A: Nuclear fuel
cycle materials come in a variety of chemical and physical forms
and the potential hazards they present differ widely. The
underlying philosophy of the IAEA Transport Regulations is that
safety is ensured principally by the package, and its design is
related to the potential hazard - the more hazardous the material
the tougher the package.
Uranium ore concentrate
Uranium ore concentrate is a material of low radioactivity. There
is a minor risk due to the toxicity of the powder if it is released
and is ingested. In this respect it is no different from most heavy
metal compounds such as lead ores.
Uranium hexafluoride (Hex)
Uranium hexafluoride is also of low activity and the
radiological risk is not great. However, there would be a chemical
hazard in the unlikely event of a release because it produces toxic
by-products on reaction with moist air.
Uranium dioxide powder
Uranium dioxide powder for the manufacture of new uranium fuel
elements is also classified as low activity material.
Uranium fuel assemblies
The fuel for the majority of nuclear reactors consists of
assemblies of rods each filled with ceramic uranium oxide pellets
enriched in the fissile component of uranium, U-235, to about
Spent fuel and vitrified high-level
Spent fuel and vitrified high-level waste are intensely
radioactive and need to be heavily shielded. However they are
inherently stable and, being a ceramic material, are very difficult
to disperse. The solid nature of the products is one of the most
important safety factors. The material is characterised by
long-term stability and low solubility in water.
Mixed oxide fuel (MOX)
Mixed plutonium/uranium oxide (MOX) fuel elements, in which the
enriched uranium isotope is replaced by plutonium, are very similar
to uranium fuel elements and also ceramic in nature. The chemical
hazard is negligible and the radiological hazard is low except in
the event of a criticality excursion. This is controlled in the
same way as for enriched uranium fuel i.e. by the design of the
package and the configuration of the package during transport.
The primary risk is due to toxicity except in the event of
criticality which is controlled by the package design.