Drawing of the proposed SPARC tokamak. Source: MITThis week, the Massachusetts Institute of Technology (MIT) in collaboration with MIT’s spinoff Commonwealth Fusion Systems (CFS) announced the development of a new design for a fusion reactor that can be ready in just 15 years. This is an outstanding development given that scientists have been struggling for many decades without success to build a working fusion reactor.

Among other investors, the Italian energy company Eni funded CFS to participate in this project. The money collected by CFS will be used as collaboration funds with MIT in the hope that the enterprise will produce the first commercial fusion power plant.

Nuclear fusion has a big problem: all fusion machines — called tokamaks — developed to this point consume more power than the power that they are able to deliver. The fusion reaction — light elements, such as hydrogen and lithium, smashing each other — produces an incredible amount of energy, but this reaction has to take place in a plasma at temperatures similar to the temperature inside the sun. This means that the plasma has to be generated in such a way that it does not touch any part of the tokamak; otherwise the plasma will melt the machine. To achieve this condition, powerful magnets are used to keep the plasma in a donut-like structure as is shown in the figure depicting the inside of a tokamak.

Diagram of the interior of a tokamak. Source: Wikipedia.

However, existing tokamaks can’t sustain the plasma for a long time. The longest sustained plasma took place in a French tokamak in 2003 and lasted only 6 minutes and 30 seconds. For this reason, tokamaks work by turning the plasma on and off in short pulses. In turn, this pulsation of the plasma requires an enormous amount of energy — more than the expected output energy. The solution is to develop a machine that can produce self-sustaining, non-pulsating plasmas.

This is where the MIT-CFS partnership could make a difference. The project calls for using special super magnets to confine the plasma. The first three years of the experiment will be dedicated to developing the world's most powerful superconductor magnets, four times stronger than any magnet used in fusion experiments. The magnets, made of the new superconductive material called yttrium-barium-copper oxide (YBCO), will drive the plasma of a compact tokamak prototype called SPARC, which the researchers think will be able to produce 100 MW of electric power, enough to support a small city with safe, sustainable, carbon-free energy.

“This is an important historical moment: Advances in superconducting magnets have put fusion energy potentially within reach, offering the prospect of a safe, carbon-free energy future,” says MIT President L. Rafael Reif. “As humanity confronts the rising risks of climate disruption, I am thrilled that MIT is joining with industrial allies, both longstanding and new, to run full-speed toward this transformative vision for our shared future on Earth.”

“Everyone agrees on the eventual impact and the commercial potential of fusion power, but then the question is: How do you get there?” adds CFS CEO Robert Mumgaard. “We get there by leveraging the science that’s already developed, collaborating with the right partners and tackling the problems step by step.”

For some researchers, to achieve a workable fusion reactor is a very far away dream — decades away — and for others it will just remain a dream. Since the start of research on fusion in the 1940s, there has never been a tokamak that has produced and self-sustained a fusion reaction. No one has been able to create a plasma at the temperatures found in the stars that has been magnetically contained for never produced a fusion reaction that produces more energy than it consumes.

The Iter Reactor Project

A $20 billion effort is going on in France with the International Thermonuclear Experimental Reactor (Iter). The purpose of the multi-country project (China, the European Union, India, Japan, Russia, South Korea and the United States) is to show that the theoretical scientific background of fusion is achievable. The Iter group expects that in a decade it will be able to control a fusion reactor. The tokamak of Iter — weighing more than three Eiffel Towers — is the largest ever built, with a plasma radius of 6.2 meters and a plasma volume of 840 m³. With a weight of 23,000 tons and working at a temperature of 150 million degrees Celsius — more than ten times the temperature at the center of the sun — it is expected to produce 500 MW of fusion power from a 50 MW input — a tenfold output power.

Diagram of the Iter tokamak. Source: Iter

The Iter is considered the most advanced and complex scientific project ever made. The tokamak will be surrounded by superconductive magnets created with 100,000 kilometers (twice the circumference of the earth) of niobium-tin wires used to create the magnets. For seven years, nine companies worked to produce the strands of metal. To work properly, the magnets had to be kept at a temperature colder than Pluto at minus 269 degrees Celsius.

The MIT project is complementary to the Iter, but by using more powerful magnets made of YBCO wires, it can reduce its size considerably to about 1/65^th of Iter. In turn, this reduces the cost and timeline required to build the machine.

If one or both projects are successful, scientists are expecting to start producing fusion energy soon. If not, we wonder if the enormous amount of money used in the projects could not have been better spent in improving solar power technology that is actually powered by the fusion reactor 150 million miles away: the sun itself.