The influence of creep damage and neutron irradiation on the tensile properties of Type 304 stainless steel

In addition to the data base used to assess normal operating conditions, licensing authorities need postirradiation mechanical properties to evaluate the effects of hypothetical core disruptive accidents in liquid metal fast breeders such as the SNR-300. In particular, the synergistic effects of creep and neutron radiation damage on tensile properties constitute a major concern. The structural steel DIN 1.4948, similar to Type 304, is used for the permanent primary structures such reactor vessel and core shield of the SNR-300. Tensile/creep specimens have been irradiated in the HFR, Petten, at 823 K to a total neutron fluence of 1024n x cm-2, the end-of-life condition of permanent primary structures. Thermal control specimens were heat-treated parallel to the irradiation. Both material conditions were subjected to stress of 155 MPa at 823 K and to creep strains in the range from 0.5 to 2.0%. Afterwards, tensile tests were conducted. This paper reports that radiation reduced the elongation and subsequently ultimate tensile strength for strain rates below 10-4 s-1