Nuclear Fuel

Nuclear Fuel

Most nuclear power reactors use Uranium-235 or plutonium-239 as its fuel for generating electricity. When the atomic nuclei of these fuels are struck by neutrons, they can split into smaller nuclei, releasing sizable amounts of energy in the process. Another very important product of this splitting process is the simultaneous release of two or more other neutrons, which can go on to split more fuel nuclei. This becomes a self-perpetuating "chain reaction". This chain reaction perpetuates the desired energy release, and, when properly moderated and controlled, the process can proceed virtually indefinitely, until the original fuel is consumed and diluted to the point where the chain reaction is no longer self-sustaining.

Nuclear Fuel Cycle

(click image to enlarge)

The nuclear fuel cycle consists of the sequence of steps that constitute the process of obtaining nuclear fuel, using it to generate electricity, and safely disposing of whatever nuclear waste remains after the fuel is fully used.


The first step in the nuclear fuel cycle consists of exploration for uranium and mining of the uranium ore. Currently, mining is usually conducted in the U.S. using a process called in-situ-leach (ISL) or in-situ-recovery (ISR). This process involves dissolving the uranium in specially prepared, slightly caustic groundwater, which is then pumped out of the mine and processed at a uranium mill.


The next sequence of steps - milling, conversion, enrichment, and fuel fabrication - constitute preparation of the mined uranium for use in a nuclear reactor. The process converts the mined uranium into fuel rods, which are then combined into assemblies that are used in the reactor. Once the assemblies have been inserted into the reactor core, water is added and the chain reaction begins that produces fission of the uranium, releasing heat that can be used to drive turbines that generate electricity.


After the uranium rod assemblies have been in use for several months, usually 12 to 24, they become hot and highly radioactive and are removed from the reactor and stored in a spent fuel pool for several years, until they have cooled and the radioactivity has diminished. At that point the assemblies are removed from the pool and permanently stored in a dry cask storage chamber at the power plant site.

Sources for Uranium

The U.S. imports almost all the uranium that it uses in its nuclear reactors. In 2017 about 7% of the uranium used in the U.S. came from U.S. mines. The following list shows the 5 most important sources for uranium imports to the U.S.:

  • Canada–35%
  • Australia–20%
  • Russia–18%
  • Kazakhstan–12%
  • Uzbekistan–5%