Effect of Neutron Irradiation on Creep Properties of 18Cr-11 Ni(DIN 1.4948) Stainless Steel Plate and Welded Joints at 823 K

摘要

Post irradiation creep data are required on structural steels according to DIN 14948 (equivalent to AISI 304) used in reactor vessel and shield structures for the fast breeder SNR 300. Most important effect of irradiation is diminished ductility of both plate and welded joints. Creep strength of plate is reduced to 50 MPa which means a reduction in creep life by a factor of about 10. Welded joints fracture in unirradiated condition along the dendrite boundaries in the weld at a creep stress 20 MPa lower than parent metal. After irradiation grain boundaries in parent metal adjacent to the weld are weaker causing a further reduction of creep strength of 30 MPa. The average post irradiation stress-to-rupture values of one heat of plate and one type of welded joints fall below the minima of VdTUV and ASME B + PV code.