What is nuclear power?

07 May 2019

NUCLEAR-POWER-PLANT

Image of nuclear power station on a sunny day

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Question

What are the pros and cons of using nuclear power?

Answer

Sam wants to know about the pros and cons of nuclear power. Izzie Clarke asked physicist Ben McAllister, from the University of Western Australia, to start by explaining what nuclear power is...

Ben - Okay. There are two primary types of nuclear power. I'll very quickly run through both of them. We already heard from Kit before that we can’t just create energy out of anywhere, we have to get it from somewhere else. In the context of nuclear power we are making use of a very famous relationship that was first, I guess you'd say discovered, by a person I mentioned before - Albert Einstein with this very famous equation e = mc squared, which tells you that the energy that a given thing has is essentially equal to its mass times a constant, the speed of light squared, which is really just a way of saying that mass, how heavy something is if you like, is just another form of energy. So, if you can change a thing’s mass then you can harness some energy by breaking off a little bit of mass and converting it into energy, and the amount of energy you can get out is really really really big.

In the context of nuclear power what we're doing is essentially taking - well I mentioned it as well before with uranium and elements that can break down and become other elements - you're taking something, for example, big like uranium, and it has a certain mass. So a uranium atom has a certain mass, it breaks down into two smaller atoms, but when you look at the mass of those two atoms combined, it doesn't quite add up to as much as the uranium atom that you started with.

Izzie - So you've lost a bit?

Ben - Well, you haven't lost it, it's just converted into energy and it’s radiated away. And that's sort of the fundamental principle of what's called nuclear fission power and that's what goes on in all nuclear power plants that actually generate energy in the world today. You could also, theoretically, make use of another nuclear process that works in a similar way, which is called nuclear fusion and that's what the Sun does when it wants to make energy. So what you would do with nuclear fusion is you take a light thing like hydrogen - the lightest element - and you’d smash a bunch of hydrogens together until you got a helium, which is the next lightest element. But, again, the mass of that helium atom is going to be slightly less than the mass of all the hydrogen that you put in so you get a bit of energy released.

And the pros and cons of these things? Well, if you're talking about nuclear fission which is the one that we know how to do, again there are no fusion plants on earth yet, although we're getting there, the Sun is an example of one. You take a nuclear fission reactor and you break down stuff like uranium. The great thing is you don't produce a lot of carbon dioxide, you don't produce a lot of other harmful greenhouse gases and it is pretty good for the environment in that way.

The cons are you can produce a lot of radioactive waste. Personally, I actually think the amount of radioactive waste that you produce is pretty acceptable from modern plants compared to the kind of toxic stuff you put out from every other kind of energy production that we use. You've got to put something out. And the other con is that there is the possibility for, essentially, huge disasters. Like you may have heard of the Chernobyl reactor meltdown, there was Fukushima in Japan a few years ago, where the reactors essentially 'run away'. They generate so much energy and they create what’s called this chain reaction that runs away and you can’t control it,and they just keep putting out so much energy and they melt down.

Izzie - Looking at nuclear fusion though, are we close to getting anywhere near getting to dod that process?

Ben - Nuclear fusion is difficult because you essentially need to create conditions similar to the Sun which means you need very very high temperatures. You need to have things very very close to each other, very condensed, very high pressures. We have been able to make nuclear fusion reactions happen on earth, it’s just that we haven’t been able to do it in such a way that we’re getting out more energy than we’re putting in, and we’re able to keep them sustained for a really long time, which is what we would want to do if we were going to build a reactor, essentially build a small sun. If we could do it would be great because nuclear fusion will get around basically the two biggest problems associated with nuclear fission, whilst also still producing no CO2.

The first one being that there’s no toxic waste or a very very small amount of waste produced. The main byproduct from a nuclear fusion reactor is helium, which is really inert, it’s not going to do anything to the environment and in fact, we actually need it to do other science. It’s a thing that we need and that we’re actually running out of. So if we could make a bunch of it as a byproduct of creating energy, that would be kind of cool. The other thing is it’s very very hard for a fusion reactor to melt down so we can reduce the danger there as well.

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