What method can be used for small power adjustments within the nuclear reactor?

Varying the speed of the recirculating pumps is an effective method for making small power adjustments within a nuclear reactor. This technique leverages the relationship between flow rates and the reactor's heat transfer capabilities. By adjusting the speed of the pumps, the flow of water (or coolant) through the reactor can be modified, thus influencing the amount of heat removed from the reactor core. This allows for fine tuning of the reactor's power output, facilitating smooth and responsive control over the thermal conditions within the reactor.

In contrast, changing reactor geometry typically involves significant structural alterations, which are not ideal for minor adjustments. Modifying fuel type impacts the reactor's fundamental operational characteristics and is generally a more extensive process. Altering steam pressure can affect the plant’s efficiency and overall operation but is less precise for making small adjustments compared to manipulating flow rates with pump speed adjustments. Thus, varying the speed of the recirculating pumps stands out as the most practical and immediate method for small-scale power control in a nuclear reactor context.