Fusion 101

Posted on May 29, 2025 by Bryson Roberson and Jake Kincer

Updated on May 29, 2025 by Bryson Roberson and Jake Kincer. Originally posted on April 30, 2020 by Cameron Terry

What if we could harness the same reaction that fuels stars to generate electricity on Earth? For decades, scientists have pursued this ambitious goal: creating fusion reactors that could supply the world with virtually limitless clean electricity using hydrogen isotopes commonly found in seawater. Fusion happens naturally in trillions of stars, but the engineering challenges of recreating the conditions of the sun on Earth have historically kept this technology in labs. However, remarkable technological breakthroughs have accelerated this industry to the point that commercial fusion energy is quickly becoming a reality. This 101 explores the fundamental principles of fusion energy, examines recent advances and explains why fusion power could play a crucial role in American energy security.

Overview

Like fission, fusion harnesses the energy contained in the atoms' nuclei. Unlike fission, which breaks apart “heavy” atoms, the reaction fuses very “light” atoms, releasing excess energy. Harnessing this energy would allow for the generation of clean electricity utilizing only tiny amounts of fuel in the form of hydrogen or helium. For fusion to occur, several conditions must be met:

Extreme temperature: The fuel must be heated at extremely high temperatures, exceeding 100 million degrees Celsius, hotter than the center of the sun, to give the nuclei enough energy to overcome their natural electromagnetic repulsion, becoming a plasma where electrons are stripped away from their atoms.
Sufficient density: The fuel particles must be close enough together to increase the probability of collisions; the more collisions, the more energy produced.
Adequate confinement time: The hot fuel must be contained long enough to create fusion reactions and useful energy.

Fusion

While these conditions are extreme, the low fuel volume means the reaction is safe at such high temperatures.

While recreating the conditions of stars here on Earth is no trivial task, there are many routes to making it happen: superconducting magnets, lasers or piston-driven pressure can force the atoms together to fuse under Earth’s conditions. The real challenge has been doing this efficiently so that the reaction produces more energy than it consumes.

One problem, different approaches

Creating a self-sustaining plasma without the sun is similar to trying to keep a campfire going in the wind and rain. We know how to create the sparks, but turning those sparks into a roaring campfire requires effort and protection from the outside in normal conditions. That’s the history of fusion—while artificial fusion was first achieved in 1951, and scientists progressively developed more sophisticated methods for decades, it was only in 2022 that we achieved “ignition.” In December 2022, an experiment at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in the U.S. sustained a net-positive fusion ignition, achieving the “scientific breakeven” (or Q>1). This means a self-sustaining fusion reaction that produces more energy than it consumes. Since that first breakthrough, NIF has replicated net-positive ignition several times. While this was an enormous scientific breakthrough, the next step – producing net electricity – will lead to commercial fusion. The quest for fusion energy has spawned numerous approaches:

Magnetic Confinement Fusion (MCF): Using powerful magnetic fields to trap and heat plasma to extreme temperatures.
Inertial Confinement Fusion (ICF): Using focused energy to compress and heat fusion fuel to extremely high temperatures quickly.
Magneto-inertial Fusion (MIF): An approach that combines magnetic confinement of plasma with inertial compression to reach the heat and density necessary for fusion conditions.

Why invest in fusion?

Like its cousin, fission, fusion reactors offer the promise of numerous economic and environmental benefits while operating without any major safety-related downsides.

Decarbonization: Fueled by hydrogen and helium, fusion generates zero greenhouse gas emissions from its energy production.
No long-lived radioactive material: Fusion reactions do not produce the high-level radioactive material that traditional nuclear fission can generate. Tritium, the main byproduct of concern, produces radiation that a single piece of paper can stop, and is already used safely around the world today.
Reliable energy: While commercial fusion plants will have an operational learning curve like any other technology, fusion promises to run 24/7, like fission, and provide clean and dependable power in large quantities.
Low security risks: Because fusion reactors do not use uranium, they have more limited non-proliferation concerns.
Abundant fuel sources: The most common forms of fusion fuel are deuterium and tritium, which are isotopes of hydrogen, one of the most abundant elements in the universe.
Fundamentally safe: The fundamental physics of fusion on Earth makes it extremely safe – remember the wind and rain around a campfire.

Currently, auxiliary parts of the plant, such as safely containing tritium and making more fuel, present the biggest cost unknowns, but the best and brightest are already on it. The Department of Energy is working with private companies on ways to design these components for a cost-effective plant. Check out this MIT report to learn how fusion plants can enter the U.S. energy market and reach commercialization.

Pathway to Commercialization

AlTwo U.S.–based fusion companies, Commonwealth Fusion Systems and Helion, announced construction of fusion power plants, delivering power to the grid as early as the 2030s. This follows significant private investment in the U.S. totaling more than $6 billion, and continued support from the government to build projects. This is creating a path towards commercialization. Still, the U.S. needs to continue to take action to support the fusion industry to maintain its leadership position, including:

Establishing an Office of Fusion Energy at the DOE.
Include fusion energy components in the 45X manufacturing tax credit to ensure technology invented in America is made in America.
Continue to fund public-private partnerships, including the Milestone-Based Fusion Development Program.

Recent Developments

The wider fusion community, both public and private, has seen concrete action in the last couple of years:

As of 2025, the U.S. Fusion industry has raised over $6 billion in private investment. However, the industry will face increasing competition abroad: China is investing $1.5 billion per year, while countries like Germany and the U.K. are taking their own steps toward commercializing fusion power.
In February 2025, the Special Competitive Studies Project, in collaboration with the Commission on the Scaling of Fusion Energy, released a preliminary report, outlining a strategy for fusion power, crucial for U.S. energy independence and technological leadership, recommending immediate, coordinated R&D, partnerships, and policy, with expert input.
In 2018, the Fusion Industry Association (FIA) was formed, representing over twenty fusion startups. Now, FIA has over 40 investor-backed companies as members and more than 100 affiliate members working to commercialize fusion energy.
The Energy Act of 2020 authorized the Milestone-Based Fusion Development Program, a public-private partnership that helps de-risk projects and catalyze investment. Eight awardees were announced in 2023, and nearly $50 million was obligated to them.
In July 2024, the ADVANCE Act was signed into law, codifying a different set of regulations for fusion energy from fission. Now, the NRC is developing that framework, which, according to NEIMA, must be created by 2027. In December 2024, the NRC released its Proposed Rule: Regulatory Framework for Fusion Machines. Currently, fusion energy is regulated under 10 CFR Part 30, a framework for byproduct material facilities.

The combined efforts of both the public and private sectors have driven the fusion industry to the point where commercial fusion is now firmly on the horizon.

Overview

One problem, different approaches

Why invest in fusion?

Pathway to Commercialization

Recent Developments

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