Because of its high resistance against stress corrosion cracking (SCC), nickel (Ni)-based alloy with high Cr concentration is expected to be applied to Boiling Water Reactor (BWR) environment. However the lab data of previous study indicated that long range ordering (LRO) could be a risk to SCC resistance for Ni-based alloy with high Cr concentration at Pressurized Water Reactor (PWR) temperature, depending
on the duration of operation. Because the hardening due to LRO could lower fracture toughness, leading to higher susceptibility to SCC especially crack propagation. On the other hand, due to the lack of data, it is unclear whether LRO could also occur in BWR environment, where the temperature is lower than that of PWR. In this work, in order to discuss this point, several Ni-based model alloys with different
concentration of Fe, Nb and Cr were fabricated according to the composition range of Alloy 52i for Vickers hardness and Charpy impact value measurement after thermal aging. The effect of solute element on LRO was also discussed with these model alloys. Besides, butt welds between Alloy 52i and Type 316L stainless steel, NCF600 and NCF690 were also prepared for observing the LRO behavior in their dilution
zone of weld. Based on the results which showed that no hardness increase in any of the materials was over + 20 HV after the thermal aging tests, we estimated that no significant LRO would occur during over 40 years in BWR environment in either Alloy 52i or the dilution zone.