Primary water stress corrosion cracking (PWSCC) refers to a specific type of degradation that occurs in nuclear power plants, particularly in the primary water system of pressurized water reactors (PWRs). It involves the cracking of materials under the combined influence of corrosive environment, stress, and high temperatures that are unique to the primary water system.
PWSCC is driven by the interaction between the corrosive primary water, high tensile stress due to operational conditions, and the presence of susceptible materials or alloys, such as stainless steels and nickel-based alloys, used in the construction of primary system components. The primary water contains a variety of aggressive species, including dissolved oxygen, chlorides, and hydrogen sulfide, which can initiate and propagate cracking under certain conditions.
The cracking mechanism in PWSCC involves the initiation of cracks at the material's surface, which then propagate through grain boundaries due to a combination of chemical reactions and mechanical stresses. The cracks usually exhibit intergranular characteristics, preferentially following the path along the grain boundaries.
The consequences of PWSCC can be severe, including leaks or ruptures of primary system components, leading to potential release of radioactive materials and compromising the safety and integrity of the nuclear power plant. Therefore, monitoring and mitigation strategies are crucial to identify and prevent PWSCC, employing techniques such as non-destructive evaluation, material selection, and maintenance practices to ensure the long-term reliability of PWR primary water systems.
