US NRC Blog Update: REFRESH: The Power of Power Uprates

REFRESH: The Power of Power Uprates

Leave a comment Posted by Moderator on July 28, 2016

Since this blog post first ran in December 2011, the NRC staff has approved 16 additional power uprates, increasing the nuclear fleet’s output by an additional 1300 megawatts electric. An additional three are under review (for the three reactors at Browns Ferry), and the staff expects to receive an additional 10 uprate applications through the end of September 2017.  David McIntyre
Neil Sheehan
Public Affairs Officer
Region I
Much news space has been devoted over the years to the prospects for new reactors in the U.S. However, new reactors are not the only way the nation’s share of nuclear-generated electricity can be increased — and it doesn’t involve earth-movers, the construction of new buildings or other changes visible to the casual observer.
Another option available to nuclear power plant owners is to pursue a power uprate, which essentially means an increase in the maximum amount of power a reactor can generate. But before a power uprate can be implemented, it must first undergo a thorough review by the NRC.
Take for example, the NRC’s approval of a 15 percent power uprate for the Nine Mile Point 2 nuclear power plant in upstate New York. That approval was the culmination of an NRC review that began with the submittal of the application on May 27, 2009.
During the course of the agency’s evaluation of the proposal, NRC staff scrutinized data regarding the proposal and posed dozens of technical questions to the plant’s owner, Constellation. They included queries about the effects of greater stresses on piping and the plant’s steam dryer, a component at the top of the reactor vessel, as a result of operations at higher power levels.
The NRC does not proceed to a final decision until all such questions are answered to our full satisfaction.
Uprates are not a new development. In fact, the NRC approved the first uprate back in 1977 and has to date approved 140 such applications. All told, the uprates have led to an increase in power output nationwide of about 6,000 megawatts electric.
There are three different kinds of power uprates: “measurement uncertainty recapture” uprates, “stretch” uprates and “extended” uprates. Here’s a brief description of each:
Measurement uncertainty recapture uprates – They involve an increase of less than 2 percent and are achieved by implementing enhanced techniques for calculating reactor power levels. State-of-the-art devices are used to more precisely measure feedwater flow, which is used to calculate reactor power.
Stretch uprates – The increases are typically between 2 and 7 percent and usually involve changes to instrumentation settings but do not require major plant modifications.
Extended uprates – Power boosts of this type have been approved for increases of up to 20 percent. They usually involve significant modifications to major pieces of non-nuclear equipment, such as high-pressure turbines, condensate pumps and motors, main generators and/or transformers. The Nine Mile Point 2 uprate would fall into this category.
For more information on power uprates, visit the NRC web site.