3DAP analysis of a neutron-irradiated stainless steel weld-overlay cladding of nuclear reactor pressure vessel

Takeuchi, Tomoaki   ; Nishiyama, Yutaka ; Katsuyama, Jinya  ; Onizawa, Kunio ; Nozawa, Yasuko*; Matsukawa, Yoshitaka*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Kameda, Jun*

Microstructure evolution on stainless overlay cladding of reactor pressure vessel was quantitatively investigated by means of three-dimensional local electrode atom probe (3DAP) in nano-scale. The cladding material was neutron-irradiated up to 710 n/cm (E 1 MeV) at JMTR. In ferrite phases of cladding material, a 12% of Cr concentration fluctuation, which was arisen through a spinodal decomposition, observed before the irradiation was progressed to 20% after the irradiation while the wave length of the fluctuation was almost not changed about 8-10 nm before and after the irradiation. In addition, Ni, Si and Mn concentration fluctuations were also observed. The concentration fluctuations of the elements other than Cr and differences from the thermal aging will be reported in presentation.