Year
2003
Abstract
The behavior of the casks used for the shipment of nuclear materials must be assessed for a set of various normal and accidental situations. Though not explicitly required in the French regulations, the security of the casks must be studied in the case of loads due either to an explosion resulting from an aggression with a large amount of explosive or to an attack with a High Energy Density Device (HEDD) like a conical shaped charge. This paper will present the physical models and the evaluation of the damage (distance and diameter of penetration by the jet in the cask) occurring to the FS47 cask (used for the shipment of PuO2 powder) as well as the quantity of nuclear material removed from the cask. To be conservative, it is assumed that the jet resulting from the detonation of the conical shaped charge hits the cask normally to its axis and at mid-height. IRSN and DGA have undertaken the development of numerical models to identify and understand the physical phenomena involved in the interaction between the jet and the multimaterial cask and to validate these models on the basis of the experimental results. As the diameter of the zone directly affected by the jet (some diameters of the jet itself) remains small in comparison with the cask’s diameter, a 2D approximation may be used. Such a 2D model is axisymmetric, its axis of symmetry corresponding with the jet axis; the cask model is planar and represents a sandwich of layers corresponding to the various materials constituting the cask (steel, plaster, copper). The calculation needs two stages: the creation of the jet which requires a detailed model of the CSC (in this stage the cask model is not considered) and in a second stage the calculation of the interaction between the jet previously calculated and the casks. As a 2D model cannot account for the loss of stability of the jet when it goes through the cask, a criterion is defined, based on a velocity threshold under which jet particles are assumed to create no damage anymore.