Ottawa (Canada): The US Department of Energy reported in December 2022 a major scientific breakthrough in the field of nuclear fusion science. For the first time, more energy was generated from the fusion reaction than was used to ignite it. While this achievement is indeed historic, it is important to pause and reflect before rushing forward for fusion energy. We are Professor of Sustainable and Renewable Energy Engineering at Carleton University, where we research alternative energy technologies and systems that can lead us to a low-carbon future. We also teach our students how to navigate risky territory from lab-based findings to real-world applications.
Defining system limits The efficiency of a potential fusion energy power plant remains to be seen. The reported fusion net gain actually requires an energy input of about 300 megajoules, which was not included in the energy gain calculation. This energy input needed to power the 192 lasers came from the electrical power grid. In other words, the experiment consumed the same amount of energy as a typical Canadian household consumes in two days. In doing so, the fusion reaction generates enough energy to light only 14 incandescent bulbs for one hour. The same is true of nuclear fission, which is the reaction inside current nuclear power plants. Complete fission of one kilogram of uranium-235 – the fissile component of nuclear fuel – can generate about 77 terajoules. But we cannot convert all that energy into useful forms like heat and electric power.
Not all uranium in the fuel is burned
Instead, we have to build a complex system that can control the nuclear fission chain reaction and convert the energy generated into more useful forms. That's what nuclear power plants do - they use the heat generated during nuclear fission reactions to make steam. This steam drives a turbine connected to an electric power generator, which produces electricity. The overall efficiency of the cycle is less than 40 percent. Furthermore, not all of the uranium in the fuel is burned. The used fuel still contains about 96 percent of the total uranium and about one-fifth of the fissionable uranium-235 content. Increasing the amount of spent uranium in our current fleet is possible – this is an ongoing area of work – but it presents enormous engineering challenges.
The enormous energy potential of nuclear fuel is currently curtailed by the engineering challenges of converting that energy into a useful form. From science to engineering Until recently, fusion has been viewed primarily as a scientific experiment, not an engineering challenge. That's changing fast and regulators are now examining how real-world deployments might play out. Regardless of the efficiency of future fusion power plants, many challenges will need to be overcome when making energy conversion from basic science to the real world. Since fission faced many of the same challenges that fusion does now, we can learn a lot from its history. Fission also had to move from science to engineering before becoming a commercial industry.
fusion power will come and electricity will be very cheap
Like nuclear fission, the science of fusion energy is also implicated in efforts to develop nuclear weapons. In particular, many of the nuclear physicists who helped develop the atomic bomb "wanted to prove that this discovery was not just a weapon." The early history of nuclear power was one of optimism—the declaration that technology would advance and will be able to meet our need for increasing amounts of energy. Eventually, fusion power will come and electricity will become very cheap. Lessons learned What have we learned in the last 70 years since the beginning of nuclear power? First, we learned about the potentially devastating risk of technology lock-in, which occurs when an industry becomes dependent on a specific product or system.
Today's light water fission reactors – reactors that use normal water as opposed to water enriched with hydrogen isotopes – are an example of this. They were not chosen because they were most desirable, but for other reasons. These factors included government subsidies that supported these designs; the US Navy's interest in developing small-scale pressurized water reactors for submarines and surface warships; advances in uranium enrichment technology resulting from the US nuclear weapons program; Uncertainties regarding nuclear cost have led to the assumption that large light water reactors are scaled-up versions of smaller reactors; and conservatism regarding design choices given the high costs and risks associated with nuclear power development. We have been fighting to move to other technologies ever since.
Second, we've learned that size matters. Large reactors cost more to build per unit of capacity than smaller units. In other words, engineers misunderstood the concept of economies of scale and ruined their industry in the process. Large infrastructure projects are extremely complex systems that rely on vast workforces and coordination. They can be managed, but they usually go over budget and fall behind schedule. Modular technologies demonstrate improved affordability, cost control and economies of scale, but micro and small nuclear reactors will also face economic challenges.
Billions of dollars needed for nuclear fission technology
Third, regulatory regimes for fusion must be developed. If the industry unifies too quickly around the first-generation design, the consequences for regulation of future reactors could be dire. Fourth, site selection and social acceptance are important for new power plants. One advantage of fusion is that its technology is like a blank slate compared to fission when it comes to public opinion. The positive engagement the public has with Fusion must be maintained through prudent design decisions and adoption of best practices for community engagement. Call to action Our research on nuclear power innovation shows that the challenges facing nuclear fusion can be overcome, but it will take prudent leadership, decades of research, significant amounts of funding and focused technology development Needed. Billions of dollars are needed to advance nuclear fission technology, and we have far more experience with fission than with fusion.
An appetite for funding must be demonstrated by governments, electric utility companies and entrepreneurs. The promise of fusion is huge and exciting work is being done to take it forward, including by private companies beyond this recent success. Decades of research and development are needed before fusion can make a meaningful contribution to our energy system. Our central message is a call to action: fusion engineers, researchers, industry and government must unite to examine and mitigate the challenges facing fusion, including the design of first generation power plants. There is no substitute for a deep and rapid decarbonization of the energy system if we are to save our planet from climate catastrophe. We pride ourselves on training the next generation of energy engineers to design new and better energy solutions.
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