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Nuclear fusion energy is always 30 years away. Nuclear fusion energy is the energy source of the future and always will be. These are some of the long-running jokes on the seemingly unattainable mirage that nuclear fusion energy is. Energy is fundamental to our existence and can be harnessed in lots of ways and forms depending on the intended use: solar energy using photovoltaic cells, burning of fossil fuels, nuclear fission, wind energy etc. However, all our current sources of energy have limitations in their use. For energy obtained from photovoltaic cells, it has proved hard to ensure constant power supply on a large scale especially when the sun is not shining. Burning of fossil fuels causes pollution (in addition to being a non-renewable source of energy hence not reliable in the long term) while nuclear fission poses the problem of nuclear waste disposal in addition to the dangers associated with radiation. These seemingly endless limitations with the current energy sources drive the search for more reliable energy sources and nuclear fusion had been touted the “Holy grail” of energy due to its minimal downsides in comparison to other power sources.
Nuclear fusion is the antipode of nuclear fission. Nuclear fission is the process by which a larger atom splits into two smaller atoms when a neutron collides with it making it unstable. Neutrons and a large amount of energy in form of heat are released in addition to the smaller atoms. These neutrons collide with, excite and split other atoms making nuclear fission a chain reaction. The released energy is then harnessed to produce steam from water which turns turbines to produce electricity.
Nuclear fusion in a thermonuclear process where two or more atomic nuclei combine to form heavier nuclei under conditions of extreme pressure and temperature and energy is released as a result. Extreme heat is required to create a plasma state where matter gets so hot that atoms are stripped off of their electrons. Large amounts of energy are thereafter required to fuse the freed nuclei as they are all positively charged and hence repel each other. The sun is powered by nuclear fusion reactions where Tritium and Deuterium combine under the intense pressure and temperature in the suns core. A neutron and a helium isotope are released together with a large amount of energy as a result. The energy from fusion is several times that from fission. For stars such as the sun, the reaction takes place due to the extreme pressures and temperatures that are in their cores. Nuclear fusion is safer than nuclear fission because:
- There is no production of the highly radioactive fusion products
- There is no nuclear chain reaction which is difficult to control. If a nuclear fusion reactor fails, the plasma would expand and hence cool off and stopping the reaction.
However, for nuclear fusion to be a viable source of energy, reactors that can create the extreme pressure and temperature conditions that are required for fusion while producing more energy than is required to power the reactors need to be developed. The fusion energy gain factor, Q is the ratio of fusion power produced in a nuclear fusion reactor to the power required to maintain the plasma in steady-state (Wikipedia). For Q=1 the power produced is equal to the power utilized for the reaction and is referred to as breakeven.
Over the last half-decade, a lot of progress has been made in the research and development of fusion reactors aided by development in simulation techniques, computing power and material science. A reactor should be able to heat the deuterium-tritium fuel to a high enough temperature while confining it long enough for energy to be produced from the fusion reaction hence igniting the reaction. The two main plasma confinement techniques being studied are magnetic confinement and inertial confinement. In magnetic confinement, strong magnetic fields are used to confine the fusion fuel in form of a plasma. The various magnetic confinement configurations include: Tokamak – consists of a vacuum chamber surrounded by electromagnetic coils that work together to confine the plasma inside the strong magnetic field, Stellarator, Reversed field pinch and magnetized target. In Inertia confinement, laser or ion beams are focused very precisely onto the surface of the fuel cell. This causes the material to be heated on its outer layer. The material generates an implosion or inwards compression hereby compressing the inner layers of the fuel cell’s materials and causing heating at its core. This compression and heat create conditions for fusion. The energy released would then heat the surrounding fuel, which may also undergo fusion leading to a chain reaction (known as ignition) as the reaction spreads outwards through the fuel.
1: Tokamak Schematic.
Some of the reactors that have been developed and achieved plasma stare include Joint European Torus (JET) that achieved a Q of 0.67 in 1997, Tokamak Fusion Reactor Test (TFTR), Japan Torus-60 (JT-60), Mega Ampere Spherical Tokamak(MAST) that achieved first plasma in 1999. No reactor so far has been able to achieve a Q that makes it viable for energy production with the current record being Q of 0.67 set by the JET. However, one is currently under construction and is expected to have a fusion energy gain, Q, of 10.
The ITER is a nuclear fusion reactor that was first conceptualized in 1985 when the Soviet Union suggested a collaboration with Europe, Japan and the USA to build the next generation Tokamak. Initial designs were drawn up between 1988 and 1990 for an International Thermonuclear Experimental Reactor as the project was known then. In November 2006, the seven members of the ITER consortium (USA, Russia, India, China, European Union, Japan, and South Korea) signed the ITER implementing agreement paving way for the project to begin. The project is set to be the world’s largest tokamak nuclear fusion reactor. The project is located in Saint-Paul-lès-Durance, France. It is jointly funded by ITER consortium members i.e. the European Union, China, the United States, South Korea, Russia and Japan with other nations also collaborating on the project. ITER is to be an experimental reactor to prove the viability of nuclear fusion on a large scale. The reactor is designed to have a Q (fusion energy gain factor) of 10. The reactor will have an output of 500 MW from an input of 50 MW. However, the power will not be harnessed for electricity as this is meant to be an experimental project for demonstration of viability. From the ITER official site, the design objectives for ITER are:
1) Produce 500 MW of fusion power – This is a ten-fold return on energy (Q=10) or 500 MW of fusion power from 50 MW of input heating power. (Source, iter.org)
2) Demonstrate the integrated operation of technologies for a fusion power plant – ITER will bridge the gap between today’s smaller-scale experimental fusion devices and the demonstration fusion power plants of the future. Scientists will be able to study plasmas under conditions similar to those expected in a future power plant and test technologies such as heating, control, diagnostics, cryogenics and remote maintenance. (Source, iter.org)
3) Achieve a deuterium-tritium plasma in which the reaction is sustained through internal heating – Fusion research today is at the threshold of exploring a “burning plasma”—one in which the heat from the fusion reaction is confined within the plasma efficiently enough for the reaction to be sustained for a long duration. Scientists are confident that the plasmas in ITER will not only produce much more fusion energy but will remain stable for longer periods of time. (Source, iter.org)
4) Test tritium breeding – One of the missions for the later stages of ITER operation is to demonstrate the feasibility of producing tritium within the vacuum vessel. The world supply of tritium (used with deuterium to fuel the fusion reaction) is not sufficient to cover the needs of future power plants. ITER will provide a unique opportunity to test mockup in-vessel tritium breeding blankets in a real fusion environment. (Source, iter.org)
5) Demonstrate the safety characteristics of a fusion device – ITER achieved an important landmark in fusion history when, in 2012, the ITER Organization was licensed as a nuclear operator in France based on the rigorous and impartial examination of its safety files. One of the primary goals of ITER operation is to demonstrate the control of the plasma and the fusion reactions with negligible consequences to the environment. (Source, iter.org)
2: ITER Tokamak and plant systems showing the central solenoid.
More images available here.
Construction of the ITER complex began in 2007. Assembly of the Tokamak was scheduled to begin in 2015. The project has been plagued by delays and budget overruns and the actual assembly of the Tokamak has begun in 2020. One can view an animation of the ITER tokamak assembly process here. Assembly is projected to be completed in 2025 with initial plasma experiments set to begin then. Full Deuterium-tritium fusion experiments are expected to begin in 2035.
ITER “the way” in Latin if successful will provide useful operational data as well as demonstrate the viability of nuclear fusion as a source of energy hence blazing a trail into nuclear fusion energy. Nuclear fusion is the energy source of the future and we can only hope ITER is our “way” into the future.
What then does this information have to do with you? What we aim to do with such articles is elicit thoughts and conversations that will lead to innovations. There is a great need for sustainable, cheap and environmentally friendly energy and nuclear fusion is a great opportunity. With these information, as engineers, could we come up with a project? Could we invest in a Masters program to learn more about nuclear energy? The movie Passengers by Chris Pratt and Jenifer Lawrence involved them migrating to another planet in a space ship that used nuclear energy! So maybe you could be writing the next movie script with such knowledge!
BY LINUS MURAGE