Plans for a nuclear fusion reactor facility are soon to be underway, with a mission to demonstrate that inertial fusion could be used as a future energy source--to power the world.
Nuclear Fusion in a Supernovae (artist's depiction)
Currently, solar and wind power are the top two renewable energy technologies. Optimistically, wind and solar power could produce, at most, 30% of the world's energy needs in the future.
Perhaps a lesser known alternative is nuclear fusion--the same process that fuels the sun and the stars. To hear its potential--a method that offers enough energy for the world's power, a limitless fuel supply, and no greenhouse gas emissions--it sounds like an ideal solution.
But while it's one of the only foreseeable methods to completely eliminate our reliance on natural gas, and reduce carbon dioxide emissions to 0%, development of a nuclear fusion reactor will take time. Actually, it already has--one of the biggest criticisms of the idea is that, after 40 years of research, there have been no significant breakthroughs. Most dishearteningly, scientists have not yet been able to contain a nuclear fusion reaction long enough to produce more energy than is required to perform the reaction.
HiPER Nuclear Reaction ChamberHowever, one of the most exciting initiatives in nuclear fusion research, HiPER (High Power laser Energy Research facility), has recently received a grant from the European Union for 738 million euros, which will be used for the initial planning of an inertial fusion reactor, with a demonstration of the proof-of-principle planned as soon as 2010.
Fifty scientists from 15 nations are already on board the two-year-old project, with UK scientist Mike Dunne of the Rutherford Appleton Laboratory heading up the initiative. Building on 40 years of research, the team claims to have a plan to put the technology on the fast track. Their goal is to have a reactor that could start delivering power for consumer electricity in 2030.
Basically, fusion is the combination of small atomic nuclei into a larger nucleus. As Einstein showed in his famous equation E=mc², a small amount of mass can be associated with a large amount of energy. So, for example, by fusing together two isotopes of hydrogen (deuterium, which has one neutron, and tritium, which has two neutrons) to form helium, which has two neutrons, one neutron is left over. In that neutron, a small amount of mass is lost, and an enormous amount of energy is released.
The challenge to this process is that it's very difficult to get two different nuclei to get close to each other, since the electromagnetic force causes the positively charged nuclei to repel each other. However, if heated to very high temperatures, they can overcome the electromagnetic force and get a little closer to each other-close enough for the strong force to take over and fuse the nuclei. The strong force only operates on very small scales; however, it is by far the strongest of the four forces when operating in its territory.
Deuterium + Tritium
For nuclear fusion to take place in the core of the sun, the temperature only needs to reach about 10 million degrees Celsius, due to the star's enormous amount of gravitational pressure. At the much lower pressure on Earth, however, scientists need to create temperatures of more than 100 million degrees Celsius-10 times hotter than the sun.
This is the main challenge of nuclear fusion-to heat and maintain the fuel at a high enough temperature and density for a sufficient duration.
The HiPER experiment plans to achieve these extreme temperatures with a unique approach: ultra-powerful lasers. According to HiPER's Web site , some of these lasers are powerful enough to concentrate the equivalent of 10,000 times the power of the UK's national grid into a spot less than a millimeter across.
Several scientists have already been working on such lasers. However, currently the best lasers take several minutes to accumulate enough power to fire at and heat the atoms. The lasers would need to fire several times a second in a fusion reactor, and also be an order of magnitude more efficient than today's beams. In an effort to close this gap, laser research is one of the largest areas of research for the HiPER collaboration.
Working with matter at such enormous temperatures presents further challenges. At 100 million degrees, matter becomes a plasma, an electrically charged substance where the electrons move freely about, rather than being chained in orbits around the atoms. In order to keep the two hydrogen nuclei together long enough to fuse, the researchers have to confine this plasma in the center of the reactor. Because the hot plasma cannot touch the walls of the reactor (no material could withstand that temperature, and the plasma would quickly cool anyway if it did touch), confinement of plasma is another extremely difficult task.
There are a few ways scientists know how to confine plasma. Do it like the sun, and confine it with a massive amount of gravity (but like the temperature challenge, this is not possible on Earth). Another option is to use magnetic fields. This technique is currently being used in a project called International Thermonuclear Experimental Reactor (ITER), a 10 billion-euro reactor being built in Cadarache, France.
But HiPER is going to try another technique: inertial confinement, which can be done with a second laser. In the set-up, one laser compresses the block of atoms-called a "fuel pellet"--while another laser, like a spark plug, ignites it. Using this technique, Dunne explained that the fuel does not need to be compressed as much as it does with the other fusion methods. Inertial confinement has already been demonstrated, though not with the laser technique. Inertial confinement was also used in the hydrogen bomb, where a fission reaction created x-rays that played the role of the laser.
One of the greatest advantages of nuclear fusion is that the supply of hydrogen isotopes is endless: they are contained in sea water. According to the HiPER Web site, one cubic kilometer of seawater could supply the same amount of energy as could the world's current oil reserves. In other words, it would likely outlast humanity.
Sea water contains deuterium
Besides being sent to steam turbines to supply electrical power, nuclear fusion could also be used to power vehicles. The high temperatures created in the reactor could be used to drive a hydrogen production cycle, and hydrogen could be used in a new car technology.
While the process releases no carbon dioxide, the scientists explain that it will produce some low-level radioactive waste--about the same amount as the radioactive by-products from a hospital. And over the life of the fusion power plant, the amount and type of waste would be manageable.
In addition to demonstrating the feasibility of laser-driven fusion as a future energy source, the project could also allow researchers to investigate extreme conditions that cannot be produced elsewhere on Earth. For example, the 100-million-degree temperature, the billion-atmosphere pressures, and the enormous electric and magnetic fields could reveal new areas of science.
As for the cost of electric power produced by nuclear fusion, researchers are still analyzing the question. In the mid-‘90s, researchers from the US presented initial estimates for a cost of 5-8 cents per kW-hour (consistent with, or even slightly less than, current electric rates).
For now, the HiPER team is trying to move the project from the science lab to the public and political arena. They explain that the work is not defense-related, and none of their research will be classified, but published to the international science community.
According to their Web site, they plan to begin the preparatory phase of the project in early 2008, preparing for a detailed design and construction phase to start in 2011-2012. Depending on these successes, the team hopes to open the facility to testing by 2020. And as stated earlier, consumer power generation could conceivably occur in 2030.
As the team notes, nuclear fusion is not an immediate solution to the world's energy demand, but rather a long-term, sustainable solution that will require more research and development. Regardless of future technical roadblocks, for now, it is worth pursuing.
HiPER Web Site
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