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Nuclear Fusion - Can We Bottle A Star?

Let me take you on a journey to the sun.


To get a sense of the scale of the journey, picture the earth and shrink it down to the size of a pebble. At this scale, the size of the sun compared to the earth would be that of a basketball.


For us to travel to the sun, we need to cover a vast distance. If you set off from a pebble-sized earth at one side of a basketball court floating just under the basket, our basketball-sized sun will be floating just under the basket on the other side of the court.


If we examine our sun more closely. What we initially see is a glowing ball of burning gas. What we are looking at is the outside layer called the Photosphere.


If we could slice the sun like an onion, we would see that it has four layers. The bit we are interested in is the core in the centre of the sun in which intense heat and a massive amount of pressure due to its size force nuclei together until they merge (fuse), releasing energy in the process.



What is happening in the sun's core is nuclear fusion, and that is why the sun seems to have virtually limitless free energy.


But can we create our own star here on earth?


What is Nuclear Fusion?

Nuclear Fusion is when two lighter atoms join (or fuse) together at extreme temperatures creating one heavy atom and a huge release of energy, when you look at the sun or the stars in the sky, that is exactly what you see, nuclear fusion in action.


Before we continue, it is time for another journey; an atom, particularly its nucleus (plural nuclei), is indescribably tiny. However, I think it is important to get some sense of the scale of the small that we are talking about.


Picture a single grain of sand in the palm of your hand. Now blow this up until you have a grain of sand that is the same size as the earth - difficult to picture, but hopefully, you are still with me. Now zoom into the earth-sized grain of sand until you find an average two-storey house - this house represents the size of one atom within the grain of sand.


[Head to Google Earth and search your address to get a visualisation].


Even though we have a house-size, atom, it is not possible to see the nucleus with the naked eye at this scale, so let's increase the size of the atom to the size of a football stadium - say Wembley Stadium in London or The Rose Bowl, California.


If our stadium was a hydrogen atom, a grain of sand would be at the centre of the pitch floating above the spot - this represents our hydrogen nucleus. One grain of sand in the centre of a 90,000-seater football stadium.


Now, if we zoom back out to the actual size we are now reading this, if you took a grain of sand in the palm of your hand, it would contain 43 billion billion billion atoms.


This should give you a sense of the scale of small we are talking about when trying to force nuclei to fuse together.


 

I am not going to get too technical here. There are some good videos that provide a more comprehensive explanation. I'll keep this at a level of base understanding needed to understand the process and be able to have a sensible conversation around the dinner table or in a nuclear job interview.


The nucleus of an atom is positively charged. If positively charged nuclei approach each other, they repel each other (known as the Coulomb Barrier) - just as two magnets do when turned the opposite way around. The closer they come together, the more force the Coulomb Barrier provides.



Now, if you can get a combination of enough heat and/or pressure to get the atoms to break through their Coulomb Barrier, they will fuse together,


releasing a massive amount of energy in the process.


The sun does this through its heat and huge gravitational pull, and we can do it here on earth through extreme temperatures (much times hotter than the sun) or slamming the nuclei together -



Sounds great. We can create our own mini-suns here on earth and use the energy they provide to boil our kettles, turn on our lights and power our cars. The problem is that this process takes up far more energy than it produces.


The Holy Grail

We have been trying to 'bottle the sun' for coming on for 85 years since the NACA Langley Research Center, in 1938, attempted unsuccessfully to achieve nuclear fusion (or plasma).


There wasn't much further process until a busy year in 1958 when the ZETA device in a town called Harwell in the UK claimed fusion before withdrawing the claim following a challenge. However, later in the same year, the first controlled thermonuclear fusion in any laboratory was achieved by Scylla I at Los Alamos, New Mexico.


Although successful, the pinch approach used by Scylla was quickly abandoned as it was impossible to scale up to produce a reactor.


I've included below a timeline which provides the developments in nuclear fusion by decade for further reading, but in short, today, in 2022, we still have not been able to generate nuclear fusion on a commercial scale, and we remain at least 10 years off doing so.


We have achieved plasma on several occasions but still remain unable to achieve an energy gain (Q).


The best energy gain we have achieved for a long time was 0.67 for JET in the UK, which has recently been bettered by the US Department of Energy’s National Ignition Facility, California, achieving Q of 0.7 both only for fractions of a second. JET separately has also achieved a Q of 0.33 for 5 seconds.


Note: the Q calculation is often debated as the above numbers are calculated using only the energy needed to generate the plasma. However, it is argued that if you use the energy needed to run the total facility, the calculation would provide much lower Q numbers.


Regardless of this, we are still a long way from providing nuclear fusion on a sustainable enough level to make it commercially viable in the foreseeable future.


Summary

Nuclear fusion is when two or more atomic nuclei join together to form a single, heavier nucleus. It is the process that powers stars and produces vast amounts of energy.


Scientists have been working for many years on Earth to develop nuclear fusion as a clean and efficient power source. Fusion reactions can be sustained by creating very high temperatures and pressures, and the resulting energy is used to generate electricity.


This process is potentially much cleaner and more efficient than current forms of nuclear power, but there are still many challenges to overcome before fusion technology can be commercialized. These include developing materials that can withstand the high temperatures and pressures needed for a sustained reaction and designing systems to handle the radioactive waste products produced.

The key benefits of nuclear fusion are that it is clean, safe, and produces no greenhouse gases. Its potential for producing large amounts of energy also makes it an attractive alternative to fossil fuels.


However, the challenges associated with nuclear fusion mean that it could be many years before we see commercialized systems on a large scale. In the meantime, research continues to make progress towards this goal, offering hope for a cleaner future.


While the future of nuclear fusion is uncertain, it has the potential to be a key part of the world's energy mix in the future.



 


The Timeline of Nuclear Fusion

The 1950s

The actual first attempt to make a working fusion reactor was in 1938. However, the NACA Langley Research Center attempt was unsuccessful. The UK's ZETA device at Harwell claimed fusion in 1958, this was later withdrawn following a challenge. However, later in the same year, the first controlled thermonuclear fusion in any laboratory was achieved by Scylla I. However, the pinch approach used by Scylla was abandoned as it was impossible to scale up to produce a reactor.


In the nuclear deterrence arena, 1952 saw the first detonation of a thermonuclear bomb. The bomb released 10.4 megatons of TNT out of fusion fuel. In 1961 the Tsar Bomba was tested by the Soviet Union. At 50 megatons, it remains the most powerful weapon ever dropped.


It was in 1955 that it was first predicted that fusion would be ready for commercial use in just two decades. This was made by Homi J. Bhabha at that year's Atoms for Peace. This stirred several countries into action to start fusion programs of their own. The race to the first fusion plasma began.


The 1960s

It was not until 1964 that plasma temperatures approximating 40 million degrees Celsius were achieved. The Scylla IV was to achieve this at the LANL facility in Los Alamos, New Mexico. In the meantime, in 1960, the concept of inertial confinement fusion (ICF) was published by John Nuckolls. Nuclear fusion was starting to look like an exciting place to be in the early 1960s.


This was short-lived. At an international meeting in 1965, it was clear that most fusion efforts had stalled. The Soviets showed great improvements in their toroidal pinch machines, which are almost identical to the ZETA design. At the same meeting, ZETA reported some strange results. All major designs at this point are losing plasma at too high of a rate to be utilised in a reactor.


Three years later, in 1968, the Soviets claimed temperatures were higher than any other by order of magnitude. This is for their T-3 tokamak, similar to their toroidal pinch machine and ZETA. This is, of course, met with scepticism. However, the Soviets were confident and invited a UK team - "The Culham Five" - to confirm their results. They published their results in late 1969 confirming the results. This led to an increase in tokamak construction all over the globe.


The 1970s

It was not until 1975 that the Princeton Large Torus (PLT) commenced operation. Quickly setting many records. The PLT surpassed any machines that had gone in the past. These results led to the US DOE funding a Tokamak Fusion Test Reactor (TFTR) in 1976. The PLT continued to set new records, and in 1978 Princeton was given additional funding to further adapt TFTR with the explicit goal of reaching breakeven.


The 1980s

It was then not until the 1980s that progress of note was made. In 1983 the Joint European Torus (JET) based in Culham, UK, achieved its first plasma. The project was the largest magnetic confinement plasma physics experiment ever. Commencing design work in 1973, it was completed on time and on budget.


In 1985 the Japanese tokamak, JT-60, achieved its first plasma. In 1988 the Tore Supra in Cadarache, France, utilising superconducting magnets, achieved the first plasma. Additionally, in 1988 the concept design for ITER (International Thermonuclear Experimental Reactor) commenced. This will be a successor for JT-60, T-15, JET and TFTR. ITER is a collaboration between many countries across the world.


One year later, in 1989, a huge 10-beam NOVA laser at LLNL, California, completed and produced 120 kilojoules of infrared laser light during a pulse experiment. This year two electrochemists from Utah made an announcement that they had achieved cold fusion. This indicated that they could achieve fusion at room temperature. However, peer reviews of their work found no credit to their claims.


The 1990s

The 1990s provided many successes and developments in the nuclear fusion space. in 1991 the START (Small Tight Aspect Ratio Tokamak) fusion experiment at Fulham achieved a record result by adapting the conventional toroidal fusion experiments into a higher spherical design. In 1993 the TFTR successfully produced 10 megawatts of power from a controlled fusion reactor. Then in 1996, utilising actively cooled plasma-facing components, the French Tore Supra generated 2.3 megawatts for a duration of 2 minutes.


The JET tokamak produced a world record 16 megawatts of fusion power in 1997. Four megawatts of self-heating were also achieved. Self-heating is an expression regarding a fusion energy gain factor. The ratio of power released by a fusion reactor versus the energy needed to power the reactor is expressed as Q. When Q is greater than 1, it is said that the fusion reactor is self-heating.


One year later, in 1998, the Japanese JT-60 tokamak produced a high-performance shear plasma. This is the current world record of a 1.25 Q fusion energy gain factor. A momentous decade for nuclear fusion was completed in the news in 1999, and the START experience was to be superseded by MAST (Mega Ampere Spherical Tokamak).


The 2000s

Following all the developments of the 1990s. The first half of the first decade of the new millennia didn't produce too much to note. There was a little excitement in 2002 when claims were made about small-scale fusion using acoustic cavitation. This will quickly be dismissed. The ITER project finally made the decision that it would be sited in Cadarache in France in 2003.


The back end of the decade started promisingly, with NIF firing its first bundle of eight beams. The National Ignition Facility (NIF) is located at the Lawrence LLNL, California. It is a large laser-based inertial confinement fusion (ICF) research device. This achieved the highest-ever energy laser pulse of 152.8 kJ in 2005.


The following year in 2006, China's test reactor was completed as the first to use superconducting magnets. It is called EAST (Experimental Advanced Superconducting Tokamak). At the Heavy Ion Fusion (HIF) Symposium in 2010 in Germany, there was a presentation in which it was claimed that HIF would be commercial within the decade.


The 2010s

The 2010s brought more development and progression. However, fusion continued to remain to be a couple of decades away. In 2012 JET announced a breakthrough in controlling instabilities in fusion plasma. The following year EAST records a confinement time of 30 seconds for H-mode plasma thanks to heat dispersal of tokamak wall improvements. Then, in 2014 there was progress in generating more energy than is used to generate fusion. This was achieved at NIF in the US.


2015 saw the Stellarator Wendelstein 7-X in Germany achieve its first steady-state plasma. This is by utilising a large-scale stellarator design. In the same year, Polywell was present at Microsoft Research. This was a proposed fusion reactor design. It is still in development. However, in 2019 the University of Sydney produced research to show that the design in practice is impossible.


Also, in 2015, the ARC (affordable, robust, compact) fusion reactor is announced by MIT. The ARC design claims to utilise a smaller configuration than other designs whilst maintaining a similar magnetic field. In 2016 the Wendelstein 7-X device produced if first hydrogen plasma.


The following year in 2017, there was quite a bit of movement. China's EAST achieves over 100 seconds of steady-state high-confinement plasma. Helion Energy's plasma machine, The Fusion Engine, goes into operation. The Tokamak Energy ST40 generates its first plasma in the UK. Also, it is announced that the Norman reactor has achieved plasma by TAE Technologies.


The momentum continued in 2018 with TAE Technologies announcing that its fusion reactor had achieved 20 million degrees Celsius. Commonwealth Fusion Systems is provided investment by Eni. The aim is to commercialise SPARC in collaboration with MIT and utilise ARC technology. Also during the same year, MIT scientists formulate a theory to remove excess heat from compact fusion reactors. General Fusion begins developing a 70% scale demo that will be ready in 2023.


The 2020s

As we approach the present day in 2017, the announcement was made on the STEP (Spherical Tokamak for Energy Production) facility. This investment has been made by the UK to have a fusion facility in 2040, which is just a couple of decades away. Finally, the following year, in 2020, the first plasma was achieved at UK’s MAST tokamak. The MAST is the forerunner to the STEP, and the successful trial is seen as a 'game-changer' when extracting excess heat.


 

Nuclear Fission vs Fusion

Nuclear Fusion and Nuclear Fission are both physical processes that produce energy from atoms. As described above, Nuclear Fusion occurs when lighter atoms join (or fuse). Nuclear Fission occurs when a heavy atom is split. Both create loads of energy.


The main difference between Nuclear Fusion and Nuclear Fission are the fuel types, by-products, amount of energy released and technology availability.


Nuclear Energy Fuels Types; Nuclear Fusion uses Hydrogen, whereas Nuclear Fission uses Uranium or Plutonium.