Tag: Nuclear Fusion

A Fusion Reactor experiment in South Korea has succeeded in maintaining a temperature of 100 million degrees for 20 seconds. Is this a breakthrough or just steady progress?

Most people know that the energy source of our Sun is nuclear fusion. That deep within the Sun’s core, at temperatures and pressures far beyond anything here on Earth the nuclei of hydrogen are squeezed together to form helium releasing massive amounts of energy in the process.

The Process of Fusion in the Sun. Starting with four Hydrogen Nuclei (Protons) we end up with a Helium Nuclei and a lot of energy! (Credit: Quora)
However Fusion is only possible under the immense pressures and temperatures found in the very centers of Stars. (Credit: Physics LibreTexts)

We’ve known for decades that if we could harness the power of fusion our energy problems would be over. We could obtain huge amounts of energy from a cheap fuel; there are two atoms of hydrogen in every molecule of water after all, and do so without producing any CO2 or other pollutants to poison our planet. Not only that but fusion is safer than nuclear fission because there are no long term radioactive waste products produced and since fusion requires such extreme conditions if anything goes wrong the whole reaction instantly shuts down. In other words no Chernobyls.

Once started a Fission Chain Reaction is hard to control, that’s what happened at Chernobyl. Fusion, on the other hard is so hard to keep going that after 70 years of trying we still haven’t succeeded in doing it! (Credit: USA Today)

So physicists and nuclear engineers have been working on the development of a fusion reactor since the 1950s, so far without success. The conditions needed to produce fusion, millions of degrees under enormous pressure are simply so difficult to achieve and sustain that for decades a successful experiment was one that lasted for milliseconds.

There has been progress however and in just the last ten years the second barrier has been broken. The current record, just achieved on the 24th of November, is continuous operation for 20 seconds at a temperature of over 100 million degrees Celsius. That success was made by the Korean Superconducting Tokamak Advanced Research (KSTR) project located in the City of Daejeon in South Korea.

The Basic Design of a Tokamak Fusion Reactor. The plasma in contained within very strong magnetic fields. (Credit: Iter)

KSTAR is a Tokamak design where the hydrogen atoms are heated until they break apart into protons and electrons forming what is known as an electrically charged plasma. This plasma is then contained within a doughnut shaped ring by powerful magnetic fields. The plasma is then further heated by a variety of means such as radio frequency heating, just like your microwave, or neutron beam injection. If the plasma can be kept enclosed within the doughnut and brought up to high enough temperature fusion can be achieved. For the last 70 years containment has been the problem.

The interior of the KSTAR Tokamak. (Credit: Steemit)

In KSTAR the doughnut containment vessel is 1.8m across with a thickness of 0.5m. The major improvement in KSTAR has been the use of superconducting magnets generating a field of 3.5 Tesla, that’s about 70,000 times the strength of Earth’s magnetic field, a field strong enough to contain a maximum plasma current of 2 million amperes.

The exterior of the KSTAR Tokamak in South Korea. (Credit: Slashgear)

And KSTAR is not the only Tokamak based experimental reactor trying to push forward the technology needed to make fusion power a reality. In fact KSTAR is just one facility in the largest multi-national scientific program ever, the International Thermonuclear Experimental Reactor or ITER. With seven main partners, the European Union, Russia, the US, China, India, Japan and South Korea, and 35 other contributing nations the goal of ITER is a Tokamak reactor that will actually produce more energy than it requires in order to run.

Construction of the ITER reactor is already underway in the Provence region of southern France with a scheduled completion date of 2025. The planned energy output of ITER is 500 Mega Watts for as long a time as twenty minutes. Experiments at ITER are expected to run from 2025 to 2035.

Construction is underway for the ITAR Tokamak reactor in Southern France. It is hoped that while ITAR will not produce commercially useful energy it will for the first time sustain a fusion reaction for a long enough period of time where useful energy could be produced. (Credit: BBC.com)

But ITER will still be an experimental reactor; there are no plans to even attempt to produce useful electricity from the heat generated by the reactor. Instead the lessons learned from ITER will be used to finally build and operate a commercial power plant using nuclear fusion. This planned power plant has tentatively been named DEMO although at present it has not been decided whether DEMO will be an actual reactor or a design that contributing member nations can then use to construct commercial power plants in their own countries. So there is real progress being made. Someday, in the not too distant future we will finally achieve the production of energy by nuclear fusion. However it is worth remembering that back in the 1960s people were predicting that fusion power was only 20 years away. That prediction has since become something of a joke. ‘Fusion power is 20 years away, and always will be!”

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