Post irradiation mechanical properties of type 304 stainless steel

Specimens of type 304 stainless steel, which is used as the structural material of Japanese prototype fast breeder reactor (FBR) Monju, were irradiated in the Japan Materials Test Reactor (JMTR) at 400 and 550°C. Three types of neutron irradiation capsules were specially designed, namely thermal neutron shielding, normal, and thermal neutron trapping types. As the result, transmutation produced helium levels were 1, 3 and 16 appm, respectively for three capsules, keeping a displacement damage level of 2 dpa. A series of tension, fracture toughness, creep, and fatigue tests has been performed on the pre- and post-irradiation specimens. TEM observation of irradiated specimens has also been performed. This paper will describe the details of the specially designed capsules and preliminary test results.