The Dynamic Response of Cracked Fast Reactor Subassembly Ducts

The dynamic elastic response of flawed and unflawed fast reactor subassembly ducts has been studied. Finite elements were used for a plane-strain analysis of hexagonal ducts containing either internal corner cracks or external midflat cracks. Two geometric loading conditions were considered: uniform internal pressurization and point loads applied at opposite midflats. The time dependence of these loads was chosen as a Heaviside step function for the worst case situation and as a triangular pulse to simulate the more likely condition. The presence of cracks in the duct walls alters the dynamic response of the duct. Although the vibrational mode associated with the response of an uncracked duct is always present, the appearance of different flexural modes and their frequencies depend on the number, depth, and location of cracks. The influence of the modal participation on the crack-tip stress-intensity factor is complex, but upper bounds are estimated for the dynamic effects.