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article imageThe ‘cold standard’: Would nuclear fusion be safer?

By Tim Sandle     Mar 7, 2017 in Science
Several teams of physicists are pursuing the goal of nuclear fusion, as a theoretically unlimited source of so-called ‘green’ power. But have the environmental implications been fully considered and just how safe and green would nuclear fusion be?
Readers were intrigued by our recent Essential Science article detailing a new potential path to nuclear fusion, and we wanted to follow up some of their questions. These questions included how likely is a malfunction of a Chernobyl or Fukushima equivalent — and, if so, what could be done? Also, how easily and safely could nuclear waste be stored?
To recap, nuclear fission refers to the splitting of large nuclei into smaller ones, while nuclear fusion is the joining of smaller nuclei to make larger ones. The fusion process generates high amounts of energy, far greater than can be achieved with nuclear fission. Nuclear fusion happens in stars and teams of physicists have been, since the 1950s, trying to replicate this process on a scale that could safely be used with a nuclear power station.
In nuclear physics  nuclear fusion is a reaction in which two or more atomic nuclei come close enoug...
In nuclear physics, nuclear fusion is a reaction in which two or more atomic nuclei come close enough to form one or more different atomic nuclei and subatomic particles (neutrons and/or protons). The difference in mass between the products and reactants is manifested as the release of large amounts of energy.
Kjerish (CC BY-SA 4.0)
The most promising method of making nuclear fusion power on Earth involves the fusion of a deuterium atom (an isotope of hydrogen, containing a single proton and neutron but no electron) with a tritium (a different isotope of hydrogen with one proton and two neutrons and two electrons outside) one.
The word ‘nuclear power’ raises concerns with many people over its environmental impact and safety. How do these concerns stack up against nuclear fusion? While examining answers to these questions, readers should bear in mind that the subject is still (largely) theoretical.
Environmental impact
A radioactivity warning symbol.
A radioactivity warning symbol.
Kenzo Tribouillard, AFP/File
The environmental impact of nuclear fusion would be very low. In theory, to run nuclear fusion, the process would require the addition of hydrogen (which is a simple, fairly safe gas produced from water). The use of water as the fuel, for sources of hydrogen isotopes like deuterium, is also relatively environmentally friendly. Using water as fuel is also sustainable compared to fission. Uranium to be used in nuclear fission reactors is running out (with just a few thousand years left) — and with only a few hundred year remaining for fossil fuels.
During the fusion process, atoms would be smashed together and helium would be produced (also a clean and safe gas). The helium would be exhausted from the facility into the atmosphere. The conversion process would generate vast quantities of heat energy. This energy would be used to power steam turbines and generators to produce electricity.
Unlike fossil fuels burning there would be no carbon dioxide (a greenhouse gas) contributing to global warming and climate change. Also, unlike nuclear fission, there would be no dangerous nuclear waste to be disposed of. In other words, nuclear fusion would produce clean and safe nuclear power.
A picture taken at Fukushima nuclear power plant on June 17  2011 by the Japanese government panel i...
A picture taken at Fukushima nuclear power plant on June 17, 2011 by the Japanese government panel investigating the accident
, Japanese government via Jiji Press/AFP
Nuclear fusion is regarded as relatively safe in relation to the production process. This is because only small quantities of fusion fuel are inside a fusion reactor at any one time. The operation of a fusion power plant would be maintained by continual refuelling with the fuel mixture (deuterium-tritium or deuterium-deuterium). Essentially, since very little of the fuel is inside the reactor it cannot explode or become a factor in an accident.
Furthermore, because of the power generation method, with hydrogen input and helium output, this means there is no risk of nuclear accidents such as those that have occurred with fission plants, like the incidents s at Chernobyl, Ukraine in 1986 and Fukushima, Japan in 2011. With nuclear fusion there can be no reactor core meltdowns and no fission product decay heat burn downs.
In terms of radioactive waste, almost all materials within the reactor will become activated to some degree by energetic neutron bombardment. However, in terms of quantities, this would be 10,000th less than with a comparable nuclear fission reactor. Moreover, the time that the material remains radioactive is around 20 years compared with hundreds of thousands of years from a nuclear fission reactor. However, it remains there will be a radioactive waste disposal issue from nuclear fusion, albeit it on a lesser scale that from nuclear fission. Importantly, from those concerned about weapons of mass production, the by-products from nuclear fusion cannot be used to make nuclear weapons.
The future
A glowing plasma lamp [Image credit: Luc Viatour /]
A glowing plasma lamp [Image credit: Luc Viatour /]
Luc Viatour via Wikimedia Commons
Nuclear fusion is theoretically safe but it is also only theoretical for the time being. The problem scientists are having is with confining a super-hot plasma (a gas in an ionized state, so hot that the atoms are blown apart into their constituent nuclei and electrons), so it remains hot enough and sufficiently energetic to allow the atoms inside it to overcome their natural repulsion and fuse together.
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