Designing Tie-Down Systems For Heavy RAM Packages – Should Revised Design Criteria Apply?

The safe transport of Radioactive Materials (RAM) is the top priority for all stakeholders and achieved through compliance with the IAEA Transport Regulations TS-R-1. These regulations cover all RAM transport package types, irrespective of the nature of their radioactive contents. In practice, the majority of package types are relatively light in weight but there are many RAM package designs that weigh over 100 tonnes. The object of this paper is to discuss issues that arise from the transport by road and rail of such packages, in particular the design and operation of the tie down systems acting between the RAM package and its conveyance. The TS-G-1 regulations do not specify acceleration factors for RAM package tie downs but the supporting advisory material TS-G-1.1 gives indicative factors that are frequently applied by designers of tie down systems. However, the tie down designer may be permitted to use lower acceleration factors, subject to agreement with competent authorities and transport modal organisations. This paper will demonstrate, in the case of heavy RAM packages, there can be issues arising from designing tie down systems, which may lead to over design without real increase in transport safety. Indeed, in some cases achieving compliance with certain transport loading conditions could potentially increase risks to operating personnel. It will be demonstrated where the RAM package weighs more than the conveyance vehicle, it is the mass and geometry of that vehicle that can determine stresses in the tie down system and not the mass of the package itself. This paper makes the case, when designing a tie down system for heavy RAM packages for routine movements by road and rail, the weight and geometry of the conveyance should be taken into account and demonstrates there will be no reduction in safety as a consequence.