Front end materials come in a variety of chemical and physical forms and the potential hazards they present differ widely. Because safety depends primarily on the package, the IAEA Regulations set out several performance standards in this area. They provide for five different primary packages and set criteria for the design according to both the activity and physical form of the radioactive material they may contain.
Uranium ore concentrate is a low specific activity material and the radiological hazard is very low. It is normally transported in sealed 200 litre drums (an Industrial Package) in standard sea (ISO) freight containers. These can be transported by road, rail or sea, and in many cases a combination of modes of transport is used.
Packages for uranium ore concentrate are required to maintain their integrity during normal transport conditions and are designed to withstand a series of tests simulating these conditions; for example, a water spray, a free drop, a stacking test and a puncture test to reproduce the kind of treatment packages may be subjected to during normal transport.
The uranium ore concentrate is transported to conversion plants for manufacture into Hex. Hex is different in so far as it is a solid which can give off a toxic vapour. In the production process, large cylindrical steel transport cylinders some 48 inches in diameter, each holding up to 12.5 tonnes of materials are filled directly with Hex which can be liquid or gaseous depending on the manufacturing process. The Hex then solidifies inside the cylinder on cooling to room temperature. In storage and during transport the Hex material inside the cylinders is in a solid form. Natural Hex is also stored in these cylinders prior to being transported to an enrichment plant.
The steel cylinders used as packages for natural and depleted Hex are internationally standardised and are subjected to a pressure test which they must withstand without leakage and unacceptable stress. In addition, they have to be evaluated against a thermal test requirement. 
Enriched Hex is transported in smaller universal cylinders. These cylinders are some 30 inches in diameter and are loaded in overpacks to guard against a criticality excursion, i.e. an unwanted chain reaction. The loaded overpacks are generally transported using ISO flat rack containers for transport to fuel fabrication plants.
Enriched front end materials, i.e. enriched Hex, uranium dioxide powder, and new fuel assemblies are fissile which means they can sustain a nuclear chain reaction. The potential hazard associated with these materials is an unwanted nuclear chain reaction. For this reason the packages are subjected to tests to guarantee that this could not occur under accident conditions which could be realistically envisaged in transport, including crashes, fires and submergence.
The IAEA Regulations for the Safe Transport of Radioactive Materials have provided a sound basis for the design of equipment and procedures for the safe and efficient transport of nuclear fuel cycle materials. On this foundation the nuclear transport industry, both those organisations solely dedicated to nuclear transport, as well as the many transport companies for which nuclear transport is only a part of their business, have operated safely and successfully for over 45 years.
