Year
2010
File Attachment
Abstract
Packages for the transport of radioactive material are generally equipped with particular components for crane operations and supporting the package during transport. This paper describes the bolted trunnion systems of Type B packages as an example of such devices. The analysis of functional capability of trunnion systems is a constituent part of package safety design. The components of the trunnion systems (trunnion, fastening bolts) have to be analysed focusing on the assembly state, strength under maximum loads and, if necessary, fatigue in view of the overall load history. Safe handling of the package during crane operations (lifting, tilting) and secure package tie-down to the transport vehicle, if the trunnions are used as attachment point during transport, have to be ensured. According to the draft of the BAM guideline [6] for analysis and assessment of bolted lid and trunnion systems, the finite element method is to be used preferably in the analysis of such structures to obtain more accurate and detailed information about their loading. The finite element model of a trunnion system should envelop the trunnion, the bolts and an appropriate part of the container wall with necessary contact conditions on all interfaces between these components. The application of solid finite elements, which is generally recommended in the BAM guideline draft [6], leads to local stress and strain fields as a result of the calculation. However the assessment concept and the corresponding safety factors in the technical standards, which have to be considered in case of the trunnion system, are usually based on nominal stresses. This paper will discuss some aspects of finite element modelling of the trunnion system. The approaches for preparation and interpretation of calculation results in connection with local or nominal assessment criteria will be discussed with general reference to BAM experience in the approval procedure of Type B packages.