Cape Town’s dependence on Eskom’s Koeberg Nuclear Power Station was brought into sharp relief when damage caused by a bolt to the Unit 1 generator, coupled with faulty power lines to the north, left much of the Western Cape in the dark.

What became very clear was that Koeberg plays an integral part in our lives. Less clear to many is how the power station actually works.

Those who live along the West Coast road probably take its stolid outline for granted. Many others have never even seen the structure. Yet hundreds of thousands of people every day rely on its electricity-generating capacity to live, work and play.

The Koeberg Nuclear Power Station is situated at Duynefontein, 27km north of Cape Town. It is just off the road that stretches out from the city centre past Milnerton, Table View, Melkbosstrand and Atlantis. The power plant borders the Atlantic Coast.

Koeberg started operating in 1984. It is the only commercial nuclear power station in Africa. Its two reactors supply 1 840MW or 6.5% of South Africa’s electricity needs.

The only purpose of a nuclear power plant such as Koeberg is to produce electricity. To do this, the power plant needs a source of heat to boil water that then becomes steam. The steam turns a turbine, the turbine turns an electrical generator and the generator produces electricity. In the case of fossil-fuel energy plants, the heat comes from burning coal, oil, or gas. In a nuclear plant the heat comes from the splitting of atoms of uranium — a process known as fission.

The reactor uses uranium rods as fuel. When a source of neutrons is introduced, these “collide” with uranium atoms in the rods. The uranium atoms are split roughly in half and release energy in the form of heat — the fission process. This heats water, which generates steam, which drives the turbines that drive the generator.

The reactor is controlled with control rods made of boron, which absorb neutrons. When the rods are lowered into the reactor, they absorb more neutrons and the fission process slows down. To generate more power, the rods are raised and more neutrons can collide with uranium atoms.

Some nuclear plants use carbon dioxide to cool the reactor, heat water and make steam. Because of Koeberg’s proximity to the sea, water is used instead, in three separate processes.

Recent damage to the Unit 1 generator has left only Unit 2 functioning. A replacement part — an extremely rare rotor — has been fetched from France, and the damaged Unit 1 generator should be up and running by mid-May.

Koeberg has operated safely for more than 20 years and has recently undergone a successful peer review by the World Association of Nuclear Operations. The power station is intended to have a further active life of 30 to 40 years, after which time it will be decommissioned in line with stringent requirements set by the National Nuclear Regulator.