Are energy equations about to change?
Atul Pant
Power generation through fusion reaction has been one of the most attractive fields of nuclear research and has consequently seen considerable investment since the middle of the last century. While the world has been awaiting a breakthrough in an affordable and clean power source for long, nuclear fusion has always been taunted, since the 1950s, as the energy source that was 50 years away from commercial availability and would always remain so. In recent years, however, there has been some noises about getting very close to the first real goals of harnessing this energy, i.e., working prototypes of fusion reactors. Advanced technologies and supercomputing have remarkably accelerated the pace of RD in this field, which has probably led to the recent confident claims.
In nuclear fusion, various isotopes of hydrogen are fused together to form a new element, helium. In the process, a small amount of matter is converted into heat energy, as in the case of nuclear fission. This energy is enormous and could be harnessed. But the temperature required for nuclear fusion to occur is in the range of 13 million degrees centigrade. No material can withstand such high temperatures. Hydrogen fusion experiments are therefore presently being carried out in apparatuses called Tokamaks (toroidal plasma chambers), where the hydrogen in extremely hot plasma form is fused together while being suspended away from the walls of the apparatus using extremely strong magnetic fields.
The problems in achieving successful nuclear fusion have mainly related to sustaining the reaction for long durations and plasma containment. The moment the plasma comes into contact with any other material in the tokamak, it immediately loses heat and the temperature required to be maintained comes down drastically, stopping the reaction. At present, it has been possible to stably hold the plasma in the tokamak only for a few seconds or at best a few minutes. Large amounts of input energy are also required for the experimental apparatus to work and to sufficiently raise the temperature of the plasma for the fusion reaction to start. In all the experimentation conducted till date, it has not proved possible to obtain a higher output of fusion energy than the input energy. The best output to input energy ratio has been 65 per cent. For fusion to become a viable source of energy generation, the reaction will have to be sustained for long durations and output energy will have to be many times greater than input energy.
In 2013, Lockheed Martins Skunk Works revealed experimental work on a new high-beta reactor design concept, a compact fusion reactor, for commercial fusion power. Skunk Works is the official pseudonym for Lockheed Martins Advanced Development Programs (ADP), formerly called Lockheed Advanced Development Projects. When the project was initiated, the aim was to achieve a working prototype compact fusion reactor in five years (2018), make it available for military applications in ten years (2022-23) and make it commercially viable in 20 years. Further, the apparatus to be developed was to be as compact as to fit on the back of a truck and produce energy equivalent to a 100 MW power plant, sufficient for the energy needs of a small city of 100,000 people. Use of the term high-beta is indicative of the high ratio of plasma pressure to magnetic pressure, loosely indicating high efficiency. If successful, compact fusion could be a revolutionary invention.
The compact fusion reactor will use deuterium and tritium isotopes of hydrogen as fuel (as in other tokomaks), and a neutron source for the reaction.4 The reactor being researched on is just about two metres long and one meter in diameter (called linear compact reactors) as against tokamaks that are comparatively huge in size.
The plasma containment concept being worked on is new and very different from tokamaks, with supposedly better results. The energy produced in the reactor would be in the form of heat which would be harnessed through a turbine as in a fission reactor. But unlike in the case of fission reactors, the by-products of the fusion reactor would be non-radioactive Helium and neutrons. The neutrons would be absorbed by a Lithium blanket on the walls of the reactor, which would produce more tritium found only in rare quantities on earth.5
Skunk Works has, however, been secretive about the degree of success of the experiment so far and not released any data to prove its claims. It has been conducting briefings and presenting the research concept in many forums, and projecting the venture as a practical solution to all of the worlds energy problems. Many in the scientific community have, however, been terming their claims as outlandish and impractical. But others have preferred to go with Skunk Works optimism based on the reputation of the company and is earlier achievements, which include the designing of a number of state-of-the-art aircraft like the U-2, SR-71 Blackbird, F-117 Nighthawk, F-22 Raptor, and the F-35 Lightning II. But the degree of success achieved so far cannot be judged with any certainty at present because of the companys policy of closely guarding data and outcomes.
Another compact fusion experiment proclaiming success in the near future is the Spherical Tokamak-40 (ST-40) experiment by Tokamak Energy, a private company in the United Kingdom.6 The experiment is on similar lines to Lockheed Martin, albeit with a spherical plasma chamber instead of a cylindrical chamber. This company is also keeping much of the experimental data classified. David Kingham, CEO of Tokamak Energy, has said that The ST40 is a machine that will show fusion temperatures 100 million degrees are possible in compact, cost-effective reactors. This will allow fusion power to be achieved in years, not decades. And he added that, We are already half-way to the goal of fusion energy; with hard work, we will deliver fusion power at commercial scale by 2030.7
The writer is Research Fellow at the Institute for Defence Studies and Analyses (IDSA), New Delhi
