MODE 5 is defined by which shielding condition?

MODE 5 is defined by which shielding condition?

• A. Shielding fully installed over the core area.
• B. Core is defueled.
• C. Reactor is at ambient temperature.
• D. Less than two layers of concrete shielding are fully installed over the top of the core area with fuel in the core.

Answer: (D)

Shielding adequacy controls how we handle radiological hazards. When fuel remains in the core and there is less than the required shielding—specifically, fewer than two layers of concrete above the core—the radiation field at accessible locations is elevated. This condition triggers Mode 5 to reflect a high-radiation situation that requires special precautions and possibly restoring shielding before continuing with normal activities. If shielding were fully installed, or if the core were defueled, or if the reactor were simply at ambient temperature, those scenarios do not represent the increased radiation hazard that Mode 5 is designed to denote.

Shielding adequacy controls how we handle radiological hazards. When fuel remains in the core and there is less than the required shielding—specifically, fewer than two layers of concrete above the core—the radiation field at accessible locations is elevated. This condition triggers Mode 5 to reflect a high-radiation situation that requires special precautions and possibly restoring shielding before continuing with normal activities. If shielding were fully installed, or if the core were defueled, or if the reactor were simply at ambient temperature, those scenarios do not represent the increased radiation hazard that Mode 5 is designed to denote.