The recent fusion energy breakthrough, announced in December 2022, deserves high attention and in a video (see link below) NNSA Deputy Administrator for Defense Programs Dr. Marvin Adams, and LLNL Director Dr. Kim Budil explain the breakthrough. Below are some background info and the key points in the hope to make this tremendous news more accessible to a larger audience.
Background
An atomic nuclei is made of protons and neutrons. They repel one another because protons are positively charged, thus they want to push apart from each other. This means that if they are moving fast enough and are close enough, they will overcome their repulsion force, and fuse into each other. When that happens some energy is released. This is because the total mass of the fusion of those nuclei is actually less than those nuclei when they are on their own, which means that some energy is released, and that energy drives a chain reaction.
Fusion is a concept that is fundamental to physics and fundamental to the energy driver of our galaxy, as the star in our sky (the sun) is driven by fusion. Only about 15% of the mass of the sun at the center is dense enough to actually drive fusion. This means that the big challenge with fusion is how to get these atomic nuclei close enough together, and moving fast enough, that they will actually fuse and release energy. That is really difficult. The reason it happens in the sun, is because the sun has so much mass that when gravity pulls all those particles together, they get close enough and hot enough, they move fast enough and fusion happens.
In the 1960s it was theorized whether we could do fusion on Earth. If we consider plasma (the atomic nuclei and the electrons have kind left the atoms, and it is just the nuclei spinning apart) you got to get the nuclei to move super fast, to the tune of tens of millions of degrees Celsius, and you got to get them really close together.
There is a couple of concepts for how to do this, one of which is called inertial confinement. This is where you basically create a little pellet of the material you are going to try and get diffused, and you put a whole lot of energy on the outside. If you can press it really hard evenly, really fast, it will form a perfect sphere and you can get it to collapse on itself very quickly (without it kind of shooting all over the place). Done right, a sufficient amount of those particles will come close enough together, fast enough, hot enough and they will start to fuse with each other.
Another way is through magnetic confinement where you use magnetic fields to create a really hot plasma get it to spin around. Then the magnet brings that super hot plasma closer and closer together, until all those particles are moving fast and they are dense enough to start fusing together.
The reason as to why this is so hard is that you have to get such an incredible density, you need to an incredible energy, meaning high temperature and high density that confines those atoms while not letting them escape and dissolve before they fuse. This is extremely difficult, as it requires so much energy, in such a controlled and precise way. It has taken us decades to develop and tune all of the digital technology, the magnets, all the measurement systems, all the software, to get everything that allows us to do this today. Now we are at the point that we may be able to start to realize production scale versions of this.
The National Ignition Facility was built in 1997 and have since spent about 3.5 billion USD to date. What they recently demonstrated was a net energy output from the fusion reaction. They used an inertial confinement system, in which they took a little pellet and that pellet was made up of deuterium and tritium. The atomic nuclei that they use (for the particles) are deuterium (a proton and a neutron stuck together), and then tritium (a proton and two neutrons stuck together). The reason for using those two combinations is that, of all the various ways you could fuse nuclei together, this has the best energy output of any kind of reaction.
Key Points
A team at Lawrence Livermore National Lab (LLNL) at the National Ignition Facility (NIF) made the following happen:
- 192 laser beams entered from the two ends of a cylinder and struck the inner wall of the cylinder and deposited energy.
- X-rays from the wall impinged on the spherical capsule.
- Fusion fuel in the capsule got squeezed.
- Fusion reactions started (which have happened many times previously), but for the first time they designed this experiment so that the fusion fuel stayed hot enough, dense enough, and round enough for long enough that it ignited and produced more energies than the lasers had deposited
- About two megajoules in, and about 3 megajoules, which leads to a gain of 1.5 (one and a half) the energy production
Fusion has the potential for abundant clean energy, and is an essential process in modern nuclear weapons. Thus, this breakthrough have enormous ramifications. This achievement will also advance US national security in at least three ways:
- It will lead to laboratory experiments that help NNSA defense programs continue to maintain confidence in US deterrent without nuclear explosive testing.
- It underpins the credibility of our deterrent by demonstrating world leading expertise in weapons relevant technologies.
- Continuing to assure US allies that US know what they are doing and continue to avoid testing will advance our non- proliferation goals (increasing US national security)
This achievement illustrates that big important accomplishments often take longer and require more effort than originally thought, and that these accomplishments are often more than worth that time and effort that they took.
Dr. Kim Budell who is the director of Lawrence Livermore National Laboratory explains that it took more than 60 years, and that thousands of people have contributed to this endeavor. It took real vision to get here. Building the National Ignition Facility (NIF) was an enormous scientific and engineering challenge. The laser has exceeded its performance goals, opened whole new areas of high energy density science to exploration and delivered the data needed to keep our nuclear deterrent safe, secure and effective. The pursuit of fusion ignition over the past decade at NIF was an incredibly ambitious technical goal, and many said it was not possible.
Last August NIF achieved a then record yield of 1.35 megajoules, putting the team at the threshold of ignition. And, last week the team pre-shot predictions improved by machine learning and the wealth of data they have collected indicated that they had a better than 50% chance of exceeding target gain of one.
60 years ago when John Hopkin Nuckolls and his team proposed that lasers could be used to produce fusion ignition in the laboratory, it was beyond audacious. The laser had just been invented and was far from the mature tool we know today. National Labs are created to tackle the most difficult scientific challenges head on, learning from the inevitable setbacks and building toward the next idea. Lawrence Livermore has been at the center of the ICF Community across these many decades, and ICF has been a centerpiece of our lab.
This achievement opens up new scientific realms for us to explore and advances our capabilities for our national security missions. It demonstrates the power of U.S leadership, science and technology and shows what US as a nation is capable of. Breakthroughs like this have generated tremendous excitement in the fusion community and a great deal of private sector investment in fusion energy, but this is only possible due to the long-term commitment of public investment in fusion science. The science and technology challenges on the path to fusion energy are daunting, but making the seemingly impossible possible is when we are at our very best. Ignition is a first step, a truly monumental one, that sets the stage for a transformational decade in high energy density science and fusion research.
There is tremendous potentially to further improve as they current lose 90% of the energy that they put into the the center of the system. Only 10% is actually used to drive the compression. The rest of it is lost and there is a lot of ways to improve the efficiency of the system from here.
Basically they put two megajoules in, and they got three megajoules out. Thus, it was the first proof of production in the 60 years that we have been theorizing about nuclear fusion here on planet Earth. Today there are about 33 private technology companies that have raised about three to four billion dollars so far this year, to pursue several other technologies besides what National Ignition Facility is showing. This is with the aim to build production-ready versions of nuclear fusion. These 33 companies are using a bunch of different types of tools, one of which is the Tokamak which is based on the magnetic confinement concept.
As a reminder, all breakthrough technology starts out seeming impossibly large, impossibly expensive and impossibly slow. Considering the Human Genome Project 20 years ago, it cost a hundred million dollars to sequence the human genome. Today we can do it in a couple of minutes, for a hundred dollars. The ENIAC, the first computer, had 500 flops of compute capacity. It filled a room and cost eight million dollars to build. 20 years later we had a mainframe. Today we have an smartphone that can do 2 trillion flops of compute in your pocket. A way to look at it, is that what we are seeing with fusion today is comparable to what we saw with the ENIAC computer in the 1950s, namely a demonstration that compute is possible. Now we are seeing a demonstration that fusion is possible and a lot of people have anticipated this moment, and they have invested ahead of this. One might estimate that we will see production demonstration fusion in the 2030s, and then we will see grid-scale systems in the 2040s. Thus, there is a way to go, but this is very promising.
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