For many people, the term ‘nuclear energy’ is associated with negative events and feelings. However, it is important to be informed about any topic before developing your own conclusions.
What is nuclear energy?
The term ‘nuclear energy’ describes exactly what it is – energy from the nucleus of an atom. The bonds that hold atoms together are extremely powerful, and we can use this power in two ways – nuclear fission and nuclear fusion.
Nuclear fission is the process commonly referred to as splitting the atom, a process first achieved by New Zealander Ernest Rutherford at Manchester, UK, in 1918 when he fired naturally occurring alpha particles into nitrogen gas.
The fission that nuclear power plants use to make electricity involves using neutrons (which were first predicted to exist by Rutherford) to split a large atom into two smaller atoms – a process that releases a large amount of energy.
Nuclear fusion is the opposite reaction where two smaller atoms are combined to make one larger atom of a different element. Fusion is how the Sun produces the solar radiation energy that heats our planet.
How is nuclear energy used to make electricity?
A nuclear power plant shares many similarities with conventional fossil fuel based power plants such as the Huntly power station. Both types of plants use energy to heat water to form steam, which then drives turbines to produce electricity.
The major difference is the source of that energy. Nuclear plants use fuel called uranium. Uranium is a naturally occurring radioactive element. It is considered a non-renewable resource but, due to its commonality (it is more common than silver) and the small amount needed to generate electricity, there is little concern about us running out of uranium any time soon.
Uranium in nature is made up of three isotopes 238U, 235U and 234U. It is 235U that is used for nuclear fission in power plants because it is the easiest to split.
During nuclear fission, a neutron collides with a 235U atom causing the atom to split into smaller atoms while releasing heat, radiation and more neutrons. These neutrons continue to hit other 235U atoms so that fission continues to occur. This is called a chain reaction. The chain reaction occurs inside a controlled environment – in the reactor core.
The heat released from the reaction is used to heat water into steam, which in turn is used to generate electricity.
All electricity generating technologies have their pros and cons.
Nuclear power emits very few pollutants into the atmosphere, especially when compared to coal burning plants. In addition, nuclear plants use less land than conventional plants and are less destructive on the land when mining uranium ore. It is for these reasons that nuclear energy is often called a clean energy.
However, it does generate waste in the form of fuel and coolants, which are highly radioactive and dangerous. The storage of these waste products is an ongoing problem, as they remain radioactive for long periods of time (some in excess of 1,000 years). Initially, the most radioactive waste is stored in a containment unit much like a pool so that the water can cool the waste.
It is then moved to a dry storage for another 1,000 years. The dry storage is usually a purpose-built underground facility.
There are some sites overseas in which contamination has occurred – these have primarily been old facilities that have been improperly managed and have been closed down. Plans are in place to clean them up to prevent future harm. There is now greater awareness of the dangers associated with nuclear waste, which ultimately means better handling, storage and overall better management.
There are no nuclear power plants in New Zealand.
Are nuclear power plants safe?
While a nuclear power plant cannot explode like a nuclear bomb (because the fission reaction is controlled), accidents do happen. These accidents have lead to many people feeling that the power plants are unsafe and a high risk.
The most infamous accident occurred in Ukraine in 1986 at a place called Chernobyl, and to this day, the town remains abandoned, and scientists are continuing to determine just how many people have been affected by the long-term effects of being exposed to radiation.
Find out more about Ernest Rutherford.
This RNZ article and audio looks at What's the deal with nuclear power in Aotearoa – the pros and the cons, it includes an interivew with Dr David Krofcheck.
Find out more about uranium fission in this example of uranium splitting to barium and krypton.
The World Nuclear Association website has information on the Chernobyl disaster.