Nuclear fusion process (environmental impact)

DEFINITION: Reaction between light atomic nuclei that produces a heavier nucleus and releases energy

Nuclear fusion can produce much more energy for a given weight of fuel than any other available energy technology. Controlled fusion reactors could generate high levels of power with uninterrupted delivery and no greenhouse gas emissions. The fusion process produces far less radioactive material than fission reactors, and the by-products generated are less damaging biologically. The radioactive wastes produced by fusion reactors would cease to be dangerous after reasonably short periods of time.

Deuterium, the primary fuel used for nuclear fusion, is abundant in seawater. When a deuterium atom and a tritium atom, both isotopes of hydrogen, are fused together, helium is formed, with the release of a neutron and 17.6 million electronvolts (MEV) of energy. To undergo fusion, the interacting nuclei need kinetic energies on the order of 0.7 MEV to overcome the electrical repulsion between their positive charges. These energies are available at temperatures around 10 million kelvins (18 million degrees Fahrenheit), which poses a major problem for the containment of the fusion fuel. In some experiments, the resulting plasma generated by heat from an electrical discharge is contained in the reactor core with appropriately shaped magnetic fields (magnetic confinement). In other experiments, fusion is initiated by heating and compressing pellets of light nuclei with a high-intensity laser beam (inertial confinement). Methods of achieving fusion at lower temperatures, known as cold fusion, continue to be studied, but none have been found that produce more energy than is consumed in the fusion process.

Environmental Advantages and Concerns

The natural product resulting from the fusion of deuterium with tritium is helium, which poses no threat to life and does not contribute to global warming. Although tritium is radioactive, it has a short half-life of twelve years, has a very low amount of decay energy, and does not accumulate in the body. It is cycled out of the human body as water, with a biological half-life of seven to fourteen days. Since fusion requires precisely controlled conditions of temperature, pressure, and magnetic field parameters in order to generate net energy, there is no danger of any catastrophic radioactive accident, as heat generation in a fusion reactor would quickly stop if any of these parameters were disrupted by a reactor malfunction. In addition, since the total amount of fusion fuel in the reactor vessel is very small (a few grams) and the density of the plasma is low, there is no risk of a runaway reaction, because fusion would cease in a few seconds if fuel delivery were stopped.

Because of the generation of high-energy neutrons in the deuterium-tritium reaction, the typical structural materials of fusion reactors, such as stainless steel or titanium, tantalum, and niobium alloys, will become radioactive when bombarded by the neutrons. The half-lives of the resulting radioisotopes are typically less than those generated by nuclear fission. Most of this radioactive material would reside in the fusion reactor core and would be dangerous for about fifty years. Low-level wastes would be dangerous for about one hundred years. Since the choice of materials used in a fusion reactor is quite flexible, low-activation materials, such as vanadium alloys and carbon fiber materials, that do not easily become radioactive can be used.

Most fusion reactor designs use liquid lithium as a coolant and for generating tritium when it is bombarded by neutrons coming from the fusion reaction. Because lithium is highly flammable, a fire could release its tritium contents into the atmosphere, posing a radiation risk. Estimates of the amount of tritium and other radioactive gases that might escape from a typical fusion power plant indicate that they would be diluted to safe levels by the time they reached the perimeter fence of the plant.

Another safety and environmental concern associated with fusion reactors is the potential that the neutrons generated in a fusion reactor could be used to breed plutonium for an atomic bomb. In order for a reactor to be used in this way, however, it would have to be extensively redesigned; thus, the plutonium production would be very difficult to conceal. The tritium produced in fusion reactors could be used as a component of hydrogen bombs, but the likelihood is minimal.

Development of Commercial Fusion Reactors

Despite fusion research that started during the 1950s, a commercial fusion reactor will most likely not be available until at least 2050. Several deuterium-tritium fusion reactors using the tokamak design have been built as test devices. Beginning in the 1980s, the United States, twenty-seven European Union countries, China, India, Japan, Korea, and the Russian Federation collaborated to build the world's largest magnetic fusion device, the International Thermonuclear Experimental Reactor (ITER), constructed in southern France. ITER is planned to fuse atomic nuclei at extremely high temperatures within a large-scale magnetic confinement device. The idea proposal and site selection were concluded in the early 2000s; construction officially began in 2007, and machine assembly began in 2020.

Funded mostly by the US Department of Energy's National Nuclear Security Administration, the Lawrence Livermore National Laboratory is a research and development center in Livermore, California, responsible for national security and the safeguarding of the country's nuclear weapons. It is a leader in high-energy-density science, including projects such as the development of a high-energy laser system capable of heating hydrogen atoms to temperatures found in stellar cores. Such a system would enable the production of more energy from controlled, inertially confined nuclear fusion than is required to drive the reaction. The facility is one of the only sites capable of performing controlled experimental studies of thermonuclear burn, which inform sophisticated weapon technology.

The Lawrence Livermore facility announced in 2022 that it had produced 3 megajoules of energy from a 2 megajoule input. This marked a significant breakthrough in nuclear fusion and supported the ambitious goals of the ITER. The ITER aims to eventually produce 500 megawatts of fusion power with 50 megawatts of input. In 2025, scientists announced they had completed all components for the powerful pulsed superconducting electromagnet system, which would be central to the function of the ITER.

Bibliography

Ball, Philip. "What Is the Future of Fusion Energy?" Scientific American, 1 June 2023, www.scientificamerican.com/article/what-is-the-future-of-fusion-energy. Accessed 9 Dec. 2025.

Barbarino, Matteo. "What Is Nuclear Fusion?" International Atomic Energy Agency, 3 Aug. 2023, www.iaea.org/newscenter/news/what-is-nuclear-fusion. Accessed 9 Dec. 2025.

Braams, C. M., and P. E. Stott. Nuclear Fusion: Half a Century of Magnetic Confinement Fusion Research. Institute of Physics Publishing, 2002.

Bryan, Jeff C. Introduction to Nuclear Science. 4th ed., CRC Press, 2023.

Krishnamurthy, Rohini. "The World’s Powerful Device Being Built in France Reaches an Important Milestone for Nuclear Fusion." Down To Earth, 1 May 2025, www.downtoearth.org.in/science-technology/the-worlds-powerful-device-being-built-in-france-reaches-an-important-milestone-for-nuclear-fusion. Accessed 9 Dec. 2025.

McCracken, Garry, and Peter Stott. Fusion: The Energy of the Universe. 2nd ed., Elsevier Academic, 2012.

Midgley, Emma. "Fusion Energy in 2025: Six Global Trends to Watch." International Atomic Energy Agency, 28 Oct. 2025, www.iaea.org/newscenter/news/fusion-energy-in-2025-six-global-trends-to-watch. Accessed 9 Dec. 2025.

Seife, Charles. Sun in a Bottle: The Strange History of Fusion and the Science of Wishful Thinking. Viking Press, 2008.