Fusion Energy’s New Record at JET

The quest for clean, limitless power took a significant leap forward as the Joint European Torus (JET) facility in the United Kingdom concluded its operational life with a historic achievement. In its final experiments, the reactor smashed its own world record for energy output. This milestone provides critical data that validates the future of magnetic fusion energy and the massive international projects currently under construction.

The Historic 69 Megajoules

In February 2024, scientists at the Culham Centre for Fusion Energy in Oxfordshire announced that JET had produced 69 megajoules (MJ) of heat during a single pulse. This output was sustained for five seconds, which is the maximum time the machine could operate before its copper electromagnets overheated.

To put this into perspective, 69 megajoules is enough energy to heat roughly 70 kettles of water. While this might not sound like enough to power a city yet, the scientific implications are massive. This achievement beats JET’s previous world record of 59 megajoules, set in 2021, by a significant margin.

The experiment used a specific fuel mixture of deuterium and tritium. These are two heavier isotopes of hydrogen that are considered the most efficient fuel for commercial fusion energy. The ability to sustain this high energy output for five seconds proves that the fusion process can be stable and controllable, rather than just a momentary burst.

Understanding the "Star in a Jar"

JET is a tokamak, a machine designed to harness the energy of fusion. Fusion is the same process that powers our Sun and other stars. Inside the reactor, gas is superheated until it becomes plasma. This plasma is contained by powerful magnetic fields because it reaches temperatures of 150 million degrees Celsius, which is ten times hotter than the center of the Sun.

At these extreme temperatures, atomic nuclei collide and fuse together. This reaction releases massive amounts of energy. For the record-breaking run, the researchers used only 0.2 milligrams of fuel to generate the 69 megajoules of energy. This highlights the incredible energy density of fusion fuel compared to fossil fuels like coal or gas.

The primary challenge in fusion research has not just been creating the reaction, but sustaining it and protecting the machine’s walls from the intense heat. JET successfully demonstrated that its internal components could withstand the punishment, marking a major engineering victory.

Why This Record Matters for ITER

The success at JET is not an isolated event. It is a direct proof-of-concept for ITER (International Thermonuclear Experimental Reactor), a mega-project currently under construction in southern France.

JET was essentially a smaller scale model for ITER. One of the most critical aspects of the recent tests was the use of a “ITER-like wall.” The interior of the JET vessel was lined with beryllium tiles and a tungsten divertor. These are the exact materials chosen for ITER.

For years, scientists theorized that these materials would work best to minimize contamination of the plasma. The record-breaking run at JET confirms that:

1. The material choice is correct.
2. The fuel mix of deuterium and tritium behaves as predicted in this environment.
3. The fusion reaction can be kept stable with these specific wall materials.

Without this confirmation from JET, the team building ITER would be moving forward based largely on theoretical models. Now, they have hard experimental data to support their design choices.

The Difference Between JET and NIF

It is important to distinguish this achievement from other recent fusion news. You may have heard about the National Ignition Facility (NIF) in the United States achieving “ignition” or net energy gain.

• NIF uses lasers to compress a tiny pellet of fuel (Inertial Confinement).
• JET uses magnetic fields to hold a large donut-shaped ring of plasma (Magnetic Confinement).

While NIF achieved a net energy gain (getting more energy out than the lasers put in), JET did not produce net energy in this experiment. JET required more energy to run the magnets and heating systems than the reaction produced. However, magnetic confinement (the JET method) is widely considered the most scalable path to continuous, commercial electricity generation. The goal of JET was to maximize fusion output, not necessarily to achieve net gain, which is the specific goal of the larger ITER machine.

What Comes Next?

This record was the final act for JET. After operating since 1983, the facility ceased plasma operations in December 2023 and is now moving into the decommissioning phase. However, its legacy is secure.

The baton now passes to ITER. While JET could only run for seconds at a time due to its copper magnets, ITER will use superconducting magnets. This will allow it to run for much longer periods. The data harvested from JET’s final run will be analyzed by scientists for years to come.

Following ITER, the roadmap includes a demonstration power plant known as DEMO. The goal of DEMO will be to put electricity onto the grid. While commercial fusion power is likely still two or more decades away, the 69 megajoule record proves that the physics works on a scale that matters.

Frequently Asked Questions

Is fusion energy safe? Yes. Unlike nuclear fission (used in current nuclear power plants), fusion does not rely on a chain reaction. If the containment fails or the magnets turn off, the plasma cools down instantly and the reaction stops. There is no risk of a meltdown.

Does fusion produce radioactive waste? Fusion does not produce long-lived, high-level radioactive waste like spent uranium fuel rods. The reactor components do become radioactive over time due to high-energy neutrons, but this material is generally safe to handle within 100 years, compared to thousands of years for fission waste.

When will we have fusion power plants? Current estimates suggest that prototype fusion power plants (like DEMO) could be operational in the 2040s or 2050s. The success at JET keeps this timeline on track by validating the technology used in the next generation of reactors.

What fuel does fusion use? The most efficient reaction uses Deuterium and Tritium. Deuterium is abundant and can be extracted from seawater. Tritium can be bred from lithium, which is a common metal found in the Earth’s crust.