Fission is the splitting of atoms into smaller parts. This process gives off energy in the form of heat.

One form of uranium is U235, which readily reacts with neutrons and splits into two new atoms. As the uranium atoms split, they cause a chain reaction by giving off other neutrons that in turn strike other U235 atoms.

Nuclear power plants use enriched U235 for fuel. The heat released during the fission process is used to boil water to make steam. The steam turns a turbine connected to a generator that spins to create electricity.

Plant operators control the nuclear reaction using rods that can be inserted between fuel assemblies in the reactor. These control rods absorb neutrons to prevent them from splitting other uranium atoms, thus stopping the chain reaction. By withdrawing or inserting control rods, plant operators can speed up or slow down the nuclear reaction. Fully inserting all the control rods at once can shut down the plant in seconds.

 

Nuclear fission

Fission is the splitting of atoms into smaller parts. This process gives off energy in the form of heat.

Control rod

These rods are inserted between the fuel assemblies to control or stop the nuclear reaction.