Resource Energy TWyears

Oil (known reserves) 202

Coal (known reserves) 790

Natural Gas (known conventional reserves) 205

Natural Gas (including sub-sea methane hydrates) 24,000

Nuclear Fission (commercial grade U ore, without reprocessing) 685

Nuclear Fission (commercial grade U ore, with fuel reprocessing) 50,000

Fusion 100,000,000,000

conventional materials, like stainless steel, the neutrons can produce some activation, resulting in the production of about 1/1,000th the radioactive waste of a fission reactor. However, if specially chosen structural materials like carbon-carbon graphite are used, there will be no activation, and the system can produce endless amounts of energy without pollution of any kind.10

Once we have fusion, we will be able to make as much methanol as we desire inorganically, simply by reacting carbon dioxide with electrolysis-produced hydrogen over copper on zinc oxide catalyst. The carbon dioxide could come from high carbon dioxide emission sources such as steel mills or cement plants, or even directly from the atmosphere itself. Under such circumstances, the Islamists' possession of the world's oil reserves will give them as much influence over the human future as they currently derive from their monopoly of camel milk.

But fusion is not just a plentiful source of energy; it is a new kind of energy, one that offers the potential to do things that are simply impossible without it. If we can get fusion, we will be able to use the superhot plasma that fusion reactors create as a torch to flash any kind of rock, scrap, or waste into its constituent elements, which could then be separated and turned into useful materials. Such technology would eliminate any possibility of resource exhaustion of this planet. Using fusion power, we will be able create space propulsion systems with exhaust velocities up to five thousand times greater than the best possible chemical rocket engines. With such technology, the stars would be within our reach.

So the fusion game is really worth the candle. It's a tough game, though, because while fusion occurs naturally in the stars, creating the conditions on Earth to allow it to proceed in a controlled way in a human-engineered machine is quite a challenge.

All atomic nuclei are positively charged, and therefore repel each other. In order to overcome this repulsion and get nuclei to fuse, they must be made to move very fast while being held in a confined area where they will have a high probability of colliding at high speed. Superheating fusion fuel to temperatures of about 100 million °C gets the nuclei racing about at enormous speed. This is much too hot to confine the fuel using a solid chamber wall—any known or conceivable solid material would vaporize instantly if brought to such a temperature. However, at temperatures above 100,000°C, gases transition into a fourth state of matter, known as a plasma, in which the electrons and nuclei of atoms move independently of each other. (In school we are taught that there are three states of matter: solid, liquid, and gas. These dominate on Earth, where plasma exists only in transient forms in flames and lightning. However, most matter in the universe is plasma, which constitutes the substance of the sun and all the stars.) Because the particles of plasma are electrically charged, their motion can be affected by magnetic fields. Thus magnetic traps such as the toroidal or doughnut-shaped tokamak (as well as a variety of alternate concepts including stellarators, magnetic mirrors, etc.) have been designed that can contain fusion plasmas without ever letting them touch the chamber wall.

At least that is how it is supposed to work in principle. In practice, all magnetic fusion confinement traps are leaky, allowing the plasma to gradually escape by diffusion. When the plasma particles escape, they quickly hit the wall and are cooled to its (by fusion standards) very low temperature, thereby causing the plasma to lose energy. However, if the plasma is producing energy through fusion reactions faster than it is losing it through leakage, it can keep itself hot and maintain itself as a standing, energy-producing fusion fire for as long as additional fuel is fed into the system. The denser a plasma is, and the higher its temperature, the faster it will produce fusion reactions, while the longer individual particles remain trapped, the slower the rate of energy leakage will be. Thus, the critical parameter affecting the performance of fusion systems is the product of the plasma density (in particles per cubic meter), the temperature (in kilo volts, or keV, 1 keV = 11,000,000°C = 20,000,000°F), and the average particle confinement time (in seconds) achieved in a given machine. The progress that the world's fusion programs have had in raising this triple product, known as the Lawson parameter, is shown in figure 11.1.

The easiest fusion reaction to drive is that between deuterium and tritium. To produce energy at a rate equal to the external power being used to heat the plasma (via microwave heaters or other means), a deuterium-tritium (D-T) fusion plasma must have a Lawson parameter of 9 x 1020 keV-particle-seconds/m3 (or keV-s/m3 for short). Such a condition is known as "breakeven" and was finally reached at the European JET tokamak in 1995. A deuterium-tritium plasma with a Lawson parameter of 4 x 1021 keV-s/m3 (the notation 4 x 1021 means a 4 with 21 zeroes after it) and a temperature of 10 keV would produce energy at a sufficient rate that no external heating power would be needed. Once started up, such a plasma would heat itself. This condition is known as "ignition," and is the next, and final, major physics milestone that needs to be achieved before actual energy-producing fusion reactors can be engineered.

A fusion reactor could be operated as a D-T system, obtaining its tritium by reacting the neutrons it emits with a lithium blanket surrounding the reactor vessel. (When a lithium nucleus absorbs a neutron it splits into a helium and a tritium, and sometimes emits a neutron, which allows yet another tritium to be produced.) First-generation fusion reactors may be designed along these lines.11 However, with a little further progress in improved magnetic confinement, this will become unnecessary. Instead, once ignition is reached, we will be able to use the plasma's own power to ramp its temperature up to 40 keV, at which point the deuterium and its by-products will burn by themselves without engineered tritium enrichment.12

Progress in Fusion Research

Year

Figure 11.1. Progress in controlled fusion. Since 1965, the world's fusion programs have advanced the achieved Lawson parameter by a factor of ten thousand. A further increase of a factor of four will take us to ignition. Note the logarithmic scale. Source: Adapted from data provided by European Fusion Development Agreement, www.efda.org.

Year

Figure 11.1. Progress in controlled fusion. Since 1965, the world's fusion programs have advanced the achieved Lawson parameter by a factor of ten thousand. A further increase of a factor of four will take us to ignition. Note the logarithmic scale. Source: Adapted from data provided by European Fusion Development Agreement, www.efda.org.

As can be seen in figure 11.1, the world's fusion programs have made an enormous amount of progress over the past thirty years, raising the achieved Lawson parameter by a factor of almost ten thousand to reach breakeven. Another factor of four, which can certainly be accomplished if funds are provided to build the next generation of experimental tokamaks, would take us to ignition.

Fusion can certainly be developed, and when it is, it will eliminate the specter of energy shortages for millions of years to come.

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