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.