Proceedings of PVP2005 2005 ASME Pressure Vessels and Piping Division Conference PVP2005-71581 THE EFFECT OF MANUFACTURING PROCESS ON RESIDUAL STRESSES OF PIPE BENDS

ABSTRACT Feeder pipes in CANDU® reactors are an integral part of the circulating heat transport system, connecting the in-reactor fuel channels with the primary heat transport pipes. The feeder pipes are 1.5" to 3.5" in nominal size and made out of SA-106 Grade B material. A typical CANDU 6 station has 760 feeder pipes, half of which are located at the fuel channel inlet and the other half are at the fuel channel outlet. In one of the CANDU 6 stations, 2 feeder bends were replaced due to through-wall cracks and 6 others were replaced due to partial cracks detected by non-destructive examination techniques. In all cases, cracks were axial in orientation and were either at the inside surface of the bend flanks (approximately 60° from the intrados symmetry plane) or at the outside surface of the bend extrados