How safe is safe enough?

The IAEA Regulations for the Safe Transport of Radioactive Material, were historically established with the objective to reduce the probability that persons be exposed to unacceptable doses due to normal operation or accident situations during transport of radioactive material. Based on the International Basic Safety Standards for Protection against Ionizing Radiation (BSS), the definition, which was adopted for an unacceptable dose for an accident situation, is the excess of the maximum dose limits permissible in a single year for the occupational exposure of a worker in the BSS. Concerning the severity of accident situations, it has always be clearly stated that the objective of the tests for demonstrating ability to withstand accident conditions of transport was not to cover every accident condition, but solely most of them. The last available evaluations regarding the rate of accidents which are covered by the standardised accident conditions of transport defined in the IAEA Regulations give a range of about 80%, plus or minus 15% which depends on transport mode and studies. Consequently, slight variations in the capabilities of the packages to meet the specified performance would probably not have significant consequences on the protection level in case of accident. In the assessment of the compliance with the regulations, the tendency of experts, taking advantage of the enhanced performances of computer calculation codes, is to ask more and more calculations, with more and more accuracy, leading to more and more restrictions. Consequently, cost and delay are considerably increased without any evidence of an equivalent effect on the level of protection. This paper will initiate a reflection on the general objectives and principles when implementing the Regulations, in such a way that demonstrations remain cost effective, taking into account evolution of the techniques and a high level of safety.