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Nuclear energy: how does it work, and how renewable is it?

By Stephen Marcus Tuesday 02 February 2021

As we look for ways to reduce our carbon, nuclear power is often raised as one potential solution. After all, it’s a reliable source of low-carbon energy – which is just what we’re looking for, right?! So why are there questions around nuclear power’s green credentials?

Well, we’re sorry to say that nuclear waste poses a threat to the environment – and investing in nuclear power plants comes with a cost. In this guide, we’ll weigh up both sides of the argument, tell you all you need to know about nuclear, and explain the environmental impacts.

What is nuclear energy? 

Nuclear power is created through a process called nuclear fission. It all starts with uranium – a silvery-grey metal refined from rocks or ore, and dug out of mines around the world.

Nuclear fission harnesses the energy inside refined uranium by splitting its tiny, microscopic atoms. To get a sense of the incredible power inside a uranium atom, let’s compare it to coal, one of our traditional, carbon-heavy sources of energy:

  • 1kg of coal will create 8 kWh of power

  • 1 kg of uranium will create 24,000,000 kWh of power!

Yes, that’s 2 to 3 million times more energy! All from something the weight of a bag of sugar.

How does nuclear power work? 

First, let’s go back to basics: so what exactly is an atom? They’re the tiny particles that make up every object in the universe – including uranium, the substance used to generate nuclear power. 

So what’s uranium? Named after our smallest planet in the solar system, uranium is a metallic substance drawn from raw deposits of a rock called uraninite. After refinement, we get pure uranium – a chemical with some pretty powerful abilities to generate energy.

Nuclear fission then breaks down its tiny particles, to release the energy inside.

How does nuclear energy make electricity?

When it comes to nuclear power plants, in some ways they work just like traditional power stations:

  • A traditional plant burns coal, oil or natural gas, using them to boil water into steam. The steam turns turbines, which drive a generator and make electricity.

  • Nuclear power plants follow the same process, but they don’t burn anything. Instead, they use nuclear fission to split uranium atoms inside a nuclear reactor. The energy released by this reaction heats the water, which creates steam – and then, well, you get the idea.

  • The big difference is the nuclear reactor, where the splitting of uranium atoms happens.

  • Here, rods of uranium, arranged in bundles, are put into a giant water tank inside the reactor. When the reactor is running, high-speed particles – known as neutrons – hit the uranium atoms and split them. This releases lots of energy, as well as even more neutrons, which split other uranium atoms, triggering a chain reaction, and releasing yet more energy!

Is nuclear energy renewable?

Nuclear energy is definitely not renewable. That’s because it’s generated using a substance that will one day run out. On the other hand, compared to fossil fuels, it’s far less damaging to the environment. But there are a few other things to think about:

  • As we said, nuclear’s not renewable – because uranium is a limited resource, unlike solar or wind energy. The fact remains, in spite of the estimate that it’s not likely to run out anytime soon (there are likely enough reserves to run the world’s reactors for 200 more years).

  • It’s not technically renewable – but nuclear power has a much smaller carbon footprint than carbon-heavy fossil fuels.

  • Nuclear may not produce carbon when electricity is actually being generated – but it’s definitely released when nuclear power stations are being built, or while they’re processing or transporting fuel.

To learn more about renewable energy, and the other ways we can combat climate change, check out some of our other guides:

Disadvantages of nuclear energy

While it’s low-carbon, and wonderful at generating lots of energy, there are some major downsides to nuclear energy. These include:

  • The upfront cost of building nuclear power plants. This is a serious investment, and critics say it’s just not worth it, considering how nuclear relies on a substance that will run out one day.

  • It makes us reliant on a handful of big power plants – unlike renewable energy, which is cheaper to build, and which we can grow by building lots of smaller energy sources.

  • The risk of accidents releasing radioactive substances into the environment. Accidents are uncommon – but, for some, it’s still too risky. Lots of ordinary things give off radiation, but nuclear radiation can be highly dangerous – it’s a risk to human health, and can change the way cells in the body behave.

  • The issue of nuclear waste – which comes from the processing of uranium and, ultimately, the demolition of nuclear power plant facilities.

Environmental impact of nuclear waste 

To understand the potential impact of nuclear waste on the environment, let’s look at the 3 main types, and their risk-factors:

  • Low-level nuclear waste – this comes from places like hospitals, universities and research centres. In fact, it’s made wherever radioactive materials are used for x-rays and sterilising equipment, as well as in the nuclear industry. It isn’t considered high-risk. 

  • Intermediate-level nuclear waste – above the upper limit of radioactivity for low-level waste, one example is the insulation and cladding used in nuclear facilities. It’s usually buried in shallow trenches in the area around a nuclear facility.

  • High-level nuclear waste – this means a wide range of radioactive and unstable compounds. This type of nuclear waste – such as liquid waste from the process of reprocessing spent fuel – can give off radiation for thousands of years. As you’d expect, this type poses the greatest risk, so it needs to be disposed of very carefully. In the UK, this usually happens in a Geological Disposal Facility, where waste is buried deep underground.

Nuclear power in the UK

How many nuclear power plants are there in the UK?

The UK built its first nuclear reactor in 1956. Since then, the number of plants and reactors has grown over time – though many have since been retired1

The UK has 7 nuclear power plants with 15 reactors2. The 7 plants are:

1. Torness, Scotland

  • Built: 1988

  • Reactors: 2

  • Capacity: 1,190 megawatts

2. Hunterston B, Scotland 

  • Built: 1976

  • Reactors: 2

  • Capacity: 967 megawatts

3. Hartlepool, England 

  • Built: 1989

  • Reactors: 2

  • Capacity: 1,180 megawatts

4. Heysham 1

  • Built: 1989

  • Reactors: 2

  • Capacity: 1,155 megawatts

5. Heysham 2 

  • Built: 1989

  • Reactors: 2

  • Capacity: 1,230 megawatts

6. Hinkley Point B 

  • Built: 1976

  • Reactors: 2

  • Capacity: 955 megawatts

7. Dungeness B 

  • Built: 1985

  • Reactors: 2

  • Capacity: 1,050 megawatts

How much electricity in the UK is generated with nuclear energy?

In the UK, nuclear power is used to generate a decent chunk of the electricity we use. Here are some of the key things you need to know:

  • 16.6% of the UK's energy came from nuclear power plants in the 12 months to March 20203

  • Half of the plants currently in operation are due for retirement by 2025 – but with the UK government continuing to explore future investment in nuclear power plants, it’s likely to be part of the way we generate energy for some time

As we’ve seen, nuclear has both advantages and disadvantages! On the one hand, there’s the low carbon emissions, and huge possibilities for generating energy – while on the other, there’s the high level of investment needed, and some potentially pretty serious impacts on the environment.

Does OVO use nuclear power in its fuel mix?

No. At OVO Energy, all of our electricity comes from renewable sources4. Discover exactly where our energy comes from.

Want an energy supplier that takes their green credentials seriously? At OVO we offer 100% renewable electricity as standard5, and plant a tree for every year that you’re with us. And we have competitive prices, too. Get a quote in 2 minutes, to see how much you could save.


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Sources and references:

The renewable electricity we sell is backed by renewable certificates (Renewable Energy Guarantee of Origin certificates (REGOs)). See here for details on REGO certificates and how these work.

The renewable electricity we sell is backed by renewable certificates (Renewable Energy Guarantee of Origin certificates (REGOs)). See here for details on REGO certificates and how these work.