MODE 3 corresponds to which reactor condition?

MODE 3 corresponds to which reactor condition?

• A. Reactor operating.
• B. Reactor shutdown.
• C. Reactor outage.
• D. Reactor secured.

Answer: (B)

Understanding reactor operation modes helps you see why Mode 3 is shutdown. This mode represents a state where the reactor is not producing power. Fission is stopped, so the core is kept subcritical by the appropriate positioning of control systems, and the plant is arranged to remove any residual decay heat safely. Even in shutdown, cooling is essential to prevent overheating, so cooling systems stay active and the plant is operated in a safe shutdown configuration. The other described conditions refer to being in operation, a maintenance window without defining a shutdown state, or a security posture, none of which define the reactor’s configured state for stopping power generation.

Understanding reactor operation modes helps you see why Mode 3 is shutdown. This mode represents a state where the reactor is not producing power. Fission is stopped, so the core is kept subcritical by the appropriate positioning of control systems, and the plant is arranged to remove any residual decay heat safely. Even in shutdown, cooling is essential to prevent overheating, so cooling systems stay active and the plant is operated in a safe shutdown configuration.

The other described conditions refer to being in operation, a maintenance window without defining a shutdown state, or a security posture, none of which define the reactor’s configured state for stopping power generation.