Inside A Reactor:

While fission may be the process that nuclear reactors run off of there are a lot of components to the reactor itself that help it maintain a fission reaction and generate electricity.

Fuel Rods:

Most nuclear reactors run on a fuel source of uranium, a metal which is primarily produced in countries like Canada, Kazakhstan, and Australia². The uranium is processed into pellets of uranium dioxide which is then placed in fuel rods which separate the uranium from the reactor coolant. Fuel cells are then arranged into fuel assemblies, like the one shown below, of which there can be hundreds inside a single reactor.

Neutron Moderators And Control Rods:

Nuclear fission often leads to the release of "fast neutrons". As the name implies fast neutrons travel at incredibly high speed, for a fission reaction around 20,000 km/s. Unfortunately, high speed neutrons are not ideal for further fission events. To fix this, neutron moderators are used.

A neutron moderator is a material which slows down neutrons within the reactor to speeds which allow for the propagation of a nuclear chain reaction. Some of the common moderators are:

• Light water (H₂O)
• Heavy water (Deuterium)
• Graphite

Each of these moderators function effectively because they're made primarily of light elements which have the unique quality of being able to both slow down neutrons but also not absorb neutrons. Ideal qualities for a nuclear reaction to continue.

Another component in the nuclear reactor are control rods. They share a similar role to neutron moderators as they are used to absorb neutrons to prevent further fission reactions, and thus are used to control the speed of a nuclear reaction.

Coolant:

The coolant within a nuclear reactor is circulated through the reactor, often directly past the fuel cells, in order to collect heat from the reactor which can then be used to generate electricity elsewhere within the nuclear power plant. The most common type of coolant is simply water, which also functions as a moderator in these reactors, but other types of less frequently used coolants are:

• Heavy water
• Carbon Dioxide
• Liquid Sodium
• Helium

Electricity Generation:

All of the factors listed above serve to allow for electricity generation. Different types of reactors generate electricity in different ways, but the standard way involves water being heated and turned into steam, which can then be used to power a generator.