Which environmental condition is associated with increased IASCC susceptibility?

• A. High-temperature oxidizing water environment
• B. Vacuum
• C. Dry nitrogen atmosphere
• D. Liquid helium

Answer: (A)

Irradiation-assisted stress corrosion cracking occurs when stainless steel is exposed to hot water that is oxidizing, and the material is also under neutron irradiation. The radiation creates defects and accelerates diffusion processes, while the oxidizing water chemistry—especially under high temperature—produces reactive species that disturb the protective oxide film on the steel and promote chromium depletion at grain boundaries. This combination weakens the metal and makes cracks more likely to initiate and grow along grain boundaries, particularly under the stresses present in reactor environments. The high temperature speeds these processes, so susceptibility rises in a high-temperature oxidizing water environment.

In contrast, environments like vacuum, dry nitrogen, or liquid helium do not supply an oxidizing aqueous medium or drive radiolytic production of corrosive species, so the protective film remains more stable and the conditions for IASCC are not met, resulting in much lower susceptibility.