Simplifying containers4 March 2011
Recent European regulations dictate how to transport different kinds of radioactive materials. Using fewer types of containers in greater quantities provides an opportunity to harmonize their design. By Niko Jezernik
Currently there are 31 countries with nuclear power plants; another 15 are planning to introduce nuclear power. Even countries with large-scale nuclear power industries cannot provide all the necessary fuel cycle services themselves, so transport of radioactive material often occurs across international borders. In Europe, this transport is regulated by domestic regulations and IAEA-ADR (European Agreement Concerning the International Carriage of Dangerous Goods by Road).
To provide a high degree of safety during transportation, packaging must provide protection for workers, public and the environment. This protection must be achieved under normal conditions of transport for weakly-radioactive materials and under accident conditions for highly radioactive materials. The current version of the regulations, TS-R-1: 2009, provides five different grades of package transport: excepted, industrial, type A, type B,
and type C. Each of these package grades must endure increasingly severe test conditions. The quantity and type of radioactive material that can be transported in a particular package depends on the package grade.
Excepted packages contain such low levels of radioactive material that they pose no significant hazards and no testing of containment or shielding is required. These are usually limited to radio-pharmaceuticals for medical purposes.
Industrial packages are used for transport of LSA (low specific activity) material that has little radioactive activity per unit mass, and for transport of SCO (surface contaminated objects) that are not themselves radioactive. Materials transported in industrial packages range from fuel cycle machinery, parts of nuclear reactors and piping that have been contaminated by coolant or process water as well as some low- and intermediate-level radioactive waste. Three levels of packages exist with increasing safety requirements (see table).
Type A packages contain a significant but limited quantity (as IAEA-ADR regulations) of radioactive material. These packages must conform to additional design and testing requirements (seals, tie-downs, temperature, containment, pressure, valves). For packages of type A and above, there are additional material requirements; all structurally-significant parts must have sufficient impact strength at temperatures down to -40°C, and the material must be traceable back to the steel producer. Type A packages are used for some fuel cycle materials.
Type B packages are required for the transport of highly radioactive material. These packages must withstand normal transport conditions and must have additional resistance to release of radiation and radioactive material in case of expected accident conditions (impact/crush, penetration, water immersion).
Type C packages are even more robustly designed and intended for transport of highly radioactive material by air. They are required to withstand puncture/tearing, higher temperatures for longer periods, and higher impact velocities that may occur in severe aircraft accidents. Test requirements for type C packages are more severe than test requirements for flight data recorders. This grade of package has not yet been developed; it may never be developed for large packages.
Transportation in freight containers
Every year, there are about 20 million consignments containing radioactive materials worldwide. These are transported on public roads, railways, sea and air using standard ISO inter-modal containers. Using ISO containers eases logistics and significantly reduces transportation costs by making one package or container available to most forms of transport. Since standard freight containers do not provide the adequate protection required for transport of radioactive materials (excluding ‘excepted’ packages), special containers need to be used.
Special freight containers of grades IP-1, 2, 3 and type A are identical to standard freight containers in shape and handling function, but have some additional properties that provide required protection for radioactive cargo. Type B containers are cylindrical in design and cannot be handled as standard freight containers; they require special devices for transport. Often they are transported within special freight containers (usually Type A) as a form of over-packing.
The vast majority of shipments of radioactive materials are performed using IP-2 and type A containers; IP-1 containers provide too low a level of protection for most applications, and IP-3 containers can be easily be substituted with type A containers.
Using fewer types of containers in higher quantities provides an opportunity to harmonize the design and reduce the need for per-project development of such special containers. In the past few years, containers that conform to these two grades of packaging have been systematized, enabling the use of a catalogue to specify an appropriate container. This way customers can choose among a number of features that define the size of container, such as gross mass, protection level, possibility of air transport, required fixing points for cargo fastening etc. This systematization was implemented in order to drive down costs and shorten delivery times of custom-made special containers.
Niko Jezernik, researcher and constructor, Container d.o.o; [email protected], Bežigrajska cesta 6, SI-3000 Celje, SloveniaTablesTesting requirements by container type (after IAEA-ADR)