Fusion Energy: Why the Hardest Engineering Problem Is Getting Closer to Being Solved

# Tokamak History: From Soviet Labs to ITER's $22 Billion Bet

The device that has dominated fusion research for sixty years was invented in the Soviet Union in the 1950s, at the Kurchatov Institute in Moscow. "Tokamak" is a Russian acronym: toroidal'naya kamera s magnitnymi katushkami — toroidal chamber with magnetic coils. It's not a glamorous name. The machine it describes has consumed the majority of the world's fusion research investment and still hasn't demonstrated commercial viability. Whether that represents a dead end or a path nearly complete is one of the central debates in fusion today.

## The Soviet Design and Its Western Adoption

The tokamak concept was developed principally by Andrei Sakharov and Igor Tamm in the early 1950s, though Sakharov has noted that others contributed significantly. The key insight was that a toroidal (donut-shaped) magnetic field, supplemented by a second magnetic field component from a current flowing through the plasma itself, could produce the helical field geometry needed for stable plasma confinement.

For years, Western physicists were skeptical of Soviet tokamak claims. Then in 1968, at the Third International Conference on Plasma Physics in Novosibirsk, Soviet scientists announced that their T-3 tokamak had achieved electron temperatures of 10 million degrees Kelvin — far higher than anyone had previously managed. The British fusion program sent a team to Moscow to verify the results using their own Thomson scattering diagnostic equipment. They confirmed the Soviet measurements.

This was a scientific turning point. By the early 1970s, research programs in Britain, the United States, Germany, Japan, and France had all pivoted toward the tokamak design.

## JET and the Record-Setting Era

The Joint European Torus (JET), built at Culham in Oxfordshire, UK, went into operation in 1983 and became for decades the world's largest tokamak. It was an international collaboration within what was then the European Community, and it was designed specifically to work with D-T fuel (rather than the safer deuterium-deuterium reactions used in most research machines).

JET set the world record for fusion power output in 1997: 16 megawatts of fusion power sustained for about 0.5 seconds. This remained the record for 24 years. In February 2022, JET broke its own record: 59 megajoules of sustained fusion energy, representing 22 megawatts of power for 5 seconds. This is the highest sustained fusion energy output from any machine to date.

Both records sound impressive. It's worth knowing that JET consumed roughly 10 times more energy to heat the plasma than it produced as fusion energy. It was a scientific instrument demonstrating plasma physics, not a power source.

## Why ITER Was Necessary

Individual national programs hitting incremental records created a recognition: fusion would require a machine larger than any country could build alone. The mathematics of plasma confinement favor larger reactors — the volume-to-surface-area ratio improves with scale, meaning you lose proportionally less plasma energy to the walls as the machine grows. ITER — International Thermonuclear Experimental Reactor — was designed to be the machine that finally demonstrates net energy from D-T fusion.

ITER involves 35 nations: the EU, US, Russia, China, Japan, South Korea, and India are the principal partners. The project was formally established in 1988, the site in Cadarache, France was selected in 2005, and construction began in 2010.

The original timeline called for first plasma in 2016. The current revised timeline calls for first plasma in 2034 — an 18-year delay. The cost estimate has grown from roughly $5 billion to over $22 billion, and some analysts put the true cost higher when accounting for in-kind contributions from partner countries.

## What the ITER Delays Reveal

The delays are not primarily engineering failures. They're lessons in the difficulty of supranational project management. ITER's components are manufactured in 35 different countries under the technical oversight of seven different domestic agencies, each with its own procurement rules, manufacturing standards, and political interests. Coordinating tolerances that are sometimes measured in tenths of a millimeter across supply chains spanning the globe is genuinely difficult.

The superconducting magnets alone are an extraordinary engineering challenge. ITER will use 18 toroidal field coils, each 9 meters tall and weighing 310 tonnes, wound with Nb₃Sn superconducting cable and operated at 4K. The coils were manufactured in Europe, Japan, and Russia with components from China and South Korea. Getting those supply chains synchronized while managing the COVID-19 disruption, the Russia-Ukraine war (which complicated Russian component shipments), and routine manufacturing problems has consumed years.

The honest assessment: ITER will eventually demonstrate whether a fusion machine can produce 10 times more energy than it consumes (Q=10 is the design target). If it does, the path to commercial fusion becomes significantly clearer. If it doesn't, thirty years of multinational investment will need to be reinterpreted. The stakes are high enough that the delays, while frustrating, are worth bearing.

Tokamak History: From Soviet Labs to ITER's $22 Billion Bet

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