When heat transfer on a control rod takes place from the center of the fuel to its outer surface, the dominant mechanism is

When heat transfer on a control rod takes place from the center of the fuel to its outer surface, the dominant mechanism is

• A. Conduction
• B. Convection
• C. Radiation
• D. Diffusion

Answer: (A)

Heat moves from hotter regions to cooler ones inside a solid mainly by conduction. In a control rod, the center is hot and the outer surface is cooler, so energy travels through the rod material by lattice vibrations and free electrons transferring energy to neighboring atoms. Convection isn’t involved inside the solid because there’s no fluid to circulate, and radiation within the solid is typically small compared to conduction at reactor temperatures. Diffusion isn’t the standard mechanism used to describe heat movement in solids here. So the dominant mode is conduction.

Heat moves from hotter regions to cooler ones inside a solid mainly by conduction. In a control rod, the center is hot and the outer surface is cooler, so energy travels through the rod material by lattice vibrations and free electrons transferring energy to neighboring atoms. Convection isn’t involved inside the solid because there’s no fluid to circulate, and radiation within the solid is typically small compared to conduction at reactor temperatures. Diffusion isn’t the standard mechanism used to describe heat movement in solids here. So the dominant mode is conduction.