Welded joints of stainless steel DIN 1.4948, which is similar to AISI Type 304, have been irradiated at 723 and 823 K up to fluences of 1 × 10²³ neutrons (n)·m⁻² and 5 × 10²⁴ n·m⁻² (E > 0.1 MeV). Tension and creep tests show considerable irradiation embrittlement, depending on fluence, test temperature, and strain rate. Creep strain values at 823 K reduce to 0.3 percent. The embrittlement is attributed to helium promoted intergranular fracture of the parent metal, the helium being formed mainly by the ¹⁰B reaction.

Low-cycle fatigue tests show considerable scatter (standard deviation 25 percent) of the fatigue life (N_f) due to weld inhomogeneities, and therefore no significant difference between irradiated and unirradiated welded joints could be observed. Fracture is located in the weld.

Fatigue life is reduced to 0.2 N_f after more than 1000 h creep exposure, due to enhanced initiation of large intergranular cracks in the heat-affected zone below the root weld of irradiated specimens. Tensile and creep properties deteriorate after prior fatigue loading up to a relatively high number of cycles (> 0.7 N_f). Residual creep strain values of irradiated welded joints reduce from 0.5 percent to zero.