ON THE DUCTILITY VARIATION OF DUCTILE CAST IRON FOR SPENT NUCLEAR FUEL PACKAGES AND ITS CORRELATION WITH CASTING DEFECTS AND MATERIAL MICROSTRUCTURE

The paper describes a study to correlate the variation in ductility in ductile cast iron to casting defects and microstructure. A large set of tensile and fracture specimens taken from three inserts for the Swedish KBS-3 programme were tested. About half the tensile specimens were analysed by microstructural analysis methods to identify and size defects and microstructural variations. The elongation at fracture was reduced by casting defects in the form of magnesium-oxide films and to a lesser extent by the graphite properties. An elastic-plastic probabilistic fracture mechanics model that relates the variation in ductility to the size and shape of casting defects is presented. The agreement between computed and measured results is quite good.