In June 1983, Barry Green vividly remembers the historic moment when the JET fusion laboratory in Oxford conducted its inaugural experiment. “It felt brilliant. One thing is to work on a design, another thing is to operate it,” he reflects.
Over the next forty years, this European endeavor diligently pursued the dream of nuclear fusion, a potential source of virtually limitless clean energy. However, this Saturday marks the winding down of the world’s most successful fusion experiment.
The origins of nuclear fusion date back to the 1920s, but initial research primarily focused on its application in nuclear weapons. It wasn’t until 1958, when the United States declassified its fusion-related war research, that the race to harness fusion for energy production began, involving Russia, the UK, Europe, Japan, and the US.
Fusion represents the holy grail of energy production due to its capacity to generate immense energy without emitting greenhouse gases. This process, which powers the Sun and stars, involves forcing pairs of light atoms together—a stark contrast to nuclear fission, which splits heavy atoms apart.
In a collaborative effort, the UK and Europe established the Joint European Torus (JET) site, attracting scientists from across the continent to Culham in Oxfordshire, where Barry Green played a pivotal role. JET employed the tokamak model, utilizing magnetic fields to confine a hot, ionized gas called plasma. This controlled environment enabled the fusion of light elements, particularly deuterium-tritium, which proved to be the most efficient fuel mix for fusion reactors.
In 1991, JET conducted the world’s first experiment with this fuel combination, achieving higher energy yields in subsequent experiments. The site holds the world record for producing the most energy from a fusion experiment, with a peak of 59 megajoules during a five-second pulse. Nonetheless, challenges and delays, including a major overhaul in the mid-2000s, hindered JET’s progress.
The dream of providing sufficient energy for homes still remains distant, as 59 MJ can only boil roughly 60 kettles’ worth of water. Joelle Mailloux, overseeing the latest round of deuterium-tritium experiments, highlights the key challenges: stabilizing the plasma, distributing the power load, and enhancing reactor materials for durability.
Once the experiments conclude, JET’s decommissioning phase will yield valuable insights into how reactor materials have endured, benefiting future fusion sites. Among these is the Iter reactor in southern France, the world’s largest fusion project, featuring a consortium of nations. However, the UK recently confirmed its non-participation in this endeavor.
Instead, the UK government has committed £650 million to a domestic fusion energy strategy, including the creation of a prototype fusion energy plant called STEP in Nottinghamshire. Paul Methven, STEP program director at the UK Atomic Energy Agency, envisions operations commencing in the early 2040s, emphasizing the need for ambitious yet realistic goals in the quest for fusion energy.