Duke Energy’s request to increase the generating capacity of Unit 1 at its Catawba Nuclear Station by 1.7% by more precisely measuring feedwater flow has been approved by federal regulators.

Staff at the Nuclear Regulatory Commission (NRC) found on May 4 that Duke Energy could safely increase the reactor’s output “primarily through more accurate means of measuring feedwater flow.” The NRC’s determination was based on its review of Duke Energy’s evaluations showing the plant’s design can handle the increased power level, it said.

The reactor near Charlotte, N.C., has a capacity of 1,167 MW. The uprate, which Duke Energy intends to complete this month, will increase that capacity to 1,187 MW.

The NRC generally considers three types of power uprates: measurement uncertainty recapture power uprates, stretch power uprates, and extended power uprates. Measurement uncertainty recapture power uprates result in power increases of less than 2%, typically achieved by implementing enhanced techniques for calculating reactor power. This involves the use of state-of-the-art feedwater flow measurement devices to more accurately 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 shutdown under postulated accident conditions,” explained the NRC.

In comparison, stretch power uprates result in increases of up to 7% and are within the design capacity of the plant. Stretch power uprates usually involve changes to instrumentation setpoints but do not involve major plant modifications. On the other hand, extended power uprates, which have been approved for increases as high as 20%, require significant modifications to major balance-of-plant equipment such as the high pressure turbines, condensate pumps and motors, main generators, and/or transformers.


Sonal Patel, associate editor (@POWERmagazine, @sonalcpatel)