
George R. Tynan and Farhat Beg: The way scientists think about fusion changed forever in 2022, when what some called the experiment of the century showed for the first time that fusion could be a viable source of tidy energy .
An experiment conducted at Lawrence Livermore National Laboratory demonstrated ignition: a thermonuclear reaction that generates more energy out than was put in.
Moreover, the last few years have been characterized by a multi-billion inflow of private investments in this field, mainly in the United States.
However, before fusion can become a sheltered and affordable source of virtually unlimited tidy energy, a number of engineering challenges must be overcome. In other words, it's engineering time.
As engineers who have been involved in the basic science and engineering of fusion for decades, we have seen much of the science and physics of fusion mature over the last 10 years.
But to make fusion a viable commercial energy source, engineers must now face a number of practical challenges. Whether the United States seizes this opportunity and emerges as a world leader in fusion energy will depend in part on how much the nation is willing to invest in solving these practical problems – particularly through public-private partnerships.
Construction of a fusion reactor
Fusion occurs when two types of hydrogen atoms, deuterium and tritium, collide under extreme conditions. Two atoms literally fuse into one atom, heating to a temperature of 180 million degrees Fahrenheit (100 million degrees Celsius), which is 10 times hotter than the core of the Sun. For these reactions to occur, fusion energy infrastructure will need to withstand these extreme conditions.
There are two approaches to achieving nuclear fusion in the laboratory: inertial fusion, which uses powerful lasers, and magnetic fusion, which uses powerful magnets.
Although the “experiment of the century” used inertial fusion, magnetic fusion has not yet demonstrated that it can interrupt energy production.
Several privately funded experiments will aim to achieve this later this decade, and a enormous, internationally supported experiment in France, ITER, also hopes to break even by the tardy 2030s. Both exploit magnetic fusion.
Challenges lie ahead
Both approaches to nuclear fusion present a number of challenges that will not be inexpensive to overcome. For example, researchers need to develop up-to-date materials that can withstand extreme temperatures and irradiation conditions.
Fusion reactor materials also become radioactive when bombarded with high-energy particles. Scientists must design up-to-date materials that can decay within a few years to levels of radioactivity that can be safely and more easily removed.
Producing enough fuel and doing so sustainably is also an significant challenge. Deuterium is copious and can be extracted from plain water.
But increasing production of tritium, which is typically made from lithium, will prove much more challenging. A single fusion reactor will require hundreds of grams to one kilogram (2.2 pounds) of tritium per day to operate.
Currently, conventional nuclear reactors produce tritium as a fission byproduct, but they cannot provide enough to sustain a fleet of fusion reactors.
Engineers will therefore need to develop the ability to produce tritium in the fusion device itself. This may involve surrounding the fusion reactor with material containing lithium, which will convert into tritium as a result of the reaction.
To scale up inertial fusion, engineers will need to develop lasers capable of repeatedly striking a fusion fuel target, composed of frozen deuterium and tritium, approximately several times per second.
However, no laser is powerful enough to do it at that speed – yet. Engineers will also need to develop control systems and algorithms that direct these lasers with extreme precision at the target.
In addition, engineers will need to scale up production of the targets by orders of magnitude: from a few hundred handmade each year costing hundreds of thousands of dollars apiece, to millions costing just a few dollars apiece.
In the case of magnetic isolation, engineers and materials researchers will need to develop more effective methods for heating and controlling the plasma and more heat- and radiation-resistant materials for the reactor walls. The technology used to heat and confine plasma until atoms melt must function reliably for years.
Here are some of the biggest challenges. They are challenging, but not insurmountable.
The current financing landscape
Investment from private companies around the world has increased and will likely continue to be an significant driver of fusion research. Over the past five years, private companies have attracted more than $7 billion in private investment.
Several startups are developing various technologies and reactor designs to bring fusion to the power grid in the coming decades. Most are based in the United States, with some in Europe and Asia.
Although private sector investment has increased, the U.S. government continues to play a key role in the development of fusion technology. We expect this to continue in the future.
It was the United States Department of Energy that invested approximately $3 billion in the mid-2000s to build the National Ignition Facility at the Lawrence Livermore National Laboratory, where the “experiment of the century” took place 12 years later.
In 2023, the Department of Energy announced a four-year, $42 million program to develop fusion centers for the technology. While these funds are significant, they will likely not be sufficient to address the major challenges facing the United States in becoming a world leader in practical fusion energy.
One way to build partnerships between the government and private companies in this space could be to create a relationship similar to that between NASA and SpaceX.
As one of NASA's commercial partners, SpaceX receives both government and private funding to develop technologies that can be used by NASA. It was the first private company to send astronauts into space and to the International Space Station.
Like many other researchers, we are cautiously positive. New experimental and theoretical results, up-to-date tools and private sector investments make us increasingly convinced that the development of practical fusion energy is no longer a matter of “if”, but “when”.
George R. Tynan, Professor of Mechanical and Aerospace Engineering, University of California, San Diego and Farhat Beg, Professor of Mechanical and Aerospace Engineering, University of California, San Diego
This article has been republished from Conversation under Creative Commons license. Read it original article.
Image Source: Pixabay.com