DETAILED 3-D FINITE ELEMENT ANALYSIS OF A BRIDGE SECTION CRUSH ACCIDENT

This report describes the extension of the validation of previous plane strain finite element analysis (FEA) model results presented in another paper. Japan Nuclear Cycle Development Institute (JNC), in cooperation with Sandia National Laboratories, has performed detailed three-dimensional FEAs of a severe hypothetical bridge section crush transportation accident using the ABAQUS/Explicit FEA code. A 50,000+ element model (shells and solids) with 35 inter-surface contact pairs was used to model the approximately quarter-symmetric package and its fresh fuel assembly contents. This model was validated by comparing analytical deformations and accelerations with empirical data obtained during regulatory 9-m side drop tests onto an unyielding target. Bridge crush analysis results show that the primary containment vessel (including its bolted closure) retained its structural integrity, despite large deformations due to extreme crush and bending loads. Fuel assembly crush forces obtained in this analysis were subsequently applied to another detailed FEA model of the fuel pins and their individual claddings, which showed sufficient secondary containment boundary integrity to avoid cladding leakage. These results show that the safety margin against failure for the package is indeed large, as was intended by IAEA regulations. Although this hypothetical accident condition would be of extremely low probability, it is of scientific interest to investigate the dynamic cask response to such postulated conditions, and such analyses should be used within the framework of a land transport risk assessment.