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Can focus fusion be used to make a bomb? Electrical power for less than a tenth of current cost sounds great. But if it allows the Timothy McVeighs, Osama bin Ladens and Gerry Adams of the world to build city-leveling bombs then I have some pretty severe reservations. [question from A. Becker]
The safety of the focus fusion derives in part from the extremely tiny amount of fuel that is burned in each shot. The speck that is raised to several billion degrees is only a few microns to tens of microns across. So even when all the fuel, or nearly all, is burned, the yield will be only about 20 or 30 kilojoules - the energy a 100 W light bulb burns in a few minutes.
It is only by pulsing the device a thousand times a second do you get 20 MW out of it.
Unfortunately, the technology to use fusion for warfare was perfected fifty years ago: the hydrogen bomb. A typical H-bomb releases several trillion times as much energy as a single focus fusion pulse, or as much energy as a focus fusion reactor will produce in a century.
If you look at how nuclear bombs work, you will see that the focus fusion reactor can’t possibly be used to make a bomb. Basically, a fusion bomb is fusible material wrapped up in a fission bomb, wrapped up in high explosives. You blow up the explosives to trigger the fission reaction, to set off the fission bomb. The fission explosion in turn compresses the fusion materials encased within it and triggers the fusion reaction.
As you can see, getting a fusion reaction to occur is so difficult that in making bombs it requires the explosion of a fission bomb.
This is great news, because, if you want to detonate a fusion bomb, you need to have the ability to make a fission bomb. So, if we promote focus fusion and get people to adopt it, we SKIP the fission step, and countries with fusion don’t have the materials or fission reactors necessary to develop fission bombs. And if they can’t develop fission bombs, they certainly can’t develop fusion bombs.
What we are attempting with the focus fusion reactor is to get fusion reactions to occur in a microscopic area with repeated pulsing to generate sustained power. The issue isn’t “will it blow up” but “can it even be achieved or sustained?”
Aside from high voltage warnings that are par for the course for any typical electricity generating power plant, a focus fusion reactor can’t be used as a weapon unless you pick it up and drop it on someone’s head.
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The end-product of Hydrogen-Boron fusion is Helium nuclei flying off at high speeds - how does that turn into electricity? Why do you need a transformer?
Consider electricity. Our normal experience with electricity is electrons flowing down a wire. But any flow of charged particles is electricity. In a battery, positively charged ions flow through the liquid or gel inside the battery to create an excess charge on the metal battery terminals which is then matched by electrons flowing through a wire outside the battery. So flowing positive ions are also electricity.
When the DPF shoots out a beam of helium nuclei (also called ions) the beam doesn’t generate electricity. It IS electricity. The only problem is that it’s not in a form that we want. We can’t let the particle beam out of the vacuum chamber, or it will collide with molecules in the air and its energy will be wasted as heat. So we have to transfer the electric energy to some electrons in a wire.
A transformer is a piece of equipment that takes energy out of one flow of electricity and adds it to another flow. It does this with magnetic fields. Using a transformer we can get the electric energy out of the particle beam and put it on a wire.
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Isn't the p-B11 reaction, strictly speaking, nuclear fission, as the reaction product immediately splits into three He4 atoms? Is it called fusion because "fission" is a dirty word in the nuclear community? [Question sent by R. Curnow]
Yes, technically, the p-B11 reaction is a fusion-fission reaction. The proton and boron-11 fuse to temporarily create an unstable isomer of carbon-12, which then fissions to create three helium-4s. However, the same can be said about the deuterium-tritium reaction, which fuses to produce an unstable helium-5 and then fissions into a helium-4 and a neutron. Like wise with deuterium-helium-3, or practically any fusion reaction. There are a few pure fusion reactions. For example, when two deuteriums fuse they will usually either produce a Tritium and a proton, or a helium-3 and a neutron, but there is a very small chance that they will stick together to form a helium-4 with the excess energy carried off by a gamma ray. This would be a fusion reaction with no subsequent fission. But this reaction happens purely by chance. There is no way to make this particular outcome happen more often. It’s just part of the random nature of quantum mechanics that decides which outcome occurs. There is no fuel combination that produces only these kind of pure fusion reactions. And even if there were this reaction really isn’t any safer than the p-B11 fusion-fission reaction which already produces no neutrons.
And yes, you are right that these reactions are called fusion and not fusion-fission to distinguish them from conventional heavy element fission. There are important differences between heavy element fission and light element fusion-fission. In particular, Light element fusion-fission cannot produce a self sustaining chain reaction. The plasma environment in which the reactions occur must be created by some external process. So there can be no runaway reactor meltdown. Also, the heavy element fission products are radioactive while the light element fusion-fission products are not (except for neutrons, which either decay into a proton and electron or are captured by an atom turning it into a different isotope which might be radioactive) This is why we make sure to call p-B11 aneutronic fusion, which is basically the safest nuclear reaction that exists. The difference between fission and fusion-fission is an important distinction to make. It’s a lot easier to make that distinction to the public if their names are a little less similar.
Put another way: Yes, you could think of it like a fusion of B11 + H to make an atom of C12 which then fissions into three He4. But it doesn’t happen in two separate steps. It’s like doing a “break” in pool, but with sticky pool balls that fly off stuck together in certain combinations. I suppose calling it fusion is mostly convention, but it shares much more in common with other types of fusion than with Uranium or Plutonium fission. It starts with light elements that cannot undergo fission by themselves until the fusion reaction occurs.
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What is this an image of?
Hot Plasma Vortex Filaments! This is an actual image of hot plasma vortex filaments pinched together by their own magnetic fields in a plasma focus fusion device. The photo was taken by Winston Bostick & Victorio Nardi with a very fast exposure time - a few nanoseconds. This is not really an image of the plasmoid, which is tiny—it is the last stage in the formation of the focus that produces the plasmoid.
The picture is actually black and white. The purple color is added purely to make a nice logo.
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Isn't Focus Fusion still nuclear energy? Won't it still create radioactive waste?
Focus Fusion reactors will create NO radioactive waste. While their energy is derived from nuclear reactions, they are very different reactions than those in present day nuclear reactors. This differs from conventional approaches to fusion, as explained further in the deuterium-tritium section.
See also “Focus Fusion vs. nuclear reactors” and “Can Focus Fusion be used to make a fusion bomb”
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What's the big difference between Focus Fusion reactors and current nuclear reactors?
In current nuclear reactors, energy is produced through nuclear fission. Here, a neutron breaks apart a uranium nucleus releasing energy and more high-energy neutrons. The nuclear fragments produced are highly radioactive. They naturally decay and give off their own energetic radiation. In addition, the neutrons smash into the nuclei of atoms in the reactor structure transmuting them to radioactive nuclei as well. All of these radioactive atoms constitute nuclear waste.
The form of nuclear fusion that the US government has funded, which uses deuterium and tritium as fuel, also produces some radioactive waste although far less than fission. Tritium, a form of hydrogen with two additional neutrons, is itself radioactive. When deuterium and tritium nuclei fuse together they produce nuclei of harmless and non-radioactive helium and a neutron. But the high energy neutron that carries most of the energy of the reaction can again smash into the reactor’s structure making it radioactive.
In focus fusion, however, none of this occurs. The fuel that will be used consists of hydrogen and boron. Both harmless, non-radioactive substances. When hydrogen nuclei (protons) and boron nuclei fuse together at extremely high temperatures they produce only helium nuclei and no neutrons.
A secondary reaction occurs when some helium nuclei fuse with boron nuclei. This does produce some neutrons. But these reactions are rare and only 1/1000th of the energy is emitted in the form of neutrons. The small number of neutrons emitted could easily be absorbed in a water shield about 1 meter thick, surrounded by 20 cm of Boron-10, which is a widely-used neutron absorber.
Focus fusion reactors are so safe that anyone could safely enter the reactor room seconds after it had been turned off even if it had previously been functioning for a year. (Due to the high-voltage equipment that focus fusion uses, it would not be advisable to be in the room when the reactor is working!) Short-lived radioactivity within the shielded reactor chamber itself would be below background levels in eight or nine hours, allowing the reactor vessel to be safely opened and maintained.
A tiny amount of radioactivity will be produced in the beryllium electrode, but it is so small, that NO radioactive waste (material that is dangerous to people) will be generated. In one year of operation a 5 MW focus-fusion reactor will generate about 5 microcuries (millionths of a curie) of radioactivity, about the same amount of radioactivity as contained in the bodies of a classroom of children. If the entire US electric power generation capacity were focus-fusion generators, 0.6 curies of radioactivity would be produced per year. By comparison, conventional nuclear energy has so far generated nearly one hundred billion curies of radioactive waste.
See also “If it’s nuclear, won’t it be radioactive.” and “Can Focus Fusion be used to make a fusion bomb”
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You say that focus fusion energy will be very cheap. But weren't such claims made about nuclear fission energy as well? And they did not pan out, did they?
Focus fusion reactors will produce electricity in a fundamentally different and much cheaper way than previous energy sources because they will avoid expensive turbines and generators.
Since Edison’s time there has been one main way to produce electricity. A heat source boils water to produce high temperature steam. The steam is fed under pressure to a turbine. The spinning of the turbine feeds power to a spinning electric generator producing electric power. Whether the source of heat is coal, oil, gas, or nuclear fission the basic process is the same. The majority of the cost of a modern power station comes from the turbine, electric generator, and the associated plumbing to handle the steam and water. So replacing the heat source cannot produce cheap electricity.
A focus fusion reactor would produce electricity very differently. The energy from fusion reactions is released mainly in the form of a high energy pulsed beam of helium nuclei. Since the nuclei are electrically charged, this beam is already an electric current. All that is needed is to capture this electric energy into an electric circuit. This can be done by allowing the pulsed beam to generate electric currents in a series of coils as it passes through them. This is much the same way that a transformer works, stepping electric power down from the high voltage of a transmission line to the low voltage used in homes and factories. It is also like a particle accelerator run in reverse. Such an electrical transformation can be highly efficient, probably around 80-90%. What is most important is that it is exceedingly cheap and compact. The whole apparatus of steam turbine and electrical generator are eliminated. A 20MW focus fusion reactor may cost around $500,000 and produce electricity for 1/20th of a cent per kWh. This is a hundred times less than current electric costs. Fuel costs will be negligible because a 20MW plant will require only twenty pounds of fuel a year.
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How can you be sure that focus fusion will work?
We can’t be sure it will work. This is why we are raising money to test it. The point of research is to test out ideas to see if they will work, and more research remains to be done. But we have good reason to believe that focus fusion will work. What is needed is a relatively modest amount of new research to improve our knowledge of the details of the focus fusion process and optimize the design of the device. No new physical theories are needed.
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If the plasma focus is not a new device, why has progress been so slow?
The immediate cause is that funding for the plasma focus has been incredibly inadequate. There are currently only five physicists working on the plasma focus device in North America, none of them full-time. In the world there are a dozen other small groups. Most only have access to devices with very small capacitor banks incapable of achieving ultra-high temperatures.
The experimental work that led to the billion-degree breakthrough was first proposed in 1987 on the basis of a detailed theory by Eric J. Lerner, President of Lawrenceville Plasma Physics and Executive Director of the Focus Fusion Society. But it took until 1994 to get the project funded by NASA’s Jet Propulsion Laboratory. Since then funding has been so minimal that over the seven years of the project only $300,000 was expended. This did not even cover equipment. A new facility had to be built entirely from government surplus equipment, a slow process.
By contrast, for most scientific programs $5 million a year is considered a small amount of funding. Tokamak research has been funded for about 25 years at $300 million a year.
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Since hydrogen-boron fusion is more difficult to fuse, why don't you start with deuterium-tritium and get that working first?
We’ve already discussed the reasons why hydrogen-boron is a better fuel for power producing fusion reactors : there is no radioactive waste, and generating electricity is less expensive because it does not require a steam turbine. But people have asked why we don’t use deuterium-tritium as an easier first step in our research program. If we achieved breakeven with deuterium-tritium it would be easier to get funding to continue on to hydrogen-boron.
The short answer is that tritium is expensive, highly regulated and radioactive. Any experiment with tritium must use additional radiation safety precautions, and comply with additional regulations. Even though deuterium-tritium fuses at lower plasma temperatures, the experiment to demonstrate breakeven would turn out to be more expensive because of the extra tritium handling costs. Our simulations tell us we should be able to achieve breakeven with hydrogen-boron fuel. So we see no reason to start with a more expensive experiment with a less desirable fuel.
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Given the promise of focus fusion, why has funding for LPP been so minimal and why is the government still concentrating on the tokamak?
There have been institutional obstacles to funding small scale fusion projects including, but not limited to, focus fusion. For the past 25 years nearly all fusion funding has been concentrated in one technology, the tokamak. The tokamak is an intrinsically large machine where the containment field is provided by external magnets. The tokamak is aimed at burning deuterium-tritium fuel whose disadvantages are noted above. In addition, the large size and complexity of tokamak reactors makes many scientists doubt that they could ever produce energy at competitive costs. But within the fusion program, as with many government programs, there is a political prejudice toward large projects because of the way that money is allocated. Large projects with corporate sponsors which generate significant numbers of jobs are supported by Congress. Small projects lack such political support.
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Does the pursuit of "instability" create funding problems?
Focus fusion represents a fundamentally different approach than the vast majority of existing technology. Since the innovation of the steam engine, most technology has aimed at controlling nature by producing conditions that are stable and homogeneous, close to equilibrium. Instabilities, rapid changes that create inhomogeneities, are avoided as they decrease predictability. The tokamak, for example, functions by attempting to produce a plasma that is stable and quiet.
In contrast, the plasma focus device functions by using instabilities that nature provides. It is natural instabilities that cause the plasma filaments to form and later to compress themselves into an ultra dense plasmoid to generate fusion temperatures. Such instabilities are common in nature and, as Nobel laureate Ilya Prigogine has emphasized, are the way that nature evolves and creates new structures and new types of order.
While the stable-state homogeneous approach to controlling nature has produced great advances it is limited and at times highly destructive. For example, the tendency toward mono-cropping in agriculture creates homogeneity and destroys the fertile diversity of nature. This is widely recognized as environmentally harmful. Yet in agriculture, as in technology, the stability approach dominates. As a result, funding agencies such as the department of energy have had difficulty accepting the instability based approach of the plasma focus device. It is likely that major government funding will not become available until the feasibility of hydrogen-boron fusion has been demonstrated experimentally.
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Could Sonofusion be coupled with the Focus Fusion process? [S. Wu-Kong]
The short answer is I don’t think so.
Here’s the long answer:
Sonofusion is a process where you use sound energy to create bubbles in heavy water. When the bubbles collapse they create a zone of very high temperature and pressure right in the center of the collapsing bubble. High enough for fusion. They have actually demonstrated this. Heavy water is Oxygen plus two deuterium atoms instead of two normal hydrogen. So they could see the neutrons produced when the deuterium fuse. Deuterium by itself doesn’t produce much energy, but it is easily available and produces a telltale signature when it fuses so it’s a commonly used diagnostic isotope. That’s what Eric used in the Texas A&M experiments.
Sonofusion is further away from breakeven than we are, but it is nonetheless a very exciting alternative. One interesting thing is that sonofusion makes use of natural instabilities to produce bursts of fusion just like focus fusion. Unlike tokomak which tries to create a stable, continuous process. If they can tune up their system and reach breakeven they could produce power with heavy water that has deuterium and tritium, or regular water with hydrogen that has boron salts dissolved in it. One disadvantage of sonofusion is that they would have to generate electricity by generating heat to drive a steam turbine. Even if they used hydrogen-boron the charged particles would get absorbed by the water, and wouldn’t come out as a beam of electricity like they do in focus fusion.
As far as combining the two I don’t see how it could be done. Sonofusion requires starting with a liquid while focus fusion requires starting with a diffuse gas. Even if you could do sonofusion with a gas or focus fusion with a liquid I don’t see how you would make the center of the collapsing bubble line up exactly with the collapsing magnetic plasmoid. The zone of fusion is only a few millionths of a meter across.
[Conjecture: Is there anything we could do to add energy to the plasmoid in addition to what it’s already getting? I’m thinking like if we can predict the location and timing of the plasmoid very precisely maybe we could hit it with lasers, or neutral beam injection? This would require more power so it might not help our breakeven story, but if we needed just a little more boost to get to the right temperature would this work? I know you want something simple so that it is cheap, but technology development sometimes takes the route through something complex that works before it can be made to work in its simplified form by lots and lots of engineering.] Links to articles describing Sonofusion:
http://www.physorg.com/news10336.html
http://www.newscientist.com/article.ns?id=dn4741
http://members.nuvox.net/~on.jwclymer/snf/
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