By Alex Kimani
Long relegated to the trash heap of utopic clean energy technologies in the realm of harvesting energy from black holes, nuclear fusion is suddenly making a big comeback–and for good reason.
Fusion is not only ultra-powerful, but it is also the cleanest and virtually limitless energy source known to man. In fact, nuclear fusion is pretty much our perfect energy source that is not only likely to play an outsized role in the shift from ‘dirty’ fossil fuels to clean energy but also power the conquest of our Final Frontier: Space.
Fusion energy has the potential to produce the safest energy with no greenhouse gases and no long-lived radioactive wastes.
Yet, somehow, practical nuclear fusion energy on our planet has remained a far off mirage.
But finally, this elusive energy source could be closer to becoming an everyday reality than we imagine.
Nuclear fission is already our most reliable clean energy source with minimal downtime albeit with a spotty safety track record including Chernobyl, Fukushima and Three Mile Island disasters. Nuclear fusion, on the other hand, is not only much more powerful than fission but also carries zero risk for a Chernobyl-like meltdown.
Practical Fusion Power
After 35 years of painstaking preparation and countless delays, scientists have finally broken ground by kicking off the five-year assembly phase of the massive (ITER), the world’s largest fusion reactor, in Saint-Paul-les-Durance, France.
Funded by six nations, including the US, Russia, China, India, Japan, and South Korea, ITER will be the world’s largest tokamak fusion device with an estimated cost of ~$24 billion and capable of generating about 500 MW of thermal fusion energy as early as 2025.
Initially, the United States and the former Soviet Union were the first countries to conduct fusion research due to its potential for the development of atomic weapons. Consequently, fusion technology remained classified until the 1958 Atoms for Peace conference in Geneva. Fusion research became ‘Big Science’ in the 1970s thanks to a breakthrough at the Soviet tokamak.
However, it soon became clear that practical nuclear fusion would only make the desired progress through international cooperation due to high costs and the complexity of the devices involved.
Nuclear fusion basically involves smashing together hydrogen atoms hard enough to form helium and release energy in the E=MC2 mass-energy equivalence. Fusion is the process through which all stars, from red dwarfs through the Sun to the most massive supergiants, generate vast amounts of energy in their cores by rising to temperatures of 4,000,000 K or higher.
Nuclear fusion generates four times as much energy from the same mass of fuel as nuclear fission, a technology that involves splitting atoms that is currently employed in the world’s nuclear reactors. Massive gravitational forces in the Sun and stars create the right conditions for fusion to proceed at considerably lower temperatures; however, earth’s much smaller mass (1/330,000th of the Sun’s mass) and smaller gravity means that much higher temperatures in the order of hundreds of millions of Kelvin are required to kick start the process of nuclear fusion and sustain it.
Unfortunately, every fusion experiment so far has been energy negative, taking in more energy than it generates.
ITER is a nuclear power plant designed to demonstrate that carbon-free, energy-positive fusion energy can become a commercial reality. ITER plans to use tokamak reactors to confine a deuterium-tritium plasma magnetically.
The big fundamental challenge here is for ITER to achieve a rate of heat emitted by a fusion plasma higher than the rate of energy injected into the plasma. It is only natural to wonder what is so different this time around that makes researchers confident that ITER will not be just another expensive experiment that will end up in nuclear fusion’s trash heap.
In a past article, we reported that ITER scientists have successfully developed a new superconducting material–essentially a steel tape coated with yttrium-barium-copper oxide, or YBCO, which allows them to build smaller and more powerful magnets. This lowers the energy required to get the fusion reaction off the ground.
According to Fusion for Energy–the EU’s joint undertaking for ITER–18 niobium-tin superconducting magnets, aka toroidal field coils, will be used to contain the 150 million degrees Celsius plasma. The powerful magnets will generate a powerful magnetic field equal to 11.8 Tesla, or a million times stronger than the earth’s magnetic field. Nearly 3,000 tonnes of these superconducting magnets will be connected by 200km of superconducting cables and kept at -269C by the world’s largest cryostat manufactured in India.
Europe will manufacture ten of the toroidal field coils with Japan manufacturing nine.
The 23,000-ton tokamak is designed to produce 500 MW of fusion power from 50 MW of input heating power, thus making it energy positive.
Cleaner Than Fission?
The world’s 440 nuclear fission reactors generate ~10% of global electricity needs. A similar amount of fusion reactors could theoretically replace all coal-powered power plants, which currently supply nearly 40% of the world’s electricity.
But other than their absurd power capabilities, fusion reactors have been touted as a perfect energy source since they cannot melt down and produce much less radioactive waste unlike fission reactors, which have in the past proven catastrophic from uncontrolled chain reactions.
But here’s the irony of it all: Fission nuclear reactors remain the only reliable source of tritium for use in fusion reactors.
The deuterium-tritium reaction is favored by fusion developers over deuterium-deuterium mainly because its reactivity is 20x higher than a deuterium-deuterium fueled reaction, and requires a temperature only a third of the temperature required by deuterium-only fusion. Unlike deuterium, which is readily available in ordinary water, tritium is rare in nature, mainly because this hydrogen isotope has a half-life of only 12.3 years.
If successful, ITER will become the world’s first source of electrical power that does not exploit a naturally occurring fuel.
It’s going to be interesting to see whether ITER and subsequent fusion power plants will incur the same ignominy that conventional nuclear energy has struggled to shake off.