New Considerations on the Safety Basis for Shipment of Surface Contaminated Objects

Solid objects that are not radioactive by themselves but contaminated by radioactive material on their surface may be classified for transport as surface contaminated object (SCO). The safety basis for SCO as given in the Advisory Material for the IAEA Regulations for the Safe Transport of Radioactive Material SSG-26, paras 413.1-413.7, is based on an estimation of the dose due to intake of activity from resuspended contamination by a person present at an accident site. This estimation is based on reasonable assumptions about these processes.During the last years, new experiments on the resuspension of surface contaminations after mechanical impact have been undertaken. Various surface materials, types of contamination and impact energies have been investigated. The number and size distribution of the resuspended particles have been measured. From these measurements fractions of resuspended and respirable particles and resulting inhalation doses have been calculated for SCO in packages under accident conditions of transport. The results that are presented in the paper show that the current limits for contamination on SCO include a reasonable safety margin regarding inhalation dose under accident conditions of transport.