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About ten years ago, the world was shocked to hear the announcement that two Utah scientists had produced more than 100 hours of energy based on a fusion reaction at room temperature, commonly known as "cold" fusion. While all the world was busy with high temperature fusion, our two Utah scientists were working on cold fusion because it doesn't have many of the problems with high temperature fusion. At the time, most fusion reactions of any type only lasted for fractions of a second before destabilizing. Cold fusion that lasted for 100 hours was amazing.
Ten miles down the road the students at a rival college conducted an experiment to see if the results could be reproduced. They were. The rest of the world rushed to duplicate the experiment. Yet, the results were mixed. No sooner did a report come in saying that the experiment had worked than one came in unable to reproduce the initial reaction.
What was this energy source? Where did it come from, and was it real? An agreement over what happened actually never has been reached. What is fusion? Why is it important and what fuels it? Why the interest in cold fusion? Why is it so difficult to achieve? This paper addresses these questions
I. What is fusion and how do we contain it?
The idea of fusion is very simple. Fuse two atoms together and release heat and energy in the process. This reaction can occur as super heated or cold reactions. This makes it sound like fusion is easy but in practice it is not so easy. The matter used for the reaction must be contained in a superheated state known as plasma. Millions of degrees are required to produce plasma and, as it heats, the plasma spreads out. This is because as matter is heated it also expands. This makes the reaction much harder to achieve as the plasma has to traverse a large distance through the reactor to fuse. Also, it is difficult to cause plasma to react in small amounts because small amounts have a harder time maintaining a chain reaction. Large amounts of plasma form a cloud. This cloud has some gravity making it easier to contain in a reactor and there is more energy produced as more fusion is taking place. However, large amounts take a lot of room to contain.
Therefore, we have to compress plasma for a sufficient number of reactions to occur and reach what is known as the "break-even point." The break-even point is when we get as much energy out of a reaction as we put in. Should we ever build a working fusion reactor, we will need to achieve much more than the break-even point to make fusion energy practical.
Super heated plasma is difficult to maintain at millions of degrees and tends to burn the reactor out. In order to contain the plasma, magnetic confinement is used. Because all the plasma molecules have a charge that is the same, a simple magnetic current can keep them contained. With magnetic confinement, the molecules of the plasma start to follow the magnetic current one behind the other. Unfortunately, the magnetic containment cannot be sustained to reach the break-even point because the reactor tends to burn itself out. This paradox can be taken care of using specific reactor designs
II. Why is fusion important and what fuels it?
Why is fusion such a potentially important source of energy? For one thing, it uses a fuel that is so plentiful in our oceans that it could last us for hundreds of millions of years. It is also the fuel that our Sun is currently using, hydrogen. Hydrogen is the fuel that could make practical fusion possible. There is another great thing about hydrogen fusion. This type of fusion would give us more energy out of less fuel than any other type of power that we currently use. That is why fusion is getting so much attention.
It fact, our true source of energy, the Sun, is powered by hydrogen. It fuses 520 million tons of hydrogen gas a second. Since the hydrogen bomb was detonated, mankind has been trying to harness this energy source. Why, if we have the hydrogen bomb do we not have fusion generators? What is the difference between the two? If we can make a bomb that uses fusion, should we not have fusion reactors?
The hydrogen bomb is an uncontrolled reaction and a reactor must have control over the reactions to be useful. An uncontrolled reaction would be damaging and it would cause the reactor to have a very short life span, to say the least. So you can now see the diffrence between a hydrogen bomb and a fusion reactor. Why does fusion work in our Sun and how can we learn from our Sun to make fusion work for us?
Another fuel for cold fusion is called "heavy hydrogen" or deuterium. This is a form of hydrogen that has the addition of a neutron in the nucleus which gives it a greater mass. This is also the type of hydrogen that was used in the Utah cold fusion experiments. With deuterium, cold fusion takes place much more quickly. The deuterium molecules are easier than "light hydrogen" to fuse as their nuclei are closer together. However, we have a lower supply of deuterium that light hydrogen in our oceans and it is more difficult to isolate so we could possibly expend more energy trying to find deuterium than we get out of the fusion reaction using deuterium.
As you can see, so far, the road to harnessing fusion has not been an easy one. While we have found several ways to get the plasma to fuse, it has not been easy to control this in a way that yields sustainable energy. To give you an idea, here are some examples of the different types of reactors that have been developed. One type uses dozens of powerful lasers to heat a single frozen pellet of hydrogen. This hydrogen is then superheated causing it to fuse, creating a miniature hydrogen bomb. The problem with this method; however, is that the break-even point is almost impossible to reach as the lasers use more energy than the reactor can collect.
There are two more types of reactors used to achieve high temperature fusion. One is known as the "Stellerator." It is basically a magnetic box or tube with powerful magnets on either side that keep the plasma from touching the walls of the reactor. The basic idea is to create a big stadium for the hydrogen to fuse in. The last and the most popular type of reactor is known as the "Tokamak." This round shaped reactor is popular with most scientists because it is created with overlapping magnetic currents which cause the plasma to fuse more often.
III. Why the interest in cold fusion?
While regular high temperature fusion might be an unlikely candidate in everyday applications, cold fusion could be easily contained almost anywhere. For example, the room of a car engine would be large enough to contain a cold fusion reaction because a cold fusion reaction doesn't spread out, requiring some sort of containment. High temperature fusion has another downside. Let us visualize for a moment. It is the year 2050, and you climb into your high temperature fusion powered car. You start the engine and disappear in millions of degrees of heat because the reactor gets so hot. That is why cold fusion is a good idea for cars lest we feel like having our "daily vaporizing." An additional problem with high temperature fusion is that without enough heat to make the atoms move fast enough, the matter cannot go fast enough to "tunnel" through the magnetic field of the atoms and create fusion. This is because all of the plasma atoms have the same charge so they repel each other inhibiting tunneling and fusion.
IV. Why is cold fusion so difficult to achieve?
Fusion doesn't occur without an outside force, because the magnetic field in the atom keeps the two nuclei from fusing. This is particularly a problem with cold fusion, because in high temperature fusion the atoms get moving fast enough to over power the magnetic field barrier. Scientists have found a way of bypassing the magnetic resistance that each hydrogen molecule has during cold fusion using a particle known as a "muon." A muon is a particle that weighs 200 times more than a regular electron. It takes the place of an electron. A muon orbits the nucleus 200 times closer than an electron. Because of the decreased distance between the muon and the nucleus, a muonic hydrogen molecule has nuclei closer together than a regular hydrogen molecule. This decreases the distance that two nuclei must travel to fuse. This increase in molecular mass may be the missing link in cold fusion. If this link could be consistently achieved, it would allow us to get out 25 times more energy than we put in. In reality, today we get far less out of the muon than we put in. It will be some time before we can exceed break-even point or get more out than we put into a reaction.
V. What are some reasons for pursuing warm and cold fusion?
What is it that fusion has that any other fuel source doesn't? With fusion we could get much more out of a fuel source than we currently do. For instance, to power a one megawatt power plant for a year with coal you would need over 500 train loads of coal. With nuclear fission you would need one train car of uranium. Fusion requires even less fuel and provides more energy. Our sun has over 500 million hydrogen fusion reactions a second and the sun produces far more that 1 megawatt of energy.
Nuclear fission is currently being used to provide 20 percent of the power used in our country. How is it different from fusion? There is a big difference between fusion and fission. "Fusion" is the fusing of atoms, while "fission" is the splitting of atoms. Fuel used for fission is more costly and dangerous than that used for fusion and also a lot of radioactive waste left behind. Moreover, uranium and other radioactive fuels are expensive, dangerous to work with and hard to find. In comparison, hydrogen, the fuel used for most fusion reactions is cheap and plentiful. Which, do you think will last longer in terms of power. Nuclear fuel will last for only 150 years. Hydrogen will last for hundreds of millions of years at our current energy consumption rate.
There are many potential uses of fusion. In fact, fusion could produce so much power that we would be able to get rid of any other power plant type. Hydrogen plasma is cheap and easy to produce. By simply running an energy current through water we could separate it into oxygen and hydrogen. Hydrogen fuel cells produce water meaning that we could extend the life of fusion for a long time.
Imagine, an energy source that replenishes itself. Since fusion reactions produce a lot of energy we would have a source that could accelerate a space ship much faster and more effectively than ion or chemical rockets. With the development of fusion, interstellar travel might be more feasible. With the massive energy released from fusion reactions, we would be able to get to the moon on less fuel, go faster, and leave only a trail of water behind.
However, there is also a downside to fusion. While fusion is what keeps the stars burning, one fact cannot be ignored. The hydrogen supplies in the universe are limited. Now it won't happen for trillions of years, but supplies will eventually run out. That is the reason why researching fusion is so important. It is the power that makes life possible and without it no life could possibly exist in it
Whatever the type of fusion that is chosen, some of the main powers of the world have decided to pool their data. The answer to the fusion problem may simply be that the world needs to ally and build one large reactor. No one college is going to be able to support the building of a mega-million dollar project. If the world is to have a reasonably big reactor for fusion, many countries and scientists need to be involved.
Currently a joint project, the International Thermonuclear Experimental Reactor (ITER) may be able to solve the problems of fusion. This giant reactor will be built by Russia, the United States, Europe and Japan. With so many countries working on it, I would say it stands a good chance at being the first successful fusion reactor. The ITER project will cost hundreds of billions of dollars but it is predicted that it eventually will produce the first fusion reactor to produce more energy than it consumes. ITER is predicted to be the reactor that sparks all of mankind to use the power of the stars. So, in conclusion, "to the stars�with fusion."
Sources
Henderson, Harry. Nuclear Physics. New York: Facts On File, Inc., 1998.
Lampton, Christopher. Fusion: The Eternal Flame. New York: Franklin Watts, 1982
Peat, F. David. Cold Fusion: The making of a Scientific Controversy. Chicago: Contemporary Books, 1989.
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