Microstructural evolution and void swelling in extra high purity Ni-base superalloy under multi-ion irradiation

Kim, G.; Shiba, Kiyoyuki; Sawai, Tomotsugu; Ioka, Ikuo  ; Kiuchi, Kiyoshi; Nakayama, Jumpei*

In the present work, irradiation effects of high-purity Ni alloys were studied in terms of microstructural changes with respect to multi-ion irradiation by using JAEA triple-ion beam irradiation facility, TIARA. The alloys investigated are designed as the MA doped MOX fuel claddings for sodium cooled fast reactor and impurities, such as C, O, N, P, S were reduced less than 100 ppm in total to improve workability, irradiation embrittlement, inter-granular corrosion, and so on. Two types of alloys (Fe-40Ni-Cr-1.5Ti-1.5Al) with different Cr contents (20 or 25%) were used for the irradiation experiments. Single (Fe or Ni), dual (single + He), and triple (dual + H) beam irradiation were conducted up to 50 dpa, 150 appmHe, and 1500 appmH at 825K to evaluate the effect of radiation damage and the effect of transmuted gaseous elements. Void swelling was evaluated and compared with type 316 stainless steel. Other microstructural features, such as precipitation stability, dislocation structures were also evaluated to discuss irradiation resistance.