Size effects in fracture mechanics: Implications for fast reactor subassembly analysis and safety

There is a size effect in fracture mechanics, and this leads to some paradoxical behavior of flawed engineering structures of which the safety analyst should be aware. In order to quantify the size effect and its implications for highly-irradiated LMFBR subassembly ducts subject to overpressurization, a two-criterion approach to fracture is employed and two duct designs are considered. It is concluded that brittle fracture may be more likely to occur in the case of thicker ducts, and that fracture-free operating experience with smaller ducts does not insure the stability of cracks in the thicker wall.