This past year has been big for nuclear fusion. First there was the announcement from Lockheed Martin claiming they could have a fusion reactor that fits in a truck. Next there is an announcement from Germany that physicists are close to finishing another fusion reactor.
I suspect that when most people read about nuclear fusion, like in this recent TIME feature on a startup called General Fusion, they just focus on the "nuclear" part. But there is a big difference between nuclear fission and nuclear fusion. Let's go over the similarities and differences.
It's All About Mass and Energy
Suppose that I had a 2 million dollars (this is clearly just a hypothetical situation). For some reason I decide to split this money two separate accounts. After doing this, I find that each account has $999,999. Yes, I am missing 2 dollars! But maybe in exchange for this missing 2 dollars, I get a whole bunch of energy. That might be ok.
This is exactly what happens with nuclear fission (fission means to break apart). If you looked at an atom, you would find it has three things: electrons, protons, and neutrons (OK, hydrogen doesn't have any neutrons). The number of protons in the nucleus tells you what element the atom is (nitrogen has 7 protons, silver has 47 protons). Then there is the atomic number atomic mass number. This tells you how many protons plus neutrons the atom has. Uranium-235 has 92 protons (because it's uranium) and 143 neutrons (because 235 - 92 = 143). Oh, one more fact for the next time you are at a party. If two atoms have the same number of protons, but different numbers of neutrons—these are isotopes (like hydrogen-1 and hydrogen-2).
But back to fission. Here is the crazy part. If you break uranium-235 into two pieces, you get krypton-92, barium-141 plus two extra neutrons. OK, that isn't crazy since all the protons and neutrons are accounted for. If you find the mass of the original uranium and the mass of all the pieces, you will find that you are missing some mass. The stuff before has a greater mass than the stuff after. That's a little crazy. It's like spitting 2 million dollars and ending up 2 dollars short. But that energy isn't really lost—it was just converted into other forms of energy. Yes, we can consider mass to be a kind of energy. This is where that famous equation comes into play.
In this expression, E is the equivalent energy, m is the mass of the particle and c is a constant that happens to be the speed of light (with a value of 2.99 x 108 m/s). Because this proportionality constant is so large (and squared), a small amount of mass can give you a HUGE amount of energy. What can you do with all of this energy you get from the change in mass? Obviously, you can heat up water and make steam. Yes, that's usually what these reactors do—they make steam to turn a turbine to generate electricity. Just like a coal burning power plant, but without the coal.
The above example looked at mass changes when you break something apart. This can also happen when you combine hydrogen and deuterium (which is just hydrogen with an extra neutron). When combining low mass elements, the product has less mass than the starting stuff and you also get energy. So, breaking large atoms gives energy (nuclear fission) and combining small atoms also gives energy (nuclear fusion).
Why Is Fission Better Than Fusion?
There are plenty of nuclear fission reactors that actually provide useful energy. As of now, there are zero useful fusion reactors. It turns out that nuclear fission isn't actually too difficult. If you take some uranium-235 and shoot a neutron at it, the uranium absorbs the neutron and becomes uranium-236. However, this uranium-236 is unstable and will break into pieces to give you nuclear fission. Even better, it also creates extra neutrons to break apart even more uranium. Oh, you can also do this with plutonium and thorium.
Fusion, on the other hand, is very difficult. Instead of shooting a neutron at an atom to start the process, you have to get two positively charged nuclei close enough together to get them to fuse. Without the electrons, atoms have a positive charge and repel. This means that you have to have super high atomic energies to get these things to have nuclear fusion. High energy particles are the problem. This is why fusion is difficult and fission is relatively simple (but still actually difficult).
Why Is Fusion Better Than Fission?
There are a couple of problems with fission reactors. First, the staring material. I think Marty McFly said it best in Back to the Future in regards to plutonium:
"Doc, you don't just walk into a store and-and buy plutonium! Did you rip that off?"
These starting materials aren't just laying around. In fact, if you went looking for some natural plutonium you wouldn't find any. The only way to get plutonium is to make it. The other problem with fission is the products. After this nuclear fission reaction, you have this left over stuff that can be both radioactive as well as chemically active. It's just nasty stuff that you have to deal with.
Nuclear fusion would solve both of these problems. It starts with simpler stuff—although deuterium isn't always so easy to find, you don't have to make it. After fusion, you get something like helium (or helium-3). Think of all the balloons you could blow up.
Published on December 14th, 2017 | by Tina Casey
Free Lunch Alert! A Hydrogen – Boron Solution For “Clean” Nuclear Fusion
December 14th, 2017 by Tina Casey
Oh come on, where’s the catch? Researchers at the University of New South Wales have described how a laser-enabled system can coax nuclear energy out of a reaction between hydrogen and boron, without generating nuclear waste. The patented system has already been spun off to an Australian startup called HB11 Energy.
Of course there is a catch. HB11 is optimistically looking at a ten-year timeline for developing a prototype reactor — and that’s assuming any significant obstacles don’t rear up as the research progresses. Considering the rapid pace of global warming, the new fusion technology is not exactly a handy solution for the global warming crisis.
On the other hand, the nations of the Earth — well, except for you-know-who — are committed to accelerating the clean energy transition, so optimistically speaking a new hydrogen/boron nuclear fusion reactor could come in handy some time in the sparkling green future.
Let’s Hear It For The Nuclear Fusion Unicorn
For those of you new to the topic, fission is the idea behind conventional nuclear energy generation. That’s when isotopes of certain elements, typically Uranium-235, are “split” to release energy in the form of heat.
Fusion is practically the opposite. Think of creating a miniature sun on Earth, and you’re on the right track. The idea is to smash nuclei together and literally fuse them. The process releases energy in the form of heat. Unlike nuclear fission (and fossil fuels, for that matter), the fuel would be virtually self-sustaining.
For you hydrogen fans, the good news is salt and water (H2O amirite?) are the only necessary ingredients, and helium is the only byproduct. Among other fuel sources the US Energy Department is looking at deuterium, an isotope of hydrogen that can be derived from seawater.
The Hydrogen – Boron Nuclear Energy Solution
Currently the global fusion research community is focused on studying fusion reactions in specialized (and quite expensive) chambers called tokamaks.
A core part of the problem is firing up the reactor with enough heat to sustain the operation, while generating more energy output than input. The University of South Wale sets the table:
…the downside has always been that this needs much higher temperatures and densities – almost 3 billion degrees Celsius, or 200 times hotter than the core of the Sun.
That’s where the new study comes in. For all the details check out the paper “Road map to clean energy using laser beam ignition of boron-hydrogen fusion” in the journal Laser and Particle Beams. Here’s the short version: skip the deuterium and go straight to the hydrogen. Here’s a snippet from the abstract:
Sixty years of worldwide research for the ignition of the heavy hydrogen isotopes deuterium (D) and tritium (T) have come close to a breakthrough for ignition. The problem with the DT fusion is that generated neutrons are producing radioactive waste. One exception as the ideal clean fusion process – without neutron production – is the fusion of hydrogen (H) with the boron isotope 11B11 (B11).
The University of New South Wales explains where the lasers come in:
Rather than heat fuel to the temperature of the Sun using massive, high-strength magnets to control superhot plasmas inside a doughnut-shaped toroidal chamber (as in NIF and ITER), hydrogen-boron fusion is achieved using two powerful lasers in rapid bursts, which apply precise non-linear forces to compress the nuclei together.
The new study pulls together “a spate of recent experiments around the world” indicating that “an ‘avalanche’ fusion reaction could be triggered in the trillionth-of-a-second blast from a petawatt-scale laser pulse, whose fleeting bursts pack a quadrillion watts of power…”
The study cites current research that confirms earlier theoretical work and takes it to the next level, according to lead researcher Heinrich Hora, Emeritus Professor of Theoretical Physics at the University of New South Wales.
According to Hora, the research has produced measurements that indicate the “avalanche” or chain reaction touched off by lasers creates “one billion-fold higher energy output than predicted under thermal equilibrium conditions.”
For the record, the international effort involved in creating the new study also included:
…Shalom Eliezer of Israel’s Soreq Nuclear Research Centre; Jose M. Martinez-Val from Spain’s Polytechnique University in Madrid; Noaz Nissim from University of California, Berkeley; Jiaxiang Wang of East China Normal University; Paraskevas Lalousis of Greece’s Institute of Electronic Structure and Laser; and George Miley at the University of Illinois, Urbana.
What’s Up With The USA?
As hinted by the lineup in Hora’s research team, the US is one of the leading centers of nuclear fusion research. However, they better act fast if they want to maintain their global status.
According to the World Nuclear Association, the US is running neck and neck with Russia and Japan, and several other countries are coming up fast including China and Brazil.
Meanwhile, the US may have a head start on sustainable hydrogen production, partly with an assist from the US Department of Defense. The US Navy is already interested in generating hydrogen from ordinary seawater as an oceangoing fuel source for submarines, with a carbon capture bonus as well.
Researchers are also tumbling over themselves to develop commercial-grade systems for powering water-to-hydrogen systems with renewable energy including solar, wind and biomass, so stay tuned for more on that.
Image: via National Ignition Facility at Lawrence Livermore National Laboratory, USA.
Tags:HB11 Energy, hydrogen/boron nuclear fusion reactor, nuclear fusion, University of New South Wales
About the Author
Tina Casey specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.