Fracture Mechanics Analysis of Cast Duplex Stainless Steel Elbows Containing a Surface Crack

Abstract

Some components of the primary loop of a PWR are made of cast duplex stainless steel. This kind of steel may age even at relatively low temperatures, (below 400‡C, which is within the temperature range of PWR service conditions), leading to a significant decrease of its toughness. This is why a large research program was initiated on the fracture behaviour of aged duplex stainless steel elbows in France. The main task of this program was to test three 2/3-scale models of aged PWR primary loop elbows. The first two tests (called SEM1 and SEM2) were conducted under in-plane closure bending at 320‡C; the third (called SEM3) was conducted under constant internal pressure and inplane closure bending at 60‡C. The first two elbows contained a semi-elliptical notch machined into the outer surface of one flank, oriented either longitudinally (SEM1 test) or circumferentially (SEM2 test); the third elbow contained both notches described above, one on each flank. This paper presents the results of the experiments, the finite element calculations and the ductile fracture mechanics analyses that were performed.