Cosmox Blogs

Dec 10, 2023

Nuclear Fusion: Unveiling the Clean Energy Revolution

Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles (neutrons and protons). The difference in mass between the reactants and products is manifested as either the release or absorption of energy. This difference in mass arises due to the difference in nuclear binding energy between the atomic nuclei before and after the reaction. Nuclear fusion is the process that powers active or main-sequence stars and other high-magnitude stars, where large amounts of energy are released. Fusion reactions occur in stars where two hydrogen nuclei fuse under high temperatures and pressure to form a nucleus of a helium isotope.

In simple words, nuclear fusion is the process that gives the Sun its energy. Scientists from more than 50 countries have been trying to recreate it on Earth since the 1960s. They hope it could eventually provide huge quantities of clean energy for the world. In nuclear fusion, pairs of tiny particles called atoms are heated and forced together to make one heavier one. It is the opposite of nuclear fission, in which heavy atoms are split apart. Nuclear power stations currently use nuclear fission to generate electricity.

Why is nuclear fusion so important?

Nuclear fusion doesn't need fossil fuels like oil or gas. It also doesn't generate greenhouse gases, which traps sun's heat and are responsible for climate change. Most fusion experiments use hydrogen, which can be extracted cheaply from seawater and lithium, meaning fuel supplies could last for millions of years. It has been described as the "holy grail" of energy production.

How does Nuclear Fusion work?

When two atoms of a light element such as hydrogen are heated and combine to form a single heavier element such as helium, the nuclear reaction produces massive amounts of energy which can be captured.

When will large-scale nuclear fusion be possible?

Despite a series of promising breakthroughs in the last few years, large-scale nuclear fusion is still several years away. In February, European scientists at the UK-based JET laboratory smashed their own world record for the amount of energy produced over five seconds. But even the successful NIF experiment in the US did not produce more energy than was needed to make the lasers work in the first place - and the research program to get to this point has cost billions of dollars. Although physicists have welcomed the US results - and described them as a true breakthrough moment - they point out that much more work is needed before nuclear fusion could be used to power homes or businesses. Scientists will now focus on reproducing fusion more quickly and cheaply.

How safe is nuclear fusion?

The International Atomic Energy Agency (IAEA) has called nuclear fusion "intrinsically safe. "The conditions required to start and maintain a fusion reaction are so extreme that it can't run out of control. "Fusion is a self-limiting process: if you cannot control the reaction, the machine switches itself off," explained the IAEA's Sehila González de Vicente. The lower level of radioactive waste produced by the process compared with nuclear fission is also much easier to handle and store.

Could nuclear fusion help tackle global warming?

Nuclear fusion does not rely on fossil fuels like oil or gas and produces none of the greenhouse gases which drive global warming. Unlike solar or wind energy it is not dependent on beneficial weather conditions. It uses two relatively abundant materials found on Earth: lithium and hydrogen. Widescale use of nuclear fusion could help countries meet their target to produce "net zero" emissions by 2050. However, it will be many years before recent experimental successes can be meaningfully scaled up.

Why is everyone so excited about Nuclear Fusion?

Nuclear fusion research has been going on for 70 years and this is the first time scientists have managed to demonstrate ignition – a positive energy gain. The results show that it is indeed possible to use laser fusion to generate energy – a crucial proof of principle that will spur research to develop the technology. That matters because it is hoped nuclear fusion will eventually provide a near-limitless, safe and clean source of energy.

Why are the scientists studying fusion energy?

Ever since the theory of nuclear fusion was understood in the 1930s, scientists — and increasingly also engineers — have been on a quest to recreate and harness it. That is because if nuclear fusion can be replicated on Earth at an industrial scale, it could provide virtually limitless clean, safe, and affordable energy to meet the world’s demand.

Fusion could generate four times more energy per kilogram of fuel than fission (used in nuclear power plants) and nearly four million times more energy than burning oil or coal.

Most of the fusion reactor concepts under development will use a mixture of deuterium and tritium - hydrogen atoms that contain extra neutrons. In theory, with just a few grams of these reactants, it is possible to produce a terajoule of energy, which is approximately the energy one person in a developed country needs over sixty years.

Fusion fuel is plentiful and easily accessible: deuterium can be extracted inexpensively from seawater, and tritium can potentially be produced from the reaction of fusion-generated neutrons with naturally abundant lithium. These fuel supplies would last for millions of years. Future fusion reactors are also intrinsicallysafe and are not expected to produce high activity or long-lived nuclear waste. Furthermore, as the fusion process is difficult to start and maintain, there is no risk of a runaway reaction and meltdown; fusion can only occur under strict operational conditions, outside of which (in the case of an accident or system failure, for example), the plasma will naturally terminate, lose its energy very quickly and extinguish before any sustained damage is done to the reactor.

Importantly, nuclear fusion— just like fission — does not emit carbon dioxide or other greenhouse gases into the atmosphere, so it could be a long-term source of low-carbon electricity from the second half of this century onwards.

Hotter than the Sun

While the sun’s massive gravitational force naturally induces fusion, without that force a temperature even higher than in the sun is needed for the reaction to take place. On Earth, we need temperatures of over 100 million degrees Celsius to make deuterium and tritium fuse, while regulating pressure and magnetic forces at the same time, for a stable confinement of the plasma and to maintain the fusion reaction long enough to produce more energy than what was required to start the reaction.

While conditions that are very close to those required in a fusion reactor are now routinely achieved in experiments, improved confinement properties and stability of the plasma are still needed to maintain the reaction and produce energy in a sustained manner. Scientists and engineers from all over the world continue to develop and test new materials and design new technologies to achieve net fusion energy.

Where do we stand on fusion technology development?

Nuclear fusion and plasma physics research are carried out in more than 50 countries, and fusion reactions have been successfully produced in many experiments, albeit without so far generating more energy than what was required to start the reaction process. Experts have come up with different designs and magnet-based machines in which fusion takes place, like stellarators and tokamaks, but also approaches that rely on lasers, linear devices, and advanced fuels.

How long it will take for fusion energy to be successfully rolled out will depend on mobilizing resources through global partnerships and collaboration, and on how fast the industry will be able to develop, validate and qualify emerging fusion technologies. Another important issue is to develop in parallel the necessary nuclear infrastructure, such as the requirements, standards, and good practices, relevant to the realisation of this future energy source.