BL Explainer: Nuclear fusion and clean energy

  What is Nuclear Fusion?

Nuclear Fusion is the science of producing energy by ‘fusing’ two atomic particles into one.

In what way is it different from Nuclear Fission?

Fission works the opposite way; energy is produced by splitting an atom open by shooting a neutron into an atom, like shooting a bullet into a watermelon. The process produces energy.

Why does fusion result in energy?

When you fuse two particles, a part of the sum of their masses (matter content) gets converted into energy. Even a very tiny mass converts into enormous amounts of energy. Remember, Einstein said that matter and energy are fungible? (By the way, in fission too, some mass gets converted into energy.)

Then, why haven’t we been doing it all this while?

The problem is, how to ‘fuse’ two particles.

Well, how?

The only way to do it is to get the two particles to collide with each other with such tremendous force that they fuse into one. To do this, you need to energise them, make them travel at extremely high speeds in random directions so that some will collide with others, and fuse.

How is that done?

Let us understand this step-by-step. First, they take the simplest of elements—hydrogen. It is simple because a hydrogen atom has just one positively charged proton in its nucleus and a negatively charged electron somewhere in an orbital path around it. But for fusion, they take isotopes of hydrogen—Deuterium (one neutron) and Tritium (two neutrons) -- because a Deuterium-Tritium fusion produces more energy than regular hydrogen.

They put the (isotopic) hydrogen gas in a chamber and make a ‘plasma’ out of it. Matter becomes plasma when superheated. Plasma exists naturally in stars because of the intense gravitational – squeezing — forces. But on earth, plasma can be artificially produced by heating a gas, usually by shooting a very bright laser light (equivalent of light produced by 20,000 of 100W light bulbs in one second, delivered in a few billionths of a second.) Or, by bombarding the gas with a microwave—it works like a micro-oven.

Ultimately, when the plasma reaches 150 million degrees, ten times as hot as the core of the sun, the particles begin to fuse and produce energy. As long as the energy obtained is more than the energy put in (we are there yet now), it makes economic sense.

Why is it called clean energy?

Because it not only does not pollute or produce greenhouse gases, but also, unlike nuclear fission, is not radio-active. Further, the fuels – Deuterium and Tritium – are easy to get. While Deuterium can be separated from sea water, Tritium can be manufactured. So, fuel is also no problem.

Still, fusion looks like a complex job. Is it worth the trouble?

Yes, because it is not only clean, but also requires very little fuel. A 1,000 MW coal plant will need 2.7 million tons of coal a year; an equivalent fusion reactor will need 125 kg each of Deuterium and Tritium.

The complexity is only while designing the reactor and getting fusion to happen. Once you are past that post, it is smooth sailing all along.

Where are we when it comes to generating energy from nuclear fusion?

We are decades away from a commercial nuclear fusion reactor. The recent success in the ‘Joint European Torus’ (JET) project, is only (but significant) milestone in the evolution of fusion reactors. A bigger experimental device — called ITER — is coming up in France, which is a collaborative project of 35 countries including India. It is still under construction. The JET success raises hope that the $25 billion ITER will also succeed, leading on to commercialisation of nuclear fusion. But that is far away.

Yet, nuclear fusion cannot be dismissed as something of the deep future, because in the fight against climate change and for provision of cheap, clean energy for all, a few decades is but a wink in time.

COMMENT NOW