What is the stated purpose of zinc injection in PWR secondary systems?

• A. Reduce corrosion product transport in the primary circuit
• B. Increase reactor power
• C. Act as a neutron poison
• D. Prevent turbine trips by maintaining steam generator systems

Answer: (D)

Zinc injection on the secondary side is used as a corrosion-inhibiting measure to protect the steam generator and maintain its heat-transfer performance. By reducing corrosion and the formation of corrosion products (crud) inside the steam generator, the tubes stay cleaner, flow remains unobstructed, and steam quality is preserved. This helps prevent conditions that could lead to a turbine trip, such as loss of heat transfer efficiency or unexpected SG-related plant trips. It is not about increasing reactor power, nor does zinc act as a neutron poison, and its purpose isn’t to shuttle corrosion products to the primary circuit. The stated goal is to keep the steam generator system running reliably to avoid trips.