THE CLAIRE FOSS JOURNAL
FISSION - vs. - FUSION
Energy of the Future
*** See updated editors note at the end of this article.
Excerpts from an article by: The Focus Fusion Society
Fission vs. Fusion
Fossil fuels are a serious concern in the world today. We rely on them almost exclusively for our power, and yet they pose serious environmental and health risks as well as being a source of international instability. Nuclear power has been suggested as a solution, but has its own environmental and health risks. What many people don't know it that there is another alternative called focus fusion power which is fundamentally different than the nuclear power in use today. It is truly a clean and safe alternative to fossil fuels.
Current nuclear reactors use uranium or plutonium fission to produce electricity. Uranium and plutonium are both radioactive. This means that occasionally an atom will split apart into two smaller atoms and some high energy neutrons. There are many ways a radioactive atom can split apart so the two smaller atoms, called reaction products, will be from a set of various elements. But these elements all have one thing in common. They are all radioactive.
Another danger comes from the high energy neutrons. These neutrons slam into whatever is in their path. This creates heat which in a nuclear power plant is used to boil water to run a steam powered generator. However, heat is not the only thing neutrons produce. A neutron can enter the nucleus of a non-radioactive atom and make it radioactive.
So fission power plants have three problems with radioactivity:
The fuel is radioactive.
There is an alternative to nuclear fission called nuclear fusion. Instead of splitting atoms, a fusion power plant takes small atoms such as hydrogen and fuses them together to make bigger atoms. This produces much less radioactive waste, and if the right atoms are chosen it produces none at all.
We know that fusion is possible. It is the energy source that powers the sun. It has also been demonstrated in laboratories on earth, but no commercially viable fusion power plant has yet been developed. One reason for this is that fusion does not happen spontaneously like fission. For fusion to occur the atoms must be confined in a magnetic field and raised to temperatures of 100 million Kelvin or more. This takes a lot of electricity, and the trick is getting out more electricity than you put in.
However, this has a serendipitous safety advantage. Fusion reactors cannot sustain a chain reaction so they can never melt down like fission reactors. Simply turn off the power and the fusion stops.
Deuterium-Tritium vs. Hydrogen-Boron
Nuclear fusion has the potential to generate power without the radioactive waste of nuclear fission, but that depends on which atoms you decide to fuse. Most fusion research today is focused on fusing deuterium and tritium. Deuterium has one proton and one neutron. Tritium has one proton and two neutrons. When they come together there are two protons and three neutrons. This unstable configuration then splits into a helium atom (two protons and two neutrons) and a high energy neutron. These neutrons create heat and radioactive materials just as in a fission reactor.
Deuterium and helium are not radioactive and occur in nature. Tritium, however, is radioactive and does not occur in nature. It must be created in the reactor by using neutrons. So deuterium-tritium fusion still has two of the disadvantages of nuclear fission:
Some of the fuel (tritium) is radioactive.
Deuterium-tritium fusion would produce much less radioactive waste than fission, but radioactive waste can be avoided altogether by choosing a better fuel. Boron-11 is an atom that contains five protons and six neutrons. Boron-11 can fuse with a hydrogen atom (one proton, no neutrons.) This makes six protons and six neutrons which is exactly enough for three helium atoms with no left over neutrons. The helium atoms then fly off at high speeds carrying the fusion energy. So hydrogen-boron fusion can create energy without releasing neutrons.
Boron-11 is a common element that exists in the earth's crust and seawater. You may even have some in your house if you own a box of Borax. Hydrogen is the most common element in the universe and is even part of water as demonstrated by the formula H2O. Helium is the second most common element in the universe and is what makes children's balloons and blimps float. Not one of these materials is radioactive.
So, when a boron-11 atom fuses with a hydrogen atom the result is three helium atoms and energy, but no radioactive waste:
The fuel (boron and hydrogen) is not radioactive.
* It is true that the hydrogen-boron reaction releases no neutrons, but as fusion progresses a greater number of helium atoms are created and occasionally a boron atom will fuse with a helium instead of a hydrogen. This produces a (non-radioactive) nitrogen atom and a neutron. However, this reaction releases very little energy and so the neutron is not the same as the high energy neutrons produced by fission or deuterium-tritium fusion. These low-energy neutrons can create a small amount of short-lived radioactive materials, but these materials decay so quickly that it would be safe to enter a room containing a focus fusion device seconds after it is turned off.
Additionally, at such high temperatures electrons do emit x-rays. These are exactly the same as the x-rays produced in your doctor's office, or in the baggage scanning machines at the airport. X-rays can be dangerous if people are exposed to large doses, but they can be stopped by lead shielding. Our society has extensive experience using x-rays safely. Together these low energy neutrons, x-rays, and short-lived radioactive materials disappear quickly and do not generate radioactive waste.
So why, you may wonder, are researchers spending so much time on deuterium-tritium fusion when hydrogen-boron has clear advantages? The reason is that deuterium-tritium fusion is easier to ignite. It requires temperatures of only 100 million Kelvin while hydrogen-boron fusion requires 1 billion Kelvin. Unfortunately, many fusion researchers have spent their careers developing a device called the tokamak which cannot reach the temperatures required for hydrogen-boron fusion. Rather than looking for new ideas, the fusion research establishment has decided that the radioactive waste produced by deuterium-tritium fusion is acceptable. However, there is a device which can reach 1 billion Kelvin called the plasma focus device.
The Plasma Focus Device
Focus fusion is the only known method that can achieve hydrogen-boron fusion. It also has other advantages over tokamak based deuterium-tritium fusion reactors. Focus fusion reactors will be much less expensive for the same amount of power. Tokamak reactors generate electricity by boiling water for a steam powered generator (high energy neutrons provide the heat.) This is the same method that coal power plants use. The only difference is the heat source. In a coal power plant the steam generator is the most expensive part of the plant so replacing the heat source will not result in a lot of savings. Also, this method of generating electricity is limited by the fundamental efficiency limits of heat engines. Focus fusion reactors do not require a heat engine. They generate electricity directly. After all, electricity is just moving charged particles. The particle decelerators in a focus fusion reactor merely transfer the electricity of charged particle beams into a wire. This process does not face the efficiency limits of heat engines.
A focus fusion reactor should be able to economically generate power in quantities as small as 20MW from a power plant the size of a two car garage. This means they will be useful for powering individual villages in the third world where regional electricity grids are not as well developed. And in developed nations focus fusion power can be generated near where it will be used to reduce transmission losses and can be owned by the communities it serves to reduce dependence on speculative energy markets.
Focus fusion will be less expensive because it does not require a large steam powered generator. Focus fusion will be decentralized so it will power the third world and promote energy self sufficiency. Finally, decentralized power also reduces the chance that natural disaster or terrorist action will cause widespread blackouts.
Thanks to the Focus Fusion Society for this information.
**The heat energy from fusion can be used thermally to split water, in order to cheaply produce hydrogen for transportation fuel. But with cheaply produced and abundant electricity the need for hydrogen as a transportation fuel may indeed be bypassed. Recently developed long lasting storage batteries may make non-polluting electrically driven land vehicles the obvious first choice in certain situations.
**Focus fusion will be the basis for a new rocket propulsion system for traveling in outer space. Focus fusion produces a beam of ions which can be decelerated to produce electricity. But instead, if you just let these ions fly off into space you have a fusion powered ion engine. This type of engine should have a specific impulse of 100,000 seconds or more. Specific impulse is a measure of how much velocity you can get from a certain amount of fuel. Chemical rocket engines have a specific impulse of 450 or less so a fusion rocket would make it much easier to get around the solar system.