Energy is commonly defined as the ability of a system to perform work and it can be converted to other forms. One significant form of energy that has attracted attention in the last few decades is Nuclear energy. Nuclear energy is the energy contained in the nucleus, where most of the mass of an atom is concentrated. This energy is released from the atom through nuclear reactions. Due to the sustainable nature of this form of energy, it works optimally for electricity generation; although it was originally developed as a weapon. The two fundamental nuclear processes to release this energy are fission and fusion. Fission is the process of spilling large atoms such as Uranium and Plutonium into smaller ones, fusion on the other hand requires combining two small atoms such as Hydrogen and Helium to form a larger atom. [1-4]
Fusion reactions has the potential to provide sustainable energy and releases more energy than fission reactions. Designing full-scale fusion electrical power units would satisfy the increasing global energy demand. Fusion is the process that powers active stars, however, creating conditions for fusion reactions to sustain ignition have not been accomplished on a commercial scale for power source development.
The energy released by fusion of light elements is essentially an interaction of two forces i.e. nuclear and coulomb; the benefits of fusion reactions decay for heavier elements. Nuclear force is stronger in an atom and hence overcomes the proton repulsion force. In fusion reactions, building nuclei through the process releases the extra energy, which is the nuclear energy. In the sun's core for example, the temperature approaches 15 million degrees Celsius. At such high temperature, the hydrogen atoms are in constant fast movement. As they collide at high speeds, the atoms fuse overcoming the electrostatic repulsion forces between their nuclei i.e. positively charged. A small amount of mass is lost, during this process of fusing hydrogen atoms to create helium, which results in an enormous energy release in the sun. [4,5]
Research has been conducted for the past 60 years to promote a controlled fusion reaction. Through Laboratory experiments, it was suggested that the fusion reactions between deuterium (D) and tritium (T), hydrogen isotopes, are the most efficient to generate the highest energy at the lowest temperature. Such reaction requires a temperature as high as 150 million degrees Celsius. The first fusion experiment was conducted in the 1930s and following that understanding the fusion process was improving. A machine called tokamak was built in 1968 that was capable of achieving high levels of temperature and plasma confinement times, which was not accessible prior to that. Thereafter, tokamak has become the trademark of fusion reactions and the dominant concept.
The largest controlled release of nuclear fusion energy was achieved in 1991 by JET (The Joint European Torus). Several other progresses have been made over the years in fusion devices around the world but none have been able to achieve the energy breakeven point. This is a point where the energy input equals the output. JET succeeded in generating 70% of the input power. One of the major ongoing projects in the field of nuclear fusion power is ITER. ITER means "the way" in latin and it is a large scale collaboration between many countries around the world to build the world's largest Tokamak machine to replicate the principles that power the sun. ITER will require an input power of 50 MW and in turn produce more output power of 500 MW. The facility will finish construction around 2019 and realize full fusion experiments starting 2027. The concept this machine works by is no different than the first Tokamak device developed by the Soviet Union in the 1960s. Under extreme pressure and temperature, the mixture of deuterium and tritium are heated to fusion temperature inside a vacuum vessel to form hot plasma. Magnetic coils are used to keep the plasma away from the walls. The plasma then becomes agitated under these conditions, start colliding and consequently overcome the inherent electromagnetic repulsion to fuse, releasing a huge amount of energy. Tokamak utilizes the heat, which is absorbed on the walls of the vessel, to produce steam and then electricity similar to the concept of turbines and generators. This machine will be the world's largest tokamak. The knowledge conceived from this large-scale experiment will fundamentally contribute to building a machine for continuous or near continuous operations to ultimately attain a sustainable electrical power source. [4,6]
The efforts towards availing alternative energy sources will never stop especially those that are carbon free. Nuclear fusion appeals to both energy and environment advocates. It can ensure energy sustainability and cause less harm to the ecological system. There are massive worldwide collaborations to make this project successful and the first milestone towards attaining this goal is the introduction of the Tokamak machine currently under construction by ITER.
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[1] C. D. Ferguson, Nuclear Energy: What Everyone Needs to Know (Oxford University Press, 2011).
[2] R. Murray and K. E. Holbert, Nuclear Energy, 7th Ed. (Butterworth-Heineman, 2014).
[3] P. H. Raven, D. H. Hassenzahl, and L. R. Berg, Environment, 8th Ed. (Wiley, 2012).
[4] F. I. Petrescu, Cold Nuclear Fusion (CreateSpace Independent Publishing, 2012).
[5] H. A. Bethe, "The Hydrogen Bomb," B. Atom, Sci. 6, No. 4, 99 (April 1950).
[6] C. M. Braams and P. E. Stott, Nuclear Fusion: Half a Century of Magnetic Confinement Fusion Research (CRC Press, 2002).