Sooner or Later we’ll get Nuclear Fusion, I think.

When I was young the promise of nuclear energy to transform the world was taken for granted. There were even those who predicted that in just a few years people wouldn’t even have to pay for energy anymore it would be so cheap. Things didn’t quite work out that way.

Nuclear Fission, which produces energy by splitting the biggest of atomic nuclei, uranium and plutonium, produced so much dangerous radioactive material that it soon became very costly, and after a few catastrophic accidents Nuclear Fission was largely, and probably correctly pushed well off to the side.

There’s another kind of nuclear power however, nuclear fusion where the smallest of atoms are forced together to release energy. Fusion actually releases more energy than fission, it is the source of the energy of the Sun and while the fusion process does produce radiation it is much less than in fission and there is none of the nasty leftover radioactive waste that can remain dangerous for hundreds of years.

The problem with fusion is that it is much harder to initiate and sustain a fusion reaction than a fission reaction. For example in an H-bomb the heat and pressure required to trigger the fusion reaction in the first place actually has to be supplied by the fission of an A-bomb. Scientists have been trying for the past 50 years to contain and control a fusion reaction in the labouratory as a precursor to building and fusion power plant. The image below shows an experimental fusion setup at Princeton University’s Plasma Physics Laboratory.

Experimental Fusion Reactor at Princeton (Credit: Elle Starkman, PPPL)

Over the past 5 to 10 years it is European scientists who have taken the lead in this effort with the construction of what it is hoped will be the world’s first fully operational fusion power plant. Named the International Thermonuclear Experimental Reactor (ITER) the plant’s construction in southern France has now reached the halfway point and it is possible that the first plasma ignition could occur by 2025 with full energy production by 2030. The image below shows the ITER reactor building under construction.

ITER Reactor Building under Construction (Credit: ITER)

The type of fusion reactor that ITER will use to produce its energy is known as a Tokamak design that employs a doughnut shaped ring of electromagnets 300,000 times stronger than Earth’s magnetic field. This powerful magnetic field is needed in order to contain the 150 million degree hot, electrically charged plasma in which the fusion reaction takes place. The image below illustrates how a Tokamak reactor works.

Elements of a Tokamak Fusion Reactor (Credit: PD)

Thirty-six nations are contributing to the $26 billion dollar cost of ITER with the European Union paying about half. Once ITER is completed humanity will have a new star, a second sun of its own creation right here on Earth providing almost limitless clean energy.

 

Or maybe it could happen sooner. That’s what a team of researchers led by physicist Heinrich Hora of the University of South Wales in Australia hope to demonstrate with a new formula for the fusion reaction.

The Doctor Hora and his team point out that the Tokamak/Plasma style of fusion reactor like that at ITER has two big drawbacks that are the main reason it has taken practical fusion so long to be achieved. First: the fusion reactions in a Tokamak produce large numbers of neutrons, which can escape from the magnetic field carrying a substantial fraction of the energy produced away with them. Second: the energy produced in a Tokamak cannot be directly converted into electricity, it must be used first as heat to generate steam that then drive an electric generator, with a substantial fraction of the energy wasted in each step.

What Doctor Hora and his team suggest instead is a reaction where a single hydrogen atom, really just a single proton, fuses with an isotope of the element Boron, Boron-11. This reaction would produce three nuclei of helium with no escaping neutrons and since the helium nuclei would be ionized the charged particles could then be directly turned into electricity.

The experimental setup the researchers suggest is to have a small sphere of boron-11 in a hydrogen gas. Powerful lasers are then used to literally drive the hydrogen’s protons into the boron nuclei producing fusion and releasing energy.

While no experimental tests of the reaction have been conducted so far Doctor Hora hopes to begin labouratory tests soon. If the reaction proves to be practical a hydrogen-boron reactor could be a simpler and cheaper alternative to achieving practical fusion energy.

 

 

Nuclear Fusion: Has MIT Found the right Recipe?

For over half a century now Hydrogen Fusion has been the Holy Grail of energy production for the human race. Fusion is the energy source that powers the stars themselves and the potential for Fusion power plants to provide cheap, inexhaustible, pollution free energy was never in doubt. The question has always been whether the extreme conditions necessary for Fusion to occur could be controlled and maintained, whether a reliable Fusion reactor was possible or, like the Holy Grail, just a dream.

Let me take a moment to provide a little background. The chemical elements we’re all familiar with from high school run from the simple ones like Hydrogen, just a proton and electron, to extremely complex ones such as Uranium with 92 protons, 92 electrons along with 146 neutrons.

Now it turns out that you can release energy by either splitting big atoms like Uranium, this is called Fission, or Fusing small ones like taking 4 Hydrogen atoms to form one Helium atom. The pictures below show the two different types of reactions.

Fission of a Uranium Nuclei (Public Domain)
Fusion of Hydrogen into Helium (Public Domain)

We all know that Atomic Fission reactors have been producing energy for over 50 years but they’re dangerous, even after you’ve shut them down they remain hot and if the reaction gets out of control a tremendous amount of harmful radiation can be released, as in Chernobyl or Fukashima. Another problem with Fission reactors is that the leftover fuel rods are also highly radioactive and storing them safely is a very difficult problem.

Fusion reactors on the other hand would have a number of clear advantages. First of all Hydrogen Fusion simply produces more energy per kilo of fuel. More importantly however is the fact that Fusion would produce zero dangerous waste. Also, the conditions needed to produce Fusion are difficult to initiate and maintain, so difficult in fact that if anything were to go wrong the reaction would just instantly stop with no chance of a meltdown or release of radiation.

So if Fusion is such a better form of energy production why aren’t we building them by the hundreds in order to satisfy the need for pollution free energy? Well, as I said the conditions needed for Fusion are difficult to initiate and maintain, so difficult in fact that the world’s best scientists have been unable to maintain a Fusion reaction for more than a fraction of a second.

A recent advance may help to change that however. Scientists at MIT’s Plasma Science and Fusion Center have been experimenting with a new recipe for the fuel in their Alcator C-Mod Tokamak reactor. Now a Tokamak is a doughnut shaped vacuum chamber that uses intense magnetic fields to confine plasma, a gas of atoms that have been stripped of one or more electrons. Producing and heating plasma to extremely high temperatures and pressures is how you initiate a Fusion reaction. The picture below shows the MIT Tokamak.

Inside MIT’s Tokamak (Credit: Bob Mumgaard-Plasma Science and Fusion Center)

For the last several decades the fuel recipe that researchers have used has consisted of about 5% ordinary Hydrogen and 95% Deuterium, Hydrogen with a neutron attached to the proton. Microwaves then heat the ordinary Hydrogen and Fusion occurs as the superheated Hydrogen slams into the Deuterium. As I said earlier no one has succeeded in keeping this reaction going for more than a second.

Now the team at MIT has added a trace, less than 1%, of Helium-3 to the mixture. (Helium-3 is an atom of Helium lacking a neutron) When the Helium-3 is heated by microwaves they were able to increase the Helium-3 to energy levels ten times greater than previously seen!

The results obtained by the MIT team were so exciting that they quickly shared their results with colleagues at the Joint European Torus (JET in Culham UK), which is the world’s largest experimental Fusion reactor. The JET team soon confirmed MIT’s results and so now both teams are fine-tuning the recipe in order to get the highest energy levels possible.

Whether or not this breakthrough will soon lead to practical Nuclear Fusion only time will tell. It is possible however that before too long humanity may possess an almost limitless supply of pollution free energy.

If you’d like to read more about the research at MIT click on the link below to be taken to the Plasma Science and Fusion Center webpage.

https://www.psfc.mit.edu/news/2017/fusion-heating-gets-a-boost