What is a nuclear power station?

Jack Unwin 14 May 2019 (Last Updated June 18th, 2020 13:42)

What is a nuclear power station, how does it create energy and what really are the benefits? Jack Unwin finds out.

What is a nuclear power station?
Three Mile Island nuclear plant will close in September 2019. Credit: Z22

As well as being the unwilling workplace of Homer Simpson, the nuclear power station is the breeding ground of civil nuclear power across the world. According to the World Nuclear Association nuclear power forms about 11% of the world’s electricity, with 450 reactors providing 424GW of power, making it the second largest source of low-carbon power in the world.

How does a nuclear power station work exactly? And what are the benefits and perils of nuclear power?

How nuclear energy is made

Nuclear plants are different to energy plants such as coal and natural gas, because despite being a thermal generation process they do not need to burn anything to create steam.

In a nuclear plant, uranium atoms are split in a process called fission, which requires low-enriched uranium fuel. Uranium fuel is formed into pellets, one of which can produce as much energy as one tonne of coal, three barrels of oil or 17,000 cubic feet of natural gas. These pellets are generally stacked into 12-foot metal fuel rods, which are grouped together in bundles that are called fuel assemblies.

Thanks to nuclear fission, heat and neutrons are released from uranium as the atoms split. The neutrons hit other uranium atoms causing them to split, continuing the cycle. Meanwhile, the released heat causes water within the reactor to boil, which in turn creates the steam that powers the turbines, which powers the generators to make electricity.

Types of nuclear reactors

There are two standard types of nuclear reactor, firstly boiling water reactors (BWR), which simply heat up water until it boils to spin turbines and generate electricity. Secondly, pressurised water reactors (PWR), which heat up water to close to boiling point before this water is pumped into a separate supply of water. In this compartment, it becomes steam that is used to powers a turbine.

Pros and cons of nuclear power

As nuclear power does not need to burn anything to create steam it does not emit greenhouse gases like methane or CO2. Once a nuclear plant is up and running, the electricity it produces is inexpensive due to the low cost of uranium. Unlike wind and solar, nuclear is a consistent, reliable source of energy, which can run uninterrupted for up to a year.

However, the initial cost of building a nuclear plant is steep. A recent versatile test reactor (VTR) project in Idaho is estimated to initially cost between $3.9 and $6bn and $550-850m every year for seven years. This is much more than the initial $3.5bn estimate given by Idaho National Laboratory head Kemal Pasamehmetoglu. While the running cost over seven years is itself more than the 2019 budget for the Department of Energy’s entire nuclear technology development program, which sits at $740m. A similar story is true around the world, with reactors often coming in over budget and delayed.

Nuclear plants, like all thermal generation, produce waste.  However unlike other waste streams as it is radioactive. But 97% of the waste produced is considered low- or intermediate-level waste, and as such is easily disposed of. The nuclear industry produces 34,000m³ of high-level waste globally a year, but counter to what many people believe, it does not take forever to degrade. It is generally stored in interim storage facilities, where within just forty years its radioactivity levels decrease to one-thousandth of the level.

Finally, the potential for disasters such as Chernobyl and Fukushima is a constant concern when considering nuclear power. Both had devastating effects upon their environments and the communities close by. However it is important to remember that together with Three Mile Island, they are the only major incidents in over 17,000 cumulative reactor-years of commercial nuclear power operation in 33 countries.