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Fuel

Koeberg Experience

Fuel

Splitting the Atom

Nuclear power provides electricity through the process of splitting a nucleus of a uranium or plutonium atom which then creates heat. This process is known as fission

 

                                     An Atom

Everything is made up of atoms. Atoms are made up of a cloud of electrons which have a negative electrical charge and a nucleus in the centre of the electrons. The nucleus is made up of protons with a positive electrical charge and neutrons which have no charge.

Chain Reaction

Uranium is one of the heaviest atoms. Uranium always have 92 protons but the number of neutrons can vary. Therefore U-238 will have 92 protons and 146 neutrons while U-235 has 92 protons and 143 neutrons. Number of electrons is always equal to the number of protons.

                 Schematic diagram of a chain-reaction

Inside the fuel a chain reaction has to happen. A chain reaction is caused when a loose neutron hits a U235-atoms and causes it to split. The splitting process gives off smaller atoms, more loose neutrons and heat. If the loose neutrons hit more U-235 then a chain reaction is set up.

Fuel Element

In Koeberg's case the Uranium level is enriched. In other words a certain amount of extra U-235 is found in the Fuel inside the reactors at Koeberg. The level of U235 is 4% which is just enough to maintain the chain reaction which gives off the heat that is used to heat up the steam generator tubes.


 

The enriched uranium is manufactured into fuel pellets which are placed inside the zirconium alloy tubes. These tubes are placed together into what is known as a fuel element.

Fuel Pool

There are 157 fuel elements in the reactor. One third of the fuel is replaced every 16.5 months. This spent fuel is stored on site in the fuel building in what is known as the fuel pool.

                                                                                                                     

                                The fuel pool at Koeberg