A fieldtrip to ITER, a work-in-progress that will test fusion’s feasibility

ST. PAUL-lez DURANCE, France—Rolling hills and oak woodlands dominate rural Southern France. However, about 35km north of Aix-en-Provence, nature has given way to a team of 1,000 construction workers who are laboring around the clock to build the largest physics experiment that’s never been discussed by Sheldon, Leonard, Raj, and Howard.

Known as ITER, this experimental Tokamak fusion reactor is intended to be the last necessary step to prove the scientific and technological feasibility of fusion as a commercial energy source. It is a collaborative effort of China, the European Union (through Euratom), India, Japan, Korea, Russia, Switzerland (also through Euratom), and the United States. In total, it will include 35 countries.

The scale of this project, in so many dimensions, is nothing short of awe inspiring and humbling. Physically, the main buildings used to assemble and house the Tokamak reactor stand 60m (~200ft) tall and sit in a leveled area of 40 hectares (~100 acres). The entire site, adding the open space and office buildings, measures 180 hectares. Logistically, as a construction project, the ITER team is tracking over 200,000 actions necessary to bring the effort to fruition.

The project’s chronology is equally vast. It began with discussions between General Secretary Gorbachev and President Ronald Reagan in 1985, and ITER is scheduled to run through 2046—it’ll represent more than 60 years of effort.

Still, none of these metrics will measure up to ITER’s weight on the scale of human achievement. The project’s potential impact for humanity is immeasurable. In short, fusion could provide a much safer and cleaner method of generating energy than current methods using fission and fossil fuels.

Containing a plasma

The Tokamak fusion reactor, which the ITER team refers to as “the machine,” will use deuterium and tritium (two hydrogen isotopes) as fuel. Under extreme heat, the hydrogen isotopes fuse into helium, releasing high energy neutrons. When ITER’s Tokamak reactor is operational, it will contain 10 times the volume of plasma in today’s reactors. The knowledge gained from the operation of the plant, materials and control experiments, and study of plasma will pave the way for the commercial production of fusion power.

Within the Tokamak, superconducting electromagnets will create fields that contain and control the plasma. The coils are composed of niobium-titanium (Nb-Ti) and niobium-tin (Nb3Sn) and cooled by super critical helium at four Kelvin. The toroidal field created by the coils gives the particles in the plasma a spiraling path through the machine, aiding in confinement. The coils also create a poloidal field that prevents the plasma ring from expanding and holds it in the desired shape. The central solenoid in the middle of the machine drives the plasma current.

The magnets create fields in the range of 12 to 13 Tesla (T)—by comparison, the magnets of the Large Hadron Collider (LHC) produce about 8T. ITER’s magnets also have the capability to store over 50 Gigajoules (GJ) of energy, while the magnets in the LHC are limited to about 12GJ. In certain sections of the magnets, one meter of coil can have over 50 metric tons (112,000 lbs) of force pushing it. At the central solenoid, the inward pushing forces can reach 40,000 to 50,000 metric tons. Because the forces generated by the magnets are greater than the mass of the structure housing the machine, theoretically they could lift the entire building.

Sustainable fusion

In addition to functioning as a platform for experimenting with plasma, the machine will provide the capability to test ways of using fusion to produce additional tritium fuel. It will host different configurations of tritium breeding blankets, a critical technology for the large-scale production of fusion power.

The neutrons released in fusion reactions can produce tritium when they interact with lithium (high energy neutrons react with the lithium atoms, producing tritium and helium). Tritium has a short half-life; it’s also rare and expensive. That combination makes it a limiting material for fusion. By placing a “blanket” of lithium around the reactor, fusion itself can help us overcome this limit. During its functional life, ITER will use tritium already in the global supply, but it will produce critical data needed on tritium breeding blankets.

Ultimately, the Tokamak reactor is projected to produce 500MW of fusion energy while consuming 50MW to heat the hydrogen. Because the primary purposes of the reactor are to learn more about the properties of plasma, the means of controlling plasma, and the production of tritium by lithium breeder blankets, the excess energy will not be harnessed to produce electricity.

Close up of Assembly Hall.

Dave Loschiavo

Close up of Assembly Hall. Dave Loschiavo

Future site of Tokamak Reactor. Note the rounded footing.

Dave Loschiavo

Future site of Tokamak Reactor. Note the rounded footing. Dave Loschiavo

Close up of section where the Tokamak Reactor will reside.

Dave Loschiavo

Close up of section where the Tokamak Reactor will reside. Dave Loschiavo

Future site of Tokamak Reactor. Note the rounded footing. Dave Loschiavo

Close up of section where the Tokamak Reactor will reside. Dave Loschiavo

Workers in construction site.

Dave Loschiavo

Example of a Bioshield Section: The bioshield is a 3.5m thick concrete barrier, protecting the people and equipment from radiation. In addition to the concrete, it contains steel re-bar measuring up to 50mm in diameter. In some sections of the bioshield, the density of the steel re-bar reaches 600k/m3 of concrete.

Dave Loschiavo

Flags of the entities making up the ITER coalition: China, European Union (Euratom), India, Japan, Korea, Russia, and the United States of America.

Construction

The project recently crossed a major milestone with the delivery of the first components of the machine. These pieces, once assembled on-site, will make up the cryostat—the world’s largest stainless steel high-vacuum vessel with a volume of 16,000 m3. The cryostat is essentially a large thermos within which the rest of machine will reside. Ultimately, it will stand nearly 30m (~100ft) high with a similar width. The cryostat will maintain its internal temperature at -269° C, allowing the magnets to function as superconductors.

The size of some of the components used during construction at the site has provided its own set of logistical challenges. For example, a set of two cranes provides a combined lifting capacity of 1,500 tons. They were delivered partially assembled, but even then, one section measured 47m in length. To get the cranes from the Marseille Fos Port to ITER, they were put on a barge and transported over the Étang de Berre inland sea, transferred to a special vehicle in Berr-L’etag, and then driven at 5km/h over 104km of specially reinforced road. The cranes were moved only at night in order to minimize the disruption to local traffic.

As with many projects of this physical scope and duration, progress hasn’t come without difficulties and missteps along the way. Across the years, overly optimistic projections for budgets and schedules were made. Consequently, cost overruns and schedule delays have taken their toll on the project’s credibility. Most recently, ITER announced 4 billion Euro ($4.4 billion) in overruns and said the first tests with plasma would likely be delayed an additional five years to 2025.