What is nuclear energy and how does it work?

People are curious about nuclear energy but don't fully understand how it works. (ABC: Graphic by Sharon Gordon)

In June, the Coalition released the locations and timelines of proposed nuclear power plant sites, as part of its telegraphed stance on moving Australia towards nuclear as an energy source.

The debate quickly moved to costings, gigawatts and energy grids. But if this is all new to you, it can be hard to find a reputable source for the most basic of facts. We break down a couple of your most commonly asked questions on nuclear energy, with the help of three experts.

What is nuclear energy?

In a nutshell, nuclear power plants create electricity by producing steam that's used to power a turbine.

"This is the same process that's used in a coal-fired power station, and the process of spinning a turbine is exactly the same as when you look at a wind turbine," said Bjorn Sturmberg, a senior research fellow at Australian National University.

"If you think of a mouse on a cartoon hamster wheel, you're just spinning something, and that gives you electricity."

While the process of using steam to spin turbines is the same as coal- or gas-fired power station, the heat source is different, said Edward Obbard, director of the University of New South Wales's Nuclear Innovation Centre.

"The heat to drive a nuclear power station comes from breaking up uranium atoms in the core of the reactor … then that hot nuclear fuel is used to boil water, like in a giant kettle," he said.

Uranium is a super-dense substance, and Dr Sturmberg said that makes it easy to split apart.

"That large atom is like a really blown-up balloon, you only need to give it a really little prick to burst that balloon into smaller pieces."

The process of breaking apart atoms to create energy is called nuclear fission. It's different from nuclear fusion, which is when two smaller atoms are smashed together to create a bigger atom.

"This is what happens in the sun, and in all other stars, and is what how they produce light. Humans have tried to harness the process [of nuclear fusion] … to create electricity. But so far, we've not had success," Dr Sturmberg said.

How many countries use nuclear energy?

There are 32 countries with operational nuclear reactors, with another 30 countries considering or starting their industries.

The World Nuclear Association found nuclear energy accounted for about 10 per cent of the global energy mix, but as international nuclear energy lawyer Helen Cook said, some countries rely on nuclear more heavily.

"France today generates about 70 per cent of its electricity from nuclear, and historically produced even more, up to about 85 per cent," said Ms Cook, who is also a board member of tech company Silex.

"The United States has the world's largest fleet, with 94 operating reactors."

What's a small modular reactor?

Edward Obbard acknowledged there's a lot of confusion around small-scale and large-scale reactors.

"The whole small modular reactor [SMR] thing has been talked up until we almost think that there are different kinds of technology. They're not; they're just small," he said.

According to the International Atomic Energy Agency, a SMR has a power capacity of 300 megawatts, which is about a third of a traditional-capacity reactor.

Unlike larger plants, which need a lot of water to cool, SMRs are small enough to cool themselves.

The idea with SMRs is that their size means they're faster and more cost-effective to build, Dr Obbard said.

"They're a kind of business model more than a new technology."

The drawback is that they don't actually create a whole lot of energy, Dr Obbard said.

The Clean Energy Finance Corporation announced the funding of one of the biggest batteries in the world, to be built in Victoria, which will store 300 megawatts of energy.

It'll cost $160 million, a fraction of the cost of building a new nuclear power station.

Why is nuclear energy so expensive?

Most of the cost of nuclear energy comes from building a plant in the first place.

Dr Obbard said much of that cost is associated with safety measures around cooling down a reactor or stopping operations in an emergency.

"That makes the whole power station huge and expensive, because you need all these safety systems and backup generators and emergency water supplies," he said.

"Nuclear is just so much more expensive to build up front, and then does have ongoing costs in terms of it's a really high tech, really high risk kind of facility to operate," Dr Sturmberg said.

"And you still need a fuel source of enriched uranium to power, and then you've got to deal with the waste," he added.

In a recent report, national science agency the CSIRO, estimated nuclear power to be at least 50 per cent more expensive than wind and solar power backed by batteries, and estimated it would cost at least $8.5 billion to build one large-scale reactor.

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However, reactors can have a long lifespan. The average age of operational reactors in the US is 42 years, with the oldest clocking in at 55 years.

By comparison, wind turbines last between 20 and 30 years.

How much waste does nuclear power produce?

In short, not much.

"If you were to use nuclear energy for your entire life, so one person for his or her entire life, the high-level waste generated would fit inside a can of Coke," Helen Cook said.

She added that much of the waste can be reused in future nuclear projects.

According to the World Nuclear Association, about 90 per cent of low-level waste with very small amounts of radiation, can be reused. Around three per cent of high-level waste with big amounts of radiation can be reused.

Associate professor Edward Obbard acknowledged that radioactive waste was "very hazardous", but that the "hazard is controlled through engineering to be safe".

"You still have to worry about it because you create that stuff, and so you have to make sure that there are people and organisations and expertise around to look after it."

Bjorn Sturmberg said it was important to remember that radioactive waste is dangerous to humans and animals, and remains so for a very long time.

"The critical thing about these radioactive materials is that they're going to stay radioactive for thousands of years. And humans have never really undertaken the task of managing such dangerous material over thousands of years," he said.

Is nuclear power a 'green' technology?

While the process is the same in a nuclear reactor and a coal-fired power plant (creating steam from heating water), the outcome is quite different.

Creating nuclear energy produces zero emissions.

"Coal-fired power plants emit harmful carbon dioxide and other harmful substances into the air while they are producing electricity. Whereas … nuclear energy and its operating phase produces none of that harmful stuff," lawyer  Helen Cook said.

Nuclear power creates as many emissions as wind turbines, and fewer than solar panels.

Both coal and nuclear require digging up natural substances but the quantities required differ significantly.

A research paper by the New South Wales Parliamentary Library Service found the energy released by 1 kilogram of uranium was the same as burning 22,000 kilograms of coal.

But then there's the question of water.

Dr Obbard said nuclear and coal power plants used roughly the same amount of water.

"Coal uses a hell of a lot of water to dig up the coal as well. If we switch our coal to nuclear power stations, we'll use a lot less water," he said.

Research by Stanford University found American nuclear reactors used about 480,000 Olympic pools' worth of water in 2015 alone.

The paper concluded nuclear power used much more water than solar, a point Bjorn Sturmberg is keen to make too.

"Renewables don't do any heating of water, and therefore they don't need a reservoir of water, they don't consume lots of water," he said.