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Tie-Down Assessment of Radioactive Material Packages on Conveyances: Approach to Competent Authority Approval Applications in Accordance with TS-R-1 (july 2004) and TS-G-1.1 (June 2002)

Abstract The design and assessment of tie-down arrangements are integral parts of substantiating the performance of a package for transport of radioactive material. The package and tie-down system must remain intact under all routine (everyday) conditions. During such circumstances the tie-down materials, components and attachments must remain within accepted stress limits, with acceptable fatigue performance for their usage. Under more extreme mishap or accident conditions the package may detach from the conveyance. This must occur in a way that avoids impairing the integrity of the package or its ability to comply with regulations. Normal mishaps must not cause the package components or attachment point(s) to yield. The regulatory framework against which tie-downs are assessed has been subject to review and gradual amendment, culminating in the issue of TS-R-1 in June 2000 (Revised 2003) and the further advisory guidance of TS-G-1.1 in June 2002. This paper will consider the common arrangements for tie-down, with general reference to the authors' experience of preparing and reviewing substantiations for 10 different package tie-downs of varying configuration. The configurations for tying down larger packages and some of the potential engineering considerations of each will be discussed. Consideration of possible loadpaths is vital to an understanding of tie-down performance. It is necessary to clearly understand the method of transferring forces corresponding to package accelerations about each axis. This conceptual understanding is a precursor to appreciating the way in which the package might be expected to detach under accident conditions. This 'weak link' behaviour is a key part of an assessment. 'Weak link' performance will be discussed along with particular key issues such as the performance of bolted and welded connections, fatigue stresses (including the potential for local stress concentration factors) and the use of materials. The application and interpretation of the latest IAEA regulations regarding tie-down will be discussed along with approaches used to assess both modification of existing package arrangements and new tie-down designs. In conclusion the paper will discuss lessons learned that may be applicable to future conveyance designs.