What effect does a reflector have on the power distribution of a nuclear reactor core?

A reflector in a nuclear reactor core plays a crucial role in optimizing the power distribution by improving the form factor. The form factor refers to the ratio of the maximum power density to the average power density within the core. The presence of a reflector can enhance the thermalization of neutrons, enabling them to be scattered back into the core rather than escaping. This process leads to a more even distribution of neutron population and, subsequently, a more uniform power output across the reactor core.

By minimizing hot spots and ensuring that the fuel is utilized more efficiently, the reflector aids in achieving a flatter power profile, thereby enhancing reactor performance and safety. This improved power distribution is essential for maintaining operational stability and efficiency, allowing for better heat management and overall reactor control.

The other options do not accurately capture the role of a reflector in a nuclear reactor. While a reflector does significantly influence power distribution, attributing no effect to it or suggesting that it decreases efficiency does not align with its intended purpose and function within the reactor design.