DYNAMIC ANALYSIS OF AGR FUEL ASSEMBLIES

The procedures for the handling of fuel assemblies in an advanced gas reactor (AGR) have to be demonstrated as being safe and reliable befor e they can be applied. This requires, amongst other considerations, th e study of stresses and assessment of structural integrity of the asse mblies during the normal operating and postulated fault conditions. Wh ilst normal operating conditions are nominally static situations, faul t conditions generally involve shock loadings which induce appreciable dynamic stresses. A suitable and practical method of analysis for sho ck loads on the large complex structure without involving the minute d etail necessary for the finite element method is by a multi-body lumpe d mass-spring damper mechanisms analysis. The mechanisms model utilise d in this study is a generally elastic model which has a small number of nonlinear springs located at the critical regions to quantify the m agnitude of plastic deformations. The springs represent the nonlinear inelastic response with the realistic unloading and reloading force ag ainst displacement characteristics of the critical components. A mecha nism analysis code is utilised for solving the rigid body mechanism pr oblem while subroutines represent the deformable spring stiffnesses. T his paper presents the development of the model and the results of the hangman's drop type shock loading due to a postulated fault. The nume rical predictions from this model have been compared to one fault load ing experimental test with reasonable accuracy.