Impact of a double containment boundary requirement on small type B (U) package safety case

The United Kingdom (UK) Government has tasked the Nuclear Decommissioning Authority (NDA) with the decommissioning and clean up of the legacy of UK’s civil nuclear sites. This task requires a well organised and flexible transport network to relocate radioactive material (RAM) from the producing site to intermediate and final storage facilities. International Nuclear Services (INS), as a subsidiary company of the NDA, is supporting the Site Licence Companies that operate the various nuclear sites to establish, optimise and coordinate their RAM transport systems. This includes helping to ensure that each off-site move is performed in compliance with current legislation and to high safety standards, and that the transport system represents good value to the taxpayer. There are many existing packages available to conduct these transports, but in some cases the nature of the material to be transported, safety benefits, and/or commercial benefits justify the development of a new package. When such a business case exists it is important that the new package has a high degree of flexibility. It needs to be adaptable to any receipt facility from the most simplistic to the most sophisticated and to be able to carry a wide range of types of radioactive material produced though the lifetime of operating plant. The INS3578, a new package designed by INS, maximises content and enhances flexibility of use thanks to its double containment boundary and its unique shielding design. Loading capability and undemanding handling requirements present a real advantage in comparison to other package options. The aim of this paper is to present the advantages of a double containment boundary, and to describe the impact of this design solution for a type B(U) licensed package safety case (i.e. mechanical/thermal behaviour, containment, activity release, shielding, etc). It also discusses how simplicity of operation and maintenance has been achieved.