Fusion energy: The holy grail of clean power
In light of the escalating challenges associated with climate change, the pursuit of a sustainable, renewable, clean, and plentiful source of energy has reached unprecedented importance. Accordingly, physicists have been investigating the energy released during nuclear fusion reactions, but the challenge of converting it into a viable source of energy has proven to be persistently difficult.
However, the question persists regarding the potential of nuclear fusion to become a primary source of energy for our increasingly power-dependent world. If this possibility is indeed attainable, will it be achieved in time to prevent the catastrophic consequences of climate change?
For all latest news, follow The Daily Star's Google News channel. Nuclear fusion replicates the mechanism that fuels the stars, presenting the prospect of a clean and nearly unlimited supply of energy. In contrast to fossil fuels, fusion does not emit greenhouse gases (GHGs). The fusion reaction, which involves the combination of light atomic nuclei—specifically, isotopes of hydrogen such as deuterium and tritium—offers the promise of generating energy with minimal carbon dioxide (CO2) emissions while avoiding the hazardous, long-lasting radioactive waste linked to current nuclear fission reactors that split heavy radioactive nuclei, uranium-235 or plutonium-239.
The Earth possesses virtually inexhaustible reserves of the raw materials—deuterium and tritium—essential for a fusion reactor. Deuterium is abundantly available in ocean water, with sufficient quantities to feed a reactor for billions of years, but naturally occurring tritium is exceedingly scarce. Nevertheless, it can be generated in a reactor through the neutron activation of lithium, which can be sourced from brines, minerals, and clays.
Despite notable advancements, many challenges remain in the development of a commercially viable fusion reactor. The major ones are: i) reaching the temperature (exceeding 100 million degrees Celsius) necessary to initiate a self-sustaining fusion reaction; ii) containing the extreme heat produced in the plasma, an ultra-hot mixture of gases where electrons are entirely separated from their atomic nuclei; and iii) maintaining the plasma at this superhot temperature for a sufficient duration so that the energy produced surpasses the input energy needed to sustain the process.
The International Thermonuclear Experimental Reactor (ITER), a collaborative project involving 35 nations and currently under construction in Cadarache, France, represents the world's largest fusion reactor. Once operational, it is expected to achieve continuous energy output at a power plant scale, approximately 500 megawatts. However, since its establishment in 2006, the ITER has experienced uneven progress, facing numerous technical setbacks, a complex decision-making framework, and a significant increase in cost projections, which have escalated from five billion euros to nearly 20 billion euros. Additionally, the planned operational start in 2035 may be pushed back to the 2040s.
One of the challenges the ITER faces is how to control the hot plasma at a temperature of around 100 million degrees and keep it away from the walls of the container. No known material can withstand such a high temperature; even extremely heat-resistant metals such as tungsten would melt instantly.
Physicists have developed two rival methods for managing the hot plasma and preventing it from contacting the walls of its containment vessel. These methods are known as magnetic confinement and inertial confinement. The procedures necessitate exceptional precision. Additionally, the intensely heated plasma is inherently unstable—it tends to form large temperature gradients, resulting in powerful convection currents that make the plasma turbulent and difficult to control.
Moreover, a sustained fusion reaction that produces substantially more energy than it consumes has never been achieved. The ITER, which uses magnetic confinement by employing a doughnut-shaped chamber in which magnetic fields keep the plasma in perpetually looping paths without touching the walls, still has not produced a sustained reaction. The longest fusion reaction achieved so far is 17 minutes and 46 seconds, set recently in China.
Attaining the sought-after goal of "net energy" in nuclear fusion has been the holy grail for scientists working in this domain. A net energy gain was notably demonstrated in December 2022 at the National Ignition Facility (NIF), a laser-based inertial confinement fusion research lab located at Lawrence Livermore National Laboratory in California. At the NIF, plasma is produced by directing intense lasers at a small pellet filled with deuterium and tritium.
The ratio of output energy to input energy at the NIF was 1.5. Although this accomplishment represents an important milestone, it is still far from establishing fusion as a practical source of energy. For fusion reactors to be deemed viable for commercial energy generation, they must attain a threshold ratio of 10. The challenges associated with inertial confinement are considerable as well, and at present, only a handful of facilities around the globe are dedicated to its research.
The widely reported success at the NIF elicited a typical range of responses: fervent endorsement from proponents of the technology and scepticism from detractors, who contend that scientists have consistently claimed that practical fusion energy is just two decades away—or three or five decades, depending on the viewpoint. Furthermore, energy production is not a primary objective of the NIF. The facility was primarily designed to initiate nuclear reactions for the purpose of studying and maintaining the US's nuclear arsenal.
As we look to the future, there are compelling reasons to believe that fusion energy will play a consequential role in the energy landscape, particularly as more developing and underdeveloped nations begin to demand levels of energy consumption comparable to those of Western countries. That being said, fusion is not a panacea for mitigating the devastating effects of climate change. Addressing climate change requires decarbonisation of the atmosphere using available technologies, including renewable sources such as solar and wind power, hydropower, geothermal energy, and potentially carbon capture methods.
As for the question of when nuclear fusion will become a reality, there is no clear answer. Nonetheless, experts generally agree that the likelihood of achieving large-scale energy production through nuclear fusion is unlikely before 2050, with some more cautious projections suggesting an even longer timeline. Given that the rise in global temperatures over the coming decades will likely be heavily influenced by our actions—or lack thereof—regarding GHG emissions during this period, it is evident that fusion cannot be considered a near-term solution.
Dr Quamrul Haider is professor emeritus at Fordham University in New York, US. He is one of the authors of the book 'Nuclear Fusion: One Noble Goal and a Variety of Scientific and Technological Challenges' (Intech Open, London, UK, 2019).
Views expressed in this article are the author's own.
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