Table of Contents
Fuel
It probably goes without saying, it is impossible to have a nuclear reactor without fuel. But what is fuel?
Fuel is exactly what it says on the tin – it is a source of energy, and a nuclear reactor is no different.
Nuclear Fuel is the substance within the reactor that contains fissile nuclei – i.e. nuclei that can undergo fission and sustain a chain reaction. When nuclei within the fuel undergo fission, they produce thermal energy (amongst other things) – this heat is used to heat the primary coolant and eventually generate electricity.
What is inside nuclear fuel?
The exact composition of nuclear fuel depends on the reactor technology, but most common is uranium.
For uranium (U), it is the 235U isotope that is fissile. Typically, this comprises up to 5% of the uranium content, with the remainder being heavier 238U. This is a greater percentage of 235U than is naturally occurring, so must be enriched – check out our Nuclear Fuel Cycle pages to find out more about this.
Uranium Dioxide
Uranium Dioxide
At this point, it is important to note that not all nuclear fuel is uranium or uranium oxide. Alternatives include isotopes of thorium (Th) and plutonium (Pu), but these are much less common. It is also possible to use Mixed Oxide, or MOx, fuel – this contains a combination of different oxides of uranium and plutonium, often recycled from reprocessed spent fuel.
How is nuclear fuel made into fuel rods?
Forming
Step 1: Forming
Sintering
Step 2: Sintering
Assembly
Step 3: Assembly
The cladding around the fuel rod is really important. It captures highly radioactive fission products! It is important that the material used to form the cladding is relatively transparent to neutrons – to mitigate degradation.
What about more novel reactor designs?
Often, more novel reactor designs also use more novel fuels…
Fertile Fuels
Advanced Fuels
Adam Piatt
What is Nuclear Energy? The Science of Nuclear Power, IAEA
Nuclear Fuel Cycle Overview, World Nuclear Association
How is uranium made into nuclear fuel?, World Nuclear Association
Nuclear Fuel and its Fabrication, World Nuclear Association
Mixed Oxide (MOx) Fuel, World Nuclear Association
Thorium, World Nuclear Association
Nuclear Fuel, Nuclear-Power.com
Indian test reactor reaches operation landmark, World Nuclear News
UO2 Powder, Chemolunatic – Licence CC BY-SA 4.0 DEED
Nuclear Fuel Pellets, US DOE – Public Domain
Magnox fuel cans from Sizewell-A Nuclear Power Station, 1968, Science Museum Group – Licence CC BY 4.0 DEED
Advanced Gas-cooled Reactor (AGR) fuel pin, about 1958-1982, Science Museum Group – Licence CC BY 4.0 DEED
Fast-Breeder Test Reactor at the Kalpakkam, Petr Pavlicek / IAEA – Licence CC BY-SA 2.0 DEED
Cross-section of a fuel pellet containing TRISO particles, US DOE – Licence Public Domain
