Video: Understanding Nuclear Fusion Reactors

Which three of the following are advantages of nuclear fusion reactors over nuclear fission reactors? [A] Nuclear fusion reactors do not produce highly radioactive waste products that need to be stored for hundreds or thousands of years. [B] The fuel for nuclear fusion, heavy hydrogen, is easily available in the world’s oceans. [C] Nuclear fusion reactor technology has been used for decades, whereas nuclear fission technology is still being developed. [D] Nuclear fusion does not produce by-products that can be used for nuclear weapons.

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Video Transcript

Which three of the following are advantages of nuclear fusion reactors over nuclear fission reactors? a) Nuclear fusion reactors do not produce highly radioactive waste products that need to be stored for hundreds or thousands of years. b) The fuel for nuclear fusion, heavy hydrogen, is easily available in the world’s oceans. c) Nuclear fusion reactor technology has been used for decades, whereas nuclear fission technology is still being developed. d) Nuclear fusion does not produce byproducts that can be used for nuclear weapons.

Okay, so in this question, we’ve been asked to state which three of the following are advantages of nuclear fusion reactors over fission reactors. Let’s go through them one by one and discuss them briefly.

So a) says that nuclear fusion reactors do not produce highly radioactive waste products that need to be stored for hundreds or thousands of years. Now, this is true. In a nuclear fusion reactor, most commonly isotopes of hydrogen are used as fuel. So for example, here we’ve taken a deuterium nucleus and another deuterium nucleus as fuel in the fusion reactor and produced a helium nucleus as a product.

Now, of course, deuterium is an isotope of hydrogen, which contains one proton and one neutron, and a helium nucleus contains two protons and often two neutrons. But the point is that the product in this case, which is a helium nucleus, is indeed not highly radioactive.

So the waste products of fusion reactors are not highly radioactive and they do not need to be stored for hundreds or thousands of years. Therefore, this is an advantage of a nuclear fusion reactor over a nuclear fission reactor.

Moving on to part b) then, the fuel for nuclear fusion, heavy hydrogen, is easily available in the world’s oceans. Now, this is also true. As we’ve seen already, heavy hydrogen or isotopes of hydrogen which contain one or more protons are used as fuel. One example of heavy hydrogen is deuterium, one proton and one neutron.

Now, deuterium is fairly abundant in the Earth’s oceans. This is because water, which obviously fills up the world’s oceans, has a chemical formula H₂O. This means that every water molecule is made up of two hydrogen atoms and one oxygen atom.

Now, these hydrogen atoms most commonly just have one proton in the nucleus. However, sometimes these hydrogen atoms can also be isotopes of heavy hydrogen, such as deuterium for example. And it turns out that about one in every 6420 hydrogen atoms that makes up the water in the oceans is deuterium; it’s a heavy hydrogen isotope.

Now, this abundance is fairly high. So heavy hydrogen is indeed easily available in the world’s oceans. Therefore, statement b) is also true. It is an advantage of fusion reactors over fission reactors because fuel for fusion reactors is highly abundant.

Okay, so let’s move on to point c) then: nuclear fusion reactor technology has been used for decades, whereas nuclear fission technology is still being developed. Now, this instantly we can say is not true. This is because we already have nuclear fission reactors up and running in many countries.

But as of yet, there are no nuclear fusion reactors that produce power for consumers. This is because nuclear fission technology is the one that’s been used for decades and fusion technology is the one that’s still being developed.

This means we can move on to point d). Nuclear fusion does not produce byproducts that can be used for nuclear weapons. Now, in nuclear weapons, we primarily need some radioactive material that will be the source of energy for these weapons.

But as we’ve already seen in point a), the products of nuclear fusion reactors tend to be something like helium, which is not radioactive. Therefore, this cannot be used nuclear weapons. This is contrary to nuclear fission reactors, which produce highly radioactive waste products that can also be used in nuclear weapons. Therefore, point d) is an advantage of fusion reactors over fission reactors.

And therefore, at this point, we found the three statements that are advantages of fusion reactors over fission reactors: firstly, that nuclear fusion reactors do not produce highly radioactive waste products that need to be stored for hundreds or thousands of years; secondly, that the fuel for nuclear fusion, heavy hydrogen, is easily available in the world’s oceans; and thirdly, that nuclear fusion does not produce byproducts that can be used for nuclear weapons.

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