THE TRANSPORT OF URANIUM SWARF IMMERSED IN OIL - Presentation

Uranium swarf is considered to be a pyrophoric material liable to spontaneous combustion and is therefore immersed in oil when machined, stored or transported. It is typically packaged in a combination package comprising a plastic drum within a steel outer drum. The oil used is generally a water based emulsion and the material is stored in a non-corroding plastic drum. To avoid further handling of the material the same container is also used for transport. As a radioactive material, transport is subject to the IAEA Regulations for the Safe Transport of Material. For a package carrying natural or depleted uranium for which the A2 value is unlimited the IAEA Regulations require transport within an IP-1 Package which is not subject to testing. Consideration must however be given to any other dangerous properties of the material which requires compliance with the packaging requirements of the relevant dangerous goods transport regulations which would normally require the use of a metal package for pyrophoric substances. This paper will present a justification for the transport of uranium swarf in a plastic drum when the pyrophoricity is suppressed by immersion in oil. It will review the status of the payload by reference to the UN Recommendations on the Transport of Dangerous Goods (UNRTDG) to determine the classification of the material. The paper will review the requirements of the UNRTDG and the modal transport regulations and demonstrate that the proposed package complies with these requirements taking account of the other dangerous properties of the payload. A further problem is that hydrogen may be produced as a result of radiolysis and corrosion. Since retention of hydrogen would raise further issues due to pressurisation of the package which would then be carrying a flammable gas, the hydrogen is vented. At the same time the oil must be retained to prevent spontaneous combustion of the uranium swarf. The paper will discuss these issues and the features adopted demonstrating compliance with the various regulations. The paper will conclude by proposing a suitable package design that satisfies the various requirements and summarising the issues raised.