DESIGN LOADING FACTORS IN ROAD TRANSPORT OF VERY HEAVY PACKAGES

The vast majority of shipments of radioactive material in Europe are small in bulk and mass, representing medical isotopes, laboratory instruments or industrial radiography sources. These are generally carried in packages of mass only a few kilogrammes, and certainly less than a few tonnes. Conveyances used will generally be road vehicles of appropriate size, such as light and medium vans, or light trucks. It is evident that the payloads in these vehicles are usually small in proportion to the vehicle mass, and of necessity the vehicles are loaded within their certified limits such that they continue to comply with all relevant Construction and Use regulations. This paper discusses some of the issues that become relevant to the safe securing of a load when the package mass becomes a significant proportion of the gross vehicle mass, specifically when a heavy package takes the gross vehicle weight beyond the 44 tonnes routinely permitted in parts of Europe under Heavy Goods Vehicle regulations. The focus is on shipments where a very heavy package is carried on a relatively lightweight trailer. Examples could be where boilers from decommissioned civil nuclear plant are carried on multi-axle trailers, but also heavy packages for used fuel can fall into this category. Conventional approaches for the design of securing systems are discussed, and their relevance to these heavy load cases is considered. Alternative approaches are suggested, such as for reduced load multiplication factors where instability or overturning could result from the use of more general road transport load factors, and the adoption of so called ‘weak link’ attachments for the control of package configuration under hypothetical accident conditions of transport.