Fission vs fusion and the limits of utopian energy

Flat White

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Flat White

13 February 2023

6:30 AM

All operational nuclear power plants are based upon the breakthrough technology of nuclear fission. A controlled chain reaction is initiated where a large nucleus, such as Uranium-235, absorbs a neutron and then splits into lighter elements. This process produces heat. In its simplest terms, this heat is transferred to a gas or liquid which then moves a turbine to generate enormous amounts of electricity. At present, there are 422 nuclear reactors for energy and 223 research reactors – such as the ANSTO reactor in New South Wales.

According to Wikipedia:

‘The fission of 1 kg of uranium-235 releases about 19 billion kilocalories, so the energy released by 1 kg of uranium-235 corresponds to that released by burning 2.7 million kg of coal.’

In other words, it is an extremely efficient way of producing energy. Even before we get to modified reactors, humans have 4 billion years of nuclear fuel. We have solved our energy problems.

For some, this is not enough. They pursue the bigger dream of nuclear fusion. Instead of splitting apart large atoms, two light atoms would be forced to combine – or fuse – together to form a heavy nucleus. It’s the same process in reverse.

This is not an impossible technology. Look up to the sun during the day or to any of the trillion stars in the night sky and you can see working examples of fusion reactors producing energy. Fusion is a natural behaviour when light elements are put under immense gravitational forces.

Hydrogen, as the lightest element in the universe, fuses first providing the dominant source of energy for a star’s fusion reactor. It is the most efficient fuel source for a fusion reactor as it takes the least energy to fuse and yields the most from the process.

Nuclear fusion in stars is not a calm or safe process. It usually ends in a supernova – or catastrophic collapse of the star’s core accompanied by a violent expulsion of its outer layers. Sometimes the core collapses entirely. There are many circumstances that may cause the process of nuclear fusion to go wrong along the way, leading to dangerous and bizarre stellar deaths that wipe out solar systems. It’s not the sort of technology you want to bring along to the science fair.

In order to fuse anything, the ‘Coulomb barrier’ has to be reached. The gravity generated by the mass of stars does this easily, but that kind of gravitational power does not exist on Earth for obvious reasons. (After all, we don’t want to collapse ourselves into a black hole by accident – CERN, we’re watching you in particular.)

Maintaining this high pressure environment to create and contain plasma to facilitate fusion is expensive, difficult, fragile, and ultimately dangerous – far more so than nuclear reactors (which look rather dull in comparison). Despite fusion and fission developing side-by-side, there are only a few experimental fusion reactors that have produced positive tests, but no power.

As an example, fusion reactors are trying to heat their fuel to 100 million degrees while the expelled neutrons eat away at most materials used to construct the reactor – like salt rusting away your beach house.

Fusion’s promises are utopian – a near-unlimited fuel resource, very little nuclear waste, and more power than humanity can use. The trick is not blowing ourselves up trying to harness it.

Normal hydrogen under Earth conditions isn’t a very good fuel, which is why there has been a lot of interest in the vanishingly rare radioactive isotope of hydrogen ‘tritium’ valued at $30,000 a gram.

‘When tritium is combined at high temperatures with its sibling deuterium, the two gases can burn like the Sun. The reaction could provide abundant clean energy – just as soon as fusion scientists figure out how to efficiently spark it.’ – Science.

There is next to no naturally occurring tritium and the little that does exist has to be harvested from the upper atmosphere. Even then it can’t be easily stored with its short half-life of 12.3 years. Ironically, the other producer of tritium is … a nuclear reactor.

‘The world’s only commercial sources are the 19 Canada Deuterium Uranium (CANDU) nuclear reactors, which each produce about 0.5 kg a year as waste product, and half are due to retire this decade.’

Even designs to make tritium inside fusion reactors are a non-starter because there is not enough to get the system going. It is a technology forever circling its failures, much like solar energy and wind turbines which will eventually crumble under their drawbacks.

A lack of fuel is only one of many significant problems facing fusion reactors – and it is not for a lack of money. The Global Fusion Industry said that it has $2.83 billion on the investment table. Meanwhile, 60 fission reactors are under construction in 15 countries. The advancements made to nuclear reactors make them the reliable clean energy champions – which Australia will probably never be allowed to use.

Nuclear fusion, the Holy Grail of energy, is a great idea if you’re a giant ball of plasma floating in space. For a small power station on Earth, it is probably more trouble than it is worth – a romantic but ultimately bad fit for the problem at hand.

Got something to add? Join the discussion and comment below.

Published by Nelle

I am interested in writing short stories for my pleasure and my family's but although I have published four family books I will not go down that path again but still want what I write out there so I will see how this goes

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