A special case of nuclear materials transport is that of irradiated fuel, that is, nuclear fuel that has been used in nuclear power plants to produce power.

From the point of view of transport regulations, irradiated fuel is treated as any other radioactive material to which the general requirements of those regulations apply (labelling and marking, documentation, radiological protection, etc.) as well as those specific to nuclear materials.

Irradiated fuel is one of the materials with the highest risk within the transport activity since it combines properties of high radioactivity level, heat emission and fissionable nature. For this, the packaging used for its transport is of complex design since it must comply with very rigorous technical requirements that reduce radiation risks, high temperature and criticality as far as possible. For example, during transport, this type of package  includes elements called impact limiters, designed to absorb the energy from a serious accident, as well as elements that passively favour the removal of heat and materials that reduce the criticality risk.

The design of the casks used for its transport also requires an approval certificate from the relevant authorities. This approval is based on a document, the Safety Study, which includes analyses that show, for the approved content, compliance with all the safety requirements that guarantee safe transport without risks to the public, the workers or the environment.