both fronts.
MG: What's the promise here? What is being tangled in front of us?
DENNIS WHYTE: So what's been dangled in front of us is that the science of fusion a big because it uses a fuel which is effectively inexhaustible and available to everyone because it just comes out of water and it has a scalability which which looks like it could. If we meet the full science, technological and economic promise of fusion, it can literally supply the power demands of humanity forever. That's been the promise forever of a fusion. So it is you say this is this is the holy grail. It's been hard to grasp, but it seems to be getting closer.
MG: How close is it? Again, I go back to the, you know, it's 30 years away for 30 years and 30 years before that. How far off is this, do you think?
DENNIS WHYTE: Well, honestly, we I think we we stagnated for for a little while. One of the impetus of this now is that and why there's so many more efforts going on is about climate change and understanding. It can't just be forever away. We need to have a timeline such that it is appropriate for tackling this extremely difficult problem of decarbonising. So. So how close is this always the question that we get I. Our own effort here at MIT and with Commonwealth Fusion says that we believe we can get sooner if we if we come up with the right sets of strategies about coupling scientific and technological innovations. We bring the private sector in in more to it and earlier on for thinking about commercialisation. And honestly, the other part of it is to get incentives for the Canadian audience. More shots on goal, like get the shots on goal, have more attempts at this across the board, both in the public and in the private sector, then that that ecosystem will probably give us a much better chance of pulling fusion closer. So our hope is in, you know, in the next decade. And we have a very aggressive timescale and others think that it's more like, you know, 20 or 25 years away, but the whole world is pressing. The whole fusion research world is pressing to try to reduce the time scale because of the urgency of climate change.
MG: This is before you in this world, we're just about out of time, but there is real excitement in this like this. This is this is the unravelling of an incredibly complex question.
DENNIS WHYTE: Exactly. And so I started my fusion career started over 30 years ago as a graduate student in Canada. So I've seen a lot evolve and I have never personally been more excited for fusion, but also the 20 somethings that are coming in as our students to places like MIT have never been more motivated towards pursuing the solution. So it's really hard not to be excited by that.
MG: The graduate work in Canada would perhaps explain the hockey analogy as well. Denis, great to talk to you about this. I appreciate it. Thank you very much.
DENNIS WHYTE: Thank you. Thank you for your questions.
MG: Dennis Whyte is the director of the Plasma Science and Fusion Centre at M.I.T., and we reached him in Boston.
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https://www.scientificamerican.com/article/u-s-project-reaches-major-milestone-toward-practical-fusion-power/
U.S. Project Reaches Major Milestone toward Practical Fusion Power
In a world first, the National Ignition Facility has generated a “burning plasma,” a fusion reaction on the cusp of being self-sustaining
By Philip Ball on February 2, 2022
U.S. Project Reaches Major Milestone toward Practical Fusion Power
A metallic case called a hohlraum holds the fuel capsule for NIF experiments. Target handling systems precisely position the target and freeze it to cryogenic temperatures (18 kelvins, or -427 degrees Fahrenheit) so that a fusion reaction is more easily achieved. Credit: Lawrence Livermore National Laboratory (CC BY-NC-SA 4.0)
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Nuclear fusion could potentially provide abundant, safe energy without the significant production of greenhouse gas emissions or nuclear waste. But it has remained frustratingly elusive as a practical technology for decades. An important milestone toward that goal has now been passed: a fusion reaction that derives most of its heat from its nuclear reactions themselves rather than the energy pumped into the fuel from outside.
A team at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) in California has reported this so-called burning plasma condition using an approach called inertial-confinement fusion, where the ferociously high temperatures and pressures needed to initiate fusion in a fuel of hydrogen isotopes are produced by intense pulses of laser light. The researchers’ findings appear in Nature, with companion papers published in Nature Physics and on the preprint repository arXiv.org. “The data clearly show that they have reached that condition,” says fusion physicist George Tynan of the University of California, San Diego, who was not involved in the work.
“The NIF results are a really big deal,” says fusion physicist Peter Norreys of the University of Oxford, who was not part of the studies. “They show that the pursuit of an inertial fusion reactor is a realistic possibility for the future and not built upon difficult and insurmountable physics.” Plasma physicist Kate Lancaster of the University of York in England, who was also not involved in the research, agrees. “This is an incredible achievement, which is a culmination of a decade of careful, incremental research,” she says.
Nuclear fusion, the process that fuels stars and that is triggered explosively in hydrogen bombs, requires extreme heat and pressure to give atoms enough energy to overcome the electrostatic repulsion between their positively charged nuclei so that they can fuse and release energy. The usual fuel for producing controlled fusion in reactors consists of a mix of the heavy hydrogen isotopes deuterium and tritium, which may unite to make helium. The energy this releases can be harnessed for electricity generation—for example, by using the heat to drive conventional power turbines. Unlike nuclear fission—the process used in all nuclear power plants today—fusion does not use or generate large quantities of long-lived radioactive materials. And in contrast to fission, fusion does not involve a chain reaction, which makes it inherently safer: any changes to the working conditions of a fusion reactor will cause it to automatically shut down in an instant.
Fission’s advantage is that it typically occurs in reactors at temperatures of a little more than 1,000 kelvins, whereas deuterium-tritium (D-T) fusion starts at temperatures of around 100 million kelvins—hotter than the heart of the sun. Handling such a seething plasma is, to put it mildly, immensely challenging. One approach is to confine it with magnetic fields into a doughnut shape inside a chamber called a tokamak. This is the method of choice for many fusion projects, including the International Thermonuclear Experimental Reactor (ITER). for which a global collaboration is building a massive experimental reactor in France that is slated to achieve sustained fusion no earlier than 2035.
Inertial fusion does not try to trap the plasma but instead relies on inertia alone to hold it together for a brief instant after fusion is triggered by an ultrafast compression of the fuel. That creates a very brief outburst of energy—a tiny thermonuclear explosion—before the burning fuel expands and dissipates its heat. “Fusion energy schemes based on inertial confinement involve repeating the pulsed process over and over again, much like the pistons in an internal combustion engine, firing several times per second to give nearly continuous power,” says Omar Hurricane of LLNL, chief scientist for the NIF’s Inertial Confinement Fusion program, who was a team leader for the latest experiments.
Although inertial-confinement fusion does not have to solve the problem of maintaining a hot, wobbly plasma inside a tokamak, it does require tremendous inputs of energy to trigger the fusion process. The NIF team used 192 high-power lasers, all focused into a chamber called a hohlraum that is about the size and shape of a pencil’s eraser and contains the fuel capsule of deuterium and tritium. The laser energy heats and vaporizes the capsule’s outer layer, blowing it away and creating a recoil that compresses and heats the fuel in the center. In the NIF method, the laser beams do not directly spark detonation but instead strike the hohlraum’s inner surface, unleashing a furious bath of capsule-compressing x-rays within the tiny chamber.
Researchers demonstrated the feasibility of starting fusion this way back in the 1970s. But getting to the burning-plasma point has been a slow process, full of technical hurdles and setbacks. “For many decades, researchers have been able to get reactions to occur by using a lot of external heating to get the plasma hot,” says Alex Zylstra of LLNL, a member of the NIF team. “In a burning plasma, which we have now created for the first time, the fusion reactions themselves provide most of the heating.” Those conditions last only for about 100 trillionths of a second before the plasma’s energy is dissipated.
“There was no one secret that allowed them to make this breakthrough but a whole bunch of smaller advances,” Tynan says. To have any hope of getting the fusion process to sustain itself, the energy it produces should be deposited mostly in adjacent fuel layers rather than leaking from the capsule to heat the surroundings. This means that the capsule has to be sufficiently large and dense to keep the energy inside while still collapsing symmetrically—which is one of the issues the NIF team has cracked. The researchers have also tweaked the hohlraum’s design to ensure its interior uniformly fills with x-rays, ultimately creating a smoother, stronger and more efficient implosion of the fuel capsule. “We had to learn how to better control the symmetry while making the implosion bigger,” Hurricane says. Such improvements have required decades of effort. “It’s been a very long trial-and-error process, guided by computations,” Tynan says.
Of the experimental runs that the NIF researchers have reported, four conducted in 2020 and early 2021 exceeded the threshold fusion output for a burning plasma. The most recent of these were in February 2021, so “it clearly took some time for them to convince colleagues of the validity of their results,” says Vladimir Tikhonchuk, a plasma physicist at the University of Bordeaux in France, who was not involved with the work. But they have evidently done so. “I truly believe publication of these papers is an important scientific event,” Tikhonchuk adds.
Making fusion viable requires more than merely burning plasma, however. For one thing, although the plasma is self-heating, it might still radiate more heat than it generates, including the energy lost when the implosion blows itself apart after reaching peak compression. “Even if you have burning, the reaction fizzles out if the radiative losses are too high,” Tynan says. But the NIF team notes that, in one of its runs, the heating exceeded such losses.
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That brings the scientists closer to the next big goal: ignition, where the net energy release from the fusion reaction exceeds the energy injected to produce it. On average, they can produce about 0.17 megajoule of fusion energy for an input laser energy of 1.9 megajoules. In other words, these NIF shots channel the energetic equivalent of a half-kilogram of exploding TNT into the tiny hohlraum only to get about 10 times less energy out. But that is still close enough to the break-even point to get fusion researchers fired up. “They are right on the threshold of achieving a propagating ignition burn,” Tynan says.
Lancaster is optimistic about that. “We are now in a regime where modest improvements can create massive gains in output energy,” she says. “We have definitely moved from an ‘if’ to a ‘when’ for ignition.”
Even achieving ignition would be just the end of the beginning for fusion. For one thing, net energy gain must not only be demonstrated but also improved to compensate for inefficiencies in converting the heat into electricity. Better methods must also be developed for on-site production and handling of tritium to use as fuel. And in the specific case of inertial-confinement fusion, the exquisitely designed fuel capsules must somehow be made in abundance—and on the cheap. “Right now they cost $1 million and are custom pieces of kit made in the lab,” Tynan says. But for any inertial fusion power plant to turn a profit, “you have to be able to make hundreds of thousands of them a day at 10 cents a piece.” And these spectacular results for burning plasma in inertial confinement “do not really translate to tokamaks” at all, Hurricane warns.
“People working in this domain understand very well that there is a large gap between the [eventual] demonstration of ignition and a commercial fusion reactor,” Tikhonchuk says. That gap certainly will not be closed at NIF, which is geared toward exploring the basic physics of fusion, especially in the context of nuclear stockpile management and national security. “We do not yet have lasers of a needed energy and power operating with a repetition rate of a few shots per second,” Tikhonchuk adds—although Lancaster says that these “are well on the way, with big programs in the U.K., the U.S., France and Germany, for example.”
“Now that NIF has demonstrated that [burning plasma conditions] can be done in a controlled laboratory setting,” Norreys says, solutions to the remaining challenges “need to be studied in the coming years with renewed vigor.”
“The challenge is [pivoting] from ‘Is the physics even possible?’ to ‘Can we engineer a viable system that has sufficient lifetime and that is safe enough and do all those things at an affordable price?’” Tynan says. “That’s still the big open question in front of the research community.”
