Types of Power Uprates
The design of every U.S. commercial reactor has excess capacity needed to potentially allow for an uprate, which can fall into one of three categories: 1) measurement uncertainty recapture power uprates, 2) stretch power uprates, and 3) extended power uprates.

1) Measurement uncertainty recapture power uprates are power increases less than 2 percent of the licensed power level, and are achieved by implementing enhanced techniques for calculating reactor power. This involves the use of state‑of‑the‑art devices to more precisely measure feedwater flow which is used to calculate reactor power. More precise measurements reduce the degree of uncertainty in the power level which is used by analysts to predict the ability of the reactor to be safely shut down under possible accident conditions.

2) Stretch power uprates are typically between 2 percent and 7 percent, with the actual increase in power depending on a plant design’s specific operating margin. Stretch power uprates usually involve changes to instrumentation settings but do not involve major plant modifications.

3) Extended power uprates are greater than stretch power uprates and have been approved for increases as high as 20 percent. Extended power uprates usually require significant modifications to major pieces of non-nuclear equipment such as high-pressure turbines, condensate pumps and motors, main generators, and/or transformers.