The standing joke in thermonuclear fusion research has been that the power from fusion was just around the corner; albeit a perpetually receding corner. The in-exhaustible and safe carbon-free energy source that would solve world’s energy problems once and for all was thus a chimera until the idea of building ITER took shape. The world was assured that the time was ripe to start building the reactor by the leading countries of international fusion research. Countries such as China, Korea and India joined the international effort and thus was born the partnership to build ITER.
ITER is under construction in Caderache, in southern France. The estimated cost is close to $22 billion. ITER is making good progress despite challenges arising from having to harness new technologies. In the 29th meeting held in November 2021, the ITER Council assessed the performance metrics of the project and reported satisfactory progress.
ITER will not lead directly to a commercial reactor. A further series of prototypes have to be built. China is already planning to build Fusion Engineering Testing Reactor in the 2030s. South Korea, China and the European Union have plans to build demonstration power plants as a sequel to ITER.
The primary challenge of fusion is that the fusile medium — electrically charged plasma of Deuterium and Tritium — has to be heated to a temperatures of a hundred million degrees Kelvin and the internal energy confined for sufficiently long time for sizeable number of fusion reactions to happen. Complex magnetic field topologies confine the plasma and keep it from contact with cold walls. However, plasma in a magnetic field is the hotbed of instabilities which cause leakage of the internal energy. So far the instabilities have been the major bane of magnetic confinement fusion.
Fusion as a Carbon free energy option is getting a boost from the realisation of the profound effects of climate change. A remarkable recent development has been the involvement of private industry in Fusion research. The startup concept which is driving innovation in the high-tech sphere has now appropriated the problem of fusion. Investment in private fusion developers has been growing for several years and has reached close to 2 Billion dollars. The number of private companies working towards fusion has increased over the last 30 years, with accelerated growth more recently.
There is remarkable similarity with the happenings in space technology. Once a part of the government-run R&D effort, the technology development efforts are benefiting from the drive and imagination of private enterprise like the SpaceX. Startups bring great diversity of solutions to a problem. They are far more agile than projects like ITER which are governed by international protocols on engagement between sovereign nations.
Parallel to this, the collaboration between public laboratories and private industry to leverage expertise, facilities, and public investment is also growing. Regulators are determining the appropriate frameworks to support research and development. National laboratories are spinning off companies: Commonwealth Fusion Systems (CFS) in Massachusetts affiliated to MIT and and the General Fusion in Culham affiliated to Oxford University are examples.
These companies are also very young. 15 of the 23 respondents of a recent survey by the Fusion Industries Association were founded in the last decade, and 12 of them in the last 5 years alone. As characteristic of the youth, they are also very optimistic: the majority of participants in the survey thought that fusion would power electrical grids in the 2030s.
The approach followed by most of the industries is the magnetic confinement, followed by magneto-inertial confinement. However, the approaches are quite diverse in terms of specific techniques. In addition to electricity generation, an application to space propulsion is also popular.
Some private fusion companies are following the tokamak concept, but with radically different approaches to technology. At Tokamak Energy, a spherical tokamak, a very compact version of the conventional tokamak is the goal. Its diameter of 3.5 metres, is one-fourth that of the ITER plasma.
The CFS adapts a variation on the magnet construction. Ribbons of high-temperature superconducting (HTS) material will be used for winding the magnets. Magnetic fields much stronger than those produced by conventional superconducting magnets used by ITER is possible. Another advantage of the HTS magnet is that they can be cooled with liquid nitrogen, unlike the liquid Helium cooling required for the ITER magnets.
FirstLight Fusion, a company originated from the University of Oxford, UK, in 2011, is pursuing an approach termed inertial fusion (1). As the name implies, the hot plasma is held together without magnetic fields for a time comparable to the inertial time of its self-disassembly. The plasma acts as a target for compression by a shock wave to the high densities required for fusion. After a thermonuclear burn takes place, the plasma will spread out and dissipate its energy. The shock waves are generated mechanically by firing a small piece of material by an electromagnetic gun. They have not yet achieved the threshold velocity of 50 km/sec required for breakeven.
The approach taken by GF is called magnetized target fusion, which is a compromise between the magnetic confinement fusion which requires energy-expensive high field magnets and the shock waves generated by intense laser pulses which also demand very high energy. The US Naval Research Laboratory had pursued this approach in the 1970s. A chamber containing molten lead and Lithium is spun at high speeds. The centrifugal expansion creates a cavity at the centre. The high temperature plasma to be compressed is created in the cavity. When a piston pumps more liquid metal into the chamber, the cavity gets compressed along with the plasma. Once the compression creates the density and temperature threshold, fusion burn happens following which, the plasma expands and disintegrates. The advantage of this approach is that the confining Lithium wall is also the source of Tritium generated by neutron bombardment. The first hurdle of creating a target plasma has been crossed by GF recently.
TAE Technologies has a novel approach. They are aiming at fusing Boron and Hydrogen atoms. This is a neutron free reaction, and the fuel is abundant. However it is more difficlut to achieve than DT fusion, since it requires a temperature of 1 Billion degrees. The plasma is confined inside a straight magnetic field produced by solenoid magnetic coils (1). The plasma is made to spin by imparting to it momentum by tangentially injected Boron neutral beams. The spin makes the plasma stable.
Helion Energy in Washington plans to compress plasma injected from multiple plasma sources in a linear reactor by a rapidly rising magnetic field. When the target plasma is heated and undergoes fusion burn, its internal pressure will rise up and make the plasma expand, pushing against the confining magnetic field and compress it. This change in magnetic field drives a current in solenoids which surround the reactor. This approach does away with using the fusion neutrons to transfer heat in the regular steam cycle to generate power. The reactor, which they have named Polaris is likely to begin operation by 2024. Their design is for a compact, small sized reactor.
In India, a private initiative “Project Sanlayan” has been initiated with initial funding from Albot Technologies Pvt Ltd (Set up by Dr Akash Singh, Innovator and Investor based in Silicon Valley). Initial work is being nucleated at D Y Patil International Univ, Pune with its Vice Chancellor, Prof Prabhat Ranjan as its Chief Mentor. Project is focusing initially on using fusion reaction to develop Modular Volume Neutron Source in the early stage to start commercial applications which includes breeding of fissile fuel from Thorium. Initial prototypes would be developed in Pune, Maharashtra.
Prometheus dreamed of bringing fire from the Sun down to earth. The inveterate inventors behind the Fusion startups are following exactly same vision. Fusion is like the other human dreams, like going to moon, thought unachievable by many for a long time.